Patent Publication Number: US-2018038013-A1

Title: Process for making a fabricated article from polyolefin

Description:
BACKGROUND 
     Previously, carbonaceous articles, such as carbon fibers, have been produced primarily from polyacrylonitrile (PAN), pitch, or cellulose precursors. The process for making carbonaceous articles begins by forming a fabricated article, such as a fiber or a film, from the precursor. Precursors may be formed into fabricated articles using standard techniques for forming or molding polymers. The fabricated article is subsequently stabilized to allow the fabricated article to substantially retain shape during the subsequent heat-processing steps; without being limited by theory, such stabilization typically involves a combination of oxidation and heat and generally results in dehydrogenation, ring formation, oxidation and crosslinking of the precursor which defines the fabricated article. The stabilized fabricated article is then converted into a carbonaceous article by heating the stabilized fabricated article in an inert atmosphere. While the general steps for producing a carbonaceous article are the same for the variety of precursors, the details of those steps vary widely depending on the chemical makeup of the selected precursor. 
     Polyolefins have been investigated as an alternative precursor for carbonaceous articles, but a suitable and economically viable preparation process has proven elusive. Of particular interest is identifying an economical process for preparing carbonaceous articles from polyolefin precursors. For example, maximizing mass retention during the stabilization and carbonization steps is of interest. 
     STATEMENT OF INVENTION 
     The present disclosure describes a method for preparing a carbonaceous article comprising: providing a crosslinked polyolefin fabricated article; stabilizing the crosslinked polyolefin fabricated article by air oxidation to provide a stabilized fabricated article; treating with a boron-containing liquid (BCL) during or intermediate to at least one of the preceding steps; and carbonizing the stabilized fabricated article. In one instance the present disclosure describes a method for preparing a stabilized article. 
    
    
     DETAILED DESCRIPTION 
     Unless otherwise indicated, numeric ranges, for instance “from 2 to 10, ” are inclusive of the numbers defining the range (e.g., 2 and 10). 
     Unless otherwise indicated, ratios, percentages, parts, and the like are by weight. 
     Unless otherwise indicated, the crosslinkable functional group content for a polyolefin resin is characterized by the mol % crosslinkable functional groups, which is calculated as the number of mols of crosslinkable functional groups divided by the total number of mols of monomer units contained in the polyolefin. 
     Unless otherwise indicated, “monomer” refers to a molecule which can undergo polymerization, thereby contributing constitutional units to the essential structure of a macromolecule, for example, a polyolefin. In one aspect, the present disclosure describes a process for producing a carbonaceous fabricated article from a polyolefin resin. As is described in more detail herein, the carbonaceous fabricated article is prepared by the following method: (a) providing an olefin resin; (b) forming a fabricated article from the olefin resin; (c) crosslinking the fabricated article to provide a crosslinked fabricated article; (d) stabilizing the fabricated article by air oxidation to provide a stabilized fabricated article; (e) treating with a boron-containing liquid (BCL) during or intermediate to at least one of the preceding steps; and (f) carbonizing the stabilized fabricated article. 
     Suitable BCLs include liquids which include a boron-containing species. Examples of suitable boron-containing species include borane, borate, borinic acid, boronic acid, boric acid, borinic ester, boronic ester, boroxine, aminoborane, borazine, borohydrides and derivatives and combinations thereof. Elemental boron is also a suitable boron-containing species. Examples of derivatives of boric acid include metaboric acid, and boron oxide. Examples of borate derivatives include inorganic borates such as zinc borate and organoborates such as tributyl borate. In one instance the BCL is prepared with only the boron-containing species. In one instance, the BCL also includes another component with the boron-containing species, and is chosen such that the other component is miscible, forms a suspension with, or otherwise is carried with the boron-containing species and is compatible with the overall process. In one instance, the other component is a polar or non-polar liquid. For example, an alcohol, such as isopropanol, is a suitable constituent of the BCL. In one instance, at least a portion of the boron-containing species is carried as a suspension in the BCL. 
     Unless stated otherwise, any method or process steps described herein may be performed in any order. 
     Polyolefins are a class of polymers produced from one or more olefin monomer. The polymers described herein may be formed from one or more types of monomers. Polyethylene is the preferred polyolefin resin, but other polyolefin resins may be substituted. For example, a polyolefin produced from ethylene, propylene, or other alpha-olefin (for instance, 1-butene, 1-hexene, 1-octene), or a combination thereof, is also suitable. The polyolefins described herein are typically provided in resin form, subdivided into pellets or granules of a convenient size for further melt or solution processing. In one instance, the polyolefin resins are treated with a BCL prior to being formed as a fabricated article. The polyolefin resins may be treated with the BCL by any mechanism known in the art, such as spraying, dipping, or imbibing. The BCL may be introduced in a suitable liquid form, for example neat, or as part of a solution, or as a suspension in a liquid. The BCL may be introduced as part of a continuous process or as part of a batch process. 
     The polyolefin resins described herein are subjected to a crosslinking step. Any suitable method for crosslinking polyolefins is sufficient. In one instance, the polyolefins are crosslinked by irradiation, such as by electron beam processing. Other crosslinking methods are suitable, for example, ultraviolet irradiation and gamma irradiation. In some instances, an initiator, such as benzophenone, may be used in conjunction with the irradiation to initiate crosslinking. In one instance, the polyolefin resins have been modified to include crosslinkable functional groups which are suitable for reacting to crosslink the polyolefin resin. Where the polyolefin resin includes crosslinkable functional groups, crosslinking may be initiated by known methods, including use of a chemical crosslinking agent, by heat, by steam, or other suitable method. In one instance, copolymers are suitable to provide a polyolefin resin having crosslinkable functional groups where one or more alpha-olefins have been copolymerized with another monomer containing a group suitable for serving as a crosslinkable functional group, for example, dienes, carbon monoxide, glycidyl methacrylate, acrylic acid, vinyl acetate, maleic anhydride, or vinyl trimethoxy silane (VTMS) are among the monomers suitable for being copolymerized with the alpha-olefin. Further, the polyolefin resin having crosslinkable functional groups may also be produced from a poly(alpha-olefin) which has been modified by grafting a functional group moiety onto the base polyolefin, wherein the functional group is selected based on its ability to subsequently enable crosslinking of the given polyolefin. For example, grafting of this type may be carried out by use of free radical initiators (such as peroxides) and vinyl monomers (such as VTMS, dienes, vinyl acetate, acrylic acid, methacrylic acid, acrylic and methacrylic esters such as glycidyl methacrylate and methacryloxypropyl trimethoxysilane, allyl amine, p-aminostyrene, dimethylaminoethyl methacrylate) or via azido-functionalized molecules (such as 4-[2-(trimethoxysilyl)ethyl)]benzenesulfonyl azide). Polyolefin resins having crosslinkable functional groups may be produced from a polyolefin resin, or may be purchased commercially. Examples of commercially available polyolefin resins having crosslinkable functional groups include SI-LINK sold by The Dow Chemical Company, PRIMACOR sold by The Dow Chemical Company, EVAL resins sold by Kuraray, and LOTADER AX8840 sold by Arkema. 
     As described above, the polyolefin resin is processed to form a fabricated article. A fabricated article is an article which has been fabricated from the polyolefin resin. The fabricated article is formed using known polyolefin fabrication techniques, for example, melt or solution spinning to form fibers, film extrusion or film casting or a blown film process to form films, die extrusion or injection molding or compression molding to form more complex shapes, or solution casting. The fabrication technique is selected according to the desired geometry of the target carbonaceous article, and the desired physical properties of the same. For example, where the desired carbonaceous article is a carbon fiber, fiber spinning is a suitable fabrication technique. As another example, where the desired carbonaceous article is a carbon film, compression molding is a suitable fabrication technique. In one instance, the fabricated article is treated with a BCL. In one instance, the fabricated article is treated with the BCL prior to crosslinking the polyolefin resin. The fabricated article may be treated with the BCL by any mechanism known in the art, such as spraying, dipping, or imbibing. The BCL may be introduced in a suitable liquid form, for example neat, or as part of a solution, or as a suspension in a liquid. The BCL may be introduced as part of a continuous process or as part of a batch process. 
     As noted above, at least a portion of the polyolefin resin is crosslinked to yield a crosslinked fabricated article. In some embodiments, crosslinking is carried out via chemical crosslinking. Thus, in some embodiments, the crosslinked fabricated article is a fabricated article which has been treated with one or more chemical agents to crosslink the crosslinkable functional groups of the polyolefin resin. Such chemical agent functions to initiate the formation of intramolecular chemical bonds between the crosslinkable functional groups or reacts with the crosslinkable functional groups to form intramolecular chemical bonds, as is known in the art. Chemical crosslinking causes the crosslinkable functional groups to react to form new bonds, forming linkages between the various polymer chains which define the polyolefin resin having crosslinkable functional groups. The chemical agent which effectuates the crosslinking is selected based on the type of crosslinkable functional group(s) included in the polyolefin resin; a diverse array of reactions are known which crosslink crosslinkable functional groups via intermolecular and intramolecular chemical bonds. A suitable chemical agent is selected which is known to crosslink the crosslinkable functional groups present in the fabricated article to produce the crosslinked fabricated article. For example, without limiting the present disclosure, if the crosslinkable functional group attached to the polyolefin is a vinyl group, suitable chemical agents include free radical initiators such as peroxides or azo-bis nitriles, for example, dicumyl peroxide, dibenzoyl peroxide, t-butyl peroctoate, azobisisobutyronitrile, and the like. If the crosslinkable functional group attached to the polyolefin is an acid, such as a carboxylic acid, or an anhydride, or an ester, or a glycidoxy group, a suitable chemical agent can be a compound containing at least two nucleophilic groups, including dinucleophiles such as diamines, diols, dithiols, for example ethylenediamine, hexamethylenediamine, butane diol, or hexanedithiol. Compounds containing more than two nucleophilic groups, for example glycerol, sorbitol, or hexamethylene tetramine can also be used. Mixed di- or higher-nucleophiles, which contain at least two different nucleophilic groups, for example ethanolamine can also be suitable chemical agents. If the crosslinkable functional group attached to the polyolefin is a mono-, di- or tri-alkoxy silyl group, water, and Lewis or Bronsted acid or base catalysts can be used as suitable chemical agents. For example, without limiting the present disclosure, Lewis or Bronsted acid or base catalysts include aryl sulfonic acids, sulfuric acid, hydroxides, zirconium alkoxides or tin reagents. 
     Crosslinking the fabricated article is generally preferred to ensure that the fabricated article retains its shape at the elevated temperatures required for the subsequent processing steps. Without crosslinking, polyolefin resins typically soften, melt or otherwise deform or breakdown at elevated temperatures. Crosslinking adds thermal stability to the fabricated article. In one instance, the fabricated article is treated with a BCL following crosslinking and prior to stabilization. The crosslinked fabricated article may be treated with the BCL by any mechanism known in the art, such as spraying, dipping, or imbibing. The BCL may be introduced in a suitable liquid form, for example neat, or as part of a solution, or as a suspension in a liquid. The BCL may be introduced as part of a continuous process or as part of a batch process. 
     The crosslinked fabricated article is heated in an oxidizing environment to yield a stabilized fabricated article. In some embodiments, the temperature for stabilizing the crosslinked fabricated article is at least 120° C., preferably at least 190° C. In some embodiments, the temperature for stabilizing the crosslinked fabricated article is no more than 400° C., preferably no more than 300° C. In one instance, the crosslinked fabricated article is introduced to a heating chamber which is already at the desired temperature. In another instance, the fabricated article is introduced to a heating chamber at or near ambient temperature, which chamber is subsequently heated to the desired temperature. In some embodiments the heating rate is at least 1° C./minute. In other embodiments the heating rate is no more than 15° C./minute. In yet another instance, the chamber is heated step wise, for instance, the chamber is heated to a first temperature for a time, such as, 120° C. for one hour, then is raised to a second temperature for a time, such as 180° C. for one hour, and third is raised to a holding temperature, such as 250° C. for 10 hours. The stabilization process involves holding the crosslinked fabricated article at the given temperature for periods up to 100 hours depending on the dimensions of the fabricated article. In one instance, the fabricated article is treated with a BCL during the stabilization process. The crosslinked fabricated article may be treated with the BCL during stabilization by any mechanism known in the art, such as spraying, dipping, or imbibing. The BCL may be introduced in a suitable liquid form, for example neat, or as part of a solution, or as a suspension in a liquid. The BCL may be introduced as part of a continuous process or as part of a batch process. The stabilization process yields a boron-treated stabilized fabricated article which is a precursor for a carbonaceous article. Without being limited by theory, the stabilization process oxidizes the crosslinked fabricated article and causes changes to the hydrocarbon structure that increases the crosslink density while decreasing the hydrogen/carbon ratio of the crosslinked fabricated article. Without being limited by theory, the stabilization process in the presence of boron modifies the oxidation chemistry and increases the crosslink density. 
     Unexpectedly, it has been found that introducing boron via a BCL in the fabricated article improves mass retention of the subsequently produced stabilized article and carbonaceous article. It has also been found that treating the fabricated article with a boron-containing species improves form-retention of the subsequently produced carbonaceous article. 
     In another aspect, the present disclosure describes a boron-treated stabilized fabricated article which is formed from a polyolefin precursor (resin). In one instance, the boron-treated stabilized fabricated article is formed according to the process described herein. 
     In yet another aspect, a carbonaceous article and a process for making the same are provided. Carbonaceous articles are articles which are rich in carbon; carbon fibers, carbon sheets and carbon films are examples of carbonaceous articles. Carbonaceous articles have many applications, for example, carbon fibers are commonly used to reinforce composite materials, such as in carbon fiber reinforced epoxy composites, while carbon discs or pads are used for high performance braking systems. 
     The carbonaceous articles described herein are prepared by carbonizing the stabilized fabricated article by heat-treating the boron-treated stabilized fabricated articles in an inert environment. The inert environment is an environment surrounding the boron-treated stabilized fabricated article that shows little reactivity with carbon at elevated temperatures, preferably a high vacuum or an oxygen-depleted atmosphere, more preferably a nitrogen atmosphere or an argon atmosphere. It is understood that trace amounts of oxygen may be present in the inert atmosphere. In one instance, the temperature of the inert environment is at or above 600° C. Preferably, the temperature of the inert environment is at or above 800° C. In one instance, the temperature of the inert environment is no more than 3000° C. In one instance, the temperature is from 1400-2400° C. Temperatures at or near the upper end of that range will produce a graphite article, while temperatures at or near the lower end of the range will produce a carbon article. 
     In order to prevent bubbling or damage to the fabricated article during carbonization, it is preferred to heat the inert environment in a gradual or stepwise fashion. In one embodiment, the boron-treated stabilized fabricated article is introduced to a heating chamber containing an inert environment at or near ambient temperature, which chamber is subsequently heated over a period of time to achieve the desired final temperature. The heating schedule can also include one or more hold steps for a prescribed period at the final temperature or an intermediate temperature or a programmed cooling rate before the article is removed from the chamber. 
     In yet another embodiment, the chamber containing the inert environment is subdivided into multiple zones, each maintained at a desired temperature by an appropriate control device, and the boron-treated stabilized fabricated article is heated in a stepwise fashion by passage from one zone to the next via an appropriate transport mechanism, such as a motorized belt. In the instance where a boron-treated stabilized fabricated article is a fiber, this transport mechanism can be the application of a traction force to the fiber at the exit of the carbonization process while the tension in the stabilized fiber is controlled at the inlet. 
     Some embodiments of the invention will now be described in detail in the following Examples. 
     In the Examples, overall mass yield is calculated as the product of oxidation mass yield and carbonization mass yield (calculated as provided below). PHR refers to parts per hundred resin (mass basis). MI refers to melt index which is a measure of melt flow rate. Wt % refers to parts per 100 total parts, mass basis. PE refers to polyethylene. BA refers to boric acid. MBA refers to metaboric acid. BO refers to boric oxide. ZB refers to zinc borate. T 95 % refers to the temperature at which 5% mass loss (° C.) is observed. T 50 % refers to the temperature at which 50% mass loss (° C.) is observed. T 5 % refers to the temperature at which 95% mass loss (° C.) is observed. Definitions of measured yields: 
     
       
         
           
             
               Oxidation 
                
               
                   
               
                
               mass 
                
               
                   
               
                
               yield 
                
               
                 : 
               
                
               
                   
               
                
               
                 Y 
                 O 
               
             
             = 
             
               
                 m 
                 OX 
               
               
                 m 
                 PE 
               
             
           
         
       
       
         
           
             
               Carbonization 
                
               
                   
               
                
               mass 
                
               
                   
               
                
               yield 
                
               
                 : 
               
                
               
                   
               
                
               
                 Y 
                 C 
               
             
             = 
             
               
                 m 
                 CF 
               
               
                 m 
                 OX 
               
             
           
         
       
       
         
           
             
               Overall 
                
               
                   
               
                
               mass 
                
               
                   
               
                
               yield 
                
               
                 : 
               
                
               
                   
               
                
               
                 Y 
                 M 
               
             
             = 
             
               
                 Y 
                 O 
               
                
               
                 Y 
                 C 
               
             
           
         
       
       
         
           
             
               Overall 
                
               
                   
               
                
               mass 
                
               
                   
               
                
               yield 
                
               
                   
               
                
               
                 ( 
                 
                   carbonaceous 
                    
                   
                       
                   
                    
                   mass 
                    
                   
                       
                   
                    
                   per 
                    
                   
                       
                   
                    
                   initial 
                    
                   
                       
                   
                    
                   mass 
                    
                   
                       
                   
                    
                   of 
                    
                   
                       
                   
                    
                   PE 
                 
                 ) 
               
                
               
                 : 
               
             
              
             
                 
             
           
         
       
       
         
           
             
               Y 
               
                 M 
                 , 
                 PE 
               
             
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                   Y 
                   O 
                 
                  
                 
                   Y 
                   C 
                 
               
               
                 M 
                 
                   % 
                    
                   PE 
                 
               
             
           
         
       
     
     Where m PE  is the initial mass of polyethylene; m OX  is the mass remaining after oxidation; m CF  is the mass remaining after carbonization; M %PE  is the mass % of polyethylene in the original formed article. 
     Soxhlet extraction is a method for determining the gel content and swell ratio of crosslinked ethylene plastics. As used herein, Soxhlet extraction is conducted according to ASTM Standard D2765-11 “Standard Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics.” In the method employed, a crosslinked fabricated article between 0.050-0.500 g is weighed and placed into a cellulose-based thimble which is then placed into a Soxhlet extraction apparatus with sufficient quantity of xylenes. Soxhlet extraction is then performed with refluxing xylenes for at least 12 hours. Following extraction, the thimbles are removed and the crosslinked fabricated article is dried in a vacuum oven at 80° C. for at least 12 hours and then weighed, thereby providing a Soxhlet-treated article. The gel content (%) is then calculated from the weight ratio (Soxhlet-treated article)/(crosslinked fabricated article). 
     Comparative Example 1 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201, supplied by King Industries, for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 61.4-61.9% by Soxhlet extraction. The crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 1 with temperature ramp rates of 10° C./min Table 2 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 1 
                 10 
                 190 
                 190 
                 800 
               
               
                 2 
                 10 
                 230 
                 230 
                 800 
               
               
                 3 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Mass retained during 
                 Overall mass 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 97.34 
                 5.90 
               
               
                 2 
                 81.17 
                 14.11 
               
               
                 3 
                 78.50 
                 12.53 
               
               
                   
               
            
           
         
       
     
     Example 1A 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201, for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 61.4-61.9% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % solution of boric acid in isopropanol for the times reported in Table 3. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The mass of the fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 4. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 Boric acid treatment time 
               
               
                   
                 Segment 
                 (min) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 30 
               
               
                   
                 2 
                 60 
               
               
                   
                 3 
                 300 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                 Mass of fiber 
                 Mass of fiber 
                   
               
               
                   
                   
                 before BA 
                 after BA 
                 Mass change 
               
               
                   
                 Segment 
                 treatment (g) 
                 treatment (g) 
                 (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 1 
                 0.4816 
                 0.5053 
                 4.92 
               
               
                   
                 2 
                 0.4679 
                 0.4906 
                 4.85 
               
               
                   
                 3 
                 0.4703 
                 0.4940 
                 5.04 
               
               
                   
                   
               
            
           
         
       
     
     The boric acid treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 5 with temperature ramp rates of 10° C./min. Table 6 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                   
                 Starting 
                 Final 
               
               
                   
                 Hold, 
                 Isothermal Hold, 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 Time (hr) 
                 Temperature (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A 
                 10 
                 190 
                 190 
                 800 
               
               
                 B 
                 10 
                 230 
                 230 
                 800 
               
               
                 C 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                   
                 Mass retained during 
                   
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 Char yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 1A 
                 83.86 
                 18.38 
                 19.28 
               
               
                 1B 
                 86.99 
                 22.09 
                 23.18 
               
               
                 1C 
                 73.56 
                 27.23 
                 28.57 
               
               
                 2A 
                 89.79 
                 14.29 
                 14.98 
               
               
                 2B 
                 88.13 
                 20.75 
                 21.76 
               
               
                 2C 
                 82.86 
                 14.34 
                 15.04 
               
               
                 3A 
                 94.51 
                 7.28 
                 7.65 
               
               
                 3B 
                 89.90 
                 17.78 
                 18.68 
               
               
                 3C 
                 86.23 
                 14.25 
                 14.97 
               
               
                   
               
            
           
         
       
     
     Example 1B 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 61.4-61.9% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % solution of boric acid in isopropanol for the times reported in Table 7. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The dried, boric acid treated fibers undergo thermal treatment (80°C.) overnight in a vacuum oven. The mass of the fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 8. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                   
                 Boric acid treatment time 
               
               
                   
                 Segment 
                 (min) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 30 
               
               
                   
                 2 
                 60 
               
               
                   
                 3 
                 300 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                   
                 Mass of fiber 
                 Mass of fiber 
                   
               
               
                   
                   
                 before BA 
                 after BA 
                 Mass change 
               
               
                   
                 Segment 
                 treatment (g) 
                 treatment (g) 
                 (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 1 
                 0.2338 
                 0.2483 
                 6.20 
               
               
                   
                 2 
                 0.2339 
                 0.2421 
                 3.51 
               
               
                   
                 3 
                 0.2340 
                 0.2422 
                 3.50 
               
               
                   
                   
               
            
           
         
       
     
     The thermally treated, boric acid treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 9 with temperature ramp rates of 10° C./min for oxidation and carbonization regimes. 
     reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 9 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                   
               
            
           
           
               
               
               
            
               
                   
                 Isothermal 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Hold, 
                 Starting 
                 Final 
               
               
                   
                 Isothermal 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 Hold, Time (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A 
                 10 
                 190 
                 190 
                 800 
               
               
                 B 
                 10 
                 230 
                 230 
                 800 
               
               
                 C 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 10 
               
               
                   
               
               
                   
                 Mass retained during 
                   
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 Char yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 1A 
                 86.39 
                 14.64 
                 15.55 
               
               
                 1B 
                 63.63 
                 30.72 
                 32.62 
               
               
                 1C 
                 70.96 
                 35.29 
                 37.48 
               
               
                 2A 
                 96.15 
                 5.59 
                 5.79 
               
               
                 2B 
                 81.58 
                 17.03 
                 17.63 
               
               
                 2C 
                 78.76 
                 25.76 
                 26.66 
               
               
                 3A 
                 91.99 
                 14.99 
                 15.51 
               
               
                 3B 
                 70.07 
                 29.59 
                 30.63 
               
               
                 3C 
                 86.81 
                 18.61 
                 19.26 
               
               
                   
               
            
           
         
       
     
     Comparative Example 2 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1945.8 total denier, 2.25 gf/den, 12.17% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 5 seconds. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 58.2-58.9% by Soxhlet extraction. The crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 11 with temperature ramp rates of 10° C./min Table 12 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 11 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 Time (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A 
                 2 
                 270 
                 270 
                 800 
               
               
                 B 
                 3 
                 270 
                 270 
                 800 
               
               
                 C 
                 4 
                 270 
                 270 
                 800 
               
               
                 D 
                 5 
                 270 
                 270 
                 800 
               
               
                 E 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 12 
               
               
                   
               
               
                   
                   
                   
                 Overall Mass 
               
               
                   
                 Mass retained during 
                   
                 Yield (%, per mass 
               
               
                 Segment 
                 oxidation (%) 
                 Char yield (%) 
                 PE) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 A 
                 47.91 
                 25.69 
                 25.69 
               
               
                 B 
                 44.53 
                 25.85 
                 25.85 
               
               
                 C 
                 41.83 
                 23.83 
                 23.83 
               
               
                 D 
                 41.05 
                 23.60 
                 23.60 
               
               
                 E 
                 38.37 
                 19.95 
                 19.95 
               
               
                   
               
            
           
         
       
     
     Example 2A 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1945.8 total denier, 2.25 gf/den, 12.17% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 5 seconds. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 58.2-58.9% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % solution of boric acid in isopropanol for the times reported in Table 13. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The dried, boric acid treated fibers undergo thermal treatment (80° C.) overnight in a vacuum oven. The mass of fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 14 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 13 
               
               
                   
                   
               
               
                   
                   
                 Boric acid treatment time 
               
               
                   
                 Segment 
                 (min) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 5 
               
               
                   
                 2 
                 10 
               
               
                   
                 3 
                 20 
               
               
                   
                 4 
                 30 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 14 
               
               
                   
                   
               
               
                   
                   
                 Mass of fiber 
                 Mass of fiber 
                   
               
               
                   
                   
                 before BA 
                 after BA 
                 Mass change 
               
               
                   
                 Segment 
                 treatment (g) 
                 treatment (g) 
                 (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 1 
                 0.1150 
                 0.1235 
                 7.39 
               
               
                   
                 2 
                 0.1155 
                 0.1233 
                 6.75 
               
               
                   
                 3 
                 0.1188 
                 0.1296 
                 9.09 
               
               
                   
                 4 
                 0.2213 
                 0.2246 
                 1.49 
               
               
                   
                   
               
            
           
         
       
     
     The thermally treated, boric acid treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 15 with temperature ramp rates of 10° C./min Table 16 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 15 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                   
                 Starting 
                 Final 
               
               
                   
                 Hold, 
                 Isothermal Hold, 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 Time (hr) 
                 Temperature (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A 
                 5 
                 270 
                 270 
                 800 
               
               
                 B 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 16 
               
               
                   
               
               
                   
                 Mass retained during 
                   
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 Char yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 1A 
                 66.25 
                 41.47 
                 44.53 
               
               
                 1B 
                 62.81 
                 36.72 
                 39.43 
               
               
                 2A 
                 65.44 
                 40.92 
                 43.68 
               
               
                 2B 
                 61.97 
                 36.91 
                 39.40 
               
               
                 3A 
                 65.28 
                 38.53 
                 42.03 
               
               
                 3B 
                 62.81 
                 37.27 
                 40.66 
               
               
                 4A 
                 66.24 
                 38.23 
                 38.80 
               
               
                 4B 
                 64.25 
                 38.77 
                 37.35 
               
               
                   
               
            
           
         
       
     
     Example 2B 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1945.8 total denier, 2.25 gf/den, 12.17% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 5 seconds. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 58.2-58.9% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % solution of boric acid in isopropanol for the times reported in Table 17. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The dried, boric acid treated fibers undergo thermal treatment (80° C.) overnight in a vacuum oven. The mass of the fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 18. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 17 
               
               
                   
                   
               
               
                   
                   
                 Boric acid treatment time 
               
               
                   
                 Segment 
                 (min) 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 5 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 18 
               
               
                   
               
               
                   
                 Mass of fiber before 
                 Mass of fiber after 
                 Mass 
               
               
                 Segment 
                 BA treatment (g) 
                 BA treatment (g) 
                 change (%) 
               
               
                   
               
             
            
               
                 1 
                 0.1150 
                 0.1235 
                 7.39 
               
               
                   
               
            
           
         
       
     
     Thermally treated, boric acid treated crosslinked fibers were oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 19 with temperature ramp rates of 10° C./min. Table 20 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 19 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 A 
                 2 
                 270 
                 270 
                 800 
               
               
                 B 
                 3 
                 270 
                 270 
                 800 
               
               
                 C 
                 4 
                 270 
                 270 
                 800 
               
               
                 D 
                 5 
                 270 
                 270 
                 800 
               
               
                 E 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 20 
               
               
                   
               
               
                   
                 Mass retained during 
                 Char 
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                 1A 
                 74.79 
                 38.42 
                 41.26 
               
               
                 1B 
                 70.48 
                 43.32 
                 46.52 
               
               
                 1C 
                 68.91 
                 43.23 
                 46.42 
               
               
                 1D 
                 66.25 
                 41.47 
                 44.53 
               
               
                 1E 
                 62.81 
                 36.72 
                 39.43 
               
               
                   
               
            
           
         
       
     
     Comparative Example 3 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 60° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 55.59-56.30% by Soxhlet extraction. The crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 21 with temperature ramp rates of 10° C./min Table 22 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 21 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 1 
                 10 
                 230 
                 230 
                 800 
               
               
                 2 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 22 
               
               
                   
               
               
                   
                 Mass retained during 
                 Overall mass 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
               
               
                   
               
             
            
               
                 1 
                 84.68 
                 11.36 
               
               
                 2 
                 81.17 
                 11.05 
               
               
                   
               
            
           
         
       
     
     Example 3A 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 60° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 55.59-56.30% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a saturated solution of boric oxide in isopropanol for the times reported in Table 23. After the boric oxide solution treatment, the fibers are dried overnight in air at ambient conditions. The mass of the fibers prior to/and after boric oxide treatment and relative change in mass are reported in Table 24. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 23 
               
               
                   
                   
               
               
                   
                 Segment 
                 Boric oxide treatment time (min) 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 10 
               
               
                   
                 2 
                 30 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 24 
               
               
                   
               
               
                   
                 Mass of fiber before 
                 Mass of fiber after 
                 Mass 
               
               
                 Segment 
                 BO treatment (g) 
                 BO treatment (g) 
                 change (%) 
               
               
                   
               
             
            
               
                 1 
                 0.2349 
                 0.2268 
                 −3.45 
               
               
                 2 
                 0.2221 
                 0.2141 
                 −3.60 
               
               
                   
               
            
           
         
       
     
     The boric oxide treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 25 with temperature ramp rates of 10° C./min Table 26 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 25 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 A 
                 10 
                 230 
                 230 
                 800 
               
               
                 B 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 26 
               
               
                   
               
               
                   
                 Mass retained during 
                 Char 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
               
               
                   
               
             
            
               
                 1A 
                 74.08 
                 10.47 
               
               
                 1B 
                 58.36 
                 17.81 
               
               
                 2A 
                 76.08 
                 10.70 
               
               
                 2B 
                 56.94 
                 17.94 
               
               
                   
               
            
           
         
       
     
     Example 3B 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 30 min The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 60° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 55.59-56.30% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % suspension of zinc borate, (Firebrake ZB-XF) in isopropanol for the times reported in Table 27. After the zinc borate suspension treatment, the fibers are dried overnight in air at ambient conditions. The dried, zinc borate treated fibers underto thermal treatment (80° C.) overnight in a vacuum oven. The mass of the fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 28. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 27 
               
               
                   
                   
               
               
                   
                 Segment 
                 Zinc borate treatment time (min) 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 10 
               
               
                   
                 2 
                 30 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 28 
               
               
                   
               
               
                   
                 Mass of fiber before 
                 Mass of fiber after 
                 Mass 
               
               
                 Segment 
                 ZB treatment (g) 
                 ZB treatment (g) 
                 change (%) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 1 
                 0.2404 
                 0.2571 
                 6.95 
               
               
                 2 
                 0.2262 
                 0.2542 
                 12.4 
               
               
                   
               
            
           
         
       
     
     Zinc borate treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 29 with temperature ramp rates of 10° C./min. Table 30 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 29 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 A 
                 10 
                 230 
                 230 
                 800 
               
               
                 B 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 30 
               
               
                   
               
               
                   
                 Mass retained during 
                 Char 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
               
               
                   
               
             
            
               
                 1A 
                 75.11 
                 25.76 
               
               
                 1B 
                 74.53 
                 17.64 
               
               
                 2A 
                 84.38 
                 23.04 
               
               
                 2B 
                 79.62 
                 26.28 
               
               
                   
               
            
           
         
       
     
     Example 4 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1978.2 total denier, 2.31 gf/den, 12.94% elongation-to-break. The prepared fibers are continuously treated in a vessel containing an isopropanol solution with 5 wt % of an aryl sulfonic acid, Nacure B201 for 30 min. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 5 days. The gel fraction is determined to be 61.4-61.9% by Soxhlet extraction. The crosslinked fibers are subsequently treated with a 5 wt % solution of boric acid in isopropanol for the times reported in Table 31. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The dried, boric acid treated fibers undergo thermal treatment (80° C.) overnight in a vacuum oven. The mass of the fibers prior to/and after boric acid treatment and relative change in mass are reported in Table 32. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 31 
               
               
                   
                   
               
               
                   
                 Segment 
                 Boric acid treatment time (min) 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 30 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 32 
               
               
                   
               
               
                   
                 Mass of fiber before 
                 Mass of fiber after 
                 Mass 
               
               
                 Segment 
                 BA treatment (g) 
                 BA treatment (g) 
                 change (%) 
               
               
                   
               
             
            
               
                 1 
                 0.2363 
                 0.2536 
                 7.32 
               
               
                   
               
            
           
         
       
     
     The thermally treated, boric acid treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 33 with temperature ramp rates of 10° C./min. Table 34 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 33 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 A 
                 10 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 34 
               
               
                   
               
               
                   
                 Mass retained during 
                 Char 
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                 1A 
                 61.97 
                 38.66 
                 41.49 
               
               
                   
               
            
           
         
       
     
     Example 5 
     An ethylene/octene copolymer (density=0.941 g/cm 3 ; MI=34 g/10 min, 190° C./2.16 kg) is reactive extruded with vinyl trimethoxysilane (VTMS) to form a VTMS-grafted ethylene/octene copolymer (MI=19 g/10 min, 190° C./2.16 kg; 1.4 wt % grafted silane content determined by  13 C NMR) precursor resin. The VTMS-grafted precursor resin is melt spun to form fibers with the following properties: 1573 filaments, 1945.8 total denier, 2.25 gf/den, 12.17% elongation-to-break. Fiber tows are continuously treated in a vessel containing an isopropanol solution with 5 wt % of boric acid. Fiber residence time in the solution is 5 seconds. The treated fibers are allowed to dry cure for 3 days. The fibers are subsequently moisture cured at 80° C. (100% relative humidity) for 1-5 days, as reported in Table 35. Gel fraction is determined by Soxhlet extraction. Complete results are reported in Table 36. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 35 
               
               
                   
                   
               
               
                   
                 Segment 
                 Moisture Curing Time (days) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 1 
               
               
                   
                 B 
                 3 
               
               
                   
                 C 
                 5 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 36 
               
               
                   
                   
               
               
                   
                 Segment 
                 Gel Fraction (%) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 42.9 
               
               
                   
                 B 
                 53.3 
               
               
                   
                 C 
                 55.2 
               
               
                   
                   
               
            
           
         
       
     
     Three segments (A, B, and C) prepared and crosslinked are treated with a 15 wt % solution of boric acid in methanol for various times reported in Table 37. After the boric acid solution treatment, the fibers are dried overnight in air at ambient conditions. The dried, boric acid treated fibers next undergo thermal treatment (80° C.) overnight in a vacuum oven. Mass of the fiber prior to and after boric acid treatment and relative change in mass are reported in Table 38. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 37 
               
               
                   
                   
               
               
                   
                 Segment 
                 Boric acid treatment time (min) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 1 
                 5 
               
               
                   
                 2 
                 30 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 38 
               
               
                   
               
               
                   
                 Mass of fiber before 
                 Mass of fiber after 
                 Mass 
               
               
                 Segment 
                 BA treatment (g) 
                 BA treatment (g) 
                 change (%) 
               
               
                   
               
             
            
               
                 A1 
                 0.2418 
                 0.2877 
                 18.98 
               
               
                 B1 
                 0.2476 
                 0.3013 
                 21.69 
               
               
                 C1 
                 0.2315 
                 0.2732 
                 18.01 
               
               
                 A2 
                 0.2600 
                 0.3104 
                 19.38 
               
               
                 B2 
                 0.2338 
                 0.2854 
                 22.07 
               
               
                 C2 
                 0.2356 
                 0.2858 
                 21.31 
               
               
                   
               
            
           
         
       
     
     The thermally treated, boric acid treated crosslinked fibers are oxidized and carbonized using a Thermogravimetric Analysis (TGA) instrument using the conditions outlined in Table 39. Temperature ramp rates are maintained at 10° C./min for oxidation and carbonization regimes. Table 40 reports the mass retained during air oxidation and final mass yield after both oxidation and carbonization treatments. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 39 
               
             
            
               
                   
                   
               
               
                   
                 Oxidation (air) 
                 Carbonization (nitrogen) 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Isothermal 
                 Isothermal Hold, 
                 Starting 
                 Final 
               
               
                   
                 Hold, Time 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 Segment 
                 (hr) 
                 (° C.) 
                 (° C.) 
                 (° C.) 
               
               
                   
               
               
                 A-C 
                 5 
                 270 
                 270 
                 800 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
             
               
                 TABLE 40 
               
               
                   
               
               
                   
                 Mass retained during 
                 Char 
                 Overall Mass Yield 
               
               
                 Segment 
                 oxidation (%) 
                 yield (%) 
                 (%, per mass PE) 
               
               
                   
               
             
            
               
                 A1 
                 68.78 
                 45.87 
                 56.62 
               
               
                 B1 
                 67.71 
                 45.44 
                 58.03 
               
               
                 C1 
                 71.35 
                 39.46 
                 48.13 
               
               
                 A2 
                 68.11 
                 43.81 
                 54.34 
               
               
                 B2 
                 68.04 
                 43.87 
                 56.29 
               
               
                 C2 
                 68.92 
                 43.96 
                 55.86 
               
               
                   
               
            
           
         
       
     
     Comparative Example 6 
     A vinyl trimethoxysilane-grafted ethylene/octene copolymer (MI=7 g/10 min, 190 ° C./2.16 kg; 1.6 wt % grafted silane content) is used as a precursor resin. Films are compression molded using a Carver press at 180° C. into thin films measuring 3 millimeters (76.2 microns) thick by micrometer. All films are crosslinked by treating the films with a commercial aryl sulfonic acid catalyst in isopropanol solution (Nacure B-201, King Industries) for 12 hours, followed by moisture curing at 60-80° C. for 72 hours. Gel fraction is determined to be 81.8% by Soxhlet extraction. Nine (9) smaller circular films are sectioned from the prepared film and weighed. The films are oxidized in a convection oven at 270° C. for 5 hours under air (21% oxygen content). The nine (9) films are weighed after air oxidation. Mass retention during air oxidation (oxidation mass yield) is reported in Table 41. Oxidized films are then carbonized under nitrogen from 25° C. to 800° C. using a ramp rate of 10° C./min. Mass retention during carbonization (carbonization mass yield) is reported in Table 41. Calculated overall mass yield is reported in Table 41. Mean oxidation mass yield, carbonization mass yield, and overall mass yield are 43.5%, 45.7%, and 19.7%, respectively. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 41 
               
               
                   
                   
               
               
                   
                   
                 Oxidation Mass 
                 Carbonization 
                 Overall Mass 
               
               
                   
                 Example 
                 Yield (%) 
                 Mass Yield (%) 
                 Yield (%) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 43.50 
                 51.01 
                 22.19 
               
               
                   
                 B 
                 42.19 
                 43.59 
                 18.39 
               
               
                   
                 C 
                 41.58 
                 50.52 
                 21.00 
               
               
                   
                 D 
                 43.81 
                 45.03 
                 19.73 
               
               
                   
                 E 
                 45.31 
                 42.46 
                 19.24 
               
               
                   
                 F 
                 40.26 
                 52.07 
                 20.96 
               
               
                   
                 G 
                 43.87 
                 43.11 
                 18.91 
               
               
                   
                 H 
                 49.09 
                 42.74 
                 20.98 
               
               
                   
                 I 
                 41.85 
                 41.13 
                 17.21 
               
               
                   
                   
               
            
           
         
       
     
     Example 6 
     A vinyl trimethoxysilane-grafted ethylene/octene copolymer (MI=7 g/10 min, 190° C./2.16 kg; 1.6 wt % grafted silane content) is used as a precursor resin. Films are compression molded using a Carver press at 180° C. into thin films measuring 3 millimeters (76.2 microns) thick by micrometer. All films are crosslinked by treating the films with a commercial aryl sulfonic acid catalyst in isopropanol solution (Nacure B-201, King Industries) for 12 hours, followed by moisture curing at 60-80° C. for 72 hours. Gel fraction is determined to be 81.8% by Soxhlet extraction. Four (4) films labeled A-D are submerged in vials containing solutions of methylene chloride and tributyl borate according to Table 42. Films are treated in tributyl borate solution overnight. Film weights are recorded before and after treatment with tributyl borate. Table 43 reports weight change for each film. The films are oxidized in a convection oven at 270° C. for 5 hours under air (21% oxygen content). The films are weighed after air oxidation. Mass retention during air oxidation (oxidation mass yield) is reported in Table 44. Oxidized films are then carbonized under nitrogen from 25° C. to 800° C. using a ramp rate of 10° C./min Mass retention during carbonization (carbonization mass yield) is reported in Table 44. Mean oxidation mass yield increases 5.5-42.1% for films treated with tributyl borate prior to oxidation compared with control films (Comparative Example 6). Mean carbonization mass yield increases 13.6-24.5% for films treated with tributyl borate prior to oxidation and carbonization compared with control films (Comparative Example 6). Mean overall mass yield increases 25.4-78.2% for films treated with tributyl borate prior to oxidation and carbonization compared with control films (Comparative Example 6). 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 42 
               
               
                   
                   
               
               
                   
                   
                 BCL Methylene chloride:tributyl 
               
               
                   
                 Example 
                 borate (vol:vol) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 19:1  
               
               
                   
                 B 
                 9:1 
               
               
                   
                 C 
                 2.33:1   
               
               
                   
                 D 
                 1:1 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 43 
               
               
                   
                   
               
               
                   
                 Example 
                 Weight change (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 A 
                 −2 
               
               
                   
                 B 
                 0 
               
               
                   
                 C 
                 5 
               
               
                   
                 D 
                 14 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 44 
               
               
                   
                   
               
               
                   
                   
                 Oxidation Mass 
                 Carbonization 
                 Overall Mass 
               
               
                   
                 Example 
                 Yield (%) 
                 Mass Yield (%) 
                 Yield (%) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 49.5 
                 51.9 
                 25.7 
               
               
                   
                 B 
                 45.9 
                 53.7 
                 24.7 
               
               
                   
                 C 
                 54.1 
                 55.3 
                 29.9 
               
               
                   
                 D 
                 61.8 
                 56.9 
                 35.1 
               
               
                   
                   
               
            
           
         
       
     
     Comparative Example 7 
     An ethylene/octene copolymer (density=0.950 g/cm 3 ; MI=17 g/10 min, 190° C./2.16 kg) is melt blended at 160° C. in a DSM Xplore 15 micro-compounder under nitrogen. A film is compression molded using a Carver press at 160° C. The film is oxidized in the convection oven at 250° C. for 10 hours under air (21% oxygen content). The film is weighed after air oxidation. Mass retention during air oxidation (oxidation mass yield) is reported in Table 45. The oxidized film is then carbonized under nitrogen from 25° C. to 800° C. using a ramp rate of 10° C./min. Mass retention during carbonization (carbonization mass yield) is reported in Table 45. Calculated overall mass yield is reported in Table 45. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 45 
               
               
                   
                   
               
               
                   
                   
                 Oxidation Mass 
                 Carbonization 
                 Overall Mass 
               
               
                   
                 Example 
                 Yield (%) 
                 Mass Yield (%) 
                 Yield (%) 
               
               
                   
                   
               
             
            
               
                   
                 7 
                 54.2 
                 15.4 
                 7.7 
               
               
                   
                   
               
            
           
         
       
     
     Example 7A 
     An ethylene/octene copolymer (density=0.950 g/cm 3 ; MI=17 g/10 min, 190° C./2.16 kg) is melt blended with polybutadiene, used as received from Sigma Aldrich (average M n  1,530-2,070; catalog #434779), at 5 wt % at 160° C. in a DSM Xplore 15 micro-compounder under nitrogen. A film is compression molded using a Carver press at 160° C. The film is oxidized in the convection oven at 250° C. for 10 hours under air (21% oxygen content). The film is weighed after air oxidation. Mass retention during air oxidation (oxidation mass yield) is reported in Table 46. The oxidized film is then carbonized under nitrogen from 25° C. to 800° C. using a ramp rate of 10° C./min Mass retention during carbonization (carbonization mass yield) is reported in Table 46. Calculated overall mass yield is reported in Table 46. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 46 
               
               
                   
                   
               
               
                   
                   
                 Oxidation Mass 
                 Carbonization 
                 Overall Mass 
               
               
                   
                 Example 
                 Yield (%) 
                 Mass Yield (%) 
                 Yield (%) 
               
               
                   
                   
               
             
            
               
                   
                 7A 
                 59.9 
                 13.7 
                 7.5 
               
               
                   
                   
               
            
           
         
       
     
     Example 7B 
     An ethylene/octene copolymer (density=0.950 g/cm 3 ; MI=17 g/10 min, 190° C./2.16 kg) is melt blended with polybutadiene, used as received from Sigma Aldrich (average M n  1,530-2,070; catalog #434779), at 5 wt % at 160° C. in a DSM Xplore 15 micro-compounder under nitrogen. A film is compression molded using a Carver press at 160° C. A 300 mL 6.66 mM BH 3  (borane) solution was prepared in a glovebox by dissolving 2.01 mL of 1M BH 3  solution in THF in 300 mL of THF. The film was immersed in 100 mL of the BH 3  solution overnight. After removal from the solution, the film was dried in the glovebox atmosphere. After 16 hr, the film is removed from the glovebox. The film is oxidized in the convection oven at 250° C. for 10 hours under air (21% oxygen content). The film is weighed after air oxidation. Mass retention during air oxidation (oxidation mass yield) is reported in Table 47. The oxidized film is then carbonized under nitrogen from 25° C. to 800° C. using a ramp rate of 10° C./min. Mass retention during carbonization (carbonization mass yield) is reported in Table 47. Calculated overall mass yield is reported in Table 47. A relative increase in carbonization mass yield of 221-261% is observed for a film treated with borane (Example 7B) compared with control films (Comparative Example 7 and Example 7A). A relative increase in overall mass yield of 297-308% is observed for a film treated with borane compared with control films (Comparative Example 7 and Example 7A). 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 47 
               
               
                   
                   
               
               
                   
                   
                 Oxidation Mass 
                 Carbonization 
                 Overall Mass 
               
               
                   
                 Example 
                 Yield (%) 
                 Mass Yield (%) 
                 Yield (%) 
               
               
                   
                   
               
             
            
               
                   
                 7B 
                 61.9 
                 49.5 
                 30.6