Patent Publication Number: US-4320216-A

Title: Fluoroelastomer gelling agents and products made therefrom

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 107,012, filed Dec. 26, 1979 and now abandoned, which is, in turn, a divisional of U.S. patent application Ser. No. 042,946, filed May 29, 1979, now U.S. Pat. No. 4,211,868. 
    
    
     DESCRIPTION 
     Technical Field 
     This invention relates to novel and extremely efficient gelling agents for fluoroelastomers, to gelled fluoroelastomers made with these novel gelling agents, and to blends of such gelled fluoroelastomers with non-gelled fluoroelastomers, which gelled fluoroelastomers and blends possess improved processing properties, particularly as compared with non-gelled fluoroelastomers, but even as compared with blends of non-gelled fluoroelastomers with fluoroelastomers gelled with agents other than the novel gelling agents of the present invention. In particular, the gelling agents of the present invention achieve extremely high levels, e.g., approximately 90%, of gel (i.e. crosslinking) with very low levels, less than 0.5 weight percent, of gelling agent. Fluoroelastomer blends made with these gelling agents exhibit improved extrusion and milling. 
     Background Art 
     U.S. Pat. No. 4,115,481, granted Sept. 19, 1978, to Finlay and Omura, discloses the use of bromotrifluoroethylene as a gelling agent for certain fluoroelastomers and peroxide curable fluoroelastomer blends of non-gelled fluoroelastomer with bromotrifluoroethylene gelled fluoroelastomer. Such blends are disclosed as offering improved milling and extrusion properties. The bromotrifluoroethylene gelled fluoroelastomer of Finlay and Omura, however, exhibits a gel content of only about 50-65% even though up to 3% by weight of gelling agent is used. In addition, although the blends disclosed by Finlay and Omura offer improved processability in rubber mills and extruders as compared with prior fluoroelastomer compositions, the blends of the present invention exhibit further improvements in processability. 
     U.S. Pat. No. 3,851,018, granted Nov. 26, 1974, to Kelly discloses the use of certain perfluorodivinyl ethers of the formula 
     
         CF.sub.2 ═CF--O(CF.sub.2).sub.n --O--CF═CF.sub.2 
    
     where n is an integer from 2-24 as gelling agents for certain fluoroelastomers and also discloses blends of non-gelled fluoroelastomers with perfluorodivinylether gelled fluoroelastomers. Such blends are disclosed as offering improved milling and extrusion properties. As with the gels of Finlay and Omura, the gelled fluoroelastomers exemplified by Kelly exhibit a gel content of only about 50% even though up to 20% by weight of gelling agent is used, and although the blends disclosed by Kelly offer improved processability as compared with prior fluoroelastomer compositions, the blends of the present invention exhibit further improvements in processability. Further, although Kelly does disclose that fluoroelastomers with a gel content of up to 100% would be useful, there are no examples of such fluoroelastomers; and even if Kelly&#39;s gelling agent could produce a 100% gelled fluoroelastomer, it would only be possible with excessive quantities of gelling agent. 
     DISCLOSURE OF THE INVENTION 
     The present invention relates to novel and extremely efficient gelling agents for fluoroelastomers, the gelling agents being hexafluorotriallylisocyanurate, i.e. 1,3,5-tris-(3,3,-difluoro-2-propenyl)-s-triazine-2,4,6-(1H,3H,5H)-trione, hereinafter HFTAIC, ##STR1## and N-methyltetrafluorodiallylisocyanurate, i.e. 1,3-bis-(3,3-difluoro-2-propenyl)-5-methyl-s-triazine-2,4,6-(1H,3H,5H)-trione, hereinafter TFDAIC, ##STR2## to HFTAIC and TFDAIC gelled fluoroelastomers, to curable blends of non-gelled fluoroelastomers with HFTAIC and TFDAIC gelled fluoroelastomers, to methods of making HFTAIC and TFDAIC, to the process of making gelled fluoroelastomers using HFTAIC or TFDAIC, to the process of making curable fluoroelastomer blends using HFTAIC or TFDAIC gelled fluoroelastomers and to vulcanized articles made from such blends. It should be understood that by HFTAIC or TFDAIC gelled fluoroelastomers there is meant partially gelled fluoroelastomers as well as those substantially completely gelled fluoroelastomers. As is discussed hereinafter, a gel content of a least 50% in the gelled fluoroelastomer is generally required to realize the significant improvements made possible by the present invention. 
     The preferred novel gelling agent of the present invention, HFTAIC, can be prepared in a four step synthesis which is summarized by the following schematic equations: ##STR3## Details concerning the preparation of dibromodifluoropropane as shown schematically in equation (1) above can be found in an article by Blomquist and Longone, JACS, 97, 4981 (1957). 
     An alternative to the process described above starts with chlorobromodifluoromethane and goes through substantially the same steps except that the product in step (2) is chlorinated (not brominated) and the catalyst in step (4) is LiBr/DMAc. 
     A further alternative to steps (3) and (4) would be cyclization of an isocyanate: ##STR4## 
     A more preferred two step synthesis of HFTAIC is disclosed in copending U.S. patent application Ser. No. 042,947, now U.S. Pat. No. 4,211,868 filed May 29, 1979 by John Paul Erdman, which is summarized by the following schematic equations: ##STR5## 
     Alternatively, the cyanuric acid (compound VI) can be converted to the sodium salt which is, in turn, converted to the desired HFTAIC: ##STR6## It should be noted that in the reactions represented by equation (5&#39;) above, the base can be eliminated, but generally this will be accompanied by a considerable loss of yield. 
     The less preferred gelling agent of the present invention, TFDAIC, can be prepared in a three step synthesis which is summarized in the following schematic equations: ##STR7## 
     Details of the reaction shown in (6) can be found in W. J. Close, JACS, 75 3617 (1953). 
     As indicated above, HFTAIC is preferred over TFDAIC, because it provides three sites of unsaturation per molecule, rather than two, and is therefore a more efficient gelling agent. One would have to use a greater molar quantity of TFDAIC than would be required if one used HFTAIC to achieve otherwise equivalent results. 
     As stated above, HFTAIC and TFDAIC are extremely efficient gelling agents for fluoroelastomers. Fluoroelastomers which can be efficiently gelled with HFTAIC or TFDAIC include those compolymers with interpolymerized units consisting essentially of vinylidene fluoride units, at least one type of fluorine containing olefin unit, and, optionally, units selected from one or more of the following: perfluoroalkyl perfluorovinyl ethers, bromotrifluoroethylene and bromotetrafluorobutene as well as those copolymers with interpolymerized units consisting essentially of tetrafluoroethylene, perfluoro (methyl vinyl ether) and a third monomer selected from the group consisting of: 
     (a) perfluoro (4-cyanobutyl vinyl ether), 
     (b) perfluoro (4-carbomethoxybutyl vinyl ether), 
     (c) perfluoro (2-phenoxypropyl vinyl ether), 
     (d) perfluoro (3-phenoxypropyl vinyl ether), and 
     (e) perfluoro (8-cyano-5-methyl-3,6-dioxa-1-octene). 
     The novel gelling agent of the present invention can also be used to further gel partially gelled fluoroelastomers, such as those containing bromotrifluoroethylene or perfluorodivinyl ethers in addition to the interpolymerized units mentioned immediately above. 
     Preferred fluoroelastomers which can be efficiently gelled with HFTAIC or TFDAIC include copolymers with interpolymerized units derived from any of the following combinations: 
     (a) vinylidene fluoride and hexafluoropropylene or pentafluoropropylene; 
     (b) vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene or pentafluoropropylene; 
     (c) vinylidene fluoride, perfluoroalkyl perfluorovinyl ethers, and at least one of hexafluoropropylene, pentafluoropropylene, and tetrafluoroethylene; 
     (d) vinylidene fluoride, perfluoroalkyl perfluorovinyl ethers, bromotetrafluorobutene, and at least one of hexafluoropropylene, pentafluoropropylene and tetrafluoroethylene; 
     (e) vinylidene fluoride, bromotetrafluorobutene, and at least one of tetrafluoroethylene and hexafluoropropylene; and 
     (f) tetrafluoroethylene, perfluoro (methyl vinyl ether), and perfluoro (2-phenoxypropyl vinyl ether). 
     For example, suitable polymers can be composed of about 30-70 weight % vinylidene fluoride units and about 70-30 weight % hexafluoropropylene units (see, e.g., U.S. Pat. No. 3,051,677, granted August 28, 1962 to Rexford). Alternatively, suitable polymers can be composed of about 25-70 weight % vinylidene fluoride units, about 19-60 weight % hexafluoropropylene units, and about 3-35 weight % tetrafluoroethylene units (see, e.g., U.S. Pat. No. 2,968,649, granted Jan. 17, 1961 to Pailthorp and Schroeder). Alternatively suitable polymers can be composed of about 4-15 weight % tetrafluoroethylene units, about 48-65 weight % vinylidene fluoride units, about 8-23 weight % hexafluoropropylene units and about 17-30 weight % of perfluoroalkyl perfluorovinyl ether units wherein the alkyl group contains 1-5 carbon atoms (see, e.g., U.K. Pat. No. 1,496,084, complete specification published Dec. 21, 1977). Alternatively, suitable polymers can be composed of about 10-85 mole % vinylidene fluoride units, about 2-50 mole % of said perfluoroalkyl perfluorovinyl ether units, and about 3-80 mole % of a component consisting of one or more of the following: hexafluoropropylene units and tetrafluoroethylene units (see, e.g., U.S. Pat. No. 3,235,537, granted Feb. 15, 1966 to Albin and Gallagher). Alternatively, suitable polymers can be composed of up to 3 mole % of bromotrifluoroethylene units or bromotetrafluorobutene units incorporated into polymers as described immediately above (see, e.g., U.S. Pat. No. 4,035,565, granted July 12, 1977 to Apotheker and Krusic). Alternatively, suitable polymers can be composed of about 53-79.8 mole % of tetrafluoroethylene, about 20-45  mole % of perfluoro (methyl vinyl ether) and 0.2-2 mole percent of perfluoro (2-phenoxypropyl vinyl ether). (See e.g., U.S. Pat. No. 3,467,638, granted Sept. 16, 1969 to Pattison). 
     The HFTAIC and TFDAIC gelled fluoroelastomers of the present invention are prepared so that their gel content is greater than 50%, preferably so that the gel content is from 80-95%, and most preferably between 85-90%. The gel content can be determined as follows: a solution-dispersion of a known concentration (about 1% by weight polymer) in methyl ethyl ketone is placed in a closed centrifuge tube and centrifuged at about 17,000 rpm (RCF 34,800×G) for one-half hour. The concentration of polymer in the supernatant liquid is determined by evaporation to dryness of a known volume. The amount of gel polymer is calculated from the difference in concentration of total polymer and concentration of polymer in the soluble portion. Alternatively, solvents other than methyl ethyl ketone can be used, e.g., a mixed solvent comprising 40 parts (by volume) 2,2,3-trichloro-heptafluorobutane, 60 parts perfluoro-2-butyltetrahydrofuran and 3 parts diglyme. 
     A gel content of greater than 50% is generally achieved by incorporating into the fluoroelastomer 0.05-3.0% by weight of HFTAIC or TFDAIC. Where a fluoroelastomer with a gel content substantially above 90% is desired, one can use quantities of HFTAIC or TFDAIC at the higher end of the above-stated range. Fluoroelastomers with a significant gel content, i.e. at 50% or above, can generally be achieved with amounts of HFTAIC or TFDAIC as small as 0.05% by weight. Although one could use even less HFTAIC or TFDAIC, the processability of blends made therefrom is not likely to offer significant processability advantages as compared with non-crosslinked fluoroelastomer. As indicated above, for a given fluoroelastomer composition, the quantity of TFDAIC required to cause a certain degree of gel formation is greater than the quantity of HFTAIC required to produce that same degree of gel formation in a polymer otherwise equivalent. Depending on the gel content desired, a preferred minimum quantity of HFTAIC is about 0.25% by weight. Depending on economics and the sacrifice of vulcanizate properties that can be tolerated, a preferred maximum quantity of HFTAIC is about  0.5% by weight. For an optimum balance between processability, cost and vulcanizate properties, the most preferred range of HFTAIC is about 0.35-0.45% by weight. 
     In preparing the gelled fluoroelastomer of the present invention it is preferred that the reaction mixture of monomer components also contains a free-radical initiator, and the copolymer-forming reaction is carried out as a free-radical emulsion polymerization reaction. Among the most useful free-radical initiators to use in such a reaction are ammonium persulfate, sodium persulfate, potassium persulfate, or a mixture of two or more such compounds. Also useful are other water-soluble inorganic peroxide compounds, for example, sodium, potassium and ammonium perphosphates, perborates, and percarbonates. The initiator can be used in combination with a reducing agent such as sodium, potassium, or ammonium sulfite, bisulfite, metabisulfite, hyposulfite, or phosphite, or in combination with a ferrous or a cuprous salt, or a salt of other easily oxidized metal compounds. Known organic free-radical initiators can also be used, preferably in combination with a suitable surfactant such as sodium lauryl sulfate or ammonium perfluorooctanoate. The surfactant can be selected from those known to be useful in the manufacture of fluoropolymers. A suitable known chain transfer agent can also be present during the emulsion polymerization reaction, but in many cases this is not preferred. 
     After completion of the preferred emulsion polymerization reaction, the copolymer can be isolated from the resulting polymer latex by known methods, for example by coagulation by adding an electrolyte or by freezing, followed by centrifuging or filtering and then drying the copolymer. 
     During preparation of the copolymer, the reaction mixture is preferably heated in a reactor which has been flushed with an inert gas at about 50°-130° C. under superatmospheric pressure, for example under a pressure of about 7-140 kg/cm 2 , preferably about 35-105 kg/cm 2 . In some of the most useful procedures, the polymerization is carried out as a continuous process and the reaction mixture has an average residence time in the reactor of about 5 to 30 minutes in some cases and up to 2 or 3 hours in others. Residence time can be calculated by dividing the reactor volume by the volume of latex produced per hour. In preparing the tetrafluoroethylene, perfluoro (methyl vinyl ether) copolymers, preferably the polymerization is carried out as a batch process. 
     The fluoroelastomer blends of the present invention can be prepared by mixing a latex of HFTAIC or TFDAIC gelled fluoroelastomer with a latex of a non-crosslinked fluoroelastomer, and isolating the blended fluoroelastomer of the latex mixture. The gel content of the fluoroelastomer blend can be from 10-90%, preferably will be from 10-75%, more preferably from 25-75%, and most preferably will be from 30-55%. In peroxide-curable fluoroelastomer blends, such as those derived from TFE, VF 2 , HFP and BTFB, it is most preferred that the gel content be about 50%. In other fluoroelastomer blends it is most preferred that the gel content be about 35%. It should be understood that one can achieve the desired gel content of the blend by adjusting the quantity of gel component in the blend, by adjusting the quantity of gel in the gel component of the blend, or by a combination of these. The monomer composition of the gelled fluoroelastomer may be the same as or different than the monomer composition of the non-crosslinked fluoroelastomer. 
     The latex mixture itself can be considered as a useful article of commerce since it can be shipped to the plants of customers who will blend it with various additives or subject it to certain processes which will convert it into final products such as coating compositions, extruded articles or molded or laminated products. 
     The fluoroelastomer blends of the present invention can also be prepared by mixing the two different fluoroelastomers in the form of solid particles (e.g., wet or dry crumb), on a high shear mixing device (e.g. Banbury, extruder or rubber mill), or by mixing while they are in the form of a dispersion in an organic liquid. 
     Before the fluoroelastomer blends of this invention are formed into shaped structures by extrusion or molding it is usually preferred to mix them with various additives which include metal oxides, crosslinking agents, unsaturated coagents, accelerators, stabilizers, pigments, pore-forming agents and plasticizers. Such compounding and subsequent vulcanization can be achieved by methods and with materials such as are generally known in the arts relating to fluoroelastomers, which techniques and materials are typified by those disclosed in U.S. Pat. Nos. 2,968,649, 3,051,677, 3,235,537, 3,851,018, 4,035,565 and 4,115,481 and U.K. Pat. No. 1,496,084. 
     The fluoroelastomer blends of the present invention have superior processing properties, particularly with respect to extrusion and milling. Such blends can be made into extrudable fluoroelastomer compositions. Extrusion can be carried out in an extruder of the type commonly used for processing fluoroelastomers. The milling performance of the fluoroelastomer blends of the present invention is markedly improved as compared with the performance of non-crosslinked fluoroelastomers. 
     The following examples identify various specific fluoroelastomers of the present invention and methods of making them. In addition, certain of the examples compare processing properties of the fluoroelastomer blends of the present invention with the same properties of similar fluoroelastomers outside the scope of the present invention. In these examples, all parts and percentages are by weight unless stated otherwise. 
    
    
     EXAMPLE 1 
     Synthesis of HFTAIC by process of equations (1), (2) and (4) 
     To a 1000 cm 3  shaker bomb was added 400 ml CF 2  Br 2  (900 g, 4.29 mol) and 4 g (0.02 mol) benzoyl peroxide. The bomb was closed and evacuated at -60° C. A 40 g (1.43 mol) sample of ethylene was then introduced and the bomb was heated to 80° C. for 4 hours. At the end of this period, the bomb was cooled to room temperature and vented to atmospheric pressure. A total of five runs were carried out in this manner and the combined product obtained after removal of excess CF 2  Br 2  was fractionated in a spinning band column to give 1250 g CH 2  BrCH 2  CF 2  Br, b.p. 120° C., n D   20  =1.4450, d=2.0353. This represents a 79% yield based on 35% conversion. 
     To a 1 liter flask equipped with a stirrer, thermometer, N 2  inlet and condenser in series with 2 dry ice/acetone traps and a funnel was added 220 g (5.5 mol) NaOH, 150 g H 2  O and 2-3 g Aliquat 336 (trioctoyl methyl ammonium chloride, available from General Mills Chemicals, Inc., Minneapolis, Minn.). The solution was warmed to 90° C. and 500 g (2.10 mol) 1,1-difluoro-1,3-dibromopropane was added dropwise with a N 2  flow through the reactor and traps. The material in the traps was fractionally distilled to give 178 g CH 2  ═CHCF 2  Br, b.p. 40° C., n D   20  =1.3773 and 65 g BrCF 2  CH 2  CH 2  Br. Yield: 62%; conversion: 87%. 
     To a 400 cm 3  stainless steel shaker bomb was added 43 g (0.22 mol) trisodium cyanurate and 120 g (0.76 mol) CH 2  ═CHCF 2  Br dissolved in 250 ml DMAc. The bomb was closed and evacuated at -75° C. The contents were heated to 60° C. They were maintained at this temperature for 6 hours. The bomb was cooled to room temperature and vented to atmospheric pressure. A total of seven such runs yielded about 500 g of crude product which was fractionally distilled to yield 295 g HFTAIC, b.p. 135° C./1.0 mm, n D   20  =1.4557. 
     Analysis: Calculated for C 12  H 9  F 6  N 3  O 3 , C: 40.3%, H: 2.5%, F: 31.9%, N: 11.8%; Found: C: 40.8%, H: 2.5%, F: 32.0%, N: 11.8%. 
     EXAMPLE 2 
     Synthesis of HFTAIC by process of equation (5) 
     To 550 ml dimethylacetamide in a stirred flask with a water-cooled reflux condenser there was added 64.4 g (1.15 mol) calcium oxide, 40.3 g (1.0 mol) magnesium oxide, 45 g (0.35 mol) cyanuric acid. To this heterogeneous mixture there was then added onefourth (63.4 g) of a total of 253.5 g (1.066 mol) dibromodifluoropropane to be added. The temperature was raised to 90° C. over one-half hour. As the exothermic reaction progressed heat was removed, but the temperature was allowed to rise to about 125° C., and the remaining dibromide was then added over about 35 minutes at a rate to maintain the temperature at about 130° C. The reaction mixture was stirred and maintained at about 130° C. for an additional 6 hours, allowed to stand overnight, and treated in portions with 4 N HCl (total 450 ml) and water (total 225 ml) until all solids dissolved, and an oil separated. The oil (118.5 g) was obtained, analyzing 75.6% HFTAIC and 12% DMAc, for a yield 71.7% of theoretical, based on cyanuric acid. 
     EXAMPLE 3 
     Synthesis of HFTAIC by process of equation (5&#39;) 
     In a manner generally similar to that of Example 2, 19.5 g (˜0.10 mol) trisodium cyanurate and 11.2 g (0.20 mol) calcium oxide were slurried in 110 ml dimethyl acetamide, and reacted with 71.1 g (0.30 mol) dibromodifluoropropane, half of which was added at room temperature, the remainder being added after heating to about 80° C. On further heating to 110° C., the temperature rose to 150° C. over 10 minutes as the result of a brief exothermic reaction. The mixture was stirred an additional three hours at 120° C., cooled, and treated with 200 ml 4 N HCl and 100 ml H 2  O. An oil (29.0 g) separated, which contained 23 g hexafluorotriallylisocyanurate by analysis, for a yield 65% of the theoretical amount. 
     EXAMPLE 4 
     Preparation of HFTAIC gelled fluoroelastomer 
     A curable fluoroelastomer of this invention was prepared by a continuous process composed of the following steps: 
     (1) Gaseous monomers were fed continuously to a 2 liter stainless steel autoclave while the stirrer of the reactor was operated at 885 rpm for thorough mixing of the reactor contents. The contents of the reactor were heated at 105° C. under a pressure of 6.31 MPa so that the reaction mixture formed in operation (2) below would undergo an emulsion polymerization reaction as it passed through the reactor. The reactor residence time was about 15 minutes based on a water flow of about 8 liters/hr. The monomers used and the feed rate of each are shown in Table I below; 
     (2) During each hour of operation (1) a solution composed of 6.8 g ammonium persulfate and 0.8 g sodium hydroxide in 4 liters of water was continuously fed to the reactor through a first metering pump, a solution of 2.0 g of sodium sulfite in 4 liters of water was continuously fed to the reactor through a second metering pump, and a solution of 19 g hexafluorotriallylisocyanurate in 28.5 g of t-butyl alcohol was continuously fed to the reactor through a third metering pump. 
     (3) The resulting copolymer latex was continuously removed from the reactor by passing it first through a back pressure regulating valve set to maintain the desired reactor pressure of 6.31 MPa, and then through a sealed container from which the unreacted monomers were led to a gas chromatograph where the composition of the stream was determined. The off gas rate for each monomer and the amount of each monomer incorporated into the polymer are also shown in Table I. 
     (4) After discarding the latex obtained during the first four residence times, the desired quantity of latex having a solids content of about 19% was collected. 
     (5) The resulting copolymer was then isolated from the latex by gradually adding a 4% aqueous solution of potassium aluminum sulfate until the polymer was coagulated, washing the copolymer particles with water, removing the water by filtration, and then drying the copolymer obtained in a circulating air oven at about 65° C. to a moisture content of less than 1%. 
     
                       TABLE I                                                     
______________________________________                                    
Feed        Off Gas   Incorporated in polymer                             
g/hr        g/hr      g/hr    wt. %  Mole %                               
______________________________________                                    
TFE     475      5        470   25.2   21.9                               
VF.sub.2                                                                  
        860      15       845   45.3   61.5                               
HFP     660     129       531   28.5   16.5                               
HFTAIC   19      --        19    1.0   0.16                               
        2014    149       1865                                            
______________________________________                                    
 
    
     The gel content of this polymer was determined to be about 97.0%. 
     EXAMPLE 5 
     Preparation of HFTAIC gelled fluoroelastomer 
     A gelled terpolymer of TFE, VF 2 , HFP and HFTAIC was prepared as described in Example 4 above at a temperature of 105° C. and a pressure of 6.31 MPa with a latex residence time of 15 min. Monomers were fed to the reactor at the following rates: TFE: 475 g/h; VF 2  : 860 g/h; HFP: 660 g/h and HFTAIC: 38.2 g/h. Also present in the latex were 0.51 g ammonium persulfate/100 g polymer produced, 0.12 sodium sulfite/100 g polymer produced and 0.06 g sodium hydroxide/100 g polymer produced. Conversion of monomers to polymers was 65.9%. The dried copolymer comprised 30.6 wt. % TFE, 53.1 wt. % VF 2 , 13.4 wt. % HFP and 2.8 wt. % HFTAIC. It had a gel content of 98.0%. 
     EXAMPLE 6 
     Preparation of HFTAIC gelled fluoroelastomer 
     A curable fluoroelastomer of this invention was prepared by the process described in Example 3 except that the gaseous monomers were fed at rates as shown in Table III below and liquid feeds (per hour) comprised (1) 5.83 g ammonium persulfate and 1.67 g sodium hydroxide in 3 liters water, (2) 0.72 grams sodium sulfite in 3 liters water, and (3) 18.6 g HFTAIC in sufficient t-butyl alcohol to obtain a volume of 50 ml. 
     
                       TABLE II                                                    
______________________________________                                    
Feed        Off Gas   Incorporated in polymer                             
g/hr        g/hr      g/hr     wt. %  Mole %                              
______________________________________                                    
VF.sub.2                                                                  
       1130      72       1058   64.3   81.2                              
HFP    870      302       568    34.5   18.6                              
HFTAIC 18.6      --       18.6   1.1    0.26                              
       2018.6   374       1644.6                                          
______________________________________                                    
 
    
     The gel content of this polymer was determined to be about 96.6%. 
     EXAMPLE 7 
     Preparation of HFTAIC gelled fluoroelastomer 
     A curable fluoroelastomer of this invention was prepared by the process described in Example 6 except that the feed of HFTAIC was 9.28 g in 25 ml total solution, the results obtained are summarized in Table III. 
     
                       TABLE III                                                   
______________________________________                                    
Feed        Off Gas   Incorporated in polymer                             
g/hr        g/hr      g/hr     wt. %  Mole %                              
______________________________________                                    
VF.sub.2                                                                  
       1130     32        1098   69.3   78.2                              
HFP    870      156       714    39.2   21.7                              
HFTAIC 9.26     --        9.26   0.51   0.12                              
       2009.26  188       1821.26                                         
______________________________________                                    
 
    
     The gel content of this polymer was determined to be about 92.9%. 
     EXAMPLE 8 
     Preparation of HFTAIC gelled fluoroelastomer 
     A curable fluoroelastomer of this invention was prepared by continuous emulsion polymerization in a stirred 2 liter autoclave maintained at 115° C., 6.31 MPa, with a latex residence time of 20 minutes in the reactor, using as the free radical initiator 0.3 grams ammonium persulfate per 100 g polymer produced. In addition, 0.05 grams sodium hydroxide per 100 g polymer produced and 0.05 grams ammonium perfluorooctanoate per 100 g of polymer produced was also present. Monomers were fed to the reactor at the following rates: 493 g/h tetrafluoroethylene (TFE), 913 g/h vinylidene fluoride (VF 2 ), 691 g/h hexafluoropropylene (HFP), 26 g/h 4-bromo-3,3,4,4-tetrafluorobutene-1 (BTFB) and 7.33 g/h hexafluorotriallylisocyanurate (HFTAIC). Conversion of total monomers to polymer was 87.6%. The latex was coagulated by addition of potassium aluminum sulfate solution, the resulting crumb then being washed several times and dried at about 60° C. in a circulating air oven. The dried copolymer comprised 25.7 wt. % TFE, 46.9 wt. % VF 2 , 25.6 wt. % HFP, 1.37 wt. % BTFB and 0.39 wt. % HFTAIC. The polymer had a gel content of 89.1%, as determined by a method based on high speed centrifugation of a dilute solution of the polymer in ethyl methyl ketone. 
     EXAMPLE 9 
     Preparation of HFTAIC gelled fluoroelastomer 
     A curable fluoroelastomer of this invention was prepared in a manner similar to that described in Example 8 above, in the presence of 0.3 g ammonium persulfate/100 g polymer produced using monomer flows per hour of 486 g TFE, 901 g VF 2 , 682 g HFP, 27.6 g BTFB and 1.38 g HFTAIC. The residence time in the reactor was 20 minutes and the reaction temperature was 105° C. The resulting product contained 25.4 wt. % TFE, 45.6 wt. % VF 2 , 26.5 wt. % HFP, 1.46 wt. % BTFB and 0.073 wt. % HFTAIC. It had a gel content of 58% and a Mooney viscosity [ML-10 (100° C.)]=170. This fluoroelastomer was designated Sample B. 
     EXAMPLE 10 
     Preparation of HFTAIC gelled fluoroelastomer 
     A 400 cc stainless steel shaker bomb was charged with 1 g of ammonium persulfate, 0.2 g of sodium sulfite, 200 ml of water, 1.0 g of the ammonium salt of perfluorooctanoic acid, 2.5 g of sodium pyrophosphate decahydrate, 2 drops of a 5% aqueous solution of copper sulfate, 2 g perfluoro(2-phenoxypropyl vinyl) ether and 0.25 g HFTAIC. The vessel was cooled and evacuated three times. Then 26 g of TFE and 54 g of perfluoro(methyl vinyl) ether were introduced. The mixture was allowed to react at 50° C. for 8 h under autogenous pressure conditions. The vessel was then cooled and vented. The product was collected, washed with water and dried in vacuo at 70° C. to give 35 g polymer having 67.6 gel 1 . The soluble portion had η inh  0.92 2 . Composition (by infrared analysis): 1.2% 2-perfluoro(2-phenoxypropyl vinyl)ether, 40.4% perfluoro(methyl vinyl)ether. 
    
    
     EXAMPLE 11 
     Preparation and properties of fluoroelastomer blends 
     A gelled fluoroelastomer prepared as described in Example 8, above, was blended with an essentially gel-free copolymer similarly prepared using monomer flows per hour of 615 g TFE, 1118 g VF 2 , 852 g HFP and 39.5 g BTFB. Also present in the latex of the gel-free polymer were 0.39 g ammonium persulfate per 100 g polymer produced and 0.09 g sodium hydroxide per 100 g polymer produced. Conversion of total monomers to gel-free polymer was 87%. Product composition: 26.1 wt. % TFE, 46.9 wt. % VF 2 , 25.2 wt. % HFP and 1.73 wt. % BTFB. The gel-free polymer had inherent viscosity 1.39 and Mooney viscosity [ML-10 (121° C.)]=80. 
     A 640 g sample of the gelled polymer was millmixed with a 360 g sample of the sol (gel-free) polymer to give a blend of the present invention having a gel content of 58%. This blend was designated as Sample A. 
     A control gelled fluoroelastomer was prepared in the manner described in Example 9 above. Composition of the isolated polymer was approximately 25 wt. % TFE, 45 wt. % VF 2 , 30 wt. % HFP and 0.8 wt. % BTFE (bromotrifluoroethylene). This polymer was mill-blended with a 60:40 VF 2  /HFP copolymer in a ratio of 9:1. The gel content of the resultant control blend was 58%. The Mooney viscosity was [ML-10(121° C.)]˜90. The resultant blend is substantially as described by Finlay and Omura in U.S. Pat. No. 4,115,481 cited and discussed above. This control blend was designated as Sample C. 
     A control sol (non-gelled) polymer composed of 25.0 wt. % TFE, 45.5 wt. % VF 2 , 27.8 wt. % HFP and 1.72 wt. % BTFB was prepared as generally described above at 105° C., residence time was 20 minutes, in the presence of 0.5 grams ammonium persulfate/100 g polymer produced. The product had Mooney viscosity [ML-10(121° C.)]=78 and was designated as Sample D. 
     The gelled fluoroelastomers of the present invention as described in detail in Examples 8 and 9 (i.e., Samples A and B), above, and the control blend and control sol polymers described immediately above (i.e., Samples C and D), were compounded according to the following recipe: 
     
         ______________________________________                                    
Polymer                   100 parts                                       
Carbon Black              30 parts                                        
Litharge (PbO)            3 parts                                         
Diak #7 (Triallylisocyanurate)                                            
                          2.5 parts                                       
Luperco 130XL (45% 2,5-dimethyl-2,5-di-                                   
t-butylperoxyhexene-3, 55% inert filler)                                  
                          2.5 parts                                       
VPA #2 (Rice bran wax)    2.0 parts                                       
______________________________________                                    
 
    
     Samples A, B, C and D, compounded as above, were extruded through a 2 inch Royle Extruder, equipped with a 3/8 inch cord die, at the following conditions: barrel 60° C.; head, 77° C.; feed, 46° C.; die, 100° C. (center); screw 60° C., 30 rpm. Results are shown in Table IV. 
     
                       TABLE IV                                                    
______________________________________                                    
Polymer  Extrusion Rate (g/min)                                           
                          Die Swell (g/mm)                                
______________________________________                                    
A        200              0.202                                           
B        200              0.195                                           
C        200              0.226                                           
D        200              0.289                                           
A        300              0.204                                           
B        300              0.200                                           
C        300              0.228                                           
D        300              0.309                                           
______________________________________                                    
 
    
     Samples A, B, C and D, compounded as above, were cured at 170° C. for 30 minutes and post-cured at 232° C. for 24 hours. Physical properties of the vulcanizates were determined by the procedures of ASTM 412 and D-395 and were as noted in Table V. 
     
                       TABLE V                                                     
______________________________________                                    
            Sample                                                        
            A      B        C        D                                    
______________________________________                                    
Room Temp.                                                                
T.sub.B (MPa) 14.1     13.8     10.0   17.6                               
M.sub.100 (MPa)                                                           
              7.9      6.2      6.5    5.2                                
E.sub.B (%)   185      180      165    240                                
Set at Break  4        6        4      5                                  
Heat Aged 70h/275° C.                                              
T.sub.B (MPa) 12.1     9.7      8.3    12.4                               
M.sub.100 (MPa)                                                           
              5.5      3.1      4.6    3.1                                
E.sub.B (%)   185      300      180    300                                
Set at break  7        10       6      9                                  
Compression set                                                           
(70h/204° C.)                                                      
              34       41       37     30                                 
______________________________________                                    
 
    
     EXAMPLE 12 
     Preparation and properties of fluoroelastomer blends 
     Three fluoroelastomers having compositions as shown in Table VI were prepared as described above. 
     
                       TABLE VI                                                    
______________________________________                                    
     Blend                                                                
     Com-                                                                 
     po-                               HFT-                               
Sam- nents   TFE     VF.sub.2                                             
                           HFP   BTFB  AIC   BTFE                         
ple  (%)     (wt.%)  (wt.%)                                               
                           (wt.%)                                         
                                 (wt.%)                                   
                                       (wt.%)                             
                                             (wt.%)                       
______________________________________                                    
E    90      25      45    30    --    --    0.8                          
E    10      --      60    40    --    --    --                           
F    62.5    26.1    46.6  25.5  1.44  0.41  --                           
F    37.5    25.6    45.4  27.3  1.70  --    --                           
G    100     25.6    45.4  27.3  1.70  --    --                           
______________________________________                                    
 Sample E: % gel in blend: 58%, ML10(121° C.) = 106                
 F: % gel in blend: 54%                                                   
 G: ML10(121° C.) = 92                                             
 
    
     These samples were compounded using the recipe in Example 11 above. Instron capillary rheometer extrusions at 70° C. afforded the following comparisons. 
     
                       TABLE VII                                                   
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
E       3.01      3.18     21.5    3.51.sup.1                             
F       3.01      3.18     18.7    3.23.sup.1                             
G       3.01      3.18     17.2    3.58.sup.1                             
E       30.1      3.18     33.7    3.40.sup.2                             
F       30.1      3.18     25.6    3.25.sup.2                             
G       30.1      3.18     23.1    3.51.sup.2                             
E       150.7     3.18     43.7    3.40.sup.3                             
F       150.7     3.18     37.5    3.20.sup.3                             
G       150.7     3.18     31.2    3.48.sup.3                             
______________________________________                                    
 .sup.1 torn surface                                                      
 .sup.2 rough surface                                                     
 .sup.3 dull surface  no irregularities at 10× magnification        
 
    
     The above data show that at identical extrusion rates, the diameter of Sample F extrudate more nearly conformed to the die diameter than did the diameters of either Sample E or Sample G extrudates. 
     Similar results were obtained at 120° C. In addition, the surface of Sample F extrudate was superior to that of Samples E or G when the extrusion was carried out at 120° C., as summarized in Table VIII. 
     
                       TABLE VIII                                                  
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
E       3.01      3.18     11.2    3.30.sup.2                             
F       3.01      3.18     8.4     3.15.sup.1                             
G       3.01      3.18     10.0    3.40.sup.2                             
E       30.1      3.18     14.4    3.30.sup.1                             
F       30.1      3.18     9.4     3.23.sup.1                             
G       30.1      3.18     16.2    3.66.sup.3                             
E       150.7     3.18     21.2    3.40.sup.4                             
F       150.7     3.18     20.6    3.28.sup.3                             
G       150.7     3.18     21.9    3.63.sup.3                             
______________________________________                                    
 .sup.1 smooth and shiny surface                                          
 .sup.2 torn surface                                                      
 .sup.3 rough surface 10× magnification                             
 .sup.4 cracked surface                                                   
 
    
     Further extrusion of Sample F and G stocks through a 2&#34; Royle Extruder with a 9.5 mm cord die at a rate of approximately 400 g/min. afforded the following die swell measurements: 1.90 g/mm for the blend and 3.46 g/mm for the non-crosslinked rubber stock. 
     Samples E, F and G, as compounded, were cured as described in Example 11. Physical properties after cure, measured as described in Example 11, are as shown in Table IX. 
     
                       TABLE IX                                                    
______________________________________                                    
Sample                                                                    
Properties at Room Temp.                                                  
               E         F         G                                      
______________________________________                                    
T.sub.B (MPa)  13.1      18.0      15.9                                   
M.sub.100 (MPa)                                                           
               6.6       9.0       7.2                                    
E.sub.B (%)    160       160       185                                    
Set at Break   4         4         4                                      
Compression Set                                                           
               29        27        30                                     
______________________________________                                    
 
    
     EXAMPLE 13 
     Preparation and properties of fluoroelastomer blends 
     The gelled fluoroelastomer of Example 5 was mixed on a rubber mill with an equal weight of an allsol TFE/VF 2  /HFP copolymer comprising 25 wt. % TFE, 45 wt. % VF 2  and 30 wt. % HFP. Samples of the gelsol blend and the sol polymer were compounded according to the following recipe (in parts by weight). 
     
         ______________________________________                                    
Polymer                   100                                             
Carbon Black              30                                              
Magnesium Oxide           15                                              
N,N&#39;-dicinnamylidene-1,6-hexane-                                          
diamine                   3                                               
______________________________________                                    
 
    
     Properties of the samples are shown in Table X. 
     
                       TABLE X                                                     
______________________________________                                    
                    Blend   Sol                                           
______________________________________                                    
Mooney Viscosity [ML-10(121° C.)]                                  
                      100       64                                        
Properties of Stocks Cured 24h/232° C.                             
Compression Set.sup.1 (70h/232° C.)                                
                      79        83                                        
Properties at 150° C.                                              
T.sub.B (MPa).sup.2   4.0       3.5                                       
E.sub.B (%).sup.2     40        112                                       
Set at break.sup.2    1         2                                         
Properties at 20° C.                                               
T.sub.B (MPa).sup.2   12.4      16.2                                      
M.sub.100 (MPa).sup.2 --        5.0                                       
E.sub.B (%).sup.2     70        230                                       
Hardness.sup.3        92        76                                        
______________________________________                                    
 .sup.1 ASTM D395                                                         
 .sup.2 ASTM 412                                                          
 .sup.3 ASTM D2240                                                        
 
    
     Instron capillary rheometer extrusions at 70° C. gave the following data. 
     
                       TABLE XI                                                    
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
Sol     8.5       1.27     31.2    1.37.sup.1                             
Blend   8.5       1.27     39.3    1.27.sup.1                             
Sol     2115      1.27     143.5   1.40.sup.2                             
Blend   423       1.27     152.9   1.30.sup.1                             
______________________________________                                    
 .sup.1 Surface rough                                                     
 .sup.2 Tears, jagged surface                                             
 
    
     Similar results in die swell with improved surface properties are seen when the extrusion was run at 120° C. 
     
                       TABLE XII                                                   
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
Sol     8.5       1.27     32.5    1.37.sup.1                             
Blend   8.5       1.27     32.5    1.30.sup.2                             
Sol     8460      1.27      88.9*  1.47.sup.1                             
Blend   8460      1.27     146.6*  1.32.sup.2                             
______________________________________                                    
 *Force was read after only 1.5 min from start of extrusion since fast    
 extrusion depleted sample from reservoir. Other data taken at 4.0 min    
 after start.                                                             
 .sup.1 Irregularities visible at 10× magnification.                
 .sup.2 Smooth at 10× magnification. Surface Rating: excellent.     
 
    
     EXAMPLE 14 
     Preparation and properties of fluoroelastomer blends 
     A gel-sol blend was prepared in a manner similar to that described in Example 13 above. The following conditions were used for preparation of the gel. 
     
         ______________________________________                                    
Reaction Temp (°C.)                                                
                        105                                               
Pressure (MPa)          6.31                                              
Residence time (min)    15                                                
g NH.sub.4 S.sub.2 O.sub.8 /100 g polymer                                 
                        0.36                                              
g NaSO.sub.3 /100 g polymer                                               
                        0.107                                             
g NaOH/100 g polymer    0.043                                             
TFE (g/h)               475                                               
VF.sub.2 (g/h)          860                                               
HFP (g/h)               660                                               
HFTAIC (g/h)            19                                                
Conversion (%)          92.6                                              
______________________________________                                    
 
    
     The product contained 25.2 wt. % TFE, 45.3 wt. % VF 2 , 28.4 wt. % HFP and 1.0 wt. % HFTAIC. % Gel=96%. It was mill-mixed with an equal portion of the sol polymer used in Example 13. 
     Samples of the gel-sol blend and the sol were compounded using the recipe in Example 13. Physical properties were measured as described in Example 13 and are shown in Table XIII. 
     
                       TABLE XIII                                                  
______________________________________                                    
                   Blend   Sol                                            
______________________________________                                    
Mooney Viscosity [ML-10 (121° C.)]                                 
                     93        64                                         
Compression Set (70h/232° C.)                                      
                     77        83                                         
Properties at 150° C.                                              
T.sub.B (MPa)        3.5       3.5                                        
E.sub.B (%)          45        112                                        
Set at Break         1         2                                          
Properties at 20° C.                                               
T.sub.B (MPa)        13.1      16.2                                       
M.sub.100 (MPa)      12.9      5.0                                        
E.sub.B (%)          105       230                                        
Hardness             88        76                                         
______________________________________                                    
 
    
     Instron rheometer extrusions at 70° C. showed the following comparisons. 
     
                       TABLE XIV                                                   
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
Sol     8.5       1.27     31.2    1.37.sup.1                             
Blend   8.5       1.27     35.6    1.27.sup.2                             
Sol     2115      1.27     143.5   1.40.sup.3                             
Blend   8460      1.27     162.2   1.30.sup.4                             
______________________________________                                    
 .sup.1 Surface rough                                                     
 .sup.2 Smooth at 10× magnification. Surface rating: excellent      
 .sup.3 Tears, jagged surface                                             
 .sup.4 Irregularities visible only at 10× magnification.           
 
    
     Similar results were obtained at 120° C. as summarized in Table XV. 
     
                       TABLE XV                                                    
______________________________________                                    
        Extrusion Die      Extrusion                                      
                                   Extrudate                              
        Rate      Diam     Force   Diam                                   
Sample  (mm.sup.3 /s)                                                     
                  (mm)     (MPa)   (mm)                                   
______________________________________                                    
Sol     8.5       1.27     32.5    1.37.sup.1                             
Blend   8.5       1.27     33.1    1.27.sup.2                             
Sol     8460      1.27     88.9    1.47.sup.1                             
Blend   8460      1.27     137.5   1.32.sup.2                             
______________________________________                                    
 .sup.1 Irregularities visible at 10× magnification                 
 .sup.2 Smooth at 10× magnification. Surface rating: excellent      
 
    
     EXAMPLE 15 
     Preparation and properties of fluoroelastomer blends 
     A terpolymer was prepared as described in Example 4 above at a temperature of 115° C. and a pressure of 6.31 MPa with a latex residence time of 15 min. 
     Monomers were fed to the reactor at the following rates: VF 2 , 1380 g/hr; HFP, 1020 g/hr; HFTAIC, 5.15 g/hr. Also fed to the latex were ammonium persulfate, 6.0 g/hr; sodium hydroxide, 0.8 g/hr; and &#34;Zonyl&#34; UR long chain fluorinated surfactant, 7.0 g/hr. Conversion of monomers to polymer was 93.7%, the dried copolymer comprising 60.2 wt. % VF 2 , 39.6 wt. % HFP, and 0.22 wt. % HFTAIC. It had a microgel content of 79.0% and a Mooney viscosity ML-10=104 at 121° C. 
     This terpolymer was formulated on a rubber mill as follows: 
     
         ______________________________________                                    
                  A     B      C      D                                   
______________________________________                                    
Precompounded Sol Fluoroelastomer                                         
Control*            100     --     --   --                                
Gelled terpolymer described above                                         
                    --      25     37.5 50                                
Sol control without curatives                                             
                    --      75     63.5 50                                
Benzyltriphenyl phosphonium                                               
                    --      0.5    0.5  0.5                               
chloride                                                                  
Bisphenol AF        --      1.2    1.6  2.0                               
Ca(OH).sub.2        6       6      6    6                                 
MT black (carbon black)                                                   
                    30      30     30   30                                
Magnesium oxide     3       3      3    3                                 
______________________________________                                    
 *A sol copolymer of 60 wt % VF.sub.2 and 40 wt % HFP com? pounded with   
 0.55 parts benzyl triphenyl phosphonium chloride and 2.0 parts bisphenol 
 AF                                                                       
 
    
     Properties of Samples A-D, measured as described in Example 13 are shown in Table XVI. 
     
                       TABLE XVI                                                   
______________________________________                                    
                  Samples                                                 
                  A (sol)                                                 
                        B      C      D                                   
______________________________________                                    
Mooney Viscosity [ML-10(121° C.)]                                  
                    37      42     45   49                                
Properties of Stocks Cured 24h/                                           
232° C.                                                            
Compression Set (70 h/232° C.)                                     
Pellets             39      52     39   35                                
&#34;O&#34; Rings           33      46     36   31                                
Properties at 20° C.                                               
T.sub.B (MPa)       12.4    11.6   13.8 12.6                              
E.sub.B (%)         170     240    200  190                               
M.sub.100 (MPa)     6.2     3.8    5.9  6.9                               
Permanent Set.sup.1 5       5      6    6                                 
Heat Aged (7d/275° C.)                                             
T.sub.B (MPa)       12.4    10.7   12.4 12.4                              
E.sub.B (%)         170     290    220  200                               
M.sub.100 (MPa)     6.7     3.8    5.5  6.4                               
Permanent Set       6       8      6    8                                 
______________________________________                                    
 .sup.1 ASTM 412                                                          
 
    
     Samples A-D were extruded in a Monsanto Processability Tester (a type of capillary rheometer). A Garvey Die (a die with 180° entrance angle having an irregularly shaped cross section and producing an extrudate with sharp edges) was used. Temperatures of 93° C. and 132° C. and piston speeds of 0.254 cm/min and 2.29 cm/min were used. 
     The extrudates were cut into equal lengths after cooling and were then weighed to determine the relative die swell (Barus effect). The greater the weight of the extrudate per unit length, the larger was its cross section and hence its relative die swell. Data obtained is summarized in Tables XVII and XVIII and in FIGS. 1 and 3. Some of the die swell data presented below is the average of two replications. 
     
                       TABLE XVII                                                  
______________________________________                                    
                                     Extrusion                            
                                     Temp = 93° C.*                
      Wt %      Amount of Gel                                             
                             Piston  Relative                             
      HFTAIC    Component    Speed   Die Swell                            
Blend in Gel    in Blend(%)  (cm/min)                                     
                                     (g)                                  
______________________________________                                    
A     0.22      0            0.254   2.58                                 
B     0.22      25           0.254   2.15                                 
C     0.22      37.5         0.254   1.98                                 
D     0.22      50           0.254   1.89                                 
A     0.22      0            2.29    2.56                                 
B     0.22      25           2.29    2.22                                 
C     0.22      37.5         2.29    2.08                                 
D     0.22      50           2.29    2.00                                 
______________________________________                                    
 *At this low extrusion temperature all samples showed some tearing at the
 edges, making the errors in measuring relative die swell somewhat greater
 than at higher temperatures where extrudates were smoother.              
 
    
     
                       TABLE XVIII                                                 
______________________________________                                    
                                     Extrusion                            
                                     Temp = 132° C.                
      Wt %      Amount of Gel                                             
                             Piston  Relative                             
      HFTAIC    Component    Speed   Die Swell                            
Blend in Gel    in Blend(%)  (cm/min)                                     
                                     (g)                                  
______________________________________                                    
A     0.22      0            0.254   2.00                                 
B     0.22      25           0.254   2.17                                 
C     0.22      37.5         0.254   1.83                                 
D     0.22      50           0.254   1.82                                 
A     0.22      0            2.29    2.51                                 
B     0.22      25           2.29    2.18                                 
C     0.22      37.5         2.29    1.93                                 
C     0.22      50           2.29    1.85                                 
______________________________________                                    
 
    
     The data summarized above demonstrates that in all cases except one (Table XVIII, 25% gel component, in blend, piston speed=0.254), the blend gives a product which exhibits less die swell than the sol polymer. 
     EXAMPLE 16 
     Preparation and properties of fluoroelastomer blends 
     A terpolymer was prepared as described in Example 4 above at a temperature of 115° C. and a pressure of 6.31 MPa with a latex residence time of 15 min. 
     Monomers were fed to the reactor at the following rates: VF 2 , 1380 g/hr; HFP, 1020 g/hr; HFTAIC, 10.3 g/hr. Also fed to the latex were ammonium persulfate, 6.0 g/hr; sodium hydroxide, 0.8 g/hr; and &#34;Zonyl&#34; UR long chain fluorinated surfactant, 7.0 g/hr. The dried copolymer comprised 61.5 wt % VF 2 , 38.0 wt % HFP, and 0.45 wt % HFTAIC. It had a microgel content of 90.8 and Mooney viscosity ML-10=116 at 121° C. 
     This terpolymer was formulated on a rubber mill as follows: 
     
         ______________________________________                                    
                  A    B      C        D                                  
______________________________________                                    
Precompounded Sol Fluoroelastomer                                         
Control*            100    --     --     --                               
Gelled terpolymer described above                                         
                    --     25     37.5   50                               
Sol control without curatives                                             
                    --     75     62.5   50                               
Benzyltriphenyl phosphonium                                               
chloride            --     0.5    0.575  0.5                              
Bisphenol AF        --     1.6    1.6    1.6                              
Ca(OH).sub.2        6      6      6      6                                
MT black (carbon black)                                                   
                    30     30     30     30                               
Magnesium oxide     3      3      3      3                                
______________________________________                                    
 *A sol copolymer of 60 wt % VF.sub.2 and 40 wt % HFP compounded with 0.55
 parts benzyl triphenyl phosphonium chloride and 2.0 parts bisphenol AF.  
 
    
     Properties of Samples A-D, measured as described in Example 13 are shown in Table XIX. 
     
                       TABLE XIX                                                   
______________________________________                                    
                  Samples                                                 
                  A(Sol)                                                  
                        B      C      D                                   
______________________________________                                    
Properties of Stocks Cured 24 h/                                          
232° C.                                                            
Compression Set.sup.1 (70 h/232° C.)                               
Pellets             41      41     39   37                                
&#34;O&#34; Rings           33      37     34   34                                
Properties at 20°  C.                                              
T.sub.B (MPa)       13.8    12.6   13.4 12.9                              
E.sub.B (%)         180     215    205  190                               
M.sub.100 (MPa)     7.2     5.7    6.6  6.9                               
Permanent Set.sup.2 5       5      6    5                                 
Heat Aged (7 d/275° C.)                                            
T.sub.B (MPa)       11.7    8.6    9.3  9.1                               
E.sub.B (%)         180     215    205  190                               
M.sub.100 (MPa)     6.6     4.1    4.8  5.2                               
Permanent Set.sup.2 6       7      7    7                                 
______________________________________                                    
 .sup.1 ASTM D395                                                         
 .sup.2 ASTM 412                                                          
 
    
     Samples A-D were extruded in a Monsanto Processability Tester using a Garvey Die at 93° C. and 132° C. and piston speeds of 0.254 cm/min and 2.29 cm/min. Relative die swell was determined as described in Example 15. Data obtained is summarized in Tables XX and XXI and in FIGS. 2 and 4. Some of the die swell data-presented is the average of two replications. 
     
                       TABLE XX                                                    
______________________________________                                    
                                  Extrusion                               
                                  Temp = 93° C.*                   
      Wt %     Amount of Gel                                              
                           Piston Relative                                
      HFTAIC   Component   Speed  Die Swell                               
Blend in Gel   in Blend    (cm/min)                                       
                                  (g)                                     
______________________________________                                    
A     0.45     0           0.254  2.50                                    
B     0.45     25          0.254  2.11                                    
C     0.45     37.5        0.254  1.88                                    
D     0.45     50          0.254  1.80                                    
A     0.45     0           2.29   2.54                                    
B     0.45     25          2.29   2.20                                    
C     0.45     37.5        2.29   1.99                                    
D     0.45     50          2.29   1.91                                    
______________________________________                                    
 *At this low extrusion temperature all samples showed some tearing at the
 edges, making the errors in measuring relative die swell somewhat greater
 than at higher temperatures where extrudates were smoother.              
 
    
     
                       TABLE XXI                                                   
______________________________________                                    
                                  Extrusion                               
                                  Temp = 132° C.                   
      Wt %     Amount of Gel                                              
                           Piston Relative                                
      HFTAIC   Component   Speed  Die Swell                               
Blend in Gel   in Blend    (cm/min)                                       
                                  (g)                                     
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A     0.45     0           0.254  2.02                                    
B     0.45     25          0.254  1.88                                    
C     0.45     37.5        0.254  1.79                                    
D     0.45     50          0.254  1.73                                    
A     0.45     0           2.29   2.41                                    
B     0.45     25          2.29   1.98                                    
C     0.45     37.5        2.29   1.85                                    
D     0.45     50          2.29   1.76                                    
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     The data summarized above demonstrates the blend gives a product which exhibits less die swell than the sol polymer. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-4 are graphs showing data derived from the experiments described in detail in Examples 15 and 16, which data is summarized in Tables XVII, XVIII, XX and XXI. 
     FIG. 1 represents data derived from experiments where the extrusion temperature was 93° C. and the piston rate was 0.254 cm./min. 
     FIG. 2 represents data derived from experiments where the extrusion temperature was 93° C. and the piston rate was 2.29 cm./min. 
     FIG. 3 represents data derived from experiments where the extrusion temperature was 132° C. and the piston rate was 0.254 cm./min. 
     FIG. 4 represents data derived from experiments where the extrusion temperature was 132° C. and the piston rate was 2.29 cm./min. 
     Industrial Applicability 
     The fluoroelastomer blends of the present invention will be useful wherever prior fluoroelastomers have found utility, but these blends will be particularly useful and advantageous in situations requiring extrusion or milling of the fluoroelastomers, for example in manufacture of tubing, hose, sheet goods, and molding preforms. 
     Best Mode 
     Insofar as the present invention comprises not only the preferred novel gelling agent, HFTAIC, but also the processes for making HFTAIC, HFTAIC gelled fluoroelastomer, and blends containing HFTAIC gelled fluoroelastomer, the best mode of practicing the present invention must relate to each of these aspects of the present invention. Beyond that, the best mode may vary depending on the particular desired end use and the specific requisite combination of properties for that use, especially as the designation of best mode relates to HFTAIC gelled fluoroelastomer and blends containing HFTAIC gelled fluoroelastomer. Within such constraints, the most preferred process for making HFTAIC is as described in Example 2; the most preferred HFTAIC gelled fluoroelastomer for the widest variety or most common end uses is as described in Example 7; and the most preferred blend containing HFTAIC gelled fluoroelastomer for the widest variety or most common end uses is as described in Example 16.