bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural modification and molding of polyacrylonitrile
Authors: Griffith Russell K. , Zorska Roman 
Published: April 2003

AbstractPolyacrylonitrile can be compression‐molded with conventional equipment if the inherent polymer particle structure is modified. With normal polymerization methods, a circumferential orientation in the polymer particle is obtained. This structure can be changed under the effects of shear to yield highly ordered, laminar particles with planar orientations. In this form, PAN can be compression‐molded into tough, clear, chemically resistant articles with retention of the laminar structure. The polymer has been characterized by its x‐ray diffraction and infrared spectrum which, in combination, distinguish it from previously observed forms of PAN.
Moisture determination in plasticizer–pigment formulations by gas chromatography
Authors: Slanski J. M. , Jacin H. , Moshy R. J. 
Published: April 2003

AbstractA rapid quantitative method has been developed for the determination of small amounts of water present in plasticizer‐pigment and epoxy resin–pigment dispersion used in polyurethane formulations. Specific dispersions examined have been the systems diisooctyl phthalate–titanium dioxide and titanium dioxide–epichlorhydrin–Bisphenol A. The samples examined contained 50–70% titanium dioxide.
Role of hydrophobic bonding in the contraction of nylon 66 in phenolic solutions
Authors: Jacobs Martin I. 
Published: April 2003

AbstractRate constants for intermolecular bond breaking (k1) and bond re‐formation (k2) were calculated from contraction measurements. Variation of ΔH‡ and ΔS‡ for k1 with phenol substituents and concentration suggests the existence of hydrophobic bonding between the solution and the polymer activated complex. This behavior has been substantiated by correlating ΔH‡ and ΔS‡ for k1 with a parameter related to hydrophobicity.
The effect of time and temperature on the mechanical behavior of a “plasticized” epoxy resin under different loading modes
Authors: Moehlenpah A. E. , Ishai O. , Dibenedetto A. T. 
Published: April 2003

AbstractEpoxy–Versamid specimens were loaded in tension, compression, and flexure at different strain rates and temperatures to determine mode of failure, yield stress and strain, and tangent and relaxation moduli. Stress‐strain curves were used to define brittle, ductile, ductile‐rubbery, and rubbery modes of behavior which prevailed in different temperature‐strain rate regions. The time‐temperature superposition principle was applied to yield stress, initial tangent moduli, and relaxation moduli data for all three types of loading.The transition regions, tangent and relaxation moduli, and shift factors were the same in tension, compression, and flexure. Thus the most convenient mode of loading can be used to determine the general time‐temperature dependence. The ratio of compressive‐to‐tensile yield stress was almost constant over the entire ductile region. Flexural yielding data were used to predict yield stress in tension and compression, and stress relaxation master curves were shown to be related to elastic modulus vs. strain rate curves. The yielding phenomenon was interpreted using Eyring's theory of non‐Newtonian viscoplastic flow. The apparent activation energy and activation volume were larger for tension than compression. A theory is offered to explain why yielding can occur in a cross‐linked system.
Use of gas‐liquid chromatography in the analysis of rigid polyurethane foam polyols
Authors: Corbett G. E. , Hughes W. , Morris‐Jones R. G. 
Published: April 2003

AbstractDetailed characterization of the low molecular weight polyols used as intermediates in rigid polyurethane foam production has not been feasible to date. Gas‐liquid chromatography of the trimethylsilyl ether derivatives of the polyols now offers a more complete picture of polyol composition, particularly with regard to the molecular weight distribution. The data may be interpreted on a semiquantitative basis. The study of processing variables in polyol manufacture, detection of impurities and analysis of unknown polyols or those based on mixed initiators may all be facilitated by use of this GLC technique.
Mechanisms of antioxidant action: Effects of sulfur compounds on the melt stability of polypropylene
Authors: Scott Gerald , Shearn Peter A. 
Published: April 2003

AbstractThe effects of a number of sulfur compounds on the melt stability of polypropylene milled at 165°C have been studied. Dilaurylthiodipropionate (DLTP), Mercaptobenzimidazole (MBI), and Mercaptobenzthiazole (MBT) are all antioxidiants in a polymer lightly stabilized with a phenolic antioxidant although the last two are initially pro‐oxidants. 2,2′‐Dibenzoylaminodiphenyldisulfide (22BDD) is a pro‐oxidant under the Conditions studied.In the absence of a phenolic antioxidant the effectiveness of DLTP is reduced in the early stages of oxidation, with increasing concentration although its over all antioxidant activity increases. The results are consistent with the view that both radical and non‐radical processes occur concomitantly.
Several reactions of poly(vinyl alcohol)–type acetaldehyde polymer
Authors: Matsubara Tsutomu , Imoto Tatsuya 
Published: April 2003

AbstractThe preparation of the acetaldehyde polymers (PACH) having a poly(vinyl alcohol)‐type structure and the thermal degradation of PACH have been reported previously. This paper will describe detailed aspects of several reactions of PACH. Copolymerization of PACH with toluene diisocyanate (TDI) was performed both thermally and catalytically. When piperidine was used as catalyst, the rate of reaction between PACH and TDI was found to depend on the concentration of both the active hydrogen of PACH and the isocynante group TDI. Acid and alkali treatment of PACH were carried out. On treatment with sulfuric acid, white polymers with good spinnability were obtained. The copolymerization of acetaldehyde with n‐butylaldehyde were performed in the presence of sodium amalgam as catalyst. The reaction products were colorless, viscous liquids and assumed from the infrared and NMR spectra, elemental analyses, molecular weight and solubility tests to be aldol condensation‐type copolymers.
Polymerization of trithiane
Authors: Takeda Jun‐Ichi , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractThe catalytic solid‐state polymerization of trithane to polythiomethylene has been studied. The polymerization can be initiated by wide varieties of substances such as metal salts, halogen, and active organic halides. The polymerization proceeds in solid‐state without topochemical process. The catalytic irreversible degradation of polythiomethylene to dimethyl sulfide and carbon disulfide has been observed.
A new method for calculating and correcting molecular weight distributions from gel permeation chromatography
Authors: Chang Kung S. , Huang Robert Y. M. 
Published: April 2003

AbstractA new method for calculating and correcting molecular weight distributions of polymer samples from GPC chromatograms is presented. The integral equation which relates the true molecular weight distribution of polymer sample to the chromatogram is reformulated into an equivalent variational problem of quadratic functional. The method of steepest descent in the function space is then applied to the minimization problem to obtain the true molecular weight distribution. This method is efficient and reduces some of the oscillation problems encountered in the previous methods. Examples are given.
Selectivity of the epoxide phenol reaction
Authors: Alvey Francis B. 
Published: April 2003

AbstractA method for determining the relative amount of alcohol side reaction which occurs in reactions of epoxy compounds with active hydrogen compounds has been investigated. It involves determining the ratio of rates of the successive reaction, epoxide‐active hydrogen compound and epoxide‐generated secondary alcohol, in the reaction of epoxide and active hydrogen compound at respectively a 2:1 mole ratio. Rate ratios are reported for the bulk reaction of bisphenol‐A and the diglycidyl ether of bisphenol‐A under different reaction conditions. The data correlated with the properties of high molecular weight polymers. Amines with β‐hydroxyl groups were very selective catalysts.
Gel permeation chromatography: The effect of treatment with hexamethyldisilazane on porous glass packings
Authors: Cooper Anthony R. , Johnson Julian F. 
Published: April 2003

AbstractPorous glass column packings have been shown to be an effective substrate for gel permeation chromatography. When carbon tetrachloride is used as a solvent in conjuction with infrared detection, the porous glass exhibits adsorptive properties with polystyrene and polyisobutene. A procedure to eliminate these undesirable properties by treatment with hexamethyldisilazane has been developed. Experiments showed complete elution of all injected polymer. The treatment thus permits quantitative fractionation studies using infrared detection.
Effects of termonomers on crosslinking rate and crosslinking structure of ethylene propylene terpolymers
Authors: Fujimoto K. , Nakade S. 
Published: April 2003

AbstractStudy was made concerning both the rate of crosslinking and the structure of crosslinks of terpolymers that have dicyclopentadiene, 1, 4–hexadiene, methylene norbornene, and ethylidene norbornene for termonomers so as to look into the role of termonomers during crosslinking of ethylene propylene terpolymers. In the study, activation energy and frequency factor, both apparent were determined by the rate constant of crosslinking and differences in crosslinks were analyzed following both chemical and physical methods. Infrared analysis into the volume of consumption of double bond was adopted to examine the manner of crosslinking. In respect to the magnitude of the rate constant, ethylidene norbornene came in first being followed by 1,4‐hexadiene, methylene norbornene, and dicyclopentadiene. The structure of termoners affected the apparent activation energy and the apparent frequency factor was subject to the influences of said structure and others including the variation in the degree of unsaturation. During the early stage of crosslinking, the formation of the crosslink of polysulfide‐type was paramount to all others and the speed of conversion therefrom either to disulfide–type or to monosulfide varied with the kind of terpolymers and was in proportion to the rate constant of crosslinking.
Modification of polyethylene surfaces with carbethoxy substituted carbenes and nitrenes
Authors: Osteraas A. Jean , Olsen Douglas A. 
Published: April 2003

AbstractCarbethoxycarbene, carbethoxynitrene, and nitrene generated respectively by the pyrolysis of ethyl diazoacetate, ethyl azidoformate, chloramine and sodium hydroxyl amine‐o‐sulfonate are shown to irreversibly modify the surface of polyethylene as shown by wettability measurements. The nature of the modification is not fully understood; however, insertion of the carbene or nitrene into a carbon‐hydrogen bond appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions as again determined by wettability measurements.
Homo‐and copolymers of vinyl esters, acrylates, and methacrylates of some derivatives of fatty acids
Authors: Chow Roberta C. L. , Marvel C. S. 
Published: April 2003

AbstractVinyl esters of some undecylenic acid derivatives and acrylates and methacrylates of undecyl and undecylenyl alcohols, which may be considered as derivaties of castor oil, have been polymerized and copolymerized with vinyl chloride to provide a variety of new polymers. The acrylate and the methacrylate of undecylenyl alcohol have been epoxidized to yield two new polymerizable monomers of potential usefulness as crosslinking agents in finished copolymers.
Thermal degradation of polymers. part IV. Vacuum pyrolysis of poly(m‐aminostyrene). The residue and the fraction volatile at pyrolysis temperature involatile at room temperature
Authors: Still R. H. , Jones P. B. 
Published: April 2003

AbstractThe effect of the extent of degradation of poly(m–aminostyrene) on the quantity and composition of the residue and the effect of pyrolysis temperature on the fraction volatile at pyrolysis temperature are discussed. The behavior of poly(m–aminostyrene) is compared to that of polystyrene; a significant difference has been found for the behavior of the residue from poly(m–aminostyrene), which is ascribed to a crosslinking reaction involving the amino substituent. Mechanisms to acount for the observed products of degradation have been suggested and are discussed. Relative thermal stability studies have also been made and compared with results from polystyrene.
Effect of lignin in graft copolymerization of methyl methacrylate on cellulose by ceric ion
Authors: Kubota Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractThe effect of lignin contained in cellulosic materials in graft copolymerization of methyl methacrylate on such materials using ceric ion as initiator was studied. It was found that the percent grafting and the average molecular weight of grafts became lower in samples having a larger lignin content but the number of grafts formed increased proportionally up to lignin content of about 2.5%. Ceric ion reacted at a faster rate with lignin than with cellulose in wood pulp, and the results indicating that the active sites formed on lignin by oxidation with ceric ion accelerate the formation of grafts and increase the number of grafts were obtained. But on the other hand, the active sites participated in the termination reaction of the growing graft polymer radicals to cause lowering of the average molecular weight of grafts.
Multiple glass transitions in butadiene‐acrylonitrile copolymers
Authors: Chandler Lyle A. , Collins Edward A. 
Published: April 2003

AbstractThe second order transition temperatures (Tg) have been determined for a range of compositions of polybutadiene‐acrylonitrile copolymers. It was found that copolymers having more than 36 percent acrylonitrile had a single Tg while copolymers with less than 36 percent acrylonitrile had two main Tg's. The analyses were carried out with differential thermal analysis (DTA). The two Tg's are interpreted as the result of incompatible phases which differ in BD and VCN ratio. The presence of two phases is discussed in terms of polymerization conditions and molecular structure.
Comparison of Fe2+H2O2 and Fe3+H2O2 initiation systems in graft copolymerization of cellulosic materials
Authors: Ogiwara Yoshitaka , Kubota Hitoshi 
Published: April 2003

AbstractStudies were carried out on decomposition of hydrogen peroxide by ferrous and ferric ions adsorbed on cellulosic materials (SP, SCP), scission of the cellulose chain and formation of grafts by graft copolymerization. As a result, it was found that the activity of ferrous ion is always higher than that of ferric ion, but there exists a common relation between the amount of decomposition of hydrogen peroxide and the number of grafts for all cellulose samples and kinds of metallic ions, and it was inferred that essentially, copolymerization takes place by the same mechanism irrespective of the kind of metallic ions. Consequently, it can be considered that the difference in degree of activity between ferrous ion and ferric ion is due to the difference in the decomposition mechanism of hydrogen peroxide by these metallic ions and it is assumed that the high activity of ferrous ion in graft copolymerization is due to the high hydrogen peroxide decomposition effect.
The stress cracking of polyamides by metal salts. Part I. Metal halides
Authors: Dunn P. , Sansom G. F. 
Published: April 2003

AbstractThe stress cracking of polyamides (nylons) by a number of metal salts, in aqueous and nonaqueous solutions, has been investigated. Many metal halides and halide‐like salts were found to be active stress‐cracking agents, while metal acetates and sulfates were inactive. Zinc chloride was found to be most active, and its activity was compared with other metal halides. Using a recording tensometer, time to crack initiation, time to crack‐through and time to rupture were determined. These parameters were found to be dependent on temperature, moisture content of the nylon, concentration of the cracking agent and level of stress. High values of all these factors favored rapid cracking. Cracking parameters were shown to be mainly independent of the surface geometry of the nylon and the hydrogen ion concentration of the cracking agent. Metal halides did not appear to cause any chain scission in the nylon and stress cracking was not due to hydrolysis or metal‐ion catalysed hydrolysis.
The stress cracking of polyamides by metal salts. Part II. Mechanism of cracking
Authors: Dunn P. , Sansom G. F. 
Published: April 2003

AbstractThe action of metal halides on polyamide (nylon 6) and secondary amide model compounds has been investigated, using infrared and NMR techniques. Metal halides, which are active stress cracking agents for polyamides, induce characteristic changes in the spectra of both nylon 6 and the model compounds. Two types of changes were observed, depending on the metal halide involved, and on this basis the metal halides have been classified as Type I or Type II. The spectral changes appear to be due to the formation of complexes between the amide group and the metal halide, and structures for these complexes are proposed. Type I metal halides, such as zinc, cobaltII, copperII and manganeseII chlorides, form complexes in which the metal atom is coordinately bonded to the carbonyl oxygen atom of the amide group. These agents cause stress cracking by interference with the hydrogen bonding in the polyamide. Type II metal halides, such as lithium, calcium and magnesium chlorides and lithium bromide in solution form proton donating, solvated, species which act as direct solvents for nylon 6 in a manner similar to phenols and formic acid. Type II agents appear to cause simple solvent cracking.
The stress cracking of polyamides by metal salts. Part III. Metal thiocyanates
Authors: Dunn P. , Sansom G. F. 
Published: April 2003

AbstractThe stress cracking of polyamide (nylon 6) by a number of metal thiocyanates in aqueous and nonaqueous solutions has been investigated. Lithium, zinc and cobaltII thiocyanates were the most active and their activity was compared with that of the corresponding metal halides. Stress cracking parameters were determined and the mechanism of cracking studied by infrared techniques. The action of metal thiocyanates on nylon 6 is similar to that of the corresponding metal halides. Some metal cobaltothiocyanates were also found to be active stress cracking agents.
Studies of water adsorbed on cellulosic materials by a high resolution NMR spectrometer
Authors: Ogiwara Yoshitaka , Kubota Hitoshi , Hayashi Shoichi , Mitomo Noriko 
Published: April 2003

AbstractA study of water contained in cellulose samples softwoods dissolving pulp (DP) and hardwoods semichemical pulp (SCP) by a high resolution NMR spectrometer indicated the presence of two regions, one where the width at half value decreased rapidly with increasing water content and the other where the width at half value decreased slowly. As a result of a treatment for increasing the hydrophilicity of cellulose fibers such as beating, swelling by sodium hydroxide, and hydrolysis with hydrochloric acid, the differential energy of water binding increased in the low water content region, whereas it either did not change or decreased in the high water content region in spite of an increase in the amount of water, which is subject to the influence of the cellulosic materials. A comparison of different cellulosic materials showed that the differential energy of water binding of SCP was larger than that of DP. Moreover, an investigation of the relationship between the width at half value and the temperature indicated that different temperature ranges exist regarding binding of water, and such ranges are affected greatly by the degree of beating and the water content of the sample.
Comments on the reactivity of methoxy pentadecyl phenyl isocyanate isomers
Authors: Carignan Yvon P. 
Published: April 2003

AbstractThe reactions of 2‐methoxy‐4‐pentadecyl phenyl isocyanate and 4‐methoxy‐2‐pentadecyl phenyl isocyanate with excess 2‐ethyl hexanol originally reported by Ghatge and co‐workers to follow zero order kinetics have been re‐examined on the basis of their data and shown to follow more realistically the product catalyzed pseudo first order kinetics. The new rate constant, ks (sec−1) for the spontaneous reaction and kp (li. mole−1 sec−1) for the product catalyzed reaction are found to be: ks = 0.57 × 10−6 and kp = 34 × 10−6 for 2‐methoxy‐4‐pentadecyl phenyl isocyanate and ks = 1.2 × 10−6 and kp = 82 × 10−6 for 4‐methoxy‐2‐pentadecyl phenyl isocyanate.
Estimation of the surface free energy of polymers
Authors: Owens D. K. , Wendt R. C. 
Published: April 2003

AbstractA method for measuring the surface energy of solids and for resolving the surface energy into contributions from dispersion and dipole‐hydrogen bonding forces has been developed. It is based on the measurement of contact angles with water and methylene iodide. Good agreement has been obtained with the more laborious γc method. Evidence for a finite value of liquid‐solid interfacial tension at zero contact angle is presented. The method is especially applicable to the surface characterization of polymers.
Kinetic studies on the cellulose–propylene system in presence of Ziegler‐Natta catalysts
Authors: Dankovics A. , Erdélyi J. , Koltai M. 
Published: April 2003

AbstractKinetics of the uptake of polypropylene by the cellulose were studied. According to the experimental results, the reaction begins with an induction period which cannot be explained on the basis of the reaction mechanism of Ziegler‐Natta catalysts. Most probable reason of this period may be the initial unsaturation of the system.Studies on the effect of concentration of the catalyst (TiCl4) showed that, above the order of magnitude of 10−2 mole/l, uptake of polypropylene by the cellulose is directly proportional to the concentration of TiCl4. The maximum catalytic activity was observed at the molar ratio of AlEt3 to TiCl4 equal to 1.5.Concentration of propylene supported by the cellulose can be increased by elevation of the temperature.By increasing the concentration or the specific surface area of the cellulose at a constant concentration of the cellulose at a constant concentration of the catalyst, a kind of saturation appears on the cellulose fibers with respect to the adsorption of the metal chloride. Thus, increasing the specific surface area does not involve an increase in the uptake of polypropylene, in fact, increasing the concentration of the cellulose results in a drop in the amount of propylene to be taken up.On the basis of the infrared spectroscopical and the X‐ray diffraction results, no differences were found between the mechanical mixture of the components and the cellulose fibers coated with polypropylene.Mechanical strength of paper sheets was poor compared with that of sheets from pure cellulose. Cellulose encapsulated with polypropylene can be used in the paper industry as an interlayer in laminated papers.