bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of polyformals of alicyclic diols
Authors: Jackson W. J. , Caldwell J. R. 
Published: April 2003

AbstractThe properties of the polyformals of several alicyclic diols were determined. Particularly unusual were the properties of the polyformal of 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol. The polymer of the 1 : 1 cis/trans diol mixture had a reversible transition in crystalline phase at about 177°C. and a crystalline melting point of 262°C. The polymer was soluble in chloroform and in hot toluene. It was resistant to hydrolysis, particularly alkaline hydrolysis. Physical properties were determined on molded specimens obtained by injection‐molding, on films obtained by casting and pressing, and on fibers obtained by melt‐spinning.
Color formation in polyurethanes
Authors: Beachell Harold C. , Son C. P. Ngoc 
Published: April 2003

AbstractThe pyrolysis of a polyurethane obtained from tolylene 2,4‐diisocyanate and ethylene glycol was studied in nitrogen, air, and oxygen from the double aspect of structural change and color formation. The dissociation of the polymer into its components followed by further reactions liberates diisocyanate, the corresponding diamine, and the polypseudourea ether, as well as other degradation products. The color is attributed to the yellowing of TDI, the oxidation of the diamine, and the presence of the polypseudourea ether.
Stress relaxation and hysteresis at various strain rates
Authors: Chang Franklin S. C. 
Published: April 2003

AbstractApplying the Boltzmann superposition principle on a generalized Maxwell model, an analysis of the relations between extension, relaxation, and hysteresis is presented, which shows that any one of these three can be calculated from the other two. It is shown that the relaxation modulus does not vary with strain rate when time is measured from the start of extension, except in the early period of relaxation. It is demonstrated that the first derivative of the ratio of extension stress‐strain rate with respect to time is the limiting value of the relaxation modulus. The short‐time end of relaxation modulustime curve can be readily extended for several decades of logarithm of time without resorting to the temperature effect. The results obtained from the treatment of experimental data on polyisobutylene verify the theoretical deductions, which may also be considered as an additional explicit proof of the Boltzmann superposition principle.
Geometry effects and high speed tensile behavior in styrene polyblend systems
Authors: Lund J. Kenneth 
Published: April 2003

AbstractCritical specimen geometry parameters are varied to determine their effect on tensile behavior as a function of rate of testing. Their influence on elongation and energy absorption is pronounced, particularly at low values of specimen cross sectional area and thickness. These effects are attributed to surface imperfections resulting from specimen preparation, and to changes occurring in the combined stress pattern in the specimen. High speed photography and microscope analysis techniques have been developed to determine strain, strain distribution, and strain rate in the specimen gage section during deformation. Elongation measured outside the gage section can be a significant portion of overall specimen deformation; actual strain rate is a fraction of that obtained by assuming all deformation takes place in the gage section. Experimentation is statistically designed and the data statistically analyzed by sequential factorial analysis. Tensile stress response surfaces are accurately predicted by this technique.
Fire‐retardant polyesters based upon 2,3‐dicarboxy‐5,8‐endomethylene‐5,6,7,8,9,9‐hexachloro‐1,2,3,4,4a,5,8,8a‐octahydronaphthalene anhydride
Authors: Roberts Carleton W. , Haigh D. H. , Rathsack R. J. 
Published: April 2003

AbstractThe Diels‐Alder adduct of cis‐4‐cyclohexene‐1,2‐dicarboxylic anhydride (II) with hexachlorocyclopentadiene, 2,3‐dicarboxy‐5,8‐endomethylene‐5,6,7,8,9,9‐hexachloro‐1,‐2,3,4,4a,5,8,8a‐octahydronaphthalene anhydride (compound III), has been incorporated as the fire‐retardant component in polyester compositions. The structure of compound III possesses inherent properties which are exhibited as improved thermal and light stability in the derived polyesters; these improvements are based upon comparisons with polyesters prepared from the chlorendic anhydride, the fire‐retardant moiety in some commercial self‐extinguishing polyesters.
Structural characterization of vulcanizates. Part III. The cis‐1,4‐polyisoprene tetramethylthiuram disulfide–zinc oxide system
Authors: Moore C. G. , Watson A. A. 
Published: April 2003

AbstractThe vulcanization of a purified synthetic cis‐1,4‐polyisoprene (100 parts) with tetramethylthiuram disulfide (TMTD; 4 parts) and zinc oxide (4 parts) at 140°C. yields a network which at short cure time (15 min.) is structurally complex, containing 13.5 atoms of sulfur and 4.3 atoms of nitrogen per chemical crosslink present. The network becomes progressively simpler in structure as crosslinking proceeds, and at full cure (10 hr.) contains 3.2 atoms of sulfur and 0.7 atoms of nitrogen per chemical crosslink present. The initial network complexity is due mainly to the presence of rubber‐bound intermediate compounds, R·SxC(:S)N(CH3)2 (R = polyisoprenyl; x ≥ 2), which yield sulfidic crosslinks and zinc dimethyldithiocarbamate (ZDMC) on heating with zinc oxide or zinc sulfide as revealed by the efficient crosslinking on further heating at 140°C. of extracted undercured vulcanizates. Evidence is presented that the intermediate compounds result from interaction of the polyisoprene with a sulfurating species formed by a prior reaction of TMTD with zinc oxide, and not, as previously supposed by others, by direct reaction of the polyisoprene with TMTD. Our knowledge of the detailed structure of the network obtained at full cure is presented, together with estimates of the principal extra‐network compounds (ZDMC, tetramethylthiourea, and zinc sulfide) formed at full cure; these compounds together with the sulfur and nitrogen combined in the network account for ca. 90% of sulfur and nitrogen originally present as TMTD.
Stress relaxation of unaccelerated natural rubber–sulfur vulcanizates before and after treatment with triphenylphosphine
Authors: Dunn J. R. , Moore C. G. , Trego B. R. 
Published: April 2003

AbstractThe aerobic and anaerobic stress relaxation of unaccelerated natural rubber–sulfur vulcanizate networks has been examined before and after treatment with triphenylphosphine, a reagent which converts polysulfidic crosslinks into di‐ and monosulfide crosslinks. This treatment reduces the rate of anaerobic stress relaxation and makes the network more susceptible to protection by zinc dibutyldithiocarbamate against aerobic stress relaxation. Aerobic stress relaxation of the network after treatment with triphenylphosphine remains nonautocatalytic, indicating that it still contains the precursor of an antioxidant, and crosslinking continues to occur during aging, showing that the presence of polysulfide groups is not a sole prerequisite for such network formation.
Investigations on thermal dehydrochlorination of poly(vinyl chloride)
Authors: Crosato‐Arnaldi A. , Palma G. , Peggion E. , Talamini G. 
Published: April 2003

AbstractThe thermal dehydrochlorination of PVC has been examined on some samples prepared by fractionation of a commercial PVC, and some other samples obtained by polymerization at different temperatures. The results disagree with the concept of a continuous dehydrochlorination from one side to the other of the chain, that necessitates initiating structural anomalies in the macromolecule itself.
The influence of fillers and degree of vulcanization on the mechanical properties of hard rubber polyblends
Authors: Meltzer T. H. , Dermody W. J. 
Published: April 2003

AbstractHard rubber polyblends, made from SBR–butyl rubber mixtures vulcanized with sulfur, show several consistent patterns of behavior in response to recipe modifications or changes in degree of vulcanization. Tg increases with degree of vulcanization, reinforcing fillers raise the modulus, and reversion is encountered upon overcure as in SBR hard rubber. The dual or stepwise transition from glassy to rubbery modulus behavior which characterizes polyblends is clearly distinguishable in all of the mixtures. The level of the polyblend modulus plateau between glassy and rubbery behavior is dependent on the proportion of butyl in the blend. The range of temperatures spanned by the polyblend modulus plateau is dependent on the degree of vulcanization of the hard rubber portion of the blend. Hard rubber dust suppresses the characteristic stepwise transition of the polyblend in proportion to the amount of dust added. The changes in the other mechanical properties investigated are consistent with the changes in modulus. The impact resistance of the polyblend appears to be effectively limited by the impact resistance of the hard rubber portion at all degrees of vulcanization.
Factors influencing the properties of pectic acid films
Authors: Masters A. T. , Richards G. N. 
Published: April 2003

AbstractA pectic acid, extracted in 11% yield from tobacco stems, contains 93% anhydrogalacturonic acid and some galactose. Plasticized films have been cast from water solution and the influences on tensile properties of casting temperature, extent of neutralization, nature of cation, and plasticizer (glycerol) content have been studied. The crystallinity of the pectate films is shown to increase very markedly with neutralization by sodium hydroxide in the range 40–100% neutralization. The ion exchange capacities of sodium hydrogen pectate films for alkaline earth cations are discussed.
Relationships between molecular weight, solution viscosity, and melt index for narrow distribution, high pressure polyethylene whole polymers. Fast M̄n determinations
Authors: Mortimer George A. , Daues Greg W. , Hamner William F. 
Published: April 2003

AbstractMelt and solution viscosity properties of laboratory‐prepared batch polymerized high pressure polyethylene have been found to correlate well with molecular weight. These polymers have narrow and nearly constant molecular weight distributions and contain essentially no long‐chain branches. Short‐chain branching was found to have little or no effect on the relationships. Polyethylene made in the same reactor having long‐chain branches had melt and solution viscosity properties which deviated seriously from these relationships. The deviations serve as a semiquantitative measure of long‐chain branching. When long‐chain branching is absent, the correlations serve as rapid methods of determining M̄n for narrow‐distribution polymers.
The effect of temperature on polyacrylate‐and CMC‐treated drilling muds
Authors: Williams S. A. 
Published: April 2003

AbstractViscometric and filtration properties have been studied at 80°F. and at elevated temperature for a saturated gypsum mud and a 20,000 ppm sodium chloride mud, treated with an acrylate‐acrylamide copolymer (0.62 mole fraction sodium acrylate) and with sodium carboxymethyl cellulose (CMC). In the muds containing CMC and also for the acrylic polymer in the sodium system, the observed plastic viscosity decrease (at 175°F.) and the API filter loss increase (at 200°F.) were about what one would predict from the change in the viscosity of water with temperature. In contrast, the polyacrylate‐treated gypsum mud showed a viscosity increase, rather than a decrease, at the elevated temperature, and the API filter loss increased to a level substantially greater than would have been predicted on the basis of the change in the viscosity of water. This anomalous behavior of the acrylate‐treated system is interpreted as evidence of polymer‐calcium ion‐clay interaction. Data are presented to illustrate the extent of degradation of the acrylic polymer and CMC in a gypsum mud when heated for 16 hr. at 350°F. under a nitrogen atmosphere. The room temperature filter loss of the acrylate‐treated mud was scarcely changed after this treatment, while the filter loss of the CMC‐treated system was comparable to that of the blank mud. These results show that, from an operational point of view, CMC was completely degraded. Despite the apparent stability of the acrylic polymer, its usefulness is severely restricted by the high viscosities and filtration rates observed at elevated temperatures in the presence of calcium ions.
Interfacial polycondensation. I. The formation of surface graft polymers on wool
Authors: Whitfield R. E. , Miller L. A. , Wasley W. L. 
Published: April 2003

AbstractBy means of interfacial polycondensation, ultrathin coatings of polyamides, polyurethanes, polyureas, polyesters, polycarbonates, and various copolymers can be formed on the surface of a substrate. If the substrate contains reactive groups (such as NH2, OH, NCO, COCl, etc.), graft polymer is formed. The graft polymer is not removed by extensive extraction with good solvents for the polymer. In contrast, if wool is used as a substrate and is acetylated prior to the polymerization (to block the grafting sites), the thin coating of polymer is readily extracted. Digestion of the treated wool with enzymes that react with the wool, but not with the grafted coating, permits a characterization of the grafted polymer; amino acid analysis of the residue from the enzyme digestion provides evidence that the grafting sites on the wool are probably the free amino and hydroxyl groups located in the N‐terminal amino acids or internal amino acids containing these groups in their side chain.
On the characterization of non‐newtonian flow. III
Authors: Sabia Raffaele 
Published: April 2003

AbstractA method is developed for testing extrapolation procedures of shear stress–shear rate data by using the dependence of the flow activation energy on shear. Three polyethylene types are studied, and it is concluded that the difference in flow activation energy observed between conventional low density polyethylene and high density polyethylene is due mainly to long chain branching.
On establishing mechanisms of radiation‐induced network formation in high polymers
Authors: Spiro J. G. , Winkler C. A. 
Published: April 2003

AbstractIn an effort to develop new techniques for studying the effects of irradiation on high polymers, the influence of molecular weight distribution has been investigated. From general mathematical expressions obtained by Saito, equations have been developed to be used for polymers of Schulz‐Zimm distributions, and their mixtures. According to the computations, it should be possible to distinguish between crosslinking and endlinking as alternative mechanisms of network formation, by comparing gelling doses for samples of different initial distributions. From gelling dose determinations for polystyrene samples of different polydispersities, it was confirmed that network formation in irradiated polystyrene takes place through crosslinking, in agreement with mechanisms suggested by several authors. It is believed that the simple technique described should be useful for studying radiation processes in polymers that form networks, especially since the method is insensitive to the extent of degradation.
Effects of morphology and molecular structure on tensile impact behavior of linear polyethylene
Authors: Pritchard R. , Dunn T. , Kelly P. 
Published: April 2003

AbstractAn instrumented tensile impact test which allows a load time curve to be obtained coincident with the energy to rupture values has been applied to the examination of a series of linear polyethylene homopolymers and copolymers of varying molecular weight and thermal history. The effect of test specimen geometry was also investigated. A morphological examination of these resins indicated a strong dependence of spherulite size on molecular weight, and to a much lesser degree on molding conditions; it appeared to be independent of comonomer. The overall crystallinity, as determined by both x‐ray and density methods, and crystallite perfection was increased by a slower crystallization rate, but was independent of molecular weight. The tensile impact strength (energy to rupture) was found to increase with molecular weight, and decrease on the introduction of comonomer. But the effect of thermal history gave rise to results which bore no clear‐cut relation to molecular and morphological parameters. The value of the instrumented tensile impact test is shown by the fact that these apparent anomalies can now be resolved by separating the elastic and plastic portions of the deformation. An increased level and perfection of crystallinity results in higher load bearing properties accompanied by a reduction in duration of impact. It is primarily the duration, rather than the peak load, which is affected by molecular weight. The main effect produced by changing from a type L (long) tensile impact specimen to a type S (short) was to reduce considerably the duration of the plastic region while simultaneously raising the maximum elastic load; this is thought to be associated with a more localized deformation and therefore a higher rate of strain.
Effects of composition and irradiation on the glass transition temperature of methyl methacrylate–styrene copolymers
Authors: Parker M. S. , Krasnansky V. J. , Achhammer B. G. 
Published: April 2003

AbstractThe glass transition temperatures of polystyrene, poly(methyl methacrylate), and copolymers prepared from their respective monomers were determined by using a volume dilatometer. The glass transition temperatures of polystyrene and poly(methyl methacrylate) were found to be 82 and 104°C., respectively. The glass transition temperatures obtained for the copolymers were between the values determined for each of the homopolymers and were a monotonic function of the polymer composition. The experimental values agree with predictions in the literature based on interpolation formulae. The effects of changes in composition and radiation‐induced crosslinking on the glass transition of the copolymer system are described.
Vulcanization with maleimides
Authors: Tawney P. O. , Wenisch W. J. , Van Der Burg S. , Relyea D. I. 
Published: April 2003

AbstractSeries of mono‐ and bismaleimides were evaluated as curing agents to determine the effect of structure on crosslinking ability. The activity of N‐phenylmaleimide derivatives (monomaleimides) as crosslinking agents is highly dependent upon the substituent on the phenyl group. The activity of bismaleimides is likewise affected by the nature of the moiety connecting the maleimide rings. Isomaleimides and itaconimides are less effective curatives. Initiators for the maleimide cures include peroxides and sulfur accelerators of the thiazole type. Saturated and unsaturated hydrocarbon rubbers, except those containing a high percentage of isobutylene units, are vulcanized by a maleimide–initiator system. One of the attractive features of a maleimide curing system is that the physical properties of the cured rubbers are independent of curing temperature. Further, these vulcanizates have the good aging characteristics typical of nonsulfur‐cured vulcanizates. In contrast to sulfur vulcanization, the maleimide curing systems do not markedly affect the ability of elastomers to crystallize when stretched. Therefore, the T50 test cannot be used to assess the state of cure of maleimide–natural rubber vulcanizates. Maleimides containing an appropriate second functional group can be used as self‐accelerating curing agents or as adhesives.
N‐chloro and N‐nitroso compounds as synergists for the self‐extinguishing action of bromine compounds in polystyrene
Authors: Ingram Alvin R. 
Published: April 2003

AbstractCompounds other than peroxides may be used to enhance the self‐extinguishing action of organic bromine compounds on polystyrene. The addition of certain chloramides or nitrosoamines converts some bromide‐containing polystyrene compositions from flammable to instantly self‐extinguishing. Two effective chloramides were N,N‐dichlorotoluene sulfonamide or N,N′‐dichloro‐N,N′‐diphenyl urea but they were of limited value because of hydrolysis by atmospheric moisture. The more effective nitrosoamines were N‐nitroso‐N‐methylaniline, N‐nitrosocarbazole and N‐nitroso‐diphenylamine. An undesirable characteristic of the three compounds is their inhibition of polymerization of styrene. The interaction of a nitrosoamine and an aliphatic bromine compound is apparent from the evolution of nitrogen, nitric oxide, and nitrous oxide. If the minimum temperature for gas evolution falls in the range of about 145–180°C. in a prescribed simple test, the nitrosoamine and bromine compound may be used for rendering polystyrene self‐extinguishing.
Penetration of water‐soluble polymers into cellulose fibers
Authors: Aggebrandt L. G. , Samuelson O. 
Published: April 2003

AbstractPolymetaphosphate and polyethylene glycol in aqueous solution are excluded completely from rayon fibers. Determinations of nonsolvent water (δ) with these reference substances give the same value which can be used as a measure of the true swelling. The polymers can, however, penetrate into porous areas present in cotton. The average polymer concentration inside these areas is lower than in the external solution. High speed centrifugation results in decreased δ values, which is explained by a compression of the porous areas. Higher δ values are obtained as the molecular weight of the reference substance is increased. With polymetaphosphate the δ values decrease when the external concentration is increased, whereas with polyglycol the δ value within a wide range is independent of the concentration.
Viscoelastic properties of styrene–acenaphthylene copolymers in the transition region
Authors: Schaffhauser R. J. , Shen M. C. , Tobolsky A. V. 
Published: April 2003

AbstractA series of styrene–acenaphthylene copolymers was prepared by thermal polymerization. Homogeneous samples were obtained except for those compositions where the initial concentration of styrene monomer was 40–60 mole‐%. Master curves and characteristic viscoelastic parameters were obtained for the homogeneous copolymers. The plot of Tg vs. copolymer composition yielded a linear relationship.
Poly(oxatetramethylene) glycol. II. Molecular weight distribution
Authors: Johnston Peter R. 
Published: April 2003

AbstractPolymer of 1200 molecular weight was prepared from tetrahydrofuran by using a catalyst mixture of ethylene oxide, BF3, and water. Fractionation was accomplished by washing a cyclohexane‐toluene solution with mixtures of methanol and water. Results, plotted on Poisson probability paper, showed that the distribution is somewhat broader than the Poisson.
Effect of structure on the glass temperature of polyamides
Authors: Temin Samuel C. 
Published: April 2003

AbstractA penetrometer method, for which validity was demonstrated, was utilized for measuring the glass temperatures of several polyamides. Adipic acid, sebacic acid, and hexamethylenediamine were used as representatives of linear aliphatic components of the nylons. Isophthalic acid, diphenic acid, and m‐xylylenediamine were employed to provide examples with phenyl rings in the polymeric chain. Piperazine was used to assay the effect of a rigid alicyclic ring. To provide bulky side groups, 9,9‐bis(2′‐carboxyethyl)fluorene and 9,9‐bis(3′‐aminopropyl)fluorene were utilized. Several new nylon salts and polyamides were prepared. The results illustrate the contribution of chain stiffness and side chain bulkiness to the glass temperature, Tg. Assuming, as did Rybnikar, a Tg of −65°C. for nylon 66 and other linear aliphatic polyamides, the elevation caused by inclusion of a m‐phenylene group in the chain was shown to be about 165°C. The piperazine ring had an effect at least equivalent to that of the m‐phenylene group. A single bulky side group elevated the glass temperature by about 185°C. over the value for linear aliphatic polyamides, the same increment observed in the cases of polyesters and addition polymers. A second bulky group made a smaller incremental addition to Tg. Thus, a value of Tg well below room temperature for linear aliphatic polyamides was found consistent with the present results.