bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile properties and equilibrium swelling of plasticized amorphous polyurethane rubbers
Authors: Oberth Adolf E. , Bruenner Rolf S. 
Published: April 2003

AbstractIncorporation of plasticizers or other inert, liquid diluents causes a profound weakening of rubbers. The modulus of elasticity and tensile strength decrease approximately with the square of the gel fraction v0 of rubber which was present at the time of formation of the three‐dimensional network. Equlibrium swelling of plasticized rubbers is well represented by v2m = kv0, where v2m is the volume fraction of rubber network in the swollen state, at equlibrium, and k a constant equal to v2m for the unplasticized rubber. This swelling law is independent of the way in which v0 is obtained; inert liquid diluents, comprising molecularly dispersed compounds, as well as suspensions of insoluble liquids, gases, and chemically inert, solid fillers yield the same relation. Further, it is independent of the chemical nature of solvent and rubber. It appears that also the mechanical properties of foams, liquid‐filled foams, and plasticized elastomers containing the same volume fraction of network rubber are very similar.
Contribution à l'étude de l'ionisation des films insolubles de polyélectrolytes stéréoréguliers
Authors: Jaffé J. , Ruysschaert J. M. , Bricman G. 
Published: April 2003

AbstractThe surface potentials of monolayers of poly(methacrylic acid) (PMA) have been studied as a function of the pH of the subsolution. The influence of the macromolecular configuration on the properties of the ionizable groups was more particularly investigated. Orientation of molecules in the monolayer may be imposed by the stereoregularity of PMA (isotactic, atactic) and by the nature of the interface (air–water, cyclohexane–water). The results are analyzed in terms of theories of the ionic double layer (Gouy model, Donnan equilibrium) which permit the determination of the degree of ionization α of the film. The value of α gives indications about the orientation of specific groups of the macromolecular chain, i.e., of the ionized monomer units. Indeed, at the air–water interface, the film of isotactic PMA is more acid than that of the atactic sample, and at the cyclohexane–water interface, the degree of ionization is greater than at the air–water interface. These properties are the consequence of a modification of orientation of the hydrophilic groups with respect to the aqueous phase as a function of the stereoregularity of the sample and the nature of the interface. The variation of α with the pH of the substrate phase may be used to calculate an intrinsic dissociation constant Ks° of the molecules in the film. The value of Ks° is not modified by spreading conditions and remains very similar to that obtained in solution.
Relation of initial supermolecular organization in crystalline polymer systems to the organization produced by stretching
Authors: Baranov V. G. , Gasparyan K. A. 
Published: April 2003

AbstractAn investigation of small‐angle scattering produced by polarized light from stretched and annealed polymer systems containing spherulites yields information on the supermolecular transitions that occur during such treatment. A series of semicrystalline polymer systems (films, fibers) show that stretching leads to deformation of spherulites and subsequent transformation to an orientational supermolecular order. The size of the single element C2 of the supermolecular order in the direction of stretching, determined from the distance between the layer lines of the scattering pattern, is related to the diameter D0 of the initial spherulites by the relation C2 = KD0λs, where λ, is the draw ratio of the macrosystem and K is a parameter determining the deformability of the spherulites. For polyethylene at room temperature K is unity and for polychloroprene it is 1.2. Changes of C2 after annealing and restretching of the systems also obey this ratio.
Dielectric absorption in oriented poly(vinylidene fluoride)
Authors: Kakutani Haruko 
Published: April 2003

AbstractThe dielectric behavior of poly(vinylidene fluoride) is affected by orientation and crystal modification. The loss peak caused by molecular motion of the molecules in crystalline regions appears at about 70°C (110 Hz) (α1 absorption) for the α form, and at about 110°C (110 Hz) (α2 absorption) for the β form. Orientation significantly affects the magnitude of the β absorption which appears at about −40°C. The very high value of the dielectric constant for stretched film is believed to be due to the orientation effect. The γ absorption, which is assumed to be local‐mode absorption, is not so much affected by orientation. An additional loss peak has been found at around 0°C in dynamic mechanical measurements, but the molecular mechanism is unknown.
Rheo‐optical studies of high polymers. XVII. Time‐temperature superposition of time‐dependent birefringence for high‐density polyethylene
Authors: Fukui Y. , Sato T. , Ushirokawa M. , Asada T. , Onogi S. 
Published: April 2003

AbstractThe strain‐optical coefficient and relaxation modulus were simultaneously measured for high‐density polyethylene at various temperatures ranging from 12 to 100°C. Not only horizontal but also vertical shifts were necessary to obtain smooth master curves by the application of time–temperature superposition. However, the relaxation modulus decreases with rising temperature while the strain‐optical coefficient increases. This behavior indicates that the variation of the relaxation modulus and the strain‐optical coefficient with time can not be explained by a decrease in crystallinity with rising temperature since a decrease in crystallinity usually causes a decrease in the strain‐optical coefficient with time can not be explained by a decrease in crystallinity with rising temperature since a decrease in crystallinity usually causes a decrease in the strain‐optical coefficient. It was emphasized that another explanation should be sought for the vertical shift in the time–temperature superposition of the time‐dependence curves of the relaxation modulus and the strain‐optical coefficient at various temperatures. The master curve of the strain‐optical coefficient at various temperatures. The master curve of the strain‐optical coefficient or the optical distribution function of relaxation times determined from it serve to distinguish the type and thermal history of the polyethylene.
ESR studies of the photodegradation of polyethylene containing trapped allylic free radicals
Authors: Shimada S. , Kashiwabara H. , Sohma J. 
Published: April 2003

AbstractChanges produced in γ‐irradiated polyethylene by subsequent ultraviolet irradiation have been investigated by ESR measurements, ultraviolet spectroscopy, and viscometric determination of average molecular weight. The photoinduced changes depend on the wavelength of irradiation. Upon irradiation at wave length greater than 3900 Å, main‐chain scission occurs by reaction of trapped allylic radicals:
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A reduction in molecular weight sndicated by this reaction was verified by fractionation experiments and molecular weight determinations.
Relationship between self‐seeded and epitaxial crystallization from polymer solutions: A potentially new method for molecular weight separation and a new decoration method for alkali halides
Authors: Carr S. H. , Keller A. , Baer Eric 
Published: April 2003

AbstractIt was established that polyethylene and polyoxymethylene crystallize epitaxially on NaCl cleavage faces over a temperature range in which the usual polymer single crystals dissolve but a crystallization memory remains due to very small quantities of self‐seeding nuclei persisting in the solution. By performing this epitaxial crystallization in the presence of self‐seeding nuclei, it could be established that epitaxial crystallization at these elevated temperatures involves only the very largest molecules in the distribution. Further, the self‐seeding nuclei themselves could be isolated for observation, and these results were found consistent with previous predictions. By utilizing both the adhesion of these nuclei to NaCl and the selective nature of the epitaxial crystallization, the largest molecules could be extracted and reintroduced again to the same or different solutions. This opens up the possibility of a novel kind of chromatography for the separation and characterization of the highest molecular weight end of a distribution to a sensitivity which cannot be approached by other methods. The epitaxy phenomenon itself, under the circumstances involved, provides a new decoration method for the study of the surface topography of alkali halides. The origin of such as epitaxy occurring at low supercoolings and terminating at a limiting thickness raises important questions regarding long‐range forces and some unsettled features in the theory of chain‐folded crystal growth in polymers.
Scattering of light from oriented polymer films. II
Authors: Stein R. S. , Hashimoto T. 
Published: April 2003

AbstractA statistical theory for the scattering of light from oriented polymer films is developed in terms of angularly dependent generalized correlation functions. Numerical calculations of scattering patterns are carried out for special cases. The scattering depends upon two types of distributions describing (1) the orientation distribution of optical axes of scattering elements and (2) the angular dependence of correlation in orientation between pairs of optic axes. These distributions are expanded in Fourier series (in a two‐dimensional treatment), the coefficients of which are functions of elongation and describe the elongation dependence of the scattering patterns.
Effect of temperature on the dynamic young's and shear moduli of unidirectional carbon fiber‐epoxy composite beams
Authors: Dudek T. J. 
Published: April 2003

AbstractThe resonance frequencies of unidirectional carbon fiber reinforced/epoxy composite beams were studied over the temperature range 24–225°C. Longitudinal Young's moduli E11 and longitudinal‐transverse shear moduli G12 were computed from the experimental data by the use of Timoshenko beam theory. The effects of transverse shear deformation (a function of E11/G12) were found to increase in importance with increasing temperature. Values of G12 were found to be approximately proportional to the shear modulus Gm of matrix material but were about 30% lower than predicted by the theory of Hashin and Rosen. The anisotropy of the carbon filaments and voids in the composite samples were proposed to account for the discrepancy between theory and experiment.
Dilute solution studies of pyrrone prepolymers
Authors: Berry G. C. , Rumon K. A. 
Published: April 2003

AbstractData on dilute solutions of a pyrrone “prepolymer” are presented and the tendency of this polymer to aggregate in certain solvents commonly used in dilute solution studies is discussed. It is concluded that reliable molecular weights can be determined if solvents that interact with the prepolymer through hydrogen bonding are used.
Polymeric nature of selenium crystallization. II. Crystallization kinetics and secondary crystallization
Authors: Crystal Richard G. 
Published: April 2003

AbstractThe crystallization of elemental selenium has been studied in light of present concepts of crystallization in organic polymers. Bulk‐crystallization kinetic data as measured by a dynamic density technique and spherulite growth‐rate data as measured by optical microscopy are presented for the temperature range 70°C to 160°C. Plots of extent of isothermal crystallization versus time were sigmoidal in shape. Spherulite growth rates were constant for a given temperature and reached a maximum at approximately 130°C. Evidence is presented for secondary crystallization in selenium, and a model is proposed for destruction of chain folds with interlamellar crystallization during the spherulitic‐to‐“metallic” transformation above 100°C.
Mass spectral characteristics of poly(2,6‐dimethyl‐1,4‐phenylene ether)
Authors: Wiley Richard H. 
Published: April 2003

AbstractThe mass spectral characteristics of poly(2,6‐dimethyl‐1,4‐phenylene ether), its monomer (2,6‐xylenol), and its dimer (3,5‐dimethyl‐4‐hydroxyphenyl 2,6‐xylyl ether) have been determined. The monomer and dimer show peaks for the molecular ions (122; 242 amu) and degradation patterns similar to those of o‐methylaryl ethers. Loss of methyl and cleavage of the ether with transfer of an o‐methyl hydrogen are observed. Metastable transitions are recorded corresponding to a loss of 15 from 122 and 56 from 107 amu (xylenol) and of 151 from 242 and 40 from 104 amu (ether). The polymer volatilizes readily at 380–400°C. (TGA shows rapid weight loss at 400°C) and gives sets of peaks at (N × 120) ± 14 up to 1080 (N = 9). The principal peak is at (N × 120) + 2, calibrated against PFA, and this is attributed to an ion of a volatilized oligomer. The oligomer is either present as such, is formed in a degradation process involving an ether redistribution, or is formed in a hydrogen transfer process in the ether cleavage reaction.
Mechanism of the three‐dimensional polymerization of glycol methacrylates. II. The system glycol monomethacrylate–glycol dimethacrylates–solvents
Authors: Kopec̆ek J. , Lím D. 
Published: April 2003

AbstractThe three‐dimensional polymerization of the system glycol monomethacrylate–glycol dimethacrylates–solvents has been studied. The kinetic dependences thus obtained were interpreted in terms of the dependence of rate constants of the individual reactions on the properties of the medium used. The three‐dimensional polymer formed was characterized in the range from medium to the highest conversions.
Formation of polyimides by COOH and CN reactions
Authors: Čefelín P. , Šebenda J. , Wichterle O. 
Published: April 2003

AbstractThe synthesis of linear polyimides by the addition of dicarboxylic acids to dinitriles has been investigated. Adipic, suberic, m‐ and p‐phenylenediacetic, isophthalic, and p‐cyanobenzoic acids as well as adiponitrile, m‐ and p‐phenylenediacetonitrile, and isophthalonitrile were studied. Fairly favorable results, low molecular weight polymers only, were obtained in the reaction of p‐phenylenediacetic acid with p‐phenylenediacetonitrile. The formation of polyimides seems to be restricted by the solubilities of the reactants and products as well as by the pK values of the starting dicarboxylic acid and of the acid which is formed.
Al(Cap)3 as initiator in the anionic polymerization of ε‐caprolactam at high temperature
Authors: Konomi T. , Tani H. 
Published: April 2003

AbstractMechanism for polymerization of ε‐caprolactam in the presence of both sodium and aluminum caprolactamate was investigated at 171°C. The role of Al(Cap)3 as an initiator was revealed. The apparent rate constant of propagation reaction decreased with the increase in the concentration of Al(Cap)3, as the two different metal salts interact even at 171°C. The activation energy of the overall polymerization reaction with this catalyst system was estimated to be 41.18 kcal/mole.
γ‐Radiation‐induced ionic polymerization of pure liquid styrene. III. Effect of temperature
Authors: Potter R. C. , Metz D. J. 
Published: April 2003

AbstractWe have extended our previously reported studies on the radiation‐induced ionic polymerization of styrene to higher dose rates and have covered a temperature range between 0 and 50°C. The data at 0°C are in striking agreement (up to 106 rad/hr) with the mechanism proposed by Williams, Okamura, et al.; on the other hand, styrene of the highest purity exhibits a very complex behavior with temperature variations, which does not agree with this mechanism. These apparent anomalies are presented and discussed. Data are also presented on the effects of adding dry oxygen or degassed water to pure styrene.
Copolymerization of propylene with acrylate by a Ziegler‐Natta type catalyst
Authors: Matsumura Kiichiro , Fukumoto Osamu 
Published: April 2003

AbstractPropylene was polymerized by using a Ziegler‐Natta type catalyst in the presence of ethylchloroaluminum acrylate, which was formed by the reaction of diethylaluminum chloride with acrylic acid. The polymer obtained contained acrylic units which were proved to be copolymerized with propylene units by solvent extraction, infrared spectrum, and NMR spectrum. The copolymer showed much improved properties compared with the polypropylene homopolymer.
Influence of monomer concentration on the structure of poly(methyl methacrylate) polymerized by butyllithium
Authors: Amerik Y. , Reynolds W. F. , Guillet J. E. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate has been studied in toluene and tetrahydrofuran solution at −78°C using butyllithium as catalyst. The structure of the polymer produced was determined by analysis of the α‐methyl groups using 100 MHz NMR. It is shown that in a noncomplexing solvent such as toluene, the number of isotactic triads increases from 70% to 93% as the monomer concentration during polymerization is reduced from 5 mole/l. to approximately zero. The value of Pss/Pis depends strongly on monomer concentration, and hence any calculations regarding penultimate effects in such systems should be made at close to zero monomer concentration. In the THF solution the penultimate effect is nearly independent of monomer concentration, and both Pii/Psi and Pss/Pis are close to unity. The results may be explained in terms of a mechanism of the polymerization process in which toluene does not complex with the active site, while monomer and THF are weak and strong complexing agents, respectively.
Synthesis and investigation of polybenzimidazoles containing alkyl substituents in aromatic nuclei
Authors: Korshak V. V. , Teplyakov M. M. , Fedorova R. D. 
Published: April 2003

AbstractPolybenzimidazoles have been synthesized from 3,3′‐diamino‐5,5′‐dimethylbenzidine, 3,3′,4,4′‐tetraamino‐5,5′‐dimethyldiphenylmethane, bis(3‐amino‐4‐methylamino)phenylmethane, bis(3‐amino‐4‐methylamino‐5‐methyl)phenylmethane, and diphenyl esters of adipic, sebacic, isophthalic, and terephthalic acids and 4,4′‐dicarboxydiphenyl oxide by solid‐phase polyheterocyclization. Properties of the polybenzimidazoles have been studied. The polymers have high thermal stability. They are soluble in a number of organic solvents and give strong, elastic films. Solubility and thermal stability of polybenzimidazoles is determined by the methyl group position in the polymeric chain. The influence of other alkyl substituents on properties of polybenzimidazoles have been investigated. The polymer structure has been studied by infrared and PMR spectroscopy and elemental analysis.
Anionic copolymerizations of acrylonitrile with β‐propiolactone
Authors: Katayama Shitomi , Horikawa Hideichi , Masuda Noboru 
Published: April 2003

AbstractAnionic copolymerizations of acrylonitrile (monomer 1) with β‐propiolactone (monomer 2) and the structures of the resulting copolymers were studied. The copolymerization with sodium cyanide in N,N‐dimethylformamide gave copolymers of the structure I containing acid anhydride linkage in the molecular chains, with the monomer reactivity ratios, r1 = 1.20, r2 = 0.00.
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The copolymerization with potassium hydroxide gave either copolymers of the structure II (r1 = 0.00, r2 = 3.64 at 30°C; r1 = 0.00, r2 = 5.00 at 40°C) in N,N‐dimethylformamide or only β‐propiolactone homopolymer in toluene.
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Anionic copolymerization of p‐anisaldehyde with dimethylketene
Authors: Hashimoto Kazuhiko , Sumitomo Hiroshi 
Published: April 2003

AbstractAnionic copolymerization of p‐anisaldehyde (ANA) with dimethylketene (DMK) was made with use of benzophenone–dilithium complex as an initiator at −78°C in a high vacuum. In spite of a copolymerization in such a good polar solvent as tetrahydrofuran, the composition of the copolymer was nearly exactly 1 : 1 over a quite wide range of the monomer feed. From the analytical data of the product after the hydrogenolysis of the copolymer with lithium aluminum hydride, the copolymer was found to have a structure resulting from the alternating addition of the CO double bond of ANA to the CC double bond of DMK. No copolymerizations of ANA with phenyl isocyanate and methyl isocyanate take place under the same conditions.
Chain scission of butyl rubber by nitrogen dioxide. II. Photo‐oxidation as function of nitrogen dioxide, oxygen pressure, and temperature
Authors: Jellinek H. H. G. , Hrdlovic P. 
Published: April 2003

AbstractStudies of chain scission of butyl rubber (1.75% by weight of isoprene) have been extended. Experiments showing chain scission as function of various oxygen and nitrogen pressures, temperatures, and near‐ultraviolet light intensity are presented. The experimental data agree with the mechanisms assumed in previous work or with elaborations of such mechanisms to include additional factors (ultraviolet radiation etc.). NO2 retards chain scission in presence of near‐ultraviolet light. Photo‐oxidation in presence of relatively high and low nitrogen dioxide pressures, respectively, show experimental curves of opposite curvature; these data have also been evaluated in terms of méchanism. Arrhenius equations are presented for experiments related to the different reaction mechanisms.
Degradation of polymers and morphology: Photo‐oxidative degradation of isotactic polystyrene in presence of sulfur dioxide as function of polymer crystallinity
Authors: Hrdlovic P. , Pavlinec J. , Jellinek H. H. G. 
Published: April 2003

AbstractThe photo‐oxidative chain scission of isotactic polystyrene films has been studied as a function of the degree of crystallinity, SO2, and NO2 pressures, and temperature. The rate of chain scission increases in the presence of SO2 with extent of crystallinity. It is assumed to be faster due to strain in and near the folds in the crystalline areas than in the amorphous regions. In the presence of NO2, chain scission increases up to about 8% crystallinity but subsequently becomes constant with further increase in crystallinity. It is suggested that the diffusion rates of oxygen and nitrogen dioxide into the films decrease with increasing crystallinity. These two processes compensate each other.
Polymerization, copolymerization, and terpolymerization of 1‐isopropylidene‐dicyclopentadiene by anionic coordination catalysts
Authors: Cesca S. , Bertolini G. , Santi G. , Duranti P. V. 
Published: April 2003

AbstractA detailed investigation of the terpolymerization reaction of ethylene and propylene with 1‐isopropylidene‐dicyclopentadiene (II) was carried out by empolying vanadiumbased anionic coordinate catalysts [preferentially V(Acac)3AlEt2Cl]. The influence of some polymerization parameters, i.e., concentration of II, of the catalyst; polymerization time, etc., were particularly examined. The catalysts were found to be active in C2H4II copolymerization also, but neither C3H6II copolymer nor II homopolymer were obtained. By using the 5,6‐dihydro derivative of II as comonomer, it was found through ultraviolet, infrared, and NMR analyses that the incorporation of II in polyethylene or ethylene–propylene chains took place randomly and by selective opening of the norbornene double bond. The quantitative determination of the unsaturation present in C2H4C3H6II terpolymer was studied by means of absorption of iodine halides and through a spectroscopic ultraviolet method. Reference was made to terpolymer samples containing 14C‐labeled II. The content of II was generally less than 35 wt‐% both in copolymer and in terpolymer prepared. The relatively high reactivity of II is discussed in terms of norbornene ring strain and compared with the reactivity of 1‐isopropylidene‐3a,4,7,7a‐tetrahydroindene (I) previously reported.