bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of crystallinity in polyester fibers by x‐ray methods
Authors: Włochowicz Andrzej , Jeziorny Andrzej 
Published: April 2003

AbstractThe methods of Hermans and Weidinger and of Wakelin et al. (the correlation and integral methods) were used to determine the degree of crystallinity in poly(ethylene terephthalate) (PET) fibers. A standarization of cutting of the amorphous background scattering in PET fibers, indispensable for the method of Hermans and Weidinger, is put forward. On using a partial standardization of the intensity diffracted and scattered in the fiber, namely, on taking into account the x‐ray density of the specimen, variability in the intensity due to differences in absorption in the specimen at different angles 2θ and variability in the specimen mass reflecting x‐rays in the function of the diffraction angle, good agreement of the PET fiber crystallinity values is observed.
Rheo‐optical studies of polyurethane block polymers
Authors: Seymour R. W. , Estes G. M. , Huh D. S. , Cooper S. L. 
Published: April 2003

AbstractStress and birefringence relaxation have been measured for two polyurethane block polymers at several temperatures to 140°C. Superposition of the stress curves is possible, but the existence of multiple relaxation mechanisms makes such a process of questionable validity. Simple superposition of the birefringence relaxation was not possible. The time and temperature dependence of the stress‐optical coefficient implies different mechanisms for mechanical and optical relaxation process. Analysis of the birefringence data requires consideration of nonorientational sources of birefringence.
Anisotropy of the dielectric relaxation of a crystalline polymer
Authors: Phillips P. J. , Kleinheins G. , Stein R. S. 
Published: April 2003

AbstractA theory which relates the change in the strength of absorption to the change in crystal orientation function is presented for the anisotropy of dielectric relaxation for the dipolar orientation change in an oriented crystalline polymer. Experimental measurements are presented for the α dielectric absorption of a stretched ethylene–carbon monoxide copolymer and compared with the orientation of crystals of this copolymer as determined by x‐ray diffraction.
Thermomechanical behavior of rubberlike materials
Authors: Peng T. J. , Landel R. F. 
Published: April 2003

AbstractA simple form of nonisothermal free energy function A(λ1, λ2, λ3, T) for rubberlike materials results from postulating that the entropy is a separable symmetric function of the extension ratios λi along the principal strain directions and considering the fundamental properties of rubberlike materials, i.e., that rubber elasticity is associated primarily with changes in entropy and the variation of elastic tension with changes in temperature is linear. The explicit representation of A is reduced to the Valanis‐Landel strain energy function for isothermal cases.
Nitric acid oxidation of irradiated polyethylene
Authors: Bodily David M. 
Published: April 2003

AbstractSamples of high‐density polyethylene were irradiated with x‐rays and oxidized with concentrated nitric acid to determine the location of unsaturated groups. Vinyl groups initially present in the polymer were rapidly oxidized to the extent of 85% and are assumed to be excluded from the crystals. Vinylene groups show a rapid oxidation followed by slow oxidation. The initial oxidation is about 35%, which is slightly greater than the 25% amorphous content of the polymer prior to irradiation. Diene groups are rapidly oxidized by nitric acid but are formed at about the same rate in crystalline and amorphous samples. This is interpreted to indicate that diene groups are formed throughout the polymer but form large defects in crystalline regions and are accessible to oxidation. Defects formed in crystalline regions during irradiation lower the melting point to a greater extent than predicted by the mole fraction of noncrystallizable units.
X‐ray study on the effect of moisture on the crystalline state of cellulose
Authors: Seitsonen Sulo , Mikkonen Ilkka 
Published: April 2003

AbstractA method is presented for measuring the change of the intensity of x‐ray diffraction peaks of cellulose specimens as a consequence of humidity changes of the specimens. Measurements performed showed a decrease of this intensity after drying pulp specimens initially kept in humid air. Thus the order in cellulose decreased during drying.
Domain structure of amorphous block copolymers cast from solution
Authors: Soen Toshiichi , Inoue Takashi , Miyoshi Katsunori , Kawai Hiromichi 
Published: April 2003

AbstractThree types of domain structures, namely spherical, rodlike, and lamellar, of A‐B and A‐B‐A (or B‐A‐B) block copolymers cast from solutions are discussed on the basis of a criterion that the structures originate at a critical micelle concentration as a result of microphase separation of the block segments and the micelles formed maintain their structures into the solid state without reorganization. It is concluded that the micelles shrink mostly in the direction perpendicular to the interface between the two phases within the micelles because of the appreciable orientation of the block segments in this direction. In other words, the spherical micelle shrinks isotropically to form a spherical domain having a diameter proportional to the 2/3 power of the degree of polymerization (molecular weight) of the corresponding block segment. Rodlike and lamellar micelles, on the other hand, shrink anisotropically to form rodlike and lamellar domains such that the diameter and the thickness of the respective domains are roughly proportional to the 1/2 power of the degree of polymerization of the corresponding block segment.
Polymerization of vinyl monomer with carbon disulfide–alkali metal complex
Authors: Yamaguchi Koichi , Minoura Yuji 
Published: April 2003

AbstractThe reaction of carbon disulfide with one or two equivalents of alkali metal (potassium‐ or sodium) was carried out, and the deep red reaction mixture obtained only in diethylene glycol dimethyl ether. The polymerization of vinyl monomers with this reaction mixture was studied. The reaction mixtures of mono‐ and dialkali metal with carbon disulfide induced the polymerization of N‐phenylmaleimide, methyl vinyl ketone, and acrylonitrile but did not induce the polymerization of methyl methacrylate and styrene. In the polymerization of acrylonitrile with this reaction mixture of carbon disulfide with monoalkali metal, the polymerization rate was found to be proportional to the initiator concentration and to the square of the monomer concentration. The activation energy was −1.1 kcal/mole. Similar results were obtained in the case of carbon disulfide with dialkali metal. The polymer yield increased with increasing solvating power of solvents, i.e., diethylene glycol dimethyl ether, dimethyl sulfoxide, hexamethylphosphoramide, dimethylformamide, tetrahydrofuran. In the copolymerization of AN with MMA, the copolymer obtained consisted almost of AN units.
High‐temperature aging of fluoropolymers
Authors: Brown Daniel W. , Wall Leo A. 
Published: April 2003

AbstractFluoropolymers including those of 3,3,3‐trifluoropropene, 2,3,3,3‐tetrafluoropropene, 3,3,4,4,5,5,5‐heptafluoropentene‐1, and their copolymers with tetrafluoroethylene, were aged in air and in its absence at 225 and 305°C. Intrinsic viscosities were measured before and after aging. Polymers of high tetrafluoroethylene content are most stable. In air the presence of tertiary hydrogens is associated with lowered stability but the presence of tetrafluoroethylene greatly mitigates this effect. Stress‐relaxation studies in air of a vulcanizate of 3,3,3‐trifluoropropene and tetrafluoroethylene cured by γ‐rays indicate that the vulcanizate degrades much more rapidly than the untreated polymer.
Alternating copolymers of styrene with tricyanoethylene and ethyl 2,3‐dicyanoacrylate
Authors: Noren G. K. , Hall H. K. 
Published: April 2003

AbstractEthyl 2,3‐dicyanoacrylate was prepared from ethyl 2,3‐dicyanopropionate. High molecular weight, 1:1 alternating copolymers of styrene with tricyanoethylene and ethyl 2,3‐dicyanoacrylate were prepared by bulk polymerization with the use of free‐radical initiators. Solution polymerization of styrene with ethyl 2,3‐dicyanoacrylate in acetonitrile gave the highest molecular weight copolymer (ηinh = 0.74). The copolymers showed unusual thermal properties, i.e., an initial break that was 50–75°C lower than that of polystyrene followed by the formation of an intermediate product that was fairly stable to approximately 500°C.
Photoinduced ionic polymerization. III. Cationic polymerization and copolymerization of cyclohexene oxide and α‐methylstyrene in the presence of pyromellitic dianhydride
Authors: Irie Masahiro , Tomimoto Setsuko , Hayashi Koichiro 
Published: April 2003

AbstractThe photoinduced ionic polymerization of cyclohexene oxide was studied in the presence of pyromellitic dianhydride. The polymerization is initiated by the excited chargetransfer complex between cyclohexene oxide and the electron‐acceptor and proceeds by a cationic mechanism. Photoinduced cationic polymerization of α‐methylstyrene was also observed in the presence of pyromellitic dianhydride. The initiation mechanism of the polymerization was elucidated by means of electron spin resonance measurements. The concentration of pyromellitic dianhydride anion‐radicals measured in this way was found to be proportional to the rate of polymerization. This result shows clearly that the photopolymerization is initiated by cation‐radicals formed from photoexcited donoracceptor complexes. The attempted photocopolymerization of cyclohexene oxide and α‐methylstyrene gave a mixture of homopolymers. The composition of the product depends on the wavelength of the light used.
Photosensitivity of polyvinylesters of substituted cinnamylideneacetic acids
Authors: Tanaka Hideaki , Sato Yoshimi 
Published: April 2003

AbstractSeveral polyvinylesters of substituted cinnamylideneacetic acids were synthesized and their photosensitivities were investigated. It was found that polyvinylesters of planar acids reacted photochemically effectively and were spectrally sensitized by usual triplet sensitizer. On the other hand, polyvinylesters of twisted acids exhibited poor photosensitive properties. Poly(vinyl α‐cyanocinnamylideneacetate) (PV‐V) was found to be an excellent photosensitive polymer with respect to both photosensitivity and thermal stability (or storage stability).
Alternative explanation for a saturation phenomenon exhibited by poly‐4(5)‐vinylimidazole and an anionic ester
Authors: Okamoto Y. , Overberger C. G. 
Published: April 2003

AbstractThe hydrolysis of a negatively charged ester, sodium 3‐nitro‐4‐acetoxybenzenesulfonate (NABS), catalyzed by poly‐4(5)‐vinylimidazole (PVIm) was reinvestigated under the conditions in which the substrate concentration was in excess of the catalyst concentration. The reaction was carried out under the same reaction conditions as previous work (28.5 vol‐% ethanol–water, pH 7.1, μ = 0.02, 26°C). Careful studies on the initial rate with a stopped‐flow spectrophotometer revealed that the initial rate at high NABS concentration did not level off (saturate) as much as expected from the previous results. This difference was ascribed to two factors. One was that in the previous study, we treated up to 5% hydrolysis, but in the present work up to 1% in order to determine the initial rate. The other was the relatively slow deacylation reaction of the intermediate, partially acetylated PVIm, which resulted in less efficiency of the catalysis. The slow deacylation was confirmed by the kinetics of the hydrolysis of NABS and also independently by measuring the deacylation rate of the acetylated (or acylated) PVIm. The deacylation was an intramolecular catalysis and the rate constant was about 0.1 min—1 in 28.5 vol‐% ethanol–water at pH 7.1 at 26°C. The whole process of the hydrolysis could be explained by a two‐step pathway: an initial burst acylation followed by the slow deacylation. The electrostatic interaction between the cationically charged imidazole groups and NABS seemed not strong enough to form a stable complex. Thus, potassium p‐toluenesulfonate showed no effect as a competing agent (inhibitor) against NABS.
Interaction of poly(styrene sulfonate) with polycations carrying charges in the chain backbone
Authors: Tsuchida Eishun , Osada Yoshihito , Sanada Kei 
Published: April 2003

AbstractThe interaction between sodium poly(styrene sulfonate) (NaSS) and side‐chain charged polycation polymer (pendent type) or main‐chain charged polycation polymer (integral type) has been studied. It was found that the polyion complex (the reaction product of these polyelectrolytes) of pendent–pendent type has an equimolar composition at any mixing ratio of two component polymers. However, a polyion complex of integral–pendent type can form a water‐soluble complex with a ratio of [polycation]/[polyanion] = 1/3, in addition to a complex with a equimolar composition. The mechanism of formation of this specific complex is discussed.
Polyampholyte synthesis by cyclopolymerization
Authors: Panzik Harold L. , Mulvaney J. E. 
Published: April 2003

AbstractThe syntheses of N‐2‐phenylallylacrylamide (I) and N‐ethyl‐2‐phenallylacrylamide (II) are described. Both monomers can be polymerized with radical initiators to form cyclopolymers although complete cyclization does not occur. Lewis acids (ZnCl2 in the case of I, Et1.5AlCl1.5 in the case of II) result in the formation of higher molecular weight polymers in a shorter period of time. Polymers of I and II have been hydrolyzed to polyampholytes. The copolymerization of α‐methylstyrene–acrylamide in the presence of azobisisobutyronitrile (AIBN) and ZnCl2 leads to the formation of a 1:1 copolymer, whereas styrene–acrylamide under the same conditions give a copolymer slightly dependent upon the monomer feed composition. Attempted cyclopolymerization of N‐allylacrylamide (monomer I without the phenyl group) with ZnCl2–AlBN was not successful, only crosslinked polymer being obtained. An explanation is offered for the fact that I does not form a perfect cyclopolymer, although the α‐methylstyrene–acrylamide system forms a 1:1 copolymer.
Thermal degradation of a polyphenylimide‐quinoxaline in air and under vacuum
Authors: Augl Joseph M. 
Published: April 2003

AbstractThree samples of poly{2,2′‐[N,N′‐bis(1,4‐phenylene)benzophenone‐3,3′,4,4′‐tetracarboxylimide‐6,6′‐bis(3‐phenyl‐quinoxaline)]} (PPIQ), were prepared, differing in molecular weights and polymer chain endings. Their thermal degradation in vacuo and in air was determined by isothermal weight loss measurements. As in the case of poly‐[2,2′‐(1,4‐phenylene)‐6,6′‐bis(3‐phenylquinoxaline)] (PPQ), the temperature coefficients of thermal degradation in air were independent of molecular weight. However, in contrast, the temperature coefficients were independent of the type of polymer endgroups. It is, therefore, concluded that, contrary to amino‐terminated PPQ's, polymer chain‐end unzipping of PPIQ is of minor importance during thermal‐oxidative degradation.
Application of dn/dc data for the determination of partial specific volumes of dissolved macromolecules. II. Partial specific volume of ovalbumin in aqueous solution
Authors: Heller Wilfried , Schwartz Ellen Shirley E. 
Published: April 2003

AbstractThe theory of an interferometric method for determining partial specific volumes of macromolecules is briefly reviewed. The experimental technique developed in this laboratory is described. Detailed results are given on the partial specific volume of ovalbumin in aqueous solution and its dependence on pH and KCl concentration. The results are compared, as far as possible, with dilatometric results obtained in another laboratory. The contribution of a change in partial specific volume of the macromolecules and in the partial specific volume of the water associated with them to the results is analyzed, and the scope of a possible complication due to changes in molecular polarizability is pointed out.
Delayed yielding in glassy polymers
Authors: Matz David J. , Guldemond William G. , Cooper Stuart L. 
Published: April 2003

AbstractA theoretical description of the ductile transition of glassy polymers in tensile creep is given. It predicts the delay time for plastic yield as a function of stress. The model assumes first‐order rate expressions for the rate of change of loadbearing elements. The rate constants are given by a modification of the absolute reaction rate concepts of Eyring, where the energy barrier for breakdown of the bonding elements is asymmetric. This leads to an equation for the yield delay time as a function of the height of the energy barrier in the unstressed state, an activation volume, and a critical stress required to overcome the initial barrier asymmetry. The model has been compared to creep delay time experiments on polysulfone, polycarbonate, and poly(methyl methacrylate). It is able to predict the stress dependence for the onset of ductility in these materials with greater accuracy than previously reported equations.
Stress—strain behavior of a polyurethane rubber in combined torsion and tension or compression
Authors: Mancke Ralph G. , Landel Robert F. 
Published: April 2003

AbstractThe biaxial response, in combined torsion and tension or compression, of a highly crosslinked polyurethane elastomer has been measured at room temperature under equilibrium conditions with the Becker‐Landel torsion‐tension tester. Cylindrical specimens of four different aspect ratios were studied. Axial strains ranged from −33% to + 17%, and twists from 0 to 0.83 radians/cm. End effects were avoided by measuring both strains in the gage length at the center of the specimen. A small error in the twist parameter, probably arising from slight misalignment of the instrument, was unresolved. Within this error the normal forces and moments of all the specimens conformed to the neohookean (Mooney‐Rivlin with C2 = 0) stored energy function for incompressible materials, and the moduli measured in extension and compression were equal.
Etching of crystalline poly(ethylene terephthalate) by hydrolysis
Authors: Miyagi Arata , Wunderlich Bernhard 
Published: April 2003

AbstractConditions have been found for the etching of poly(ethylene terephthalate) with water so that the crystalline portions alone remain. Initial sample and hydrolysis products are analyzed by extraction of low molecular weight products; density, viscosity molecular weight, and endgroup determination; heating‐rate‐dependent thermal analysis; low‐angle and wide‐angle x‐ray analysis; and electron microscopy. On hydrolysis of a 67% crystalline polymer at 180°C for about 300 min, almost fully crystalline extended‐chain oligomers can be obtained with about 65% yield. The morphology of melt‐crystallized poly(ethylene terephthalate) and the melting behavior of oligomer lamellae are discussed.
Investigation of molecular orientation distributions by polarized raman scattering and polarized fluorescence
Authors: Bower D. I. 
Published: April 2003

AbstractIt is assumed that the intensity of the vibrational Raman scattering from each of the structural units (molecular segments or crystallites) in an oriented polymer solid is determined by a symmetric second‐rank tensor. The distribution of orientations of the principle axes of the tensors is expanded in a series of generalized spherical harmonics, Zlmn(θ)e−imψe−inϕ, and it is shown that relations among the coefficients in this expansion can be obtained from suitable intensity measurements using polarized radiation. If the orientation of the tensor axes within the structural unit is known (in the general case, for several Raman lines), then the coefficients Mlmn of a similar expansion for axes fixed in the units can be obtained for l, m, and n even and l ≤ 4. The limitation to even m follows from the assumption that the solid has at least orthotropic statistical symmetry but the limitations on n and l arise from the nature of the Raman effect. Some simple special cases are considered and some orientation‐independent intensity sums are derived. It is shown that, with the simplifying assumption usually made, the theory of the polarized fluorescence method for determining molecular orientations is a special case of the theory for the Raman method.
Chain‐backbone motion in glassy polycarbonate studied by polarized infrared spectroscopy
Authors: Lunn A. C. , Yannas I. V. 
Published: April 2003

AbstractChain‐backbone motion in glassy polycarbonate has been investigated both under isothermal stress, and also under zero stress during isothermal annealing of freely contracting film specimens. In both types of experiment, backbone motion was detected by measuring the change in infrared dichroism. The dichroism of absorption bands at 1364 and 2971 cm−1, which have transition moment vectors directly related to the chain‐backbone orientation, was studied. Under tensile stress in the homogeneous region of deformation, changes of up to 2.2° in the mean chain‐backbone orientation angle were measured at 23°C. With the onset of cold drawing a total orientation change of some 8° was observed. For the isothermal annealing experiments, a film specimen holder employing conductive heating with radiative losses was employed. It enables infrared measurements to be made while the temperature of the contracting specimen is maintained constant to ± 0.5°C. Oriented specimens were prepared by isothermal stretching of polycarbonate films to strains of the order of 100%. Changes in the mean chain‐backbone orientation angle were observed during annealing of these oriented films at temperatures between 80°C and the glass transition (149°C). Chain motion proceeded during annealing, and chain segments were observed to move cooperatively. The temperature at which the polymer is prestretched has a pronounced effect on its subsequent relaxation during annealing: when the sample was stretched at 23°C. motions were detected during annealing at temperatures as low as 81°C, while, if it was stretched at 154°C, no motion was detected at annealing temperatures below 127°C. The data are discussed in comparison with theories of the glassy state that predict the absence of chain‐backbone motion at temperatures significantly below the glass transition. A shift in frequency of the νa (CH3) absorption peak in stretched polycarbonate was measured by using polarized radiation. The effect was interpreted in terms of changes in the intermolecular bonding structure of the oriented polymer.
Photoelectric effects in poly(ethylene terephthalate) and polyethylene
Authors: Comins J. D. , Wintle H. J. 
Published: April 2003

AbstractPhotocurrents induced by ultraviolet illumination of poly(ethylene terephthalate) (Mylar) and polyethylene specimens supplied with aluminum electrodes in a sandwich configuration have been studied in the wavelength range 380–180 nm. A description is given of the precautions taken to ensure that artefacts such as photoelectric emission external to the specimen do not influence the measurements. In both materials, a fast and a slow transient are present. Measurements on polyethylene show that the magnitude of the response is linearly dependent on the light intensity and is essentially thickness independent. This behavior leads to difficulties in interpretation in terms of known conduction processes. In Mylar it is shown that hole injection from the positive electrode into the polymer is responsible for the observed currents, and evidence to associate a similar process with the effects in polyethylene is presented.