bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton spin–lattice and spin–spin relaxation times in isotactic polypropylene. II. Effects of stretching ratio and temperature
Authors: Tanaka Hiroshi 
Published: April 2003

AbstractProton spin–lattice, T1, and spin–spin, T2, relaxation times of uniaxially stretched polypropylene film were measured at 40°C using a wide line pulse spectrometer operating at 19.8 MHz. T1l, the longer T1, increases almost linearly with increasing stretching ratio, and T2a, T2 of the amorphous region, decreases gradually as the stretching ratio is increased. These results can be interpreted in terms of the increased constraints to molecular motion in the amorphous region. The fraction of the rigid protons in the sample, Fc, increases with increasing stretching ratio, while the crystallinity calculated from the density, Xd, does not change largely. The difference between Fc and Xd, therefore, increases as the stretching ratio is increased. This indicates that the physical structure of the highly stretched sample is far from the ideal two‐phase model. The influence of the stretching temperature was also investigated. There are only slight increases in T1l and in Fc for the samples stretched in a temperature range from 80°C to 150°C, whereas the considerable increase in T2a occurs. The most notable change introduced at a high temperature stretching is the increase in the chain mobility in the amorphous region.
Highly deacetylated chitosan and its properties
Authors: Mima Seiichi , Miya Masaru , Iwamoto Reikichi , Yoshikawa Susumu 
Published: April 2003

AbstractA preparative method has been established for obtaining chitosan products which have a desired degree of deacetylation of up to virtually 100%. Effective deacetylation was attained by intermitently washing the intermediate product in water two or more times during the alkali treatment. The weight average molecular weight (M̄w) of the product, which was measured by gel permeation liquid chromatography, was about 5 × 105 at the highest deacetylation of nearly 100%, and the degradation of the molecular chain was not so significant. Tensile strength of the wet film increased markedly with increasing degree of deacetylation, while the dry film did not show a corresponding significant increase of the tensile strength. In the infrared spectra of chitosan film new sharp bands appeared especially at the high degree of deacetylation. This was attributed to increased “crystallization” brought about by high deacetylation.
Thermal and biological properties of tin‐modified cellulosic material derived from cotton
Authors: Carraher Charles E. , Burt W. R. , Giron David J. , Schroeder Jack A. , Taylor Michael L. , Molloy H. Michael , Tiernan Thomas O. 
Published: April 2003

AbstractThermal and biological properties of tin‐modified cellulose derived from cotton are described. The inception temperature of degradation for tin‐modified cellulosic products is inferior to that of cotton itself, but the heats of degradation in air are less than that of cotton consistent with the modified products being superior in this respect. Degradation of the modified materials in helium as monitored by coupled thermogravimetric analysis–mass spectroscopy shows that degradation occurs through a series of complex steps with the evolution of products characteristic of both the tin‐containing and cellulose materials. The tin‐modified cellulose was tested against five fungi using disk and protein assays. The fungi tested are typical and widespread, and these tests provide a good indication of the applicability of such products as retarders of fungi‐related rot and mildew. Most of the tested samples showed good inhibition of the tested fungi.
Deformation and failure of polymeric matrices under swelling conditions
Authors: Cohn Daniel , Marom Gad 
Published: April 2003

AbstractPolymers in which the diffusion mechanism was characterized by a sharp advancing boundary between the swollen shell and the core showed a highly anisotropic swelling response. The anisotropy of the swelling strains was caused by the mechanical constraints exerted mutually by the two regions of the specimen. The swelling stresses developing during the process eventually led to fracture of the polymer specimen. An analytical model which explained the modes of failure of the polymer under the swelling stresses was developed. The proposed approach was based on the general analogy existing between the studied swollen specimens and composite materials. A model for the prediction of the anisotropic hygroelastic response of the swollen systems was also proposed.
Stress–relaxattion of natural rubber under compression—depenndence on oxygen concentration
Authors: Stenberg B. , Dickman O. 
Published: April 2003

AbstractThe compression–relaxation was studied for unfilled TMTD‐vulcanized natural rubber cylinders (height = diameter = 20mm). The samples have been treated prior to compression in different oxygen media from an inert medium to pure oxygen at 2.0 MPa. Activation energies were calculated from compression–relaxation measurements made at different temperatures, and from these results conclusions were drawn concerning the diffusion control of the relaxation.
Comparison of polystyrene, poly(styrene/acrylonitrile), high‐impact polystryrene, and poly(acrylonitrile/butadiene/styrene) with respect to tensile and impact properties
Authors: Yokouchi Mitsuru , Seto Shinichi , Kobayashi Yasuji 
Published: April 2003

AbstractThe tensile behaviors of polystyrene (PS), poly(styrene/acrylonitrile) (SAN), high‐impact polystyrene (HIPS), and poly(acrylonitrile/butadiene/styrene) (ABS) were examined systematically in the wide range of strain rate, 1.7 × 10−4–13.1 m/s. When glassy and brittle PS was a criterion, the incorporation of a polar group (SAN) only strengthened the hardness, and the fracture mode was the same as for PS. The introduction of dispersed rubber particles (HIPS) weakened the hardness a little but offered a new deformation mechanism, i.e., microcrazing (whitening), and contributed to the improvement of impact strength. In the heterogeneous system, the enhancement of matrix strength [e.g., preorientation or blending with poly(phenylene oxide) for HIPS] makes possible another deformation mechanism, i.e., shear band formation (cold drawing), which is superior to microcrazing for achieving higher impact strength. ABS, which incorporates concurrently two factors (polar group to matrix phase and dispersed rubber particles), can be regarded as an enhancement of the matrix strength of HIPS. In spite of the remarkable magnitude of its impact strength compared with that of the other three polymers, the deformation mechanism of ABS was limited to microcrazing. This indicated that only the introduction of a polar group (as nitrile group) could not strengthen the matrix as much as preorientation or blending with poly(phenylene oxide).
Photopolymerization using sensitizers of binary system of aromatic hydrocarbon and amine
Authors: Kubota Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractPhotopolymerizations of acrylonitrile and methyl methacrylate, using binary sensitizers of aromatic hydrocarbon and amine, were investigated at 30°C in N,N‐dimethylformamide under the irradiation with a light of λ > 300 nm. Naphthalene, anthracene, and phenanthrene were employed as aromatic hydrocarbons in the experiment. The binary system was effective for the initiation of the monomers. The combinations of naphthalene with tertiary amines, triethylamine and N,N‐dimethylaniline, were remarkably effective among various combinations. The rate of polymerization with naphthalene–triethylamine sensitizer was observed to be proportional to the first, ½, and ½ powers of monomer, naphthalene, and triethylamine concentrations, respectively. The kinetics of the photopolymerization are proposed, and the initiation schemes are discussed, comparing them with those in the system sensitized by aromatic ketone–amine reported previously.
Photooxidation of amine crosslinked epoxies I. The DGEBA–DDM system
Authors: Bellenger V. , Verdu J. 
Published: April 2003

AbstractThe photooxidation in the solar UV range of tridimensional networks based on the diglycidyl ether of bisphenol A (DGEBA) and diaminodiphenyl methane (DDM) is characterized by the formation of carbonyl, amide, and hydroperoxide groups and by at least two types of chromophores. One absorbs strongly in the near UV, violet, and blue regions, and is responsible for the development of an internal screening effect leading to a decrease of photooxidation rate during exposure. The other, which absorbs in the red region (γmax = 615 nm), is responsible for the green color of oxidized smaples and is derived from the oxidation of the diamine bridge. The influences of hardener concentration and thermal treatments are explained in terms of a stabilizing effect of unreacted DDM molecules and a photoinitiating effect of some thermal‐oxidation products, presumably hydroperoxides.
Chemorheology of thermosetting resins. I. The chemorheology and curing kinetics of unsaturated polyester resin
Authors: Han Chang Dae , Lem Kwok‐Wai 
Published: April 2003

AbstractThe rheological properties and curing kinetics of a general‐purpose polyester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). It was found that, as cure progresses, the steady shear viscosity increases very rapidly with cure time at all shear rates investigated, and normal forces show negative values at low shear rates and positive values at high shear rates. The observed negative normal forces are believed to result from material shrinkage during cure, and positive normal forces from the deformation of large molecules, formed by crosslinking reactions during cure. Note that, in a cone‐and‐plate rheometer, the shrinkage force acts in the direction opposite to that of normal forces. It is, therefore, concluded that extreme caution is needed in the interpretation of normal force measurements with thermosetting resins, subjected to steady shearing flow. Dynamic measurements seem to offer some insight on the onset of gel formation. More specifically, we have found that, when the unsaturated polyester resin was cured at a fast rate, the time at which a maximum in the loss modulus G” occurs coincides reasonably well with the time tη∞ at which the steady shear viscosity η approaches infinity. However, at a slow rate of cure, the time at which tan δ equals unity agrees fairly well with tη∞. DSC measurement has permitted us to determine the degree of cure as a function of cure time and the kinetic parameters in an empirical expression for the curing kinetics advanced by Kamal and co‐workers. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various values of isothermal curing temperature.
Compatibility of nylon 6 and PMMA–oligoamide graft copolymer
Authors: Seo Seung Won , Jo Won Ho , Ha Wan Shik 
Published: April 2003

AbstractPMMA–oligoamide graft copolymers, which were prepared by reacting poly(methyl methacrylate‐co‐methacryloyl chloride) with oligoamide, were blended with nylon 6. The compatibility was examined by measuring thermal properties such as melting point and crystallization temperature. It was observed that the melting point was significantly depressed as the grafted PMMA was added to nylon 6, suggesting that the blend is a miscible system. It was concluded that hydrogen bonding between amide groups of the two polymers enhanced the miscibility.
Electrical and photovoltaic properties of Pb/trans‐ (CH)x and Pb/[CH(AsF5)y]x schottky barriers
Authors: Donckt E. Vander , Kanicki J. , Fedorko P. 
Published: April 2003

AbstractThe rectifying and photovoltaic properties of Pb/trans‐polyacetylene/graphite sandwich cells have been examined. The dependence of the short‐circuit current density (Jsc) and open‐circuit voltage (Voc) on light intensity have been determined. Some data on a Pb/AsF5 lightly doped polyacetylene graphite cell are also reported.
Semi‐ and fully interpentrating polymer networks based on polyurethane–polyacrylate systems. IV. Grafted semi‐1‐interpenetrating polymer networks
Authors: Hourston D. J. , Zia Y. 
Published: April 2003

AbstractA series of semi‐1‐IPNs containing 40% polyurethane and 60% polymethyl acrylate was synthesized using Adiprene L‐100, trimethylol propane, and polybutadiene diol. This diol was chosen to yield polyurethanes with a large number of potential graft sites for the methyl acrylate which was polymerized after the polyurethane network had been formed. A series of linear polyurethane–polymethyl acrylate blends, covering a range of compositions, was also prepared. The polyurethane for these polyblends was synthesized from Adiprene L‐100 and butane‐1,4‐diol. Both sets of materials were investigated by dynamic mechanical analysis. On the basis of a comparison of solubility parameters, the polyurethanes and polymethyl acrylate would be expected to be incompatible. In the dynamic loss modulus‐temperature plots of the polyblends there was a significant shift of the polyurethane Tg to higher temperature, but the polymethyl acrylate transition did not shift. The polyurethane transitions of the semi‐1‐IPNs were also shifted, but considerably more than in the case of the polyblends. For both systems, it was postulated that grafting had occured to a significant extent. With the semi‐1‐IPNs, it was found that as M̄c decreased the extent of grafting apparently increased. This was rationalized on the grounds that as the network chain lengths decrease, a higher proportion of the methyl acrylate monomer, prior to polymerization, was close to polyurethane segments and that this is a situation likely to lead to more grafting.
Dynamic moduli for short fiber‐CR composites
Authors: Ashida Michio , Noguchi Toru , Mashimo Satoshi 
Published: April 2003

AbstractThe dynamic moduli, E′ and E″, and tan δ for nylon–CR and PET–CR composites with unidirectional short fibers were studied as a function of temperature by using a Rheovibron. The temperature dependence of tan δ showed two dispersion peaks for nylon–CR composite. The peak at −28°C corresponded to the main dispersion of CR and the peak at 100°C to the α‐dispersion of nylon 6. For a PET‐CR composite, in addition to the individual dispersion of CR and PET, a small and broad peak was observed at about 90°C. The angular dependence of E′ indicated that the short fibers assumed good orientation. The storage modulus for the composites was given by the parallel model as E′ = Vf′Ef + VmE′m., where E′c, E′f and E′m were the storage modulus for the composite, fiber, and matrix and Vf and Vm were the volume fraction of fiber and matrix, respectively. In the transverse direction of fiber, the peak values of tan δ at −28°C were given by the following equation; tan δc = tan δm − δVf, where tan δc and tan δm are the loss tangent for the composite and matrix, respectively, and α is coefficient depending on fiber type. The results indicated that a region with strong interaction was formed between fibers and CR matrix.
A stochastic model for predicting the service life of photolytically degraded poly(methyl methacrylate) films
Authors: Martin Jonathan W. 
Published: April 2003

AbstractA stochastic model has been proposed and partially validated for predicting the service life of a nominal population of polymethyl methacrylate films subjected to photolytic degradation. Here, service life is defined as the time after which an unacceptable portion of a nominal population of PMMA films subjected to photodegradation have failed; failure occurs when a performance property of the film falls below a predesignated minimum value. The stochastic model has two parts. The first part uses a Poisson distribution in computing the probability that exactly K photon related chain scissions will occur in the film in the interval [0, t). The parameter of the Poisson distribution is made functionally dependent on temperature and the intensity of radiation absorbed. The second part determines the probability that a performance property will be greater than a minimum value after K chain scissions. This part is called the damage process. Together, the two parts of the model form a compound Poisson process. The main points of the models are validated against 25 published data sets. The plausibility of the Poisson process was substantiated for modeling the number of chain scissions occurring in the interval [0, t). Also, it was demonstrated that the expected change in two performance properties of the films was functionally related to the expected number of chain scissions.
Dynamic mechanical properties of partially oriented polyester (POY) and draw‐textured polyester (PTY) yarns
Authors: Miller R. W. , Murayama T. 
Published: April 2003

AbstractSpinning speed is one of the most important process parameters for change in properties of yarn and efficiency of polyester production. In this paper the effect of spinning speed (3000–6200 ypm) on dynamic mechanical properties is presented, and shows a good qualitative picture on the influence of structure change on the dynamic modulus and the height and position of glass transition peak on POY (partially oriented polyester) and PTY (draw‐textured polyester) yarns. The dynamic moduli of POY yarns in a temperature range of 25–160°C are increased with increasing spinning speed. Large glass transition peaks (α peak) are observed for POY yarn spun at 3000 and 2800 ypm at about 98°C. This indicates that the yarns are low oriented with low crystallinity (5–6%). But the Tg of POY spun at 5600 or 6200 ypm is about 125°C and shows about 35% crystallinity with high amorphous orientation. An approximately linear relation was found between the height of the loss peak (tan δ) and the degree of amorphous orientation (fa) by using these analyses.
Diffusion of dyes in polyester fibers. III. Time delay in establishment of the equilibrium concentration of dye at fiber surface
Authors: Narȩbska Anna , Ostrowska‐Gumkowska Barbara , Krzystek Henryk 
Published: April 2003

AbstractIn the dyeing process of the copolyester fiber Dilana with the disperse dye Synthene Scarlet P3GL, a deviation from the simple model of Fickian sorption occurs. It manifests itself as a time delay in establishment of the equilibrium dye concentration at the fiber surface. As has been stated, the variation of Cs (the surface dye concentration) with time of dyeing fits the equation; Cs = C∞ (1− e−βt). Regarding the relation of Cs to t, the diffusion coefficient of the dye in the studied fiber has been calculated by the theoretical equation reported in Crank's monograph. It has been proved that the experimental data on kinetics of dyeing the fiber Dilana with Synthene Scarlet P3GL fit considerably better the tested equation than the classical Hill's equation.
Chemorheology of thermosetting resins. IV. The chemorheology and curing kinetics of vinyl ester resin
Authors: Han Chang Dae , Lem Kwok‐Wai 
Published: April 2003

AbstractThe rheological properties and curing kinetics of a vinyl ester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone‐and‐plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). Also determined were the rheological properties and curing kinetics of the resin when it had been thickened using magnesium oxide (MgO), in the presence of calcium carbonate (CaCO3) as filler and polyvinyl acetate (PVAc) as low‐profile additive. The steady shearing flow behavior observed with the vinyl ester resin was found to be very similar to that observed with a general‐purpose polyester resin, reported in Paper I of this series [C. D. Han and K. W. Lem, J. Appl. Polym. Sci., 28, 3155 (1983)]. However, a significant difference in the oscillatory shearing flow behavior was found between the two resins. We have concluded that dynamic measurement is much more sensitive to variations in resin chemistry than steady shearing flow measurement. DSC measurement has permitted us to determine the degree of cure as a function of cure time. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various isothermal curing temperatures.
Polymer characteristics and fracture morphology of radiation‐polymerized styrene‐impregnated mortar
Authors: Bhattacharya Vijay K. , Maiti Mrinal M. , Adhikari Basudam , Maiti Sukumar 
Published: April 2003

AbstractMechanical and durability properties and the fracture morphology of polystyrene‐impregnated mortar composites prepared by impregnation of styrene and its in situ polymerization by gamma radiation have been studied. Variation of flexural strength of the composites, percent extractable polystyrene, and its molecular weight suggest crosslinking of the impregnated polymer under the influence of prolonged gamma irradiation. Moreover, crosslinking appears to contribute toward the improvement in flexural strength but has little effect on durability properties. SEM micrographs of the composites reveal a very weak cement–polymer interfacial bonding which is believed to be responsible for poor durability properties of the composites.
Effect of crystallinity on mechanical properties of miscible polycarbonate–copolyester blends
Authors: Preston W. E. , Barlow J. W. , Paul D. R. 
Published: April 2003

AbstractNormally amorphous miscible blends of a copolyester and polycarbonate in the form of injection molded bars and extruded film were thermally annealed above the blend Tg to cause the copolyester component to crystallize, and the resulting mechanical properties were evaluated. The properties were found to depend in a complex way on blend composition, annealing conditions employed, the initial state of molecular orientation, and the process history.
Polyurethane–urea elastomers as working substances in rubber heat engines
Authors: Lyon R. E. , Wang D. X. , Farris R. J. , MacKnight W. J. 
Published: April 2003

AbstractThe possibility of using synthetic elastomers as working substances in a rubber heat engine was investigated at the laboratory and pilot scale. Two polyurethane–urea elastomers were subjected to expermental heat engine cycles at a variety of strains and temperature differences. It was found that optimum power and thermal efficiency were obtained at small strain perturbations where the elastomers were close to mechanical equilibrium. Crystallization of the rubbery phase during large strain perturbations is a nonequilibrium process which should be avoided. Quasi‐ideal rubber behavior is approached in the pilot‐scale heat engine which supports these conclusions.
Size exclusion chromatography of urea formaldehyde resins in dimethylformamide containing lithium chloride
Authors: Ludlam P. R. , King J. G. 
Published: April 2003

AbstractA rapid, reproducible method for investigating the molecular mas distribution of urea formaldehyde resins by size exclusion chromatography has been developed. By using concentrated lithium chloride solution to prepare the sample, materials of high viscosity and high molecular mass can be easily dissolved. Chromatography in dimethyl formamide containing lithium chloride eliminates hydrogen bonding and ensures that realistic values for molecular mass averages are obtained.