bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the radiolytic degradation of cellulose acetate membranes
Authors: Ramachandhran V. , Misra B. M. 
Published: April 2003

AbstractThe effect of γ‐irradiation on the performance of wet cellulose acetate membranes in the dose range of 2.5–10 Mrads was investigated using a 60Co source. Changes in transport properties and inherent viscosity of the membranes suggested continued degradation as a result of irradiation. Solubility and specific gravity changes accompanying irradiation indicated some sort of structural aggregation occuring at higher doses. Consumption of dissolved oxygen during irradiation and the extent of deacetylation of the membrane polymer were determined to study the kinetics of the degradative process. Analysis of the end products of irradiation was attempted by UV spectroscopy. ESR spectra of membrane polymer after irradiation were analyzed to identify the free radicals generated. A tentative mechanism of radiolytic degradation causing the observed performance failure is proposed.
Water‐soluble copolymers. XI. Selectivity in the graft copolymerization of acrylamide/N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide comonomers onto dextran by Ce(IV)‐induced initiation
Authors: McCormick C. L. , Park L. S. 
Published: April 2003

AbstractCharacteristic behavior in the graft copolymerization of acrylamide/N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide (AM/DAAM) comonomers onto dextran by Ce(IV)‐induced initiation was investigated. From a preliminary study, it was found that ceric ammonium nitrate polymerized AM/DAAM comonomer mixtures and diacetone acrylamide, but not acrylamide alone in the aqueous solution. The effect of grafting conditions on the graft copolymerization product was studied with the aid of aqueous size exclusion chromatography and the anthrone reagent. The selectivity of formation of the graft copolymer over random copolymer was found to increase as the reaction temperature and AM/DAAM ratio increased and as both the Ce(IV)/Dextran molar ratio and HNO3 concentration decreased. After establishing optimum grafting conditions, graft copolymer samples were prepared, and their aqueous solution behavior studied as functions of structure, temperature, and added salts.
Investigation of block copolymer micellization by high‐performance size‐exclusion chromatography
Authors: Špaček Pavel , Kubín Miroslav 
Published: April 2003

AbstractThe formation and decomposition of micelles of the three‐block copolymer polystyrene‐block‐poly(ethene‐stat‐butene)‐block‐polystyrene (Kraton G 1652, Shell) were investigated by high‐performance size‐exclusion chromatography in a mixed solvent dioxan–heptane. The association equilibrium may be shifted from the pure unimer to pure micelles by changing the composition of the mobile phase, and also (at constant composition) by a change in temperature. The shape of the chromatograms observed under conditions of comparable equilibrium concentrations of both species may be explained by the disturbance and reestablishment of the association equilibrium during separation in the chromatographic column. Experiments with changing flow rate show the dominating effect of degrading separation efficiency with increasing linear velocity of the mobile phase.
Radiation‐induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. VI. Permeability of sodium chloride and sodium sulfate
Authors: Bhattacharyya S. N. , Maldas D. 
Published: April 2003

AbstractAcrylamide, styrene, and mixtures of acrylamide and styrene were grafted onto cellulose acetate film. The permeabilities of sodium chloride and sodium sulfate through the ungrafted and grafted cellulose acetate films were studied. Permeability increases with the increase in the extent of grafting of acrylamide; whereas it decreases with the increase in the extent of grafting of styrene onto cellulose acetate. The same trend in permeability was observed when cellulose acetate was grafted with the binary monomer mixture. Permeability is also found to depend on the nature of the solute dissolved in water. The results were discussed in terms of free volume concept of the water‐swollen films.
Infrared study of combined effect of γ‐radiation and elevated temperature on poly(vinyl chloride)
Authors: Rabie S. M. , Moharram M. A. , Daghistani A. Y. 
Published: April 2003

AbstractInfrared absorption spectroscopy has been used to investigate the combined effect of γ‐radiation and heat on poly(vinyl chloride) (PVC). The recorded spectra showed that exposure of PVC samples to gamma doses from 0.5 to 15 Mrad results in remarkable changes in the absorbances of their absorption bands. Also, the exposure to doses from 3 to 15 Mrad results in an appearance of a CO band at 1720 cm−1 and OH band at 3450 cm−1. The nature of the formation of these bands was discussed in terms of peroxide‐mediated oxidative degradation mechanism. Moreover, it was found that heat treatment of PVC samples over the temperature range 25–180°C causes no noticeable changes in their spectra apart from slight changes in the absorbances of the bands. On other hand, it was found that heat treatment of the irradiated samples causes considerable increase in the intensity of the CO band. In addition to the well‐defined and sharp band appearing at 1720 cm−1, the spectra of the samples irradiated with 10 and 15 Mrad exhibited two bands at 1070 and 1120 cm−1. The obtained data led also to the conclusion that the CCl bands cannot be used as a measure of crystallinity of PVC.
Gas transport in poly(vinyl benzoate)
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori 
Published: April 2003

AbstractThe transport parameters of nine gases (O2, N2, CO2, He, Ne, Ar, Kr, Xe) through poly(vinyl benzoate) (PVB) have been measured by the time lag method above and below the glass transition temperature, Tg The results are compared with the related data of poly(vinyl acetate) (PVAc) by Meares and discussed as the effect of replacement of the methyl group by a phenyl group in the side chain of PVAc. Small molecules, such as H2, He, and Ne, diffuse more easily through PVAc than PVB, but the tendency is reversed for the larger gases. The activation energy for diffusion is proportional to the squares of the Lennard–Jones diameters of the gases below the Tg. On the other hand, above the Tg, linear relation is obtained to the cubes of the diameters. Solubility behavior is discussed by comparing the heats of solution for PVB and PVAc.
Bisulfite–persulfate‐initiated grafting of methyl methacrylate onto gelatin
Authors: KláSek A. , BačáKová M. , Kaszonyiová A. , Pavelka F. 
Published: April 2003

AbstractGrafting of methyl methacrylate onto gelatin, initiated by the bisulfite–persulfate redox system, has been studied. Using the method of statistical planning of experiments, regression equations have been obtained describing the effects of the methyl methacrylate concentration and the composition of initiating system on the factors characterizing the grafting reaction. Possibilities of the reaction conditions optimalization are discussed.
Solution‐induced changes in the properties of polyethylenes
Authors: Ajji A. , Schreiber H. P. , Rudin A. , Teh J. W. 
Published: April 2003

AbstractThe chain entanglement states in high density, linear low density, and low density polyethylenes (HDPE, LLDPE, and LDPE) have been modified by recovering the polymers from solutions in trichlorobenzene (TCB) and p‐xylene. In the thermodynamically good solvent, TCB, the entanglement density is assumed to be sharply reduced, a condition which is carried over to the corresponding solids. These display transient, but large increments in tensile moduli, slight changes in stress at rupture, and decreases in dynamic mechanical parameters and in elongation at rupture. Scanning calorimetry also shows these solids to have reduced crystallinity. Much smaller property modifications are noted in corresponding samples recovered from p‐xylene. This liquid is a poorer solvent, particularly for HDPE and LLDPE. The results indicate that property modifications due to deliberate changes in the entanglement states of the polymers are a general phenomenon in the polyethylenes, and the magnitude of property changes depends on parameters of the molecular weight distribution. Chain branching does not seem to be a leading factor in the sensitivity of properties to modifications in the entanglement states. The property modifications produced by the present solution treatments are viewed as guides to the magnitude and duration of shear refining effects to be expected in HDPE, LLDPE, and LDPE polymers.
Dielectric behavior of wood–polystyrene composite
Authors: Poliszko Stefan , Hoffmann Grzegorz 
Published: April 2003

AbstractThe dielectric phenomena for alder wood natural and modified with polystyrene were studied. Temperature dependences of the complex permittivity components of these materials were obtained for the temperature interval from 100 to 450 K at the frequencies of measuring electric field of 420 Hz, 2 kHz, and 10 kHz. The changes in structure of wood cell walls were found, detected as an increase in number of polar functional groups taking part in the relaxation processes and as a partial freezing of conformational degrees of freedom of macromolecule fragments carrying these groups. The origin of the structural changes can be the efect of wood substance swelling caused by polystyrene, which penetrates the composite cell walls.
The viscoelastic properties of rubber–resin blends. III. The effect of resin concentration
Authors: Class J. B. , Chu S. G. 
Published: April 2003

AbstractThe viscoelastic properties of a rubber–resin blend, which influences performance of the blend as a pressure‐sensitive adhesive, depend upon the structure of the resin as well as its molecular weight. The effect of the concentration of a compatible resin in the blend was examined using a mechanical spectrometer. Four types of resins were used. These are the rosin esters, polyterpenes, pure monomer resins such as polystyrene and poly(vinyl cyclohexane), and petroleum stream resins. Each was examined in blends with both natural rubber and styrene–butadiene rubber over a range of concentrations. It is shown that the temperature of the tan δ peak for compatible systems can be predicted by the Fox equation, T = W1T + W2T, where W1 and W2 are the weight fractions of the resin and rubber, respectively, and the Tg's are the tan δ peak temperatures in K. The plateau modulus G for a blend can be identified as the G′ value in the rubbery plateau at the point where tan δ is at a minimum. The relationship between G and G, the plateau modulus for the undiluted elastomer, is shown to be proportional to the volume fraction of the elastomer raised to the 2.3–2.4 power for natural rubber with six different compatible resins. The exponent for styrene–butadiene rubber is 2.5–2.6 with four different resins. Using these relationships, both the tan δ peak temperature and plateau modulus can be predicted for a rubber–resin system from data on the unmodified elastomer and on one typical rubber–resin blend.
Simulation of Vortex growth in planar entry flow of a viscoelastic fluid
Authors: Mitsoulis E. , Vlachopoulos J. , Mirza F. A. 
Published: April 2003

AbstractA numerical simulation of entry flow in a slit die has been undertaken for a fluid that is Newtonian in shear but exhibits normal stresses (Boger fluid). Experimentally measured normal stress and viscosity data are included in a simple rheological model. Flow patterns reveal the existence of vortices in the reservoir corners. Vortex size and intensity increase rapidly with elasticity level.
Evidence for the presence of cage reaction in the initiation step of thermal polymerization of styrenes by field desorption mass spectrometry
Authors: Hara J. , Teramae N. , Saito J. , Tanaka S. 
Published: April 2003

AbstractField desorption mass spectrometry (FDMS) was applied to the study of the initiation mechanism of thermal polymerization of styrenes. The FD mass spectrum was measured for a cooligomer of α,α,β‐trideuterostyrene and p‐methoxystyrene produced by thermal polymerization using ethylbenzene as a solvent, and this was compared with the spectrum of an oligomer of p‐methoxystyrene. The above two FD mass spectra showed characteristic differences, depending upon the number of hydrogen and deuterium atoms and upon the presence or absence of the methoxy group, in the oligomers. Molecular species observed in the spectra were identified based on these considerations. As a result, we could distinguish the “true trimer” produced from three monomers from the “cross trimer” produced from fragments of five monomers. It was found that the “true trimer” was the major constituent in the trimer region, and that the “true trimer” was produced mainly by the cage reaction between initiating radicals.
Characterization of reverse osmosis membranes prepared from the oxime of poly(4‐vinylpyridine‐co‐methyl vinyl ketone)
Authors: Oikawa Eizo , Igarashi Yusuke , Tsurumaki Shigeru 
Published: April 2003

AbstractThe copolymer (4VK) of 4‐vinylpyridine (4VP) and methyl vinyl ketone (MVK) was nearly quantitatively converted into an oxime (4VKX) which could be complexed with various metal salts. 4VKX was compared with 4VK in their membrane performance. When crosslinked with divinyl sulfone (DVS), the 4VKX membrane showed a higher strength than cellulose acetate (CA) membrane and a higher performance than 4VK membrane crosslinked with dihydrazine derivatives. The most adequate DVS content and copolymer composition were found to be 25 mol % based on MVK oxime and 1:1, respectively. A metal salt taken up by the membrane in a much larger amount tended to be highly rejected. The crosslinking quaternization of 4VKX with diisobutane (DIB) very effectively improved water permeability, as did 4VK, and gave a membrane performance superior to that of 4VK. The most appropriate charge ratio of DIB was 15–20 mol % based on 4VP. Some transport characteristics and compaction in a long‐term operation were investigated and discussed.
Equation of state for polymer liquids
Authors: Hartmann Bruce , Haque Mustafa A. 
Published: April 2003

AbstractAn empirical pressure–volume–temperature (PVT) equation of state is presented for polymers in the liquid state, i.e., above the melting point of a crystalline polymer or the glass transition of an amorphous polymer. In terms of reduced variables, the equation is given by \documentclass{article}\pagestyle{empty}\begin{document}$\overline {PV^5 } = \overline {T^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} } - \ln {\rm }\overline V $\end{document}. Values of the three reducing parameters are given for 23 polymers. Comparison of the predictions of this equation with experimental data are made for all of the polymers. The data are generally available up to a pressure of 2 kbar and a temperature 100°C above the melting or glass transition temperature. Measured and calculated volumes agree within about 0.001 cm3/g, which is the accuracy of the measurements. Detailed comparisons with the empirical Tait equation are made. Equations are also presented for isothermal bulk modulus, thermal expansion coefficient, and Gruneisen parameter.
Effects of water sorption at different temperatures on permanent changes in an epoxy
Authors: Netravali A. N. , Fornes R. E. , Gilbert R. D. , Memory J. D. 
Published: April 2003

AbstractCrosslinked epoxy resins, tetraglycidyl 4,4′‐diamino diphenyl methane cured with 4,4′‐diamino diphenyl sulfone, were soaked in water at either 25°C or 70°C for varying lengths of time. The infrared spectra and DSC thermograms were obtained for samples that were soaked, or soaked and dried. There was a monotonic decrease in exothermic reaction energy with water content. The glass transition was also lowered, although samples soaked at 70°C showed a leveling in the Tg around 115°C. When the soaked samples were dried, the exothermic reaction energy showed near reversibility for samples soaked at 25°C while the 70°C samples were highly irreversible. IR of the latter samples showed that the 70°C water soaking resulted in reaction of some of the unreacted epoxide groups that remained after the initial cure.
Linear polythioesters. X. Products of interfacial polycondensation of bis(4‐mercaptophenyl)ether with izomeric phthaloyl chlorides
Authors: Podkoscielny Wawrzyniec , Wdowicka Danuta 
Published: April 2003

AbstractNew polythioesters were obtained by interfacial polycondensation of bis(4‐mercaptophenyl)ether with phthaloyl, isophthaloyl, and terephthaloyl chlorides. To determine the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: organic phase, 100% excess of sodium hydroxide, contribution of benzyltriethylammonium chloride as a catalyst, and the temperature of the reaction. A thorough examination of the process was carried out only for polycondensation of dithiol with phthaloyl chloride. Yield of all reaction products as well as reduced viscosity of only polythioesters from dithiol and phthaloyl chloride were found because these were the ones which were soluble in tetrachloroethane. The structure of all polythioesters was determined by elemental analysis and infrared spectra. Initial decomposition and initial intensive decomposition temperature were defined by the curves of thermogravimetric analysis. Some mechanical and electrical properties of polythioesters were determined.
The dynamic mechanical behavior of paper during drying
Authors: Htun Myat , De Ruvo Alf , Fellers Christer 
Published: April 2003

AbstractThe dynamic mechanical properties of paper during restrained drying are reported in this article. The apparatus used was a servohydraulic material testing system (MTS), connected to a computer unit. It has been found that the ratio of drying stress to elastic modulus at a given dry solids content corresponds to the instantaneous linear contraction of the sheet when the drying stress is relieved. It is therefore deduced that paper behaves as a linear viscoelastic body during restrained drying. The finding of a maximum loss coefficient and the drastic change in elastic modulus during drying of paper are interpreted in terms of a transitional change in the amorphous regions of wood polymers plasticized by water.
The effects of heat transfer in melt spinning
Authors: Maebius R. E. 
Published: April 2003

AbstractSeveral heat transfer models are examined in order to assess the influence of convection and radiation upon the melt spinning of a Newtonian fluid. In the spinning of glass fibers, radiation is shown to be equally as important a mode of heat transfer as convection. Small changes in the spectral emissivity are shown to have a large effect on the shape of the jet and the drawing force required to attenuate the fiber.
Coupling of glass fiber with polypropylene by gamma radiation
Authors: Mukherjee A. K. , Sharma P. K. 
Published: April 2003

AbstractThe effect of 60CO gamma radiation on polypropylene and glass‐fiber‐reinforced polypropylene was investigated. The glass fiber content in the reinforced polypropylene was observed to influence the mechanical properties of the original polypropylene. The initial modulus and off‐set yield strength (at 0.25% strain) increased with the dose and glass fiber content. The tensile strength showed an initial decrease with the increase in glass fiber content followed by an increasing trend. A similar behavior was found with increasing dosage. The extent of fiber breakage during processing was higher at higher glass fiber content. However, the fiber length distribution became narrower beyond 2.45% glass fiber content in the polypropylene.
Enthalpy relaxation of filled copolymers
Authors: Kumar S. , Salovey R. 
Published: April 2003

AbstractExcess enthalpy following annealing at various periods of time at Tg −10°C was measured by differential scanning calorimetry of electrophotographic toners, copolymers of styrene and butyl methacrylate containing carbon black. An approximate equilibrium enthalpy relaxation after annealing the pure copolymers for one month was 3.30 kJ/kg for a copolymer with 66.5% styrene and 2.72 kJ/kg for a copolymer containing 49.8% styrene. The rate of enthalpy relaxation was reduced by increasing the styrene content of the pure copolymer. The incorporation of a carbon black with high surface area reduces the rate of enthalpy relaxation, increasing in effectiveness with butyl methacrylate concentration.
Rubber‐toughening in polypropylene
Authors: Jang B. Z. , Uhlmann D. R. , Sande J. B. Vander 
Published: April 2003

AbstractTo deformation and fracture behavior of several polypropylene (PP) and rubber‐modified PP materials have been investigated. Plastic deformation mechanisms of these systems depend upon the test rate and temperature with high rates and low temperatures being in favor of crazing. The ductility and toughness of these materials are explained in light of the competition between crack formation and the degree of plastic deformation through crazing and shear yielding. The second phase morphology with smaller average rubber particle diameter D appears to be more efficient than that with larger D in toughening PP. Theoretical calculations indicate that the stresses imposed upon the rubber particles due to volume shrinkage of PP during crystallization are sufficient to compensate for the stresses due to differential thermal contraction in cooling from solidification temperature to end‐use temperature. The difference between these two is small, and therefore they provide very little contribution to interfacial adhesion between rubber particle and PP matrix, the adhesion being insufficient for the rubber particles to be effective in controlling craze propagation. The rubber particles, in addition to promoting crazing and shear yielding, can also improve the fracture resistance of PP by varying the crystalline structure of PP (e.g., reducing the spherulite dimensions).
Trifluoroethanol/chloroalkane mixtures: Excellent novel solvents for aliphatic polyamides
Authors: Aharoni Shaul M. , Cilurso Frank G. , Hanrahan James M. 
Published: April 2003

AbstractCertain mixtures of TFE/CHCl3 were found to be excellent solvents for aliphatic polyamides such as nylon‐6, nylon‐66, nylon‐11, nylon‐12, nylon‐69, nylon‐610, and nylon‐612. Intrinsic viscosities were measured and Mark–Houwink coefficients determined for nylon‐6/TFE/CHCl3, indicating TFE‐rich mixtures to be better solvents than TFE alone. Similar results were obtained for TFE/CH2Cl2. Four ternary phase diagrams were constructed for nylon‐6/TFE/chloroalkanes, of which the ones with CHCl3 and CH2Cl2 are the most interesting. In the nylon‐6/TFE/CHCl3 diagram higher nylon‐6 solubility in TFE‐rich mixtures and a biphasic region in the CHCl3‐rich compositions are evident. In the TFE/CH2Cl2 system, the higher dissolution of nylon‐6 is observed, but no biphasic regions are detected. In certain solvent compositions and/or polymer concentrations the polymer is incompletely soluble, making the phase diagrams rather complicated. Observed thermodynamic excess properties appear to relate to the quality of TFE/chloroalkanes as solvents for nylon‐6. Studies on swelling of nylon‐6 networks immersed in TFE/CHCl3 show a behaviour previously described by Krigbaum and Carpenter for a general case where the formation of contracts between molecules of the two solvents is discouraged and their preferential solvation of the polymer is, therefore, encouraged. The phenomena observed in this work can be qualitatively explained as arising from antagonistic interaction of TFE molecules with chloroalkane ones. The presence of the polyamides in solution reduces such contacts, enchancing the dissolution of the polymer in the (TFE‐rich) solvent mixtures.