bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compatibility of low‐density polyethylene–poly(ε‐caprolactone) blends
Authors: Kalfoglou Nikos K. 
Published: April 2003

AbstractThe compatibility of low‐density polyethylene (LDPE)–poly(ε‐caprolactone) (PCL) was examined using the microscopic, the dynamic mechanical, and the DSC techniques. Morphological examination revealed that at low PCL concentrations, when specimens are severaly quenched, a uniform microspherulitic structure is formed. The dynamic mechanical spectra, at isochronous conditions (110 Hz), indicate very limited mixing of the amorphous phase of the two components at the intermediate compositions. More drastic relaxation shifts were observed at the extremes of the composition range. Ultimate strength and elongation at break are characteristic of a mechanically compatible system at high and low PCL contents. In the intermediate composition range their low value indicates phase separation. DSC measurements showed a nonlinear dependence of bulk crystallinity on blend composition; also, that the presence of PE enhances the degree of PCL crystallinity. Thermal history strongly affects bulk crystallinity. At elevated temperatures, near the mp of PE, thermal treatment affects considerably the melting point of the PE crystals.
Effect of a filler on the dielectric properties of an epoxy resin
Authors: La Mantia F. P. , Schifani R. , Acierno D. 
Published: April 2003

AbstractThe effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
Isothermal degradation of cis‐1,4‐polyisoprene vulcanizates
Authors: Tamura Saburo , Murakami Kenkichi , Kuwazoe Hironori 
Published: April 2003

AbstractThe isothermal degradation of high cis‐1,4‐polyisoprene vulcanizates having different crosslinking structures was investigated by a measurement of weight loss of sample, IR and NMR, gel permeation chromatography (GPC), and gas chromatography (GC). The degradation behavior of dicumy peroxide‐cured sample is similar to that of the uncrosslinked one. On the other hand, a sulfur‐cured sample is very different from the other samples. At the initial stage of the degradation, weight loss in this sample is faster than that in an uncrosslinked one. Furthermore, a microstructural change in this polymer occurring by thermal degradation is also very much larger than microstructural changes in the others. This will be attributed to polythiyl radicals produced by the scission of polysulfide crosslinkages. Although the polyisoprene chain undergoes random scission along the main chain above 473 K under inert gas or in vacuo, a molecular weight distribution of the residue after thermal degradation was broadened as the degradation proceeded. That is to say, the fragments having enormous molecular weight increase together with the production of lower molecular weight compounds. This indicates the occurrence of crosslinking reaction and the addition of polymer radicals to carbon–carbon double bonds in another polymer molecule in the thermal degradation process. Such reactions are thought to take place in the crosslinked polymers, in particular the sulfur‐cured polymer, in larger quantities. Thermal degradation mechanisms were discussed in some detail.
Coupling of polystyrene to a silane‐treated mica
Authors: Favis B. D. , Leclerc M. , Prud'Homme R. E. 
Published: April 2003

AbstractThis paper deals with the coupling of polystyrene to a closely packed and highly ordered cationic vinylbenzyl silane (CVBS) on mica. It is shown that a thermal treatment is required for maximum retention of polystyrene on treated mica. Moreover, a thermal treatment at 250°C is much more effective than one at 170°C. The effect of the number of silane monolayers on mica was investigated. In general, one monolayer of CVBS gave optimum retention of polystyrene. The addition of peroxides further improved this retention and at the same time allowed the use of lower treatment temperatures. Some data are presented which consider the importance of the silane solution concentration and silane functional groups.
Partially imidized, water‐soluble polymeric amides. I. Partially imidized polyacrylamide and polymethacrylamide
Authors: Shepitka J. S. , Case C. E. , Donaruma L. G. , Hatch M. J. , Kilmer N. H. , Khune G. D. , Martin F. D. , Ward J. S. , Wilson K. V. 
Published: April 2003

AbstractFive to six million molecular weight polyacrylamide and polymethacrylamides of comparable post‐alkaline hydrolysis viscosities were imidized by dissolution and heating in 6N HCl. After alkaline hydrolysis, the imidized polymers demonstrated significantly better retention of viscosity to 2% NaCl than did similar partially hydrolyzed polymers. Viscosities in 0.01% NaCl and resistance to shear were not markedly affected by this modification. It is assumed that this improved performance in brine is the result of chain stiffening due to intrachain imide rings.
Retardation spectra for the existence of interphase in fiber composites
Authors: Theocaris P. S. , Kefalas V. , Spathis G. 
Published: April 2003

AbstractRetardation spectra, derived from dynamic measurements of extension compliances along three decades on the logarithmic scale of frequencies in standard specimens prepared from a fiber‐reinforced composite with their fibers parallel to the longitudinal axis of the specimens, have revealed the structure of the matrix material of the composite. The experimental results were used to prove that the physicochemical rearrangements in the vicinity of the inclusions, consisting of restrained development of the macromolecules and especially their side chains due to the presence of the other phase, concentration of voids and dirt, shrinkage stresses developed during curing and creating microcracks (radial as well as along the interface), are activated by the existence of high stress gradients and eventually stress singularities due to the strong adhesion developed between phases.
Thermal oxidation of polypropylene in the temperature range of 120–280°c
Authors: Hoff Ariel , Jacobsson Sven 
Published: April 2003

AbstractThermal oxidation of isotactic polypropylene films at 120–280°C in air was studied. Separation and identification of the volatiles formed was carried out by gas chromatography–mass spectrometry. Sixteen products were tentatively identified for the first time. Altogether, 50 compounds representing hydrocarbons, ethers, alcohols, aldehydes, ketones, and acids are reported. Oxygen deficiency is manifested in diffusion‐limited products of olefines, dienes, and aromatic compounds. The relative amounts of acetaldehyde and acetone are almost temperature independent in the range of 120–280°C. This indicates a similarity of oxidative degradation of the polymer in a broad temperature range. Addition of an antioxidant to the polymer depresses the evolution of the main volatiles by 9–10 times at 280°C. The relative amounts of the volatiles formed are, nevertheless, the same as for the polymer without an antioxidant. The mechanism of formation of the degradation products is discussed.
Diffusive permeability of solutes in poly(vinyl alcohol) membranes as a function of the degree of hydration
Authors: Kojima Y. , Furuhata K. , Miyasaka K. 
Published: April 2003

AbstractSorption and permeation of sodium chloride, Congo Red (a direct dye), and Sunset Yellow (an acid dye) in PVA membranes were measured to discuss the relation among the degree of hydration H, permeability P, and diffusion coefficient D. Above H of 0.9, the permeability and diffusion coefficient of various solutes could be described by free volume theory provided that the value of V*s/Vfw is estimated properly, where V*s is the ratio of critical volume of permeating molecule to vander Waals volume of water and Vfw is the free volume fraction of water. Below H of 0.9, however, Ogston's relation which predicts a linear relation between (1‐H) and the logarithm of P or D fits better than the free volume relation. It seemed to indicate that the polymer networks simply had a geometrical obstruction effect in the diffusion of solutes. The diffusion coefficient extrapolated at H = 1 in Ogston's plot decreased with the increase in the interaction between solute and polymer as suggested by the partition coefficient. The hydration dependence of the partition coefficient K changed at H = 0.8 corresponding to the maximum amount of the bound water.
Liquid crystalline behavior of polymeric glycols terminated with aromatic diester and diacid mesogenic groups
Authors: Hoshino H. , Jin J.‐I. , Lenz R. W. 
Published: April 2003

AbstractA series of bis(benzylterephthaloyl‐p‐oxybenzoyl)esters (mesogen I) and bis(p‐carboxybenzoyl‐p‐oxybenzoyl)esters (mesogen II) of several different polymeric glycols was prepared, and their thermotropic liquid crystalline behavior was studied by differential scanning calorimetry and by visual observation on the hot stage of a polarizing microscope. The polymeric glycols used were poly(ethylene oxide) (A), poly(tetramethylene oxide) (B), polybutadiene (C), and the hydrogenated polybutadiene (D) glycols, with molecular weights between 650 and 6000. With one exception, the benzyl ester derivations were not thermotropic, but the corresponding carboxylic acid derivatives were, and the related model compound, the bis(p‐carboxybenzoyl‐p‐oxybenzoyl)ester of 1,12‐dodecanediol, was also found to be liquid crystalline. The nature of the mesophases formed by the diacids derived from the macroglycol derivatives could not be clearly identified by their optical textures. Several of the diacid derivatives formed elastomeric films, even though they were still of low molecular weight, presumably because of chain extension by dimerization and association of the terminal mesogenic groups.
Thermal degradation of polyester thermosets prepared using dibromoneopentyl glycol
Authors: Skinner G. A. , Haines P. J. , Lever T. J. 
Published: April 2003

AbstractPolyester thermosets have been prepared from maleic anhydride, phthalic anhydride, dibromoneopentyl glycol, and styrene, and their thermal degradation has been studied. Thermogravimetry has shown that degradation in air occurs in three main stages. For the 10% bromine polyester, the weight losses corresponded to 16.3%, 69.7%, and 13.9% of the original polymer weight—the temperatures of the DTG peak maxima being 217°C, 345°C, and 530°C, respectively. Infrared analysis of the residues showed that above 250°C there was a gradual reduction in the absorbance of all peaks with increasing temperature, indicating the degradation of all parts of the 3‐dimensional polymer structure was occurring in a simultaneous manner. Degradation of the dibromoneopentyl glycol polyesters at 530°C in air proved to be a very complex process since a mixture of organic products was produced which gave rise to well over 100 peaks in the capillary column chromatograms. Under the conditions used, the low temperature degradation products proved to be rich in phthalic anhydride with no benzaldehyde being detected. The yields of benzene, toluene, styrene, and naphthalene increased with increase in temperature.
Characterization of commercial polyvinylbutyral by gel permeation chromatography
Authors: Mrkvičková L. , Daňhelka J. , Pokorný S. 
Published: April 2003

AbstractFractions of commercial polyvinylbutyral “Movital” were investigated by the “off‐line” combination of gel permeation chromatography and viscometry. Parameters of the Mark–Houwink equation were determined for polyvinylbutyral in tetrahydrofuran at 25°C. Real values of the molecular parameters were obtained by the evaluation of chromatographic data using the principle of universal calibration.
Structural heterogeneities of suspension poly(vinyl chloride). I. Compact glassy particles
Authors: Lukáš R. , Tyráčková V. , Kolínský M. 
Published: April 2003

AbstractBy using the modified suspension polymerization of vinyl chloride, samples of poly(vinyl chloride) (PVC) were prepared with a high content of unprocessible particles which were isolated and subjected to a morphological investigation. Their structure was examined viscometrically, by the light‐scattering method, GPC, IR spectroscopy, and X‐ray analysis; the specific surface area of the particles was measured, and their heat stability was determined. The results lead to a conclusion that the unprocessibility of the particles compared with the usual particles of suspension PVC is not caused by differences on the level of molecular structure, but ensues from the difference in their morphology.
High‐temperature coupling of high‐speed GPC with continuous viscometry. II. Ethylene–vinyl acetate copolymers
Authors: Lecacheux D. , Lesec J. , Quivoron C. , Prechner R. , Panaras R. , Benoit H. 
Published: April 2003

AbstractAn application of the high temperature coupling of a gel permeation chromatograph with a home‐made continuous viscometric detector is described. It concerns the comprehensive characterization of ethylene–vinyl acetate copolymers. Suitable chromatographic conditions are chosen to enable a correct use of the universal calibration concept. Through analysis of poly(vinyl acetate) fractions and commercial polyethylene samples, a comparison is made with the results of classical measurements. Average molecular weights as well as intrinsic viscosity appear to be in good agreement within experimental error, which proves the system for the characterization of random ethylene–vinyl acetate copolymers. In attempting to obtain a reliable estimate of long chain branching frequency λ, a series of commercial samples has been selected, with the vinyl acetate weight fraction within the range 0–45%. As a rule, experimental viscosity law exhibits two parts, a straight line with a Mark–Houwink exponent 0.7 in the low molecular weight region and a curvature, well smoothed by a third‐degree polynomial regression. Consequently, long chain branching does not appear before a limiting molecular weight of about 50,000. Beyond this limit, λ is 0.5 × 10−4, with no dependence on molecular weight, which resembles low density polyethylene.
Resistivity behavior of filled electrically conductive crosslinked polyethylene
Authors: Narkis M. , Vaxman A. 
Published: April 2003

AbstractThe electrical resistivity of crosslinked high‐density polyethylene loaded with conductive blacks and carbon fibers was studied as a function of filler concentration and temperature. A thermoelectric switching phenomenon (a sudden resistivity increase in the vicinity of the polyethylene melting point) in such semicrystalline conductive systems was investigated. Significant switching behavior was exhibited by compounds containing very low concentrations of carbon fibers. Some crosslinked compounds filled with mixtures of carbon black and carbon fibers were also studied.
Compatibility and thermal stability studies on PVC/chlororubber‐20‐graft polyblend‐styrene–vinyl acetate–acrylonitrile blends. II
Authors: Singh Y. P. , Singh R. P. 
Published: April 2003

AbstractCompatibility and Thermal stability studies have been performed on PVC blends with chlororubber‐20‐graft polyblend‐styrene–vinyl acetate–acrylonitrile (1:1:1) [CR‐20gp‐SVAAN (1:1:1)]. The grafting of styrene, vinyl acetate, and acrylonitrile onto chlororubber‐20 backbone chain generates some amount of heterogeneity in the system. The compatibility behavior of PVC/CR‐20gp‐SVAAN (1:1:1) blends has been reflected in the ultrasonic velocity and absolute viscosity vs. composition plots of the blend. These blends have been found to be thermally miore stable than PVC/chlororubber‐20 blends, but less stable than PVC/KM‐365B blends. The rate of degradation is equal to that of the PVC/chlororubber‐20 blends. The results have been discussed on the basis of compatibility, stabilizing, and destabilizing behavior of various component polymers with PVC matrix.
Compatibility of poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) blends. II. The influence of the AN content in SAN copolymer upon blend compatibility
Authors: Chiu Shao‐Cheng , Smith T. G. 
Published: April 2003

AbstractThe compatibility of polymer blends of poly(ϵ‐caprolactone) (PCL) and poly(styrene‐co‐acrylonitrile) (SAN) containing various acrylonitrile (AN) contents was studied to evaluate the influences of copolymer composition and PCL concentration upon blend compatibility. Blend compatibility was characterized by the occurence of a single glass transition intermediate between the transitions of the respective pure components. The glass transitions were determined by differential scanning calorimetry (DSC) and dynamic mechanical measurement (Rheovibron). It was found that SAN and PCL form compatible blends when the AN content of SAN ranges from 8% to 28% by weight. These blends are compatible in all proportions except for SAN 28 (AN wt % = 28) and PCL blends containing 70 or 85 wt % PCL. Blends of PCL and SAN were found to be incompatible when the AN content in SAN is greater than 30 wt % or less than 6 wt %. Lower critical solution temperature (LCST) behavior, which can be attributed to phase separation, was found to occur when these blends were heated to elevated temperatures. The cloud point, or phase separation, was found to vary with AN content in SAN and the concentration of SAN in the blend.
Critical stress for crystallization in the threadline during high‐speed spinning of poly(ethylene terephthalate)
Authors: Garg Sunil K. 
Published: April 2003

AbstractThe development of structure during steady‐state high‐speed spinning of poly(ethylene terephthalate) has been correlated with the stress on the threadline. In particular, it is shown that a critical stress at the freeze point of 0.08–0.09 g/denier (9.5–10.6 MPa) is necessary for the occurrence of threadline crystallization independent of polymer molecular weight or process variables such as windup speed or filament character.
Photoacoustic study of UV, UV–thermal, and weathering degradation of rigid foam polyurethane
Authors: Abu‐Zeid M. E. , Nofal E. E. , Tahseen L. A. , Abdul‐Rasoul F. A. , Ledwith A. 
Published: April 2003

AbstractDegradation of polyurethane samples by UV, combination of UV–thermal, and natural weathering were studied by photoacoustic spectroscopy. This study reveals that degradation of polyurethane could be initiated at a relatively low temperature of 40°C and low UV dosage. It was also found that the effect of heat is more pronounced than the effect of UV. The reaction mechanism of polyurethane degradation is fully in agreement with photoacoustic absorption spectra.
Experimental measurements and monte‐carlo simulation of water diffusion into epoxy matrices
Authors: Majerus M. S. , Soong D. S. , Prausnitz J. M. 
Published: April 2003

AbstractSorption and desorption data are reported for water in epoxy at 25°C and 70°C. A Monte Carlo model based on the dual‐sorption theory is formulated to explain observed diffusion behavior. Random walk of particles is followed through a regular lattice with randomly distributed adsorption sites. Comparison of predicted results with experiment shows that the model predicts sorption data well. A modification to the model is proposed to improve prediction of desorption data.
Polyurethane ionomers. I. Structure–properties relationships of polyurethane ionomers
Authors: Hsu S. L. , Xiao H. X. , Szmant H. H. , Frisch K. C. 
Published: April 2003

AbstractThe influence of chemical structure on mechanical properties of polyurethane ionomers (PU ionomers) has been examined. NCO‐terminated prepolymers prepared from primarily 4,4‐methylene bis(phenyl isocyanate) (MDI) and poly(oxytetramethylene) glycol (PTMO) were chain extended with tertiary amine‐containing diols and the ionomers obtained by quaternization of the prepolymers. The N‐methyldiethanolamine chain extender gave the best physical properties. The mechanical properties of the PU ionomers were improved with decreasing chain length of PTMO and with increasing concentration of quaternary ammonium centers (or NCO/OH ratio of PU prepolymers). A lower degree of quaternization resulted in a decrease in the mechanical properties of the resulting PU ionomers, but their properties could be improved by post‐quaternization. The adhesion of the PU ionomers to aluminum and the glass transition temperature increased with increasing concentration of quaternizing centers.
Curing reaction of epoxy resins with diamines
Authors: Riccardi C. C. , Adabbo H. E. , Williams R. J. J. 
Published: April 2003

AbstractThe curing reaction of a commercial bisphenol A diglycidyl ether (BADGE) with ethylenediamine (EDA) was studied by differential scanning calorimetry. Different kinetic expressions were found with isothermal (low temperature range) and dynamic (high temperature range) runs. Two competitive mechanisms are shown to be present: an autocatalytic one (activation energy E = 14 kcal/mol) and a noncatalytic path characterized by a second‐order reaction with E = 24.5 kcal/mol. At low temperatures both mechanisms took place simultaneously, showing a significant decrease in the reaction rate after the gel point. At high temperatures only the noncatalytic reaction was present, without showing a noticeable rate decrease in the rubber region. Also, a third‐order dependence of the glass transition temperature on reaction extent is shown.
Biodegradability of photooxidized polyalkylenes
Authors: Cornell John H. , Kaplan Arthur M. , Rogers Morris R. 
Published: April 2003

AbstractRepresentative polyolefin films were exposed to UV radiation from light sources having different intensities and spectral distribution including the quartz mercury arc fluorescent lamps, xenon arc, and sunlight. Films exposed were polyethylene, polypropylene, and sensitized polyethylene. The oligomer fractions supported microbial growth, but the high polymers gave minimal or no growth. It was concluded that photooxidative degradation of polyolefins does not per se induce progressive attack by microorganisms. Oligomers present originally in the polymer are augmented by those produced by photooxidation. These oligomers support growth if separated from the polymer matrix. These observations explain some of the contradictory reports in the literature concerning the microbial degradation of sensitized polyolefins.
Electric conductivity of silicone elastomers vulcanized by the hydrosilation reaction
Authors: Yokoyama Takashi , Kinjo Noriyuki 
Published: April 2003

AbstractElectrical conductance and hardness of silicone elastomers, prepared by the vulcanization reaction of hydrosilyl groups with vinyl groups in the presence of platinum catalyst, were measured. It is shown that the electric conductivity of the elastomers decreases as hardness increases and as the temperature decreases. An empirical equation is derived expressing electric conductivity σ as a function of hardness H and absolute temperature T, log σ = −0.03H − 3200/T − 3, where σ is S/m and H is Shore A, over the temperature range of 100–150°C.