bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composite membranes formed by plasma‐polymerized acrylic acid for ultrafiltration of bleach effluent
Authors: Cho D. L. , Ekengren Ö. 
Published: April 2003

AbstractComposite membranes were formed by deposition of plasma‐polymerized acrylic acid (PPAA) films onto porous commercial membranes to improve the rejection, especially of chlorinated compounds, in ultrafiltration of E‐stage bleach effluent. Although increased rejections were accompanied by reduced flux, in most cases, the reductions were not significant considering the extent of increased rejections. A good composite membrane showed the AOX removal of 94% (76% before the modification) and the chemical oxygen demand (COD) removal of 84% (67% before the modification) with 33% reduction of the flux. The permeate was optically clean. The improved rejection is attributed to the tightly crosslinked network of a plasma polymer film and its negatively charged surface. Ultrathin film thickness and the hydrophilic property of a plasma polymer film minimize the reduction of flux. © 1993 John Wiley & Sons, Inc.
Relative solubility of tetrachlorohexafluorobisphenol‐A polycarbonate in various compounds
Authors: Beck H. N. , Mah R. W. , Sanders E. S. 
Published: April 2003

AbstractThe relative solubility of tetrachlorohexafluorobisphenol‐A polycarbonate was observed in 127 organic compounds comprising 14 different chemical classes at room temperature and up to about 225°C. The polymer is soluble in numerous esters, ketones, halocarbons, heterocyclics, and amides. It is poorly soluble in alcohols and fluorocarbons. Correlation of observed solubility with Hildebrand total solubility parameters was poor; a much better correlation was observed with Hansen three‐dimensional parameters. The solubility parameter of the polymer was estimated to be 9.1 (cal/cm3)1/2 (18.7 MPa1/2) from the averages of the Hansen parameters for 26 experimentally identified solvents. © 1993 John Wiley & Sons, Inc.
Selection of elastomeric membranes for the removal of volatile organics from water
Authors: Nijhuis H. H. , Mulder M. H. V. , Smolders C. A. 
Published: April 2003

AbstractA wide range of homogeneous elastomeric membranes has been prepared using dicumylperoxide as a general cross‐linking agent. The membranes have been used for both equilibrium sorption measurements and steady‐state pervaporation experiments to study solution–diffusion phenomena in the removal of volatile organic components from aqueous solutions. Pervaporation experiments have been performed under identical hydrodynamic conditions in order to fix the boundary layer mass transfer coefficient at a constant and known value. For comparison of the permeabilities of different pervaporation membrane materials, this is of utmost importance. A wide range of selectivity factors up to a value of 100,000 are obtained, whereas usually the permeabilities for the organic component are in the range of 10−10−10−9m2/s and 10−14−10−12m2/s for water. The permeation and sorption data obtained for the various elastomers have been related to the chemical and physical nature of the elastomers through the solubility parameter and the glass transition temperature, respectively. Both diffusional and sorption effects seem to be important, determining the water‐transport behavior in the elastomeric membranes. The solubility of the organic component appears to be independent of this combined solubility parameter. Differences in the permeabilities of the organic component can primarily be ascribed to structural parameters in the membrane material, like degree of unsaturation and presence of steric side groups. © 1993 John Wiley & Sons, Inc.
Preparation of ethylene copolymers containing pendant unsaturation for radiation crosslinking
Authors: Ekman Kenneth B. , Näsman Jan H. , Sjöström Håkan 
Published: April 2003

AbstractThe work presented here suggests that the radiation crosslinking of particular ethylene copolymers can markedly be enhanced by introduction of pendant radiation‐sensitive functional groups and that reactive melt processing offers an attractive alternative to introduce the pendant groups. m‐Isopropenly‐α,α‐dimethylbenzyl isocyanate was found to react in high yields(>80%) during a few minutes of reactive mixing with an ethylene hydroxyethyl methacrylate copolymer, and no residual monomers were found in the polymer after 10 min of mixing. Copolymers that contained from 0.1 to 1.2 mol % of pendant unsaturation were prepared. The functionalized copolymer, which contained 1.2 mol% of pendant unsaturation were prepared. The functionalized copolymer, which contained 1.2 mol % of pendant unsaturation, formed 90% gel after having received a radiation dose of 100 kGy. The corresponding value for the unfunctionalized copolymer was 25% gel. Furthermore, ethylene copolymers containing 0.3–1.4 mol % of acrylate or 0.1–0.4 mol % of methacrylate side groups were prepared by mixing an ethylene vinyl alcohol copolymer with acrylic acid or by mixing an ethylene acrylic acid copolymer with glycidyl methacrylate. Although the conversion of these esterification reactions was low, the amount of incorporated pendant unsaturation was sufficient to crosslink the polymers to high gel contents (>80%) already at a radiation dose of 10 kGy. © 1993 John Wiley & Sons, Inc.
A comparison between miniemulsion and conventional emulsion terpolymerization of styrene, 2‐ethylhexyl acrylate and methacrylic acid
Authors: Masa Juan A. , De Arbina Lourdes López , Asua José M. 
Published: April 2003

AbstractThe kinetics of the high solids content miniemulsion terpolymerization of styrene, 2‐ethyl hexyl acrylate and the methacrylic acid and the final properties of the latexes produced by this method were compared with those resulting from the corresponding conventional emulsion polymerization process. The final latex properties considered were: latex viscosity both prior and after neutralization, mechanical stability, chemical stability, and freeze‐thaw stability. © 1993 John Wiley & Sons, Inc.
Thermally and anionically initiated cure of bismaleimide monomers
Authors: Seris A. , Feve M. , Mechin F. , Pascault J. P. 
Published: April 2003

AbstractA kinetic and thermodynamic study of the thermally or anionically induced cure of aromatic bismaleimide monomers (namely 2,4‐bismaleimidotoluene, 4,4′‐bismaleimidodiphenylmethane and their eutectic mixture) is presented. Calorimetric investigations allowed the determination of heats of polymerization and activation energies for both types of initiations, and the values found are compared with data in the literature. Isothermal cures were also carried out with and without anionic initiator (typically imidazole). SEC measurements were used to monitor the conversion of the monomers as a function of time. The thermally induced polymerization seems to proceed in a rather heterogeneous way, owing to an initiation that is too slow: gelation appears at first only as the formation of microgels, with no immediate increase in the viscosity; macrogelation occurs some time after. On the contrary, the anionically induced polymerization is more homogeneous. A complete study of a particular reacting system revealed no interference between radical and anionic polymerization over a wide range of temperatures, and in this case gelation results in an immediate increase in viscosity. However, the conversion at the gel point is unexpectedly high, which can be interpreted as the result of a very fast initiation as well as of transfer reactions. Glass transition temperatures were also measured as a function of time and curing temperature in order to study the influence of vitrification on the kinetics and to check for the existence of a unique relation between Tg and conversion. This actually proved to be correct as long as diffusion does not slow down the reaction; in this case Gillham's treatment of Tg versus in t was successfully applied and led to the correct value of the activation energy. All the measurements allowed us to establish the time‐temperature‐transformation cure diagram for a specific reacting system. © 1993 John Wiley & Sons, Inc.
Effects of the addition of a liquid crystalline copolyester to polystyrenes on blending torque and mechanical properties of blends
Authors: Ogata N. , Tanaka T. , Ogihara T. , Yoshida K. , Kondou Y. , Hayashi K. , Yoshida N. 
Published: April 2003

AbstractBlending of polystyrenes (PS) with a thermotropic liquid crystalline polymer (LCP) was performed by using a continuous corotating twin screw extruder. The influence of LCP content on the blending process was studied by changing the barrel heater temperature and the screw speed. The torque of screw shafts, generated during the blending process, was influenced by LCP content and its influence was not simple. The torque generated during the blending process was not directly related to the apparent melt viscosity of blends. Further, the effects of the matrix viscosity on the morphology and mechanical properties of the PS/LCP blends were studied using three grades of PS as matrix resins. It was found that the size of the LCP dispersed phase decreased with increasing matrix viscosity. Consequently, the mechanical properties of the PS/LCP blend were improved. © 1993 John Wiley & Sons, Inc.
Microdeformation mechanisms in propylene–ethylene block copolymer
Authors: Hayashi Kosei , Morioka Tetsuya , Toki Shigeyuki 
Published: April 2003

AbstractBlends of propylene–ethylene block copolymer (PEB) and propylene homopolymer (PP) were prepared to give various rubber contents (4–20 wt %). By diluting the PEB with PP with molecular weight equal to that of the PEB matrix, molecular characteristics of all the blends were kept constant. The rubber particle size and size distribution of all the blends were almost constant, so that the interparticle distance decreased with increased rubber content. According to the observation of the fracture behavior at −20°C, a brittle to ductile transition was found at the rubber content of 16 wt %. Microdeformation behavior of the blends was investigated in the region of brittle to ductile transition by using transmission electron microscopy. In the case of the brittle sample with low rubber content, crazing and voiding were observed. Whereas even in the ductile sample with high rubber content, crazing certainly took place before shear yielding. The origin of ductile fracture could possibly be attributed to the relaxation of strain constraint by the microvoids contained in the craze. © 1993 John Wiley & Sons, Inc.
Characterization of cellulose acetate in acetone solution. Studies on prehump II in GPC pattern
Authors: Funaki Yoshinori , Ueda Kazuyoshi , Saka Shiro , Soejima Shigeru 
Published: April 2003

AbstractCellulose acetate in acetone solution is known to show some peaks in its chromatogram as measured by gel‐permeation chromatography. These peaks are named from the shorter elution time as prehump I, prehump II, and main hump. In our previous paper, we characterized prehump I. In this study, the second peak, prehump II, was fractionated by using the large‐scale GPC column and its molecular properties were investigated. The results have shown that the molecules of prehump II are not aggregated but molecularly dispersed with some anionic residues. These anionic groups may be sulfuric acid groups introduced during the acetylation process as a catalyst that interact repulsively with the anionic groups of the GPC column gel. This resulted in the phenomenon that the prehump II elutes earlier than the main hump in the GPC chromatogram. © 1993 John Wiley & Sons, Inc.
Miscibility and phase behavior in blends of poly(hydroxyether of bisphenol A) with poly(ethylene oxide‐co‐propylene oxide)
Authors: Qipeng Guo , Keshi Sun , Tianru Fang , Yuchen Qi , Zhiliu Feng 
Published: April 2003

AbstractThe miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide‐co‐propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60°C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean‐field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting‐point depression of the crystallizable component in the blends, the binary interaction energy densities, Bij, have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen‐bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility. © 1993 John Wiley & Sons, Inc.
Graft copolymerization of 4‐vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method
Authors: Kaur Inderjeet , Misra B. N. , Barsola Raghuvir 
Published: April 2003

AbstractAn attempt has been made to graft copolymerize 4‐vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method in an aqueous medium. Polypropylene hydroperoxide has been prepared by irradiating recrystallized polypropylene beads from a Co60 source in the presence of air. The resulting polypropylene hydroperoxide beads have been used as the backbone polymer and grafting of 4‐vinyl pyridine has been studied as a function of various reaction parameters. Optimum conditions for maximum percentage of grafting have been evaluated. Rate of grafting (Rg) has been determined as a function of preirradiation dose and initial monomer concentration. Water has been found to affect percentage of grafting. The graft copolymers have been characterized by spectroscopic method and isolation of the grafted poly(4‐VP) from the graft copolymer. A plausible mechanism is proposed to explain the mutual grafting of 4‐vinyl pyridine onto polypropylene hydroperoxide. © 1993 John Wiley & Sons, Inc.
Effects of crosslinking on physical properties of phenol–formaldehyde novolac cured epoxy resins
Authors: Ogata Masatsugu , Kinjo Noriyuki , Kawata Tatsuo 
Published: April 2003

AbstractTo clarify the relationship between crosslinking density and physical properties of phenol–formaldehyde novolac cured epxy resin and factors governing their physical properties, we studied various properties of cured resins having different crosslinking densities. The resins were prepared with various curing accelerators and raw epoxy resins having different molecular weights. We found that as the crosslinking density of a cured resin increases, glass transition temperature (Tg) rises and the relaxation time becomes longer. Furthermore, in the rubbery region, the coefficient of linear thermal expansion drops and the elastic modulus become larger, while, in the glassy region, the coefficient of linear thermal expansion, specific volume, water absorption, diffusion coefficient, and permeability all increase but the elastic modulus becomes smaller. The WLF analysis on the relaxation behaviors of typical cured resin showed that cured resin with a higher crosslinking density decreases in the fractional free volume. This behavior is completely opposite from the relationship predicted from the temperature dependency of specific volume. While the coefficient of thermal expansion of free volume decreases as the crosslinking density increases for the cured resin, it coincides well with the tendency predicted from the difference in coefficient of cubic thermal expansion in the rubbery and glassy regions of each cured resin. That the free volume obtained from WLF analysis shows a relationship opposite to the predicted free volume as based on the temperature dependency of specific volume is explained as follows: Namely, the free volume obtained from the WLF analysis is a hole free volumeVhwhich contributes to fluidity andVhdecreases with the crosslinking density. On the other hand, the free volume predicted from the specific volume is a sum of the interstitial free volumeViandVh.Viincreases with the crosslinking density and thisViincrease exceeds the decrease ofVh. Therefore, the free volume predicted from the specific volume increases with the crosslinking density. Consequently, the influence of free volume on the relationship between the crosslinking density and physical properties of cured resin can be interpreted as follows. As the crosslinking density increases on cured resins,Tgrises, the relaxation time is lengthened, and the coefficient of linear thermal expansion becomes smaller in the rubbery region because, as the crosslinking density increases,Vhdecreases. Since crosslinking density increases on cured resins, the coefficient of linear thermal expansion, water absorption, diffusion coefficient, and permeability become larger, and the elastic modulus becomes smaller in the glassy region because, as the crosslinking density increases,Viincreases and, accordingly, molecular chain packing becomes looser; i.e., the specific volume increases. © 1993 John Wiley & Sons, Inc.
The structure of filled and unfilled thermotropic liquid crystalline polymer injection moldings
Authors: Plummer C. J. G. , Zülle B. , Demarmels A. , Kausch H.‐H. 
Published: April 2003

AbstractStudies of the microstructure and orientation in thermotropic liquid crystalline polymer injection moldings have been carried out using a variety of techniques to reveal the complex hierarchical structure. The effect of particle filler on the level of molecular orientation in the flow direction appears relatively weak, but at high filler contents, there is a marked disruption of coarse structure in the matrix. © 1993 John Wiley & Sons, Inc.
A new mechanism for increasing tear strength and cut‐growth resistance of elastomers
Authors: Stewart Charles W. 
Published: April 2003

AbstractA new mechanism is presented for increasing the tear strength of noncrystallizing elastomers over a broad temperature range. It is shown that the incorporation, into elastomers, of a plastic filler with the proper yield strength can substantially increase tear strength by decreasing the excess stress that develops at the tip of a sharp cut in an elastomer strip under tension. To be effective at low aspect (length/diameter) ratio, the yield strength of the plastic must be of the same order of magnitude as the tensile strength of the elastomer to which it is added. The analysis is strictly valid only for very small deformations, where crack‐tip blunting can be ignored, and for an applied stress sufficiently low that the plasticyielding zone is very small relative to the crack length. It provides a useful model, at least, for the development of a new mechanism for increasing the tear strength of fluoroelastomers at sufficiently high temperatures, which is of significant practical importance. Examples of the use of a new fluoroplastic micropowder to provide over a fourfold increase in tear strength of several fluoroelastomers at high temperatures are given. © 1993 John Wiley & Sons, Inc.
Concentration dependence of diffusivities of penetrants in glassy polymer membranes
Authors: Sada E. , Kumazawa H. , Wang J.‐S. 
Published: April 2003

AbstractSteady‐state permeation rates for pure CO2, CH4, and O2 through two kinds of homogeneous dense membranes, copolymer of methyl methacrylate and n‐butyl acrylate and poly(methyl methacrylate), were measured at three temperatures between 20 and 40°C and upstream pressures up to 3 MPa. The logarithms of the mean permeability coefficients for CO2 in both membranes increased linearly or quadratically with increasing upstream pressure, whereas the mean permeabilities for CH4 and CO2 were independent of pressure. The pressure dependence of the mean permeability coefficient for CO2 was interpreted in terms of a modified free‐volume model of diffusion for a Henry's law population in glassy polymers. © 1993 John Wiley & Sons, Inc.
Effect of MMA on the physical properties of urethane–methacrylate
Authors: Santhana Gopala Krishnan P. , Choudhary Veena , Varma I. K. 
Published: April 2003

AbstractUrethane prepolymer was prepared by reacting two moles of tolylene diisocyanate with one mole of poly(ethylene glycol) (mol wt 400), followed by end‐capping with two moles of 2‐hydroxyethyl methacrylate at room temperature (30 ± 1°C) in the presence of stannous octoate as catalyst. Different proportions of methyl methacrylate (MMA) were added to the urethane prepolymer in order to study the effect of composition on mechanical properties. Sheets were fabricated by adding 1% azobis (isobutyronitrile) (w/w) to this solution. All the copolymer sheets had a transmittance similar to the PMMA sheet, in the wavelength range of 400–800 nm. Tensile strength and modulus decreased with decreasing MMA content, whereas percent elongation at break increased. All the samples showed 2–3 stages of degradation. Initial decomposition temperature increased with increasing carbamate content. © 1993 John Wiley & Sons, Inc.
Investigations for obtaining semi‐interpenetrating polymer networks based on monomers of different reactivity toward radicals
Authors: Derrough S. N. , Rouf C. , Widmaier J.‐M. , Meyer G. C. 
Published: April 2003

AbstractClassically, the one‐step synthesis of interpenetrating polymer networks (IPNs) and related materials requires noninterfering polymerization modes to achieve distinct networks, held together by only physical entanglements. For the combination of (meth) acrylic and allylic monomers, both polymerizable by free radicals, a new in situ sequential synthesis for obtaining semi‐IPNs is proposed. Using specific initiators that decompose at two different temperatures, refractive index measurements, Fourier transform infrared spectroscopy, and dynamic mechanical analysis have shown that neat species are formed and that the two monomers do not copolymerize. © 1993 John Wiley & Sons, Inc.
Search for nonoxidative, hydrogen‐abstracting initiators useful for melt grafting processes
Authors: Xie Haiqi , Seay Michelle , Oliphant Ken , Baker Warren E. 
Published: April 2003

AbstractUsing organic peroxide initiators in the melt grafting of monomers containing amino groups onto polyethylenes is known to cause serious discoloration of the resulting polymers. To eliminate the discoloration while preserving the controlled degree of grafting, a nonoxidative and hydrogen‐abstracting initiator with appropriate thermal stability is needed. In this study, the hydrogen‐abstracting capability of three azo initiators with suitable decomposition rates in the melt grafting temperature ranges was evaluated using polyethylene cross‐linking and polypropylene degradation experiments (called “hydrogen‐abstracting experiments”). Among the three azo initiators tested, only a phenylazo initiator, 2 ‐ phenylazo ‐ 2,4 ‐ dimethyl ‐ 4 ‐ methoxyl ‐ valeronitrile (V‐19), demonstrated strong hydrogen‐abstracting capability from polymer backbones. These three azo initiators were used in the melt grafting of 2 ‐ (N, N ‐ dimethylamino) ethyl methacrylate (DMAEMA) and 2‐(N‐t ‐butylamino) ethyl methacrylate (tBAEMA) onto a linear low‐density polyethylene (LLDPE). In agreement with the results obtained from the hydrogen‐abstraction experiments, only V‐19 led to a considerable amount of grafting of both DMAEMA and tBAEMA onto LLDPE. As expected, polymers grafted with V‐19 showed significantly reduced discoloration compared with those grafted with peroxide initiators. Further examination of the grafting results indicated that the initiator efficieny, defined as the number of grafted monomer units per radical generated from initiator decomposition, was higher with the phenylazo initiator than with peroxide initiators. The hydrogen‐abstracting capability of the phenyl free radical generated from the decomposition of V‐19 was estimated to be higher than peroxide and methyl free radicals produced in the decomposition of peroxide initiatros. © 1993 John Wiley & Sons, Inc.