bluuebunny/crossref_metadata_2025_split huggingface dataset:
Melting of ultrahigh molecular weight polyethylene
Authors: Wang Xi‐You , Salovey R. 
Published: April 2003

AbstractOn heating in DSC, samples of UHMWPE show a single, fairly sharp, melting endotherm which may be increased to a peak temperature of 147°C and 77% crystallinity by annealing at elevated temperatures. An irreversible conversion of nascent to folded crystals, between 134 and 142°C, was observed by heating nascent UHMWPE powder in the calorimeter. In the presence of n‐hexatriacontane, the melting endotherm of UHMWPE was depressed and broadened and the conversion of nascent to melt‐crystallized polyethylene facilitated on heating. A melt‐crystallized mixture of ordinary linear polyethylene (HDPE) and UHMWPE was not resolved on remelting. After annealing this mixture for 12 h at 130°C, HDPE was fractionated and the melting of UHMWPE was sharpened. Crystals of UHMWPE, prepared from dilute solution in xylene, show a single sharp melting endotherm and high crystallinity, but the melting peak is reduced in temperature compared to nascent crystallized powder.
Polyacrylate‐graft silica gel as a support of lipase intersterifying triacylglycerol in organic solvent
Authors: Nakatsuka Takuo 
Published: April 2003

AbstractButyl acrylate was graft polymerized onto silica gel, which had been doubly modified with γ‐aminopropyltriethoxysilane and 4,4′‐azobis(4‐cyanovaleric acid). 2‐(Methoxycarbonnyl)ethyltrichlorosilane was treated on another silica gel. The ester groups on both silica gel surfaces were transformed to azide to immobilize lipase. The activities of the immobilized lipase for interesterfication of triacylglycerol in isopropyl ether were examined and compare with that of adsorbed lipase on silica gel, and the polyacrylate‐graft silica gel was found to be an effectual support for the enzymatic interesterification. An apparent shift of the reaction equilibrium by removing water as an azeotrope of isopropyl ether is also described.
Effect of graft copolymerization of 2‐hydroxyethyl methacrylate on the properties of polyester fibers and fabric
Authors: Abdel‐Bary E. M. , Sarhan A. A. , Abdel‐Razik H. H. 
Published: April 2003

AbstractGraft copolymerization of hydroxyethyl methacrylate (HEMA) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (BP) as initiator was carried out in water and in water/organic solvent as a reaction medium. The effect of initiator concentration, reaction time, temperature, and reaction medium as well as addition of FeSO4 to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing BP concentration up to 0.016 mol/L and then decreased upon further increase in initiator concentration. Increasing the monomer (HEMA) concentration up to 0.48 mol/L improves significantly the graft yield. Raising the polymerization temperature up to 85°C causes a significant increase in grafting yield; further increase in temperature leads to decrease in graft yield. Incorporation of Fe+2 ions in the polymerization system decrease the graft yield. The same situation is encountered when water/solvent mixture is used as reaction medium. Solvent employed were methanol, toluene, and benzene.
Copolymerization of acrylamide with cationic monomers in solution and inverse‐microsuspension
Authors: Baade W. , Hunkeler D. , Hamielec A. E. 
Published: April 2003

AbstractThe free radical copolymerization of acrylamide with three of the most commonly used cationic comonomers diallyldimethylammonium chloride, dimethylaminoethylmethacrylate, and dimethylaminoethylacrylate, the latter two quaternized with methyl chloride, was investigated. The polymerizations were carried out with azocyanovaleric acid and potassium persulfate over the temperature range 45–60°C. The copolymer reactivity ratios were determined with the error‐in‐variables method using residual monomer concentrations, measured by a Nalco HPLC method. This combination of estimation procedure and analytical technique has been found to be superior to any methods used previously for the estimation of reactivity ratios for cationic‐acrylamide copolymers.
High density polyethylene‐g‐maleic anhydride preparation in presence of electron donors
Authors: Gaylord Norman G. , Mehta Rajendra , Kumar Vijay , Tazi Mohammed 
Published: April 2003

AbstractThe reaction of molten HDPE with MAH at 215 and 250°C using di‐t‐amyl peroxide and t‐butyl cumyl peroxide as catalysts yielded HDPE‐g‐MAH accompanied by crosslinked polymer. The formation of the latter, increased by the presence of MAH and insoluble in refluxing xylene, was prevented by the presence of electron donor additives, i.e., dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tri(nonylphenyl) phosphite (TNPP). A charge containing 0.0625–0.125% catalyst, 5% MAH and 0.5% additive, all based on HDPE and added to the molten HDPE in four portions, resulted in gel‐free polymer with an MAH content of 0.7–1.7%. HDPE‐g‐MAH with the least color was obtained with TNPP, followed by DMAC and DMSO. Notwithstanding the absence of gel in the HDPE‐g‐MAH prepared from HDPE with a melt flow of 17 g/10 min, the carboxylated HDPE had a melt flow of 0.0–1 g/10 min, indicative of an increase in the molecular weight of the product. This is attributed to a coupling reaction between MAH radicals appended to the HDPE backbone (HDPE–MAH·) and HDPE radicals formed as a result of hydrogen abstraction from HDPE by radicals from the catalyst and/or excited MAH.
Preparation of glucose oxidase membrane for the application of glucose sensor by plasma activation
Authors: Hsiue G. H. , Liu C. H. , Wang C. C. 
Published: April 2003

AbstractPlasma activation is a method that takes the advantage of low temperature plasma to immobilize the bioactive materials. An active immobilized glucose oxidase membrane was obtained via plasma‐initiated polymerization of acrylic acid. The obtained immobilized enzyme is very active and stable. After 100 tests, the response error of the glucose sensor is less than 5% and its linear detecting range is 0–300 ppm. A hydrophilic PP film treated by Ar or NH3 plasma was used for the preparation of the immobilized glucose oxidase membrane. The obtained immobilized enzyme is also very active and stable. After 180 tests, the response error of the glucose sensor is less than 4% and its linear detecting range is 0–300 ppm. Furthermore, SEM was used to study the mophology of the glucose oxidase membranes obtained via both methods. And ESCA was used to analyze the plasm‐initiated polymerization products and the plasma‐treated PP films so as to obtain the optimum conditions for the immobilization of bioactive materials.
Permeability of silicone polymers to ammonia and hydrogen sulfide
Authors: Stern S. A. , Bhide B. D. 
Published: April 2003

AbstractPermeability coefficients, P̄, for NH3 AND H2S in 11 different types of silicone membranes were measured in the temperature range from 10.0 to 55.0°C and at pressures up to 115 psig (∼ 7.8 atm). The values of P̄ for NH3 and H2S in different silicone polymers decrease considerably as the bulkiness of the functional groups in the side and backbone chains of these polymers increases. the substitution of SiO bonds with stifer SiC bonds in the backbone chains also results in a considerable decrease in gas permeability. the values of P̄ for NH3 and H2S increse exponentially with incresing δp, the pressure difference across the membrancs. The temperature dependence of NH3 and H2S varies greatly: P̄ can increase, decrease, or pass through a minimum with increasing temperature, depending on the nature of the silicone polymer. The temperature dependence of P̄ is also affected in some cases by Δp. The permeability behavior of silicone polymers to NH3 and H2S is compared with that to other penetrant gases, and the factors which might affect this behavior are discussed.
A new approach for the estimation of kinetic parameters in emulsion polymerization systems. I. Homopolymerization under zero–one conditions
Authors: Asua J. M. , Adams M. E. , Sudol E. D. 
Published: April 2003

AbstractA new method for the estimation of kinetic parameters in emulsion polymerization systems is presented. This method is based on studies of the evolution of monomer conversion in chemically initiated seeded emulsion polymerization systems. In this paper, homopolymerization under zero—one conditions is considered. The method is based on a fundamental model that includes the free radical balance in the aqueous phase and fundamental parameters such as the entry and exit rate coefficients, the termination rate constant in the aqueous phase, and the rate coefficient for initiator decomposition. These parameters, as well as the propagation rate constant, are the estimable parameters. This method, which uses all available data simultaneously in order to estimate the parameters, is checked by using simulated experimental data generated with exact values of the parameters. The criteria for deciding the usefulness of the present approach are the closeness of the fit to the original data and the match of the estimated kinetic parameters to the exact values of the parameters. It was found that accurate values of the parameters are obtained with the present approach provided that a sufficient number of experiments with a minimum range of variation are available. A study of both the minimum number of experiments and the minimum range of variation of the experimental conditions needed to estimate reliable parameters is presented. Also, the effect of both random and systematic errors is included in this study. Finally, a comparison between the present approach and those previously published in the literature is presented.
Synthesis and characterization of imide end‐capped oligoesters of terephthalic acid and 2‐methyl‐2‐propyl‐1,3‐propanediol
Authors: Acevedo M. , De La Campa J. G. , Abajo J. De 
Published: April 2003

AbstractHydroxytelequelic oligoesters of molecular weight (Mn) between 500 and 3000 were prepared from dimethylterephthalate (DMT) and 2‐methyl‐2‐propyl‐1,3‐propanediol (MPPD) by ester interchange polycondensation. They were modified by reaction of their end hydroxyl groups with N‐(4‐chlorocarbonylphenyl) maleimide and N‐(4‐chlorocarbonylphenyl) nadimide. Spectroscopic (NMR), chromatographic (GPC), and calorimetric (DSC) analyses demonstrated that MPPD oligoterephthalates are less reactive than previously used glycols (diethylene glycol, DEG) and only nadimide‐modified oligomers could be readily synthesized. Attempts to introduce maleimide groups at the chain ends led to crosslinked materials. Furthermore, some relationships between molecular weight and properties (Tg, thermal stability, etc.) could be outlined. The oligomers, unmodified and modified, proved to be essentially amorphous.
Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) diols. II. Effects of variations in hard segment concentration
Authors: Harris Robert F. , Joseph Michael D. , Davidson Carla , Deporter Craig D. , Dais Virginia A. 
Published: April 2003

AbstractA series of polyurethane elastomers were studied in which the soft segment composition was a molecular weight advanced poly(ethylene ether carbonate)diol (2025 mol wt) and the hard segment composition was based on MDI/1,4‐butanediol. These polyurethane elastomers had a constant soft segment composition and block length, a constant hard segment composition, but a variable hard segment block length and concentration (31.9–65.2 wt % hard segment). Properties such as rubbery plateau modulus, solvent resistance, melting point, hardness, tensile strength, and hard segment run length all improve with increasing hard segment concentration. DMA and DSC data indicate a partially phase mixed morphology. However, phase mixing must occur at domain boundaries since the soft segment Tg is nearly invariant with hard segment concentration. Annealing studies indicate that the optimum post‐cure temperature, for 1 h, is about 175°C.
Water self‐diffusion coefficient determination in an ion exchange membrane by optical measurement
Authors: Zelsmann H. R. , Pineri M. , Thomas M. , Escoubes M. 
Published: April 2003

AbstractThe self‐diffusion coefficient of water in a perfluorinated ionic membrane has been measured for different water contents corresponding to water vapor pressures less than the saturated one. The isotope method usually employed in the liquid state was extended to vapors, which led us to an observation of three different isotopic species by quantitative far IR spectroscopy. Two measurement methods are presented permitting a determination of the time lag and hence of the diffusion coefficient. The slow variation of the diffusion coefficient with the water concentration, as well as the good agreement of the numerical results given by different methods (permeation‐sorption) are explained by the fact that no plasticization occurs. This result has been independently verified by other experiments.
Interfacial phenomena controlling particle morphology of composite latexes
Authors: Chen Yi‐Cherng , Dimonie Victoria , El‐Aasser Mohamed S. 
Published: April 2003

AbstractA thermodynamic analysis and a mathematical model were derived to describe the free energy changes corresponding to various possible morphologies in composite latex particles. Seeded batch emulsion polymerization was carried out at 70°C using as seed monodisperse polystyrene latex particles having different surface polarity. The surface polarity was estimated by contact angle measurement at the latex “film”/water interface for octane as the probe liquid. Methyl methacrylate and ethyl methacrylate were polymerized in a second stage seeded emulsion polymerization using polystyrene particles as seed in the presence of a nonionic stabilizer, nonyphenol polyethylene oxide (Igepal Co‐990). Two types of initiators, potassium persulfate (K2S2O8) and azobisiobutyronitrile (AIBN), were used to change the interfacial tension between the second stage polymer (in monomer) and water interface. The values of the interfacial tension of polymer solutions in the second stage monomer vs. the aqueous phase, measured by drop‐weight–volume method under conditions similar to those prevailing during the polymerization, correlated well with the determined particle surface polarity and the observed TEM particle morphology. The results showed that, rather than the polymer bulk hydrophilicity, the surface particle polarity is the controlling parameter in deciding which phase is inside or outside in the composite particle. The variation of the polymer phase interfacial tension with polymer concentration was also estimated. Based on experimentally measured interfacial tensions, composite particle configurations were predicted. The predicted morphologies showed good agreement with the observed particle morphologies of the composite latexes.
Ultraviolet‐curable, abrasion‐resistant, and weatherable coatings with improved adhesion
Authors: Lewis Larry N. , Katsamberis Dimitris 
Published: April 2003

AbstractA UV‐curable coating for plastics that is abrasion resistant and weatherable is described. The coating consists of colloidal silica functionalized with methacryloxypropyltrimethoxy‐silane (MAPTMS) in a matrix of acrylic monomers. The formulation employs diethoxyacetophenone (DEAP) as a photoinitiator and a sulfonated benzotriazole as a UV absorber. It has been found that the adhesion of the coating depends greatly on the type of acrylic monomers used and the application parameters. Transmission electron microscopy (TEM) analysis shows that improved adhesion is due to the formation of an interpenetrating layer between coating and substrate.
Morphological studies on roll extruded, plasticized composites
Authors: Alexandru L. , Zamin J. , Sundararajan P. R. 
Published: April 2003

AbstractA study of the morphologies of polymer/carbon black composites, plasticized with small molecule organics, is presented. Four different plasticizers and three different polymers were used. In all cases, the plasticizers depress the Tg of the polymers. Whereas in some cases the organic small molecule was found to be molecularly dispersed in the polymer matrix, phase separation occurred in other cases beyond a certain composition. In the latter instances, the excess plasticizer formed crystalline aggregates and a depression of the melting point of the plasticizer was observed. The samples were prepared by a process similar to roll extrusion, which causes biaxial orientation of the crystalline aggregates.
Permeability of vitamin B‐12 in chitosan membranes. Effect of crosslinking and blending with poly(vinyl alcohol) on permeability
Authors: Nakatsuka Shuji , Andrady Anthony L. 
Published: April 2003

AbstractThe permeability and diffusion of vitamin B‐12 in chitosan, crosslinked chitosans, and chitosan/poly(vinyl alcohol) (PVA) blends were studied using “lag time” technique. Apparently the diffusion coefficient, D, for both crosslinked and blended chitosan membranes depends solely upon the equilibrium swelling ratio, Q, of the material in water. The functional dependence of D on Q was obtained from the data. The partition coefficients calculated for vitamin B‐12 in all membranes studied were nearly constant (K ≈ 0.4). The results are shown to be consistent with the “pore type” transport mechanism for vitamin B‐12 in these chitosan membranes.
Fracture and impact properties of polycarbonates and MBS elastomer‐modified polycarbonates
Authors: Chang Feng‐Chin , Wu Jiann‐Shing , Chu Line‐Hwa 
Published: April 2003

AbstractMechanical properties of polycarbonates (PCs) and elastomer‐modified polycarbonates with various molecular weights (MW) are investigated. Higher MW PCs show slightly lower density, yield stress, and modulus. The ductile–brittle transition temperature (DBTT) of the notched impact strength decreases with the increase of PC MW and with the increase of elastomer content. The elastomer‐modified PC has higher impact strength than does the unmodified counterpart if the failure is in the brittle mode, but has lower impact strength if the failure is in the ductile mode. The critical strain energy release rate (Gc) measured at −30°C decreases with the decrease of PC MW. The extrapolated zero fracture energy was found at Mn = 6800 or MFR = 135. The Gc of the elastomer‐modified PC (MFR = 15, 5% elastomer) is about twice that of thee unmodified one. The presence of elastomer in the PC matrix promotes the plane–strain localized shear yielding to greater extents and thus increases the impact strength and Gc in a typically brittle fracture. Two separate modes, localized and mass shear yielding, work simultaneously in the elastomer‐toughening mechanism. The plane–strain localized shear yielding dominates the toughening mechanism at lower temperatures and brittle failure, while the plane–stress mass shear yielding dominates at higher temperatures and ductile failure. For the elastomer‐modified PC (10% elastomer), the estimated extension ratio of the yielding zone of the fractured surface is 2 for the ductile failure and 5 for the brittle crack. A criterion for shifting from brittle to ductile failure based on precrack critical plastic‐zone volume is proposed.
Starch–poly(ethylene‐co‐acrylic acid) composite films. Effect of processing conditions on morphology and properties
Authors: Fanta G. F. , Swanson C. L. , Shogren R. L. 
Published: April 2003

AbstractFormulations containing 4 parts cornstrach, 5 parts poly(ethylene‐co‐acrylic) (EAA), 1 part urea, and 1.6 parts of either water or aqueous ammonia were extruded at either 110–120°C or 150–160°C; and the resulting extrudates were then extrusion‐blown into films. Complex formation between EAA and starch was measured by either X‐ray diffraction or by solvent extraction of uncomplexed EAA. Although the processing temperature had only a minor effect on the amount of EAA complexed by starch, use of aqueous ammonia rather than water in these formulations increased the amount of complexed EAA by about a factor of 2. In films prepared with aqueous ammonia, the polysaccharide phase was present as submicron‐sized domains. When ammonia was omitted from these formulations, the polysaccharide phase was less uniform in size and contained particles that were over an order of magnitude larger than those observed with ammonia.
Molecular weight distribution of the methyl methacrylate (MMA) polymer separated from the MMA‐grafted silk fiber
Authors: Tsukada Masuhiro , Goto Yoko , Freddi Giuliano , Yamamoto Takashi , Nakabayashi Nobuo 
Published: April 2003

AbstractThe molecular weight distribution of poly‐methyl methacrylate (poly‐MMA) chains separated from MMA‐grafted silk fibers obtained by using potassium persulfate (KPS) and tri‐n‐butylborane (TBB) as initiator of the graft‐copolymerization reaction have been examined by gel permeation chromatography (GPC). GPC elution pattern of poly‐MMA chains shows a bimodal molecular weight distribution. The two peaks have been identified as heavy and light component. The average molecular weight of the heavy component ranges from 48.5 to 200 kD for poly‐MMA copolymerized by the KPS reaction system and from 336 to 816 kD for the poly‐MMA copolymerized by the TBB reaction system. The light component has an average molecular weight lower than 1,000 D and its value is almost similar in all the samples examined. Scanning electron microscopy (SEM) analysis revealed the presence of MMA oligomers formed on the fiber surface during grafting. The molar ratio between poly‐MMA chains and silk fibroin attains a constant value that seems to be specific for a certain reaction system. A linear correlation has been observed between the weight gain and the average molecular weight of the poly‐MMA chains. These findings suggest the effect of grafting parameters on the molecular weight and molecular weight distribution of the grafted polymer, as well as its influence on the physical properties and textile performances of MMA‐grafted silk fibers.
Residual stress in particulate epoxy resin by X‐ray diffraction
Authors: Nishino Takashi , Airu Xu , Matsumoto Takeshi , Matsumoto Kanki , Nakamae Katsuhiko 
Published: April 2003

AbstractResidual stress in particulate epoxy resin was investigated by X‐ray diffraction. Microdeformation of incorporated Al and α‐SiO2 crystal, which was induced by the residual stress, could be detected as a shift of X‐ray diffraction peak. The residual stress at the interface between the adherend and the particulate epoxy resin was found to decrease with the increase of volume fraction of filler. It was shown that the difference in the thermal expansion coefficients between the adherend and the particulate epoxy resin is much more effective on residual stress than the increment of Young's modulus owing to the incorporation of filler. When epoxy resin was cured on the Al plate, incorporated particles were subjected to a tensile stress; while cured on polytetrafluoroethylene sheet, particles were subjected to a compressive stress. The incorporation of some inorganic particles is considered effective to reduce the residual stress.
On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. I. Preparation of graft polymers
Authors: Schellenberg J. , Hamann B. 
Published: April 2003

AbstractIn order to modify the graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers), the preparation of the graft products of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber by emulsion polymerization was described and theoretically studied up to a high degree of conversion. Depending on the residual monomer content of the products, the polymer composition obtained in the experiment was compared with the theoretical one for the substitution of certain quantities of styrene, acrylonitrile, or styrene and acrylonitrile by vinyl acetate in the mass ratio of 3 : 1. Deviations were discussed. The specific viscosity of the polymers of styrene, acrylonitrile, and vinyl acetate separated from the elastomer phase, considerably decreases during the substitution of acrylonitrile by increased vinyl acetate quantities.