bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of poly(vinyl alcohol)‐graft‐N‐isopropylacrylamide copolymer membranes and permeation of solutes through the membranes
Authors: Nonaka Takamasa , Ogata Tomonari , Kurihara Seiji 
Published: April 2003

AbstractThermosensitive copolymers were prepared by graft copolymerization of N‐isopropylacrylamide onto poly(vinyl alcohol) in dimethyl sulfoxide (DMSO) using potassium peroxodisulfate as an initiator. The phase transition temperature was measured by differential scanning calorimetry. The copolymers exhibited almost the same transition temperature (about 33°C) as that of poly(N‐isopropylacrylamide) regardless of the composition of the copolymers. The copolymer membranes were obtained by evaporating solvent from the DMSO solution of the graft copolymers and were insolubilized by annealing the membranes at 120°C for 10 h. Permeation of the lithium ion and Methylene Blue through the membranes was investigated at various temperatures. The permeation of solutes was greatly affected by temperature, i.e., the permeation of the solutes could be controlled at temperatures below and above 33°C. © 1994 John Wiley & Sons, Inc.
Study of an aramid surface reactivity: Modification with a cold plasma or an electron beam followed by a postgrafting reaction
Authors: Poncin‐Epaillard Favienne , Chevet Bruno , Brosse Jean‐Claude 
Published: April 2003

AbstractDifferent modes of activation are described for a postgrafting reaction of acrylic acid on poly(p‐phenylene terephthalamid) (PPTA)mitrogen plasma or electron‐beam irradiation. Both lead to surface radical formation, and these species are able to initiate grafting. The Functionalization through amino group attachment is characteristic of plasma treatment. Degradation initiated by UV‐visible emission of plasma is noticed, leading to the amide clivage. The surface grafting is more important when the PPTA is irradiated with a cold plasma and if water is used as the solvent. The polymer crystallinity degree reduces the grafting of the electron beam‐irradiated PPTA even with a high radical concentration. © 1994 John Wiley & Sons, Inc.
Preparation of high‐strength and high‐modulus poly(vinyl alcohol) fibers by crosslinking wet spinning/multistep drawing method
Authors: Hwang Kuen‐Shan , Lin Chin‐An , Lin Chung‐Hua 
Published: April 2003

AbstractThis study is mainly focused on the preparation of high‐strength and high‐modulus poly(vinyl alcohol) (PVA) fibers by crosslinking wet spinning and multistep drawing. High strength as well as high modulus can be achieved by introduction of the crosslinks into the oriented chains to reduce entanglement degree and slippage between chains. The relationships between mechanical properties and fine structure of the drawn fibers were examined based on results of measurements of tensile property, thermal property, dynamic viscoelasticity, crystallinity, and orientation. The strength and Young's modulus of the drawn fibers are approximated to 1.82 and 51.76 GPa, respectively. The fiber has a sharp melting peak temperature that appeared at 236.7°C in the differential scanning calorimeter (DSC) curve. Our results indicate the multistep drawing procedure is superior to the conventional one‐step drawing procedure. These excellent mechanical properties can be directly attributed to their high orientation of the amorphous chains. © 1994 John Wiley & Sons, Inc.
Electrical and thermal conductivities of polyethylene composites filled with biaxial oriented short‐cut carbon fibers
Authors: Agari Y. , Ueda A. , Nagai S. 
Published: April 2003

AbstractPolyethylene composites filled with various types of carbon fiber were prepared for electrical and thermal conductivity measurements. By estimation of the anisotropic parameter (Hermans' parameter), the fibers were confirmed to be significantly biaxially oriented in the composites. The critical volume fractions in the electrical conductivity of these composites for the two oriented directions (X and Y) were equal to each other and smaller than that for a direction (Z) vertical to the above. The electrical anisotropy, i.e., ratio of electrical conductivity of the composite for the Z direction to the X and Y directions varied drastically with increase in filler content. The longer the length of carbon fiber was, the higher became the electrical conductivity of the biaxially oriented carbon fiber composites for all directions. But, the thermal conductivity of the composite was almost unchanged for the Z direction, even if fiber length was sufficiently long. Our equation, previously proposed, proved adaptable to these thermal conductivities. The factors of Cp and Cf in the equation are kept unchanged, in spite of increasing fiber length. © 1994 John Wiley & Sons, Inc.
Cold remote nitrogen plasma polymerization from 1.1.3.3‐tetramethyldisiloxane–oxygen mixture
Authors: Callebert F. , Supiot Ph. , Asfardjani K. , Dessaux O. , Goudmand P. , Dhamelincourt P. , Laureyns J. 
Published: April 2003

AbstractCold remote nitrogen plasma (CRNP) selectively reacts with silane‐terminated organosiloxane compounds such as 1.1.3.3‐tetramethyldisiloxane to give polymeric layers. Deposition rate measurements, FT‐IR and Raman spectroscopy were performed. The chemical composition of the deposited film is closely dependent on the reactive gas composition and its flowing conditions. An original effect of dioxygen addition in the nonionic reactive media is pointed out: dioxygen addition leads to a fast and highly hydrocarbonated polymer formation with a nitrogen fixation in a silazane structure. Polymerization is described by a model where SiO· type of radicals are the critical reactant. A global mechanism is proposed involving active species of the CRNP in initiation step of hydrogen abstraction and the nitrogen triplet state molecule N2(A3Σ) in methyl abstraction on Si· type of free radical. Dioxygen adjunction appears to limit the methyl abstraction steps. The efficient direct oxygen reaction on free radicals leads to an increase of the SiO· radical density and, consequently of the average length of the growing polymeric fragments. Nitrogen fixation, involving oxygenated species, is discussed. Under defined conditions, a highly hydrophobic polymeric film is obtained with a volumic mass of 1.34g/cm3 and a deposition rate of about 12 mg/cm2 h corresponding to a growth rate of 200 Å/s. © 1994 John Wiley & Sons, Inc.
Chemical modification of lignocellulosic fibers I. Functionality changes and graftcopolymerization of acrylonitrile onto pineapple leaf fibers; their characterization and behavior
Authors: Samal R. K. , Bhuyan B. L. 
Published: April 2003

AbstractThis paper is an attempt to examine the commercial significance of an agro‐waste “pineapple leaf fiber” (PALF). The quality enhancement of PALF has been tried through chemical modifications. Functionality changes in the above fiber have been done through mercerization, cyanoethylation, oxidation, and graftcopolymerization with acrylonitrile, using cericion as an initiator at varying concentrations of monomer, initiator, and mineral acid at a number of temperatures for various time intervals. The modified fibers have been characterized by FTIR spectroscopy and viscosity measurements. The extent of moisture regain, acid‐alkali solubility, tensile modulus, dye‐uptake ability, and thermal stability of the resulting materials have been tested and compared with the parent fiber. The significance of such chemical modification in the context of better textile performance and reinforcing behavior of the product in FRP has been discussed. © 1994 John Wiley & Sons, Inc.
Transient shear response of liquid crystal‐forming hydroxypropyl cellulose solution in dimethylacetamide. I. Stress growth and relaxation behavior
Authors: Suto Shinichi , Tateyama Shinichiro 
Published: April 2003

AbstractThe stress growth and relaxation behavior of liquid crystalline hydroxypropyl cellulose solutions in dimethylacetamide was characterized by using exponential functions. The parameters evaluated for the stress growth and relaxation processes were compared and the shear history effect on the parameters was determined. The exponential functions proposed were valid for our system. The isotropic solutions had one retardation time and one relaxation time, whereas the liquid crystalline solutions had plural retardation and relaxation times. The concentration dependence of the parameters for the stress growth process was similar to that for the stress relaxation process and to that for the steady‐state shear viscosity. The stress growth and relaxation behavior for the liquid crystalline solutions was originated from the change (deformation or decrease) in liquid crystalline domains. The deformation of liquid crystalline domains with shear seemed to be slower than the recovering of the domains to original shape. The stress growth process was a progressive event, whereas the relaxation process was a sudden event. Stress relaxation behavior for the liquid crystalline solutions was sensitive to the shear history. © 1994 John Wiley & Sons, Inc.
The formation of nodular structures in the top layer of ultrafiltration membranes
Authors: Wienk I. M. , van den Boomgaard Th. , Smolders C. A. 
Published: April 2003

AbstractThe formation of nodular structures in the top layer of ultrafiltration membranes is considered. A critical review of mechanisms described in the literature is given. Flat‐sheet poly(ether sulfone) membranes and hollow‐fiber poly(ether sulfone)/polyvinylpyrrolidone membranes were made by coagulation of a polymer solution in a nonsolvent medium under different circumstances. From these experiments, a number of empirical rules are found to describe the resulting morphology of the top layer. A new mechanism for the formation of a nodular structure is proposed. It is based on the small diffusion coefficient of the polymer molecules compared to the diffusion coefficient of solvent and nonsolvent combined with a high degree of entanglement of the polymer network. For unstable compositions, phase separation will proceed by growth in amplitude of concentration fluctuations. The rapid diffusional exchange of solvent for nonsolvent in the top layer leads to vitrification of the maxima of the concentration fluctuations that form the nodules. Complete disentanglement of the polymer chains between the nodules is not reached, which explains the small pores and the low porosity of ultrafiltration membranes. © 1994 John Wiley & Sons, Inc.
High‐pressure phase behavior in polyethylene/n‐butane binary and polyethylene/n‐butane/CO2 ternary systems
Authors: Xiong Yan , Kiran Erdogan 
Published: April 2003

AbstractSolubility of polyethylene molecular weight standards (Mw = 2150, 16,400, 108,000, and 420,000 and Mw/Mn = 1.14, 1.16, 1.32, and 2.66, respectively) has been studied in near‐ and supercritical n‐butane and n‐butane/CO2 mixtures at pressures up to 70 MPa. For each polyethylene/solvent system at selected compositions, demixing pressures have been determined using a high‐pressure variable‐volume view‐cell at temperatures up to 200°C. Solutions in pure n‐butane are found to display LCST (lower critical solution temperature)‐type behavior. The behavior of the solutions in n‐butane/CO2 mixtures are observed to change from the LCST to the UCST (upper critical solution temperature) with increasing CO2 content in the binary solvent. Sanchez–Lacombe theory has been used to model these systems. The predictions correctly describe the nature of the phase diagrams for both binary and ternary systems and the calculations are in reasonable agreement with experimental data. © 1994 John Wiley & Sons, Inc.
TSDC and the role of space charge in polyacrylonitrile/methylacrylate copolymer films
Authors: Migahed M. D. , Ishra M. , El‐Khodary A. , Fahmy T. 
Published: April 2003

AbstractSpace charge effects on direct current (DC) conductivity and the thermally stimulated depolarization current (TSDC) in the semicrystalline polyacrylonitrile–methylacrylate [P(AN–MA)] films have been investigated. The conduction was found to be controlled by space charge limited effect. On the other hand, the TSDC studies point to a superposition of dipole orientation and space charge effects. With the aid of the thermal sampling technique, the complex spectrum could be resolved into its elementary processes. Curve fitting has been carried out and peak parameters were determined. Information related to the motion of dipolar groups could be obtained. The compensation effects is observed to be valid and the value of the compensation temperature (Tc = 343 K) greatly differs from the glass transition temperature (Tg = 383 K). From the DC and TSDC studies considerations, the origin of the three conduction regions appearing in the 1n σ vs. 1/T could be explored. © 1994 John Wiley & Sons, Inc.
Chemical modification of poly(styrene‐co‐maleic anhydride) with primary N‐alkylamines by reactive extrusion
Authors: Vermeesch I. , Groeninckx G. 
Published: April 2003

AbstractReactive melt‐processing of poly(styrene‐co‐maleic anhydride) (SMA) with primary N‐alkylamines was carried out in one step in a twin‐screw extruder. Ring formation of the imide occurred within the residence time of the extruder, at temperatures exceeding 220°C and with an excess of primary amines. The increasing chain length of grafted amine onto the SMA backbone depressed the glass transition temperature of poly(styrene‐co‐N‐alkylmaleimides) remarkably. © 1994 John Wiley & Sons, Inc.
Electroless reduction and precipitation of gold from acid solution by polypyrrole
Authors: Kang E. T. , Ting Y. P. , Tan K. L. 
Published: April 2003

AbstractThe oxidation of the 25% intrinsically oxidized polypyrrole, containing 25% [N–] and 75% [NH], and the subsequent reprotonation and reduction of the highly intrinsically oxidized polymer in acid gold solution were utilized for the spontaneous and sustained reduction of gold. The X‐ray photoelectron spectroscopic (XPS) results indicate that only elemental gold [or Au (0)] accumulates on the polymer film or powder surfaces. The N1s core‐level spectra of the protonated and deprotonated polypyrrole after metal reduction suggest that the intrinsic structure of the polymer at the polymer/Au interface remains intact, even at [Au]/[N] mol ratios substantially above 1. The process, however, is limited by the decreasing effective surface area of the polymer due to Au coverage. The Au reduction behavior of polypyrrole was also compared to that of polyaniline. © 1994 John Wiley & Sons, Inc.
Water‐sorption properties of poly(ϵ‐lysine): Carboxymethyl cellulose (CMC) dietary complex films
Authors: Ichikawa Tomoko , Mitsumura Yukari , Nakajima Toshinari 
Published: April 2003

AbstractTo investigate the application of supersorbing materials in the food industry, the water sorption of polyion complex films, prepared by solvent‐casting from poly(ϵ‐lysine) (PEL) and carboxymethyl cellulose (CMC), were examined and some physical properties of the hydrogels were studied. Three CMC samples having various degrees of substitution (DS) and molecular weights (MW) were applied to show a variety of water‐sorption behavior and physical properties. The ratio of PEL/CMC was changed from 10/90 to 50/50. Good film swelling in water was achieved when the complex was made from PEL and CMC with a low DS and an appropriate molecular weight, and when the PEL/CMC ratio was low. This indicated that the carboxyl groups in the CMC are not readily dissociated, and that the strength of cationic and anionic interactions affects the film swelling. In line with this view, the addition of electrolytes markedly lowered the film swelling. Nonelectrolytes such as sucrose or urea had no effect. IR and NMR spectra showed that a fraction of the ionic groups in the polyelectrolytes interact. Tensile moduli of complex dry films decreased linearly as the PEL content increased. Compressive moduli of swollen films were affected by neither the degree of swelling nor the molecular weights of CMC. The lower the DS values of CMC, the higher the compressive moduli were. We also examined the relation between the rigidity of polymer component and the ratio of nonfreezable bound water in complex films. On swelling in acetone–water or ethanol–water mixed solvent, expansion–shrinkage transition of the polymer gels occurred at about 20 mol % acetone or ethanol concentrations for every complex film. The overall characterstics of PEL/CMC consisting of a linear polyanionic polypeptide and a chain of cationic rings are reminiscent of polycationic chitosan and polyanionic polyglutamic acid. © 1994 John Wiley & Sons, Inc.
Variables affecting the methylation reactions of cellulose
Authors: Mansour Olfat Y. , Nagaty Ahmed , El‐Zawawy Waleed K. 
Published: April 2003

AbstractSolubility of methyl cellulose (MC) depends on the degree of substitution (DS), the average degree of polymerization (DP), and the distribution of methoxyl groups. Of these, the DS appears to be the most important. The DS of the MC depends on the conditions of preparation. The conditions studied in this work revealed that the DS of the MC increased as the concentration of sodium hydroxide increased from 10 to 50%. This result is attributed to the increase in the extent of formation of alkali cellulose II as a result of the increase in the alkali concentration and hence the increase of the DS of the MC. Decreasing both the ratio of dimethyl sulfate: cellulose and the liquor ratio increased the DS. High DS was achieved within a period of 2 and 3 h. However, the DS increased as the time increased. The decrease of the DS as the liquor ratio increased may be attributed to the sol–gel transition due to the interaction of the hydrophobic methoxyl groups within the polymer chains. To reveal the effect of the thermal sol–gel transition, the reaction was carried out in nonaqueous medium and the results obtained showed an increase of the DS with the increase of the solvent ratio until a maximum. This result may be contributed to the breakdown of the hydrogen bonding in the presence of solvents that transfer the reaction medium to the sol‐form and hence more methylating reaction takes place. The degree of the solvation of the methyl groups into the solvents also plays a role. © 1994 John Wiley & Sons, Inc.
Peroxide modification of a multicomponent polymer blend with potential applications in recycling
Authors: Vivier T. , Xanthos M. 
Published: April 2003

AbstractA mixture of seven immiscible “virgin” plastics, namely low and high density polyethylene (LDPE and HDPE), polypropylene (PP), polyvinyl chloride (PVC), crystal and high impact polystyrene (PS and HIPS), and polyethylene terephthalate (PET), in proportions representative of those currently found in post‐consumer plastics containers, was compounded in a corotating twin‐screw extruder. The mechanical properties of the blend were improved through the addition of relatively high concentrations of a dialkyl peroxide which was also found to drastically affect the blend morphology. The results are interpreted in terms of improved dispersive mixing favored by the similarity in the rheological behavior of the modified blend components, improved physical properties of certain blend components upon peroxide modification, and, possibly, enhanced intefacial adhesion. © 1994 John Wiley & Sons, Inc.
β‐radiation effects on PVC materials: Methodology for studying chemical modifications
Authors: Yagoubi N. , Baillet A. , Legendre B. , Rabaron A. , Ferrier D. 
Published: April 2003

AbstractThe radiosterilization of plastic packaging theoretically induces two types of chemical modifications, namely reticulation and cleavage, that depend not only on the chemical structure of the polymer, but also on the kind and dose of radiation. This article proposes a methodology for studying plasticized polyvinylchloride (PVC) behavior submitted to β radiation. Analytical techniques such as thermogravimetric analysis (TGA) and size exclusion chromatography (SEC) coupled with a light scattering detector were used in this study. SEC has informed us directly on the modifications (reticulation, scission) that intervened after a radiotreatment; TGA allowed us to highlight polymer structural changes. In addition, FTIR was employed to demonstrate an intermolecular dehydrochlorination following the radiotreatment. The results of these investigations permitted us to demonstrate both a reticulation and a scission phenomena within the PVC polymer. © 1994 John Wiley & Sons, Inc.
Preparation and characterization of perlite‐filled high‐density polyethylenes. II. Thermal and flow properties
Authors: Akin‐öktem G. , Tinçer T. 
Published: April 2003

AbstractThermal and flow properties of perlite‐filled high‐density polyethylenes (HDPE), studied in the first part of the paper, are discussed. Maximum peak temperatures of endotherms (Tmp) and the corresponding relative peak heights were examined by differential scanning calorimetry (DSC). The data obtained from a Brabender torque rheometer were evaluated to find the melt viscosities at low share rate during preparation of perlite–HDPE composities. The filler concentration, type of HDPEs, and the use of γ‐APS are found to be effective and influential factors on the thermal and flow propertis of these composities. © 1994 John Wiley & Sons, Inc.
Characterization of plasma‐induced graft polymerization of 2‐hydroxyethyl methacrylate onto silicone rubber
Authors: Lee Shyh‐Dar , Hsiue Ging‐Ho , Wang Chee‐Chan 
Published: April 2003

AbstractGraft copolymerization of 2‐hydroxyethyl methacrylate (HEMA) as attempted onto the surface of silicone rubber membrane, which was pretreated by Ar‐plasma, then exposed in oxygen to introduce a peroxide group. The effect of the amount of HEMA grafted on Arplasma‐treated and graft copolymerization was examined for various parameters of power, pressure, time, reaction time, and concentration of HEMA aqueous solution. The surfaces were characterized by ATR–FTIR, ESCA, contact angle, and SEM. PHEMA was indicated by ATR–FTIR and ESCA analysis to be present successfully onto the grafted surface of silicone rubber membrane. The stable wettability, as demonstrated once the PHEMA grafted films, indicated contact with a hydrated environment by the study of contact angle. © 1994 John Wiley & Sons, Inc.
Physical and mechanical properties of highly plasticized pectin/starch films
Authors: Coffin David R. , Fishman Marshall L. 
Published: April 2003

AbstractBlends of citrus pectin and high amylose starch plasticized with glycerine were investigated to determine the effect of compositional variables on film properties. Several films with representative compositions were made from sugar beet and almond pectin, and tested for comparison. The films were cast from water onto glass plates, dried, and removed. Mechanical analysis was done using a Rheometrics RSA II solids analyzer. Increasing the glycerine concentration led to decreases in static modulus, dynamic modulus, and tensile strength, but to increases in elongation. Increasing levels of starch in the blend lowered the effect of glycerine on mechanical properties. Oxygen permeability of the films was extremely low. Sugar‐beet pectin and almond pectin gave films with mechanical properties comparable to those made with citrus pectin. © 1994 John Wiley & Sons, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.