bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasma polymer deposition from indium acetylacetonate and its application to chemical sensor devices
Authors: Inagaki N. , Ohkubo J. 
Published: April 2003

AbstractPlasma polymerization of indium acetylacetonate (InAcAc) was investigated from the viewpoint of the material preparation for application to chemical sensor devices. The plasma polymerization of InAcAc resulted in the deposition of films, which were hydrocarbon‐like polymers with fine particles of indium oxides. The deposition rate and the chemical composition of the deposited films were strongly influenced by the system pressure in operating the plasma polymerization, as well as by the substrate temperature. The deposited films possessed n‐type semiconductive properties and responded to reducing gases, such as CO, H2, C3H8, and C2H5OH, with increasing the conductivity. The sensor device composed of the films deposited from InAcAc showed extremely high sensitivity to CO and higher gas selectivity than the sensor devices consisting of SnO2 and ZnO2.
Miniemulsion polymerization—a comparative study of preparative variables
Authors: Tang P. L. , Sudol E. D. , Silebi C. A. , El‐Aasser M. S. 
Published: April 2003

AbstractVariations in the conditions used to prepare miniemulsions of monomers in water have resulted in substantial differences in polymerization kinetics and final particle sizes and distributions. These variations have included (1) surfactant amount and type; (2) cosurfactant amount and type; (3) monomer (s) type; (4) temperature of preparation and polymerization; (5) means and conditions of homogenization; and (6) degree of aging of the emulsion. In an effort to unify some of the disparate information of previous work, a systematic study of some of the above variables was undertaken using styrene as the oil phase with sodium lauryl sulfate as surfactant. Based on the polymerization kinetics and particle sizes obtained, the following conclusions are drawn: The finest droplet size miniemulsions are obtained by (1) using a cosurfactant; (2) homogenizing at elevated temperature; (3) homogenizing using a uniform high shear device (Microfluidizer); and (4) limiting the aging time prior to polymerization.
Separation of organic vapor from air by aromatic polyimide membranes
Authors: Feng Xianshe , Sourirajan S. , Tezel H. , Matsuura T. 
Published: April 2003

AbstractAn attempt was made to prepare dry asymmetric membranes of aromatic polyimide material for the separation of air–organic vapor mixtures. Membrances with the permeability of organic vapor two orders of magnitude higher than that of air could be obtained. The membrane performance depends strongly on the conditions of membrane preparation. It was found that the permeability of organic vapors exhibits a strong correlation with their cohesive energy data.
Graft copolymerization of methyl methacrylate onto polypropylene oxidized with ozone
Authors: Yamauchi Jun , Yamaoka Akiyoshi , Ikemoto Kunji , Matsui Tetsuji 
Published: April 2003

AbstractAfter the reaction of polypropylene by ozone oxidation, methyl methacrylate was graftcopolymerized onto the polypropylene. The active species determined by ESR spectroscopy as a peroxyl radical was converted to hydroperoxide, and the hydroperoxide was broken by heating, giving alkoxyl and hydroxyl radicals, the former of which initiated graft copolymerization. The effect of the ozone‐oxidation time and polymerization time on the graft copolymerization was investigated. At the constant polymerization time, the total conversion and the degree of the grafting increased with the ozone‐oxidation time, while the graft efficiency decreased. On the other hand, at the constant oxidation time, the total conversion and the degree of grafting increased with the polymerization time, while the graft efficiency decreased. These results were compared with a polyethylene case. The mechanism of the ozone oxidation and the initiation of the graft copolymerization were also discussed.
Polymerization of olefins through heterogeneous catalysis. IX. Experimental study of propylene polymerization over a high activity MgCl2‐supported Ti catalyst
Authors: Hutchinson R. A. , Ray W. H. 
Published: April 2003

AbstractResults from an experimental study of propylene polymerization in heptane diluent over a high activity Mg‐supported Ti catalyst are presented. The study provides an examination of the effect of operating conditions on polymerization rate, product melt index, and powder bulk density. Among the findings are that product bulk density decreases with increasing operating temperature and decreasing operating pressure while prepolymerization increases the bulk density. The results support the hypothesis that polymer morphology is closely linked to mass transfer limitations within the growing polymer particle during the early stages of polymerization.
A quantitative adhesion test for thin polymer films on silicon substrates
Authors: Goldberg H. D. , Cha G. S. , Brown R. B. 
Published: April 2003

AbstractThe standard 90° peel test was modified in order to apply it to testing adhesion of thin polymer films to surfaces of silicon substrates, such as the silicon nitride passivation layer used in our solid‐state chemical sensors. The goal of this task was to develop a procedure for testing adhesion of both dry and wet films, which would yield repeatable, quantitative results quickly, and with simple sample preparation. It is important to produce valid comparisons of adhesion both over variations of a given polymer composition, and between films made of dissimilar polymer matrices. The method described herein could be applied to adhesion testing of a wide variety of thin polymer layers to solid surfaces.
Competitive adsorption of water‐soluble polymers on attapulgite clay
Authors: Chang S. H. , Ryan M. E. , Gupta R. K. 
Published: April 2003

AbstractThe individual, competitive, and displacement adsorption of polyvinyl alcohol (PVOH), hydroxyethyl cellulose (HEC), and hydroxypropylmethyl cellulose (HPMC) in aqueous solution onto an attapulgite clay has been systematically studied. For the individual adsorption experiments, the amount of polymer adsorbed at equilibrium decreased in the order PVOH, HEC, HPMC. In the competitive adsorption experiments, the adsorption level of each polymer is diminished by the presence of a competing polymeric species. Binary mixtures of a cellulosic polymer (HEC or HPMC) with PVOH result in a substantial reduction in the amount of cellulosic polymer adsorbed. In the displacement adsorption studies, the sequential addition of HEC or HPMC is not able to displace previously adsorbed PVOH molecules to any appreciable extent. However, the addition of PVOH to previously equilibrated HEC/clay or HPMC/clay suspensions results in a large amount of the adsorbed cellulosic polymer being displaced by PVOH, especially under conditions of high surface coverage. These results indicate that PVOH is preferentially adsorbed on the clay surface and the strength of attachment to the surface is greater for PVOH than for either cellulosic polymer.
Preparation and electrostatic properties of antistatic acrylics
Authors: Park Yun Heum , Kim Yong Kweon , Nam Sung Woo 
Published: April 2003

AbstractVery good antistatic acrylic films or fabrics can be prepared by exposing the acrylic samples containing oxidizing agent to aniline vapor. The conductivity, the maximum static charge, and the half‐life time are used for estimation of electrostatic properties. The effects of the content of polyaniline and the temperature and time of exposure to aniline vapor on the electrostatic properties have been investigated. The stability of conductivity to ambient air exposure and the temperature dependence of conductivity for antistatic acrylic films have also been investigated.
Reinforcing effect of a magnesium silicate treated with a 4‐amino methyl pyridine in epichlorhydrin rubber (ECO) vulcanizates
Authors: González Luis , Rodríguez Andrés , Ibarra Luis 
Published: April 2003

AbstractThis paper reports on the chemical surface changes of sepiolite, a natural magnesium silicate, caused by adsorption of 4‐amino methyl pyridine, and the application of this product as a reinforcing filler in epichlorhydrin rubbers. The amine group of the reagent used in the surface modification of the mineral reacts with elastomer upon vulcanization. This gives rise to stronger rubber‐filler bonds with the consequential improvement of the technological properties of the vulcanizates.
Physical studies of ionically‐terminated polytetrahydrofuran polymers. I. Dilute solution behavior
Authors: Ali S. A. M. , Hourston D. J. 
Published: April 2003

AbstractA series of tetrahydrofuran polymers, terminating at one end with a pyridinium bromide group, were prepared; their hydrodynamic behavior contrasted with the equivalent methoxyterminated polytetrahydrofurans. This article reports viscometry studies of these polytetrahydrofurans in cyclohexane, toluene, tetrahydrofuran, methyl ethyl ketone, and cyclohexanone.
Effects of modified air quenches on the high‐speed melt spinning process
Authors: Hotter J. F. , Cuculo J. A. , Tucker P. A. 
Published: April 2003

AbstractA high molecular weight polyethylene terephthalate was spun into fibers in the speed range from 3,000–7,000 mpm. The effect of modifying threadline dynamics through a combination of enhanced and/or retarding air quenches on the resulting spinning performance, fiber structure, and mechanical properties was examined. Particular combinations of these threadline temperature profile modifications were shown to result in significant improvements in spinning performance and as‐spun fiber structure. Extensive characterization of select fiber samples revealed higher orientation and crystallinity, larger crystal dimensions, and greater mechanical properties. These results also demonstrated the ability to provide continued improvement in fiber properties at very high take‐up speeds where typically a decline is observed. It is concluded that the threadline temperature profile can be altered in such a way as to significantly enhance the resulting spinning performance and fiber structure over a wide range of take‐up speeds.
Slow‐gelling Cr+3/polyacrylamide solutions for reservoir profile modification: Dependence of the gelation time on pH
Authors: Lockhart Thomas P. , Albonico Paola , Burrafato Giovanni 
Published: April 2003

AbstractSystematic studies of the gelation of both buffered and unbuffered aqueous Cr+3/polyacrylamide solutions show that the gelation time is a strong function of pH, increasing by about one order of magnitude per unit decrease in pH for polyacrylamides less than about 7.5% hydrolyzed. The gelation rate also depends strongly on the Cr+3 concentration, the degree of polymer hydrolysis, and temperature. At 25°C, gelation delays of more than 10 months have been obtained; the maximum delay observed at 60°C is about 1 month and at 90°C 1 d. The resistance of buffered gel solutions to change in pH results in significantly longer gelation times at 90°C and low pH than for identical unbuffered solutions; at lower temperatures, however, the differences are insignificant. Most importantly, the use of low pH to control the gelation time of Cr+3/polymer solutions provides an attractive, inexpensive substitute for the environmentally unacceptable Cr+6/reductant method currently employed for profile modification treatments.
Influence of nonsolvents on dissolution characteristics of nylon‐6
Authors: Raju K. V. S. N. , Yaseen M. 
Published: April 2003

AbstractThe dissolution of nylon‐6 has been made effective by adding a nonsolvent to the primary solvents that in turn created potential combined contact sites and enhanced the process of dissolution. It is found that 50% of a primary solvent like m‐cresol or phenol could be replaced by solvents that are relatively economical and safe to handle. Nylon‐6 is found to get dissolved at a faster rate and with ease in a blend of 45 : 55 phenol‐toluene compared to other solvent blends. The dependence of limiting viscosity on solute‐binary solvent interactions is used as a measure of the solvency power of solvent blends for nylon. The lowering of temperature is found to favour the dissolution of nylon‐6 in m‐cresol. Its dissolution is found to be optimum in phenol at 55°C and further increase in temperature has adverse effects on it.
Dimethyl acetamide sorption equilibria in a urethane/urea/ether block copolymer
Authors: Gou M. M. , Koros W. J. , Goldman G. W. 
Published: April 2003

AbstractA study of the interaction of solvent in a urethane/urea/ether copolymer belonging to the spandex family of materials is presented. Sorption and desorption isotherm data for N,N‐dimethylacetamide (DMAc) in spandex solutions are used to determine thermodynamic parameters of solvent/polymer interaction. Isosteric enthalpies for sorption of DMAc tend to approach the heat of evaporation of DMAc at high sorbed concentrations. A qualitative mechanism for assemblage of hard‐segment domains in the polymer during desorption is presented and interpreted in terms of the sorption isotherms and isosteric enthalpy data. The study provides useful insights into the influence of particulate additives, such as titanium dioxide (TiO2) in the solution.
Application and development of synthetic polymer membranes. VI. Pervaporation of aqueous ethanol solution through quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile] membranes
Authors: Yoshikawa Masakazu , Ochiai Satoshi , Tanigaki Masataka , Eguchi Wataru 
Published: April 2003

AbstractMembranes obtained from polymers, quaternized poly[3‐(N′,N′‐dimethyl) aminopropylacrylamide‐co‐acrylonitrile]s, showed selective separation of water from aqueous ethanol solution by pervaporation. The separation factor toward water reached over 15,000. Membrane performance showed a good correlation to membrane polarity. Differential scanning calorimetric melting endotherms of the water‐swollen membranes were studied to clarify the state of water in the membranes. The results suggested that there are two states of water in the membrane: bound and free. The higher the fraction of bound water in the membrane, clearly, the more preferentially was water permeated.
Coated alginate microspheres: Factors influencing the controlled delivery of macromolecules
Authors: Wheatley M. A. , Chang M. , Park E. , Langer R. 
Published: April 2003

AbstractA systematic study of the mild alginate/polycation microencapsulation process, as applied to encapsulation of bioactive macromolecules such as proteins, was conducted. When protein drugs were suspended in sodium alginate solution and sprayed into 1.3% buffered calcium chloride to form cross‐linked microcapsules, large (up to 90%) losses of encapsulation species were encountered, and moderate to strong protein‐alginate interactions caused poor formation of capsules. As a result, a diffusion‐filling technique was adopted in which blank alginate beads, coated twice with small amounts of polycation, were formed prior to drug loading. Protein was then loaded into these capsules by stepwise diffusion from solutions of increasing drug concentration. The drug‐loaded capsules were coated with a final layer of polycation. In all, three polycation coatings were used, two prior to filling and one after filling. The first coating strongly influenced the size, integrity, and loading capacity of the capsules. Low concentrations of polycation resulted in poorly formed capsules with very low retention of the drug in the final capsule, while very high concentrations prevented the drug from entering the capsule at the filling stage. This first coat also affected the duration of drug release from the capsule and the size of the burst effect. The second coat had less effect on the capsule integrity, but it did influence the drug payload and relase profile. The final, sealing‐coat had little effect on drug payload and only limited effect on the release profile up to a critical concentration, above which the release profile was not affected. For all coats, increasing polycation concentration decreased the burst effect, and caused the release profile to be more sustained. Encapsulation of a series of dextrans with increasing molecular weight revealed that the release profile was directly related to the molecular weight of the diffusing species, which was more sustained as molecular weight increased. We have shown that the choice of coating parameters in the diffusion‐filled, alginate/polycation system is critical for successful drug delivery from these capsules. By carefully choosing the coating parameters, both the drug payload and the release profile can be fine‐tuned to meet the desired profile.
Enzymatic hydrolysis of water‐soluble random copolypeptides
Authors: Hayashi Toshio , Iizuka Yasuko , Oya Masanao , Iwatsuki Makoto 
Published: April 2003

AbstractTwo component water‐soluble random copolypeptides consisting of N‐hydroxyethyl L‐glutamine and hydrophobic L‐amino acids such as L‐alanine, L‐leucine, L‐phenylalanine, or L‐valine, were prepared by carrying out aminolysis reactions with 2‐amino‐1‐ethanol (E) on starting copolymers consisting of γ‐benzyl L‐glutamate (B) and the corresponding hydrophobic L‐amino acid. The effects of copolymer composition and sequential distributions, as well as molecular conformations, on the rate of degradation by bromelain in a PECF at pH 7.4 and 37.0°C to simulate in vivo polymer degradation. All the samples were found to be extensively degraded by random chain fracture with bromelain. Further, the degradation data for these samples followed the Michaelis‐Menten rate law, being of the first order in papain concentration. The nature of side chains and the molecular conformations are important to the rate of degradation by bromelain.
A new carbon fiber from lignin
Authors: Sudo K. , Shimizu K. 
Published: April 2003

AbstractA new carbon fiber was prepared from the lignin (steam‐exploded lignin), which was isolated from steam‐exploded birch wood (Betula platyphylla). The lignin was modified to melt thermally on hydrogenolysis. The chloroform soluble and carbon disulfide insoluble fraction (HL) of the reaction products was heated at 300–350°C for 30 min, giving a molten viscous material (HHL). The HHL had a softening point of 110°C and melted at over 145°C to form viscous liquid. When HHL was subjected to a spinning test, according to a conventional fusion spinning method at a speed over 100 m/min, a fine filament could be continuously formed through a pinhole (diameter: 0.3 mm). After the filaments were heated in air at 1–2°C/min up to 210°C, by which time the filament was converted to have an infusible property, the filaments were carbonized by heating from a room temperature to 1000°C at a heating rate of 5°C/min in a stream of nitrogen. The typical properties of the lignin based carbon fiber were as follows: Fiber diameter = 7.6 ± 2.7μ Elongation = 1.63 ± 0.29% Tensile strength = 660 ± 230 MPa; Modulus of elasticity = 40.7 ± 6.3 GPa. The chemical structure of the precursor was remarkably changed from that of the original lignin, indicating the elimination of aliphatic functional groups implied originally in the starting material.
Papain immobilization onto porous poly(λ‐methyl L‐glutamate) beads
Authors: Hayashi Toshio , Hirayama Chuichi , Iwatsuki Makoto 
Published: April 2003

AbstractWater‐insoluble papain was prepared by immobilizing papain onto the surface of porous poly(λ‐methyl L‐glutamate) (PMLG) beads with and without spacer. The mode of the immobilization between papain and porous PMLG beads was covalent fixation. The relative activity and the stability of the immobilized papain was investigated. The retained activity of the papain covalently immobilized by the azide method was found to be excellent toward a small ester substrate, N‐benzyl L‐arginine ethyl ester (BAEE), compared with that of the peptide binding method. The values of the Michaelis constant Km and the maximum reaction velocity Vm for free and immobilized papain on the PMLG beads were estimated. The apparent Km was larger for immobilized papain than for the free enzyme, while Vm was smaller for the immobilized papain. The thermal stability of the covalently immobilized papain was higher than that of the free papain. The initial enzymatic activity of the covalently immobilized papain remained approximately unchanged with storage time, when the batch enzyme reaction was performed repeatedly, indicating the excellent durability.
Infrared photoacoustic and dynamic mechanical spectroscopy of sheet‐molded compounds
Authors: Allen G. M. , Wu G. L. , Prentice S. A. 
Published: April 2003

AbstractChemical and physical characteristics of sheet‐molded compounds were investigated using infrared and mechanical spectroscopies. Fourier transform infrared spectroscopy with photoacoustic detection facilitated surface analysis for determination of composition, depth profile, and thermal exposure effects. Dynamic mechanical spectroscopy utilized torsion, tension, and flexure modes to evaluate temperature and frequency‐dependent viscoelastic properties.
Adhesion studies of tyre cords with rubber. I. Synthesis and characterization of natural rubber graft copolymers
Authors: Egboh S. H. O. , Mukherjee A. K. 
Published: April 2003

AbstractGlycidyl methacrylate and N‐vinyl pyrrolidone have been grafted onto natural rubber at 32°C using the simultaneous cobalt‐60 irradiation technique. The natural rubber samples were swollen in the monomers for 24 h and thereafter subjected to gamma irradiation. The homopolymers formed in the graft copolymerization reactions and unreacted monomer were removed by solvent extraction using acetone and methanol for glycidyl methacrylate and N‐vinyl pyrrolidone monomer, respectively. The influence of total dose and monomer concentration on the graft parameters was investigated. The dependence of the rate of grafting on the monomer concentration was found to be 0.93 and 0.80 for glycidyl methacrylate and N‐vinyl pyrrolidone, respectively. DSC and TGA studies of the polymers were undertaken. Grafted copolymers based on glycidyl methacrylate were relatively less thermally stable compared with ungrafted natural rubber.
Application of UV‐curable diazoresin. II. Characteristics of the immobilized glucose oxidase membrane
Authors: Liu Jui‐Hsiang , Chen Ming‐Yi , Chang Yuh‐Chwen 
Published: April 2003

AbstractThe characteristics of the enzyme electrode, developed using the immobilized glucose oxidase membranes, were investigated. The enzyme membranes were prepared from poly(vinyl alcohol)‐diazoresin and poly(vinyl alcohol)‐sensitizer systems, cross‐linked by means of ultraviolet light irradiation. Temperature and pH dependencies of the relative activity, stability in repeating usage, storage stability, and calibration plots were evaluated. The unstable phenomenon, found in the initial usage of the immobilized glucose oxidas membrane, which was prepared from poly(vinyl alcohol)‐sensitizer system, was also investigated.
Studies on enzymatic resistance and molecular structure by 13C‐NMR of cellulosic ethers
Authors: Martinez‐Richa A. , Muñoz‐Alarcon H. , Joseph‐Nathan P. 
Published: April 2003

AbstractA viscometric method to evaluate the enzymatic resistance of cellulosic ethers is proposed. The method was applied to samples of hydroxyethylcellulose (HEC) with molar substitution between 1.8 and 2.5. The results are discussed in terms of the values of Degree of Substitution and the average unsubstituted primary hydroxyl groups, obtained by high‐resolution 13C‐NMR of the neat polymers.