bluuebunny/crossref_metadata_2025_split huggingface dataset:
Free‐radical polymerization of methyl methacrylate initiated by thiol alone
Authors: Xia P. , Cheng H. , Yan D. 
Published: April 2003

AbstractThree different alkyl thiols, i.e., n‐propylthiol, isopropylthiol, and 2‐methyl‐2‐undecanethio1, were proved efficient to initiate the polymerization of methyl methacrylate at 40°C. The initial polymerization rate, Rp, increases with increasing thiol concentration but cannot be described by a single‐power law. However, Rp is proportional to 1.3th power of the monomer concentration, indicating the participation of monomer in the initiation reaction. With increase of the polarity of solvents, Rp decreases, demonstrating the polar property of the initiating intermediate. The apparent activation energy of overall polymerization was calculated to be 9.3 kcal/mol. Molecular weight measurements indicated the twofold function of the thiol as both an initiator and a regulator.
Thermal behavior and laser marking of a novel nematic liquid crystalline polymer
Authors: Kuder J. E. , Yoon H. N. , DeMartino R. N. 
Published: April 2003

AbstractThe thermal behavior and laser marking of a novel nematic liquid crystalline polymer is explored in this report. The glass transition and mesophase transition temperatures of this material are at 45 and 68°C, respectively, and allow the ready annealing of the nematic phase as well as conversion of the nematic to the isotropic phase by pulsed laser irradiation of metallized or dyed films of the polymer.
Calculation of reactivity ratio of resin copolymers derived from substituted acetophenones using Kelen–Tüdos equation
Authors: Nayak P. L. , Lenka S. , Nayak P. K. 
Published: April 2003

AbstractA number of resin copolymers have been prepared by condensing some substituted acetophenones with chloro‐substituted anilines, benzoic acids, and formaldehyde. The reactivity ratios of the monomers have been computed by using the Kelen–Tüdos equation. The results have been discussed taking into account the inductive, resonance, and steric effects of the substituents.
Effects of the organometallic coupling agents on adhesion of the carbon fiber–BMI composites
Authors: Chou S. , Chen H.‐C. , Lee K.‐S. 
Published: April 2003

AbstractIn order to increase the chemical bonding force between fiber and resin, several kinds of organometallic coupling agent (such as titanate, zirconate, and zircoaluminate) were chosen and added in the BMI resin formulation, which possess the same solvent system with those coupling agents. The DSC analysis technique was used to find the best curing condition, and TGA was used to investigate the thermal stability property of the best curing condition. For the purpose of analyzing the bonding structure, ESCA surface element analysis techniques was applied in this study. Beside that, the mechanical properties of tensile, flexural, and short‐beam shear strengths were measured for the effect of adding coupling agents, and the SEM of fracture surfaces were taken to study the fractural analysis. The results showed that composites with the application of organometallic coupling agents of [RO–Ti(OX–R′NH2)3] structure in the treatment of BMI resin were highly thermal stable. Also, it was shown that the mechanical strengths of composites fabricated by pretreatment of the carbon fibers with coupling agents were higher than those fabricated by adding coupling agents in resins, but there was no obvious improvement of mechanical properties with higher concentration of coupling agents. However, the SEM showed that the adhesion between fiber and resin can actually be improved by adding proper amount of coupling agents in the BMI resin formulation.
Mathematical model for a semicontinuous esterification process with recycle between terephthalic acid and ethylene glycol
Authors: Yamada T. 
Published: April 2003

AbstractA new mathematical model has been derived for a semicontinuous recycle esterification process that consists of two reactors, one has the recycle flow to or from another and the discharge flow of the main flow and another has only recycle flow without the discharge flow. This model can give useful information about the optimum design of a new plant through the predictions of oligomer characteristics such as concentrations of carboxyl and hydroxyl end groups, number‐average molecular weight, number‐average degree of polymerization, esterification and saponification degree, diethylene glycol content, melting point, concentrations of ethylene glycol and water in the vapor phase, and so on.
Synthesis of graft copolymers of acrylic monomers onto amylose. II. Study of the ceric ion behavior
Authors: Goñi I. , Gurruchaga M. , Vazquez B. , Valero M. , Guzman G. M. 
Published: April 2003

AbstractA study of the ceric ion consumption during graft polymerization of methyl acrylate (MA), ethyl acrylate (EA), ethyl methacrylate (EMA), and butyl methacrylate (BMA) with amylose was carried out. Grafted acrylic polymers were isolated by the acid hydrolysis method. Weight‐average and number‐average molecular weights were determined by gel permeation chromatography (GPC). The number of grafted chains (mmol) ranged from 8.70 × 10−3 to 12.35 × 10−3 for acrylates and from 3.20 × 10−3 to 6.80 × 10−3 for methacrylates. These results were related to others obtained from the ceric ion consumption studies.
Preparation of hydrophilic polymer networks by post‐curing reaction
Authors: Andreopoulos Andreas G. 
Published: April 2003

AbstractHydrophilic gels are a very important class of polymeric materials with extensive applications as biomedical products. The critical properties of hydrogels, such as sorption and desorption, mechanical behavior, swelling properties, etc., are controlled by network characteristics, i.e. degree of crosslinking and the density, distribution and length of crosslinks. Hydrogels prepared by copolymerization of 2‐hydroxyethyl methacrylate (HEMA) with ethylene glycol dimethacrylate (EGDMA) have already been studied in detail. In this work, hydrophilic networks were prepared by crosslinking HEMA with EGDMA, and poly(2‐hydroxy‐ethyl methacrylate) (PHEMA) with diphenylmethane‐4,4′‐diisocyanate (MDI). The swelling properties of both types of networks were studied and the differences in behavior were attributed to the different techniques applied for network formation.
Resistance of barrier elastomers to hazardous organic liquids
Authors: Khinnavar Rajashekhar S. , Aminabhavi Tejraj M. 
Published: April 2003

AbstractSorption and transport of several hazardous, organic chemicals into elastomer membranes have been studied using a simple gravimetric method. The Fickian model was used to estimate the diffusion coefficients of the polymer–solvent systems. The Joshi–Astarita model was employed to investigate the concentration–dependence of diffusion coefficients. From a study of the temperature dependence of the transport coefficients, activation parameters for the process of sorption, diffusion, and permeation have been estimated. Furthermore, the sorption results have also been interpreted in terms of the semiquantitative estimates of the kinetic rate constants and other thermodynamic parameters (enthalpy and entropy) of interest.
Chemical modification of silk with aromatic acid anhydrides
Authors: Tsukada M. , Goto Y. , Freddi G. , Shiozaki H. 
Published: April 2003

AbstractBombyx mori silk fibers were chemically modified by acylation with aromatic acid anhydrides, such as phthalic and o‐sulfobenzoic anhydrides. We examined the reactivity of these modifying agents toward silk fibers, the physical and thermal properties, and the dyeing behavior with acid and cationic dyes. The o‐sulfobenzoic anhydride was more reactive toward silk fibroin than phthalic anhydride. The amount of both basic and acidic amino acid residues decreased after modification with aromatic acid anhydrides. The moisture regain of silk treated with phthalic anhydride remained almost unchanged, while that of the samples modified with o‐sulfobenzoic anhydride increased linearly as the weight gain increased. Chemically modified silk fabrics showed improved crease recovery behavior, even though phthalic anhydride seemed more effective at comparatively low weight gain. The modification of silk with o‐sulfobenzoic anhydride caused a drastic a reduction of acid dye uptake and enhanced the affinity of silk for cationic dye. Silk fibers did not show any significant change in thermal behavior, regardless of the modification with o‐sulfobenzoic anhydride. Silk fibers modified with phthalic anhydride showed on differential scanning calorimetry (DSC) curves a minor and broad endothermic peak at around 210°C, attributed probably to the breaking of the crosslinks formed between adjacent fibroin molecules.
An XPS study of the surface–bulk compositional differences in siloxane‐containing block copolymers and polymer blends
Authors: Pertsin A. J. , Gorelova M. M. , Levin V. Yu. , Makarova L. I. 
Published: April 2003

AbstractX‐ray photoelectron spectroscopy (XPS) is used to compare the surface behavior in various binary systems of poly(dimethylsiloxane) with poly(bisphenol A sulfone) and poly(bisphenol A carbonate). All the systems studied show a pronounced surface enrichment in siloxane. At a fixed siloxane concentration in the bulk the lowest extent of surface enrichment is observed in the +eat copolymers, next go the blends of copolymers in homopolymers, and the highest extent of surface enrichment is characteristic of the blends of homopolymers. The blends of two copolymers show an unexpected surface behavior: The addition of minor amounts of a siloxane‐rich copolymer to another copolymer possessing a much lower siloxane content decreases (rather than increases) the surface siloxane concentration of the latter. A microscopic model is suggested to explain the observed surface behavior. The model involves the formation of a “quasi‐two‐dimensional” overlayer of additive's macromolecules on the blend surface, with the macromolecules oriented preferentially parallel to the sample surface.
Effects of particle size on mechanical and impact properties of epoxy resin filled with spherical silica
Authors: Nakamura Yoshinobu , Yamaguchi Miho , Okubo Masayoshi , Matsumoto Tsunetaka 
Published: April 2003

AbstractEffects of particle size on the mechanical and impact properties of cured epoxy resins are studied. This resin was filled with spherical silica particles prepared by hydrolysis of silicon tetrachloride. Particles were sorted into five kinds of different mean sizes in the range from 6–42 μm. A static flexural and tensile tests and an instrumented Charpy type impact test were carried out. Flexural strength, tensile strength, and impact‐absorbed energy increased with a decrease in the particle size. Fractured surfaces were observed using a scanning electron microscope to clarify the initiation point of fracture.
Effect of oxygen on vinyl acetate polymerization
Authors: Levy L. B. , Hinojosa L. 
Published: April 2003

AbstractVarious conflicting reports in the literature regarding the effect of oxygen on the stability of vinyl acetate (VA) toward polymerization led us to reexamine this topic using both isothermal stability tests and quasi‐adiabatic calorimetry. Both commercial VA stabilized with 5–20 ppm by weight of hydroquinone (HQ) and purified, unstabilized VA exhibit lower stability to thermally initiated polymerization (at 50–120°C) in the presence of oxygen than in its absence. However, when stabilized with 3–5 ppm of HQ, both air‐saturated and oxygen‐free VA exhibit adequate thermal stability at normal transport and storage temperatures (25–50°C). Oxygen destabilization of VA is probably caused by the relatively low stability of VA polyperoxide rather than by the oxidation of acetaldehyde impurity to peroxyacetic acid. The length of VA polymerization induction periods is about −0.4 order in oxygen partial pressure.
Preparation and mechanical properties of chemically cross‐linked hydroxypropyl cellulose solid films retaining cholesteric liquid crystalline order
Authors: Suto Shinichi , Tashiro Hiroshi , Karasawa Mikio 
Published: April 2003

AbstractHydroxypropyl cellulose films were cast from liquid crystalline solutions with a crosslinking agent. The solubility test and the optical measurements of the resultant films were performed. The tensile, dynamic mechanical, and creep properties of the films were determined. The data of solubility in water determined that the cast films are cross‐linked, and the data of circular dichroism spectra, that the cast films retain the cholesteric liquid crystalline order (right‐handed sense). Both findings clarified that the cast films retain the cholesteric order fixed by cross‐linking. The cross‐linking depended on the pairs of the solvent–cross‐linking agent. The mechanical properties also depended on the pairs: the tensile strength and moduli did not always increase with cross‐linking. The creep resistance improved with cross‐linking. The thermally activated Eyring process could be applied and the activated volumes were evaluated for water‐ and methanol‐cast films. There were not clear phenomenological correlations between the mechanical properties of our films.
Transition‐metal coordination for complexing poly‐(vinyl chloride)–polyurethane blends
Authors: Al‐Salah Hasan A. , Al‐Raheil Ismail A. 
Published: April 2003

AbstractBinary blends of poly(vinyl chloride) (PVC) and polyether polyurethane (PU) containing divalent transition metal (Zn2+) have been prepared by solution blending. The physical and mechanical properties of the blends are studied utilizing differential scanning calorimetry (DSC), thermogravimetry (TG), and tensile testing. The DSC results showed a high degree of molecular mixing of the two polymers. The glass transition temperatures (Tg) of the blends exhibited one major Tg whose position on the temperature scale is raised with increasing levels of PVC. The blends yielded stress–strain behavior similar to reinforced elastomers at low PVC, but at high PVC contents, they exhibited increased elongation. The latter materials showed well‐developed yield points, stress whitening, and necking. Cold drawing was exhibited by the materials under tension. The tensile strength and Young's modulus were enhanced as the PVC content was increased.
Analysis of crosslinking in amine‐cured epoxy systems: The one‐to‐one relationship between Tg and conversion
Authors: Wang Xiaorong , Gillham John K. 
Published: April 2003

AbstractNetwork formation, in a system such as a tetrafunctional aromatic diamine cured with a difunctional epoxy, is considered on the basis of only interconnected trifunctional crosslinking sites. The number‐average molecular weight, the crosslinking density, and the gel point, and also the vitrification contours of the time—temperature—transformation (TTT) isothermal cure diagram, are related to the ratio of the reaction rate constants, k2/k1, of the competing reactions of epoxy with secondary amine group (k1) and with primary amine group (k1). It is considered that the glass transition temperature, Tg, is related uniquely to conversion on the basis that the number‐average molecular weight and crosslinking density are insensitive to the ratio, k2/k1. Experimental data support the theoretical result. The potential influences of chemical structure and physical aging on Tg are discussed. © 1992 John Wiley & Sons, Inc.
Recovery of uranium from seawater. XII. Preparation and characterization of lightly crosslinked highly porous chelating resins containing amidoxime groups
Authors: Egawa Hiroaki , Kabay Nalan , Shuto Taketomi , Jyo Akinori 
Published: April 2003

AbstractA number of lightly cross‐linked poly(acrylonitrile‐co‐divinylbenzene) beads (RN‐5) have been synthesized by suspension polymerization. The use of solvating diluents such as chloroform, dichloroethane, and tetrachloroethane resulted in copolymer beads having highly porous structures. The chelating resins containing amidoxime as a functional group (RNH‐5) have been prepared by the reaction of copolymer beads with 3% hydroxylamine in methanol. A detailed analysis is made of the pore structure of lightly cross‐linked copolymers of acrylonitrile–divinylbenzene and their amidoxime derivatives in the anhydrous state including pore‐size distribution, specific surface area, and pore structure in the aqueous media by means of gel permeation chromatography (GPC). A set of experiments have been performed to ascertain the potential of the resins for the adsorption of uranium from seawater. Because of their modified pore structures, the chelating resins exhibited a marked adsorption rate for uranium in seawater as high as 23 μg of U/cm3 of resin/day without alkaline treatment.
Surface properties of graft copolymers surfactants: Behavior at the water/toluene interface
Authors: Lucas E. F. , Oliveira C. M. , Gomes A. S. 
Published: April 2003

AbstractPoly(propylene oxide‐b‐ethylene oxide) (PPOPEO) surfactant has been used as a surface tension modifier. In this study, the graft copolymer made of poly(methyl methacrylate) (PMMA) main chain and PPOPEO graft chain behavior at water/toluene interface was observed. Interfacial tension measurements were conducted by dissolving the graft copolymer in toluene at a concentration range 1 wt % −0.0003. The results confirmed the surfactant behavior of graft copolymers, which presented a PMMA/PPOPEO ratio dependence. The critical micellar concentration (CMC) was observed. Above the CMC, the graft copolymers tend to form a monomolecular association that depends upon copolymer molecular weight. © 1992 John Wiley & Sons, Inc.
Reaction kinetics and TTT cure diagrams for off‐stoichiometric ratios of a high‐Tg epoxy/amine system
Authors: Simon S. L. , Gillham J. K. 
Published: April 2003

AbstractThe cure behavior of two off‐stoichiometric ratios, one amine‐rich and the other epoxy‐rich, of a high‐Tg aromatic difunctional epoxy/aromatic tetrafunctional diamine system are studied using differential scanning calorimetry (DSC). The curing reactions are presumed to consist of competing epoxy/amine reactions and a subsequent reaction of epoxy with hydroxyl, termed etherification, that is significant in the epoxy‐rich system after depletion of amino hydrogens. A one‐to‐one relationship between conversion and Tg independent of cure temperature is found for each of the off‐stoichiometric systems in spite of the competing reactions. Since it is uniquely related to fractional conversion, sensitive, and easily measured, Tg is used to monitor the curing reactions. Kinetically controlled master curves for isothermal cure are obtained for each system by shifting Tg vs. In time data to an arbitrary reference temperature; apparent activation energies for the epoxy/amine and the etherification reaction regimes appear to be identical at 15.5 kcal/mol. Experimental DSC data are satisfactorily described for both systems by a kinetic model of the competitive epoxy/amine and etherification reactions. The ratio of the rate constants for the reactions of epoxy with the secondary amine group and epoxy with the primary amine group, α = k2/k1, is found to be approximately 0.5 (i.e., equal reactivity of amino hydrogens), whereas the ratio of the rate constants for the reactions of epoxy with hydroxyl and epoxy with the primary amine group, β = k3/k1, is found to be 0.001. Diffusion control is incorporated in the model by the use of a free‐volume theory. Vitrification and iso‐Tg contours in the time–temperature–transformation (TTT) isothermal‐cure diagram are calculated for both systems from the kinetic model. © 1992 John Wiley & Sons, Inc.
In‐plane solvent diffusion in a photosensitive polyimide
Authors: Shih Da‐Yuan , Nunes Sharon , Paraszczak Jurij , Galligan Eileen , Cataldo John , Serino Russell 
Published: April 2003

AbstractThe diffusion of an organic solvent,N‐methylpyrollidinone (NMP), in a fully imidized photosensitive polyimide, 4,4′‐benzophenone tetracarboxylic dianhydride (BTDA–tMDA), was investigated. The polyimide (PI) films were prepared by spin‐coating, soft‐bake, deep UV exposure, and final‐baked to a peak temperature ranging from 230 to 375°C. The thickness of the final films is approximately 5.0 μm. Patterned metal was then electronbeam‐evaporated through a molybdenum shadow mask over the PI surface. The rate of lateral (in‐plane) diffusion of NMP in the PI covered with metal follows Fick's\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt t $\end{document}relationship over a temperature range of 40–85°C. The rate of diffusion was shown to increase with increasing NMP temperatures, typical of a thermal‐activated process. The diffusion coefficients, as measured by the solvent penetration distance as a function of the square root of time, were found to obey the Arrhenius equation:D=D0× exp(−Q/RT) cm2/s, where the frequency factor,D0, ranges from 0.0015 to 0.0045 cm2/s, and the activation energy,Q, ranges from 5.52–6.34 kcal/mol. BothD0andQdecrease with increasing PI baking temperatures. © 1992 John Wiley & Sons, Inc.
Increased breakdown strengths of polypropylene films melt‐extruded from plasma‐treated resin
Authors: Mammone Robert J. , William L. Wade  , Binder Michael 
Published: April 2003

AbstractThin (11–36 μm) films formed by melt extruding polypropylene resin after the resin had been briefly exposed to low pressure, low temperature, 96% CF4/4% O2 gas plasma, exhibited approximately a 20% increase in dielectric breakdown strength. © 1992 John Wiley & Sons, Inc.
A study of polyindole perchlorate (PIP) prepared by electropolymerization
Authors: Choi Kyung Moon , Jang Joon Ho , Rhee Hee‐Woo , Kim Keu Hong 
Published: April 2003

AbstractPolyindole perchlorate (PIP) was obtained by electrochemical oxidation using a potential of 0.7 V as anodic precipitates. A cyclic voltammetry was performed in acetonitrile solution containing 0.2M indole and 0.1M tetraethylammonium perchlorate. The result suggested that this electrode reaction was reversible, and the peak width (ΔEp) of the anodic and cathodic peaks obtained was 58 mV. The result of IR measurements clarified that the polyindole was obtained by a 1,3‐polymerized mechanism. As for the ESCA analysis of the PIP pellet, besides a main N1s peak at 399.6 eV, a high binding energy peak at 402.3 eV was observed. Also, in the case of the C1s peak, besides a main peak at 284.6 eV, a shoulder peak at high binding energy was measured. These results suggested that an electropolymerization of indole was performed by the formation of radical cations. A thermogravimetric analysis was performed in a temperature range from 25 to 800°C. The rate of thermal decomposition (R) for the polyindole‐and polyaniline‐based polymers was calculated by a computer connected with a thermal analyzer. From the thermal analysis, it was concluded that the polyindole‐based polymers decomposed at higher temperatures than did the polyaniline‐based samples. The Rmax values of the polyindole systems were not related to the kind of dopants, but in the case of the polyaniline systems, they were seriously affected by the kind of electron acceptors. The electrical conductivity of the PIP pellet was performed in a temperature range from 150 to 25°C. The values of log σ at 25°C and Ea obtained were ‐1.63 s/cm and 0.508 eV, respectively. From the results, we suggested that a possible conduction mechanism and charge carriers for the PIP pellet were hopping conduction and polarons, respectively. The ESR measurements for the PIP powder were performed at room temperature, and the values of various ESR parameters were calculated. © 1992 John Wiley & Sons, Inc.