bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermoplastic matrix composites by aqueous electrocopolymerization onto graphite fibers
Authors: Iroh Jude , Bell J. P. , Scola D. A. 
Published: April 2003

AbstractElectrocopolymerization of 3‐carboxyphenyl maleimide and styrene onto Hercules AS‐4 graphite fiber surfaces has been successfully carried out from an aqueous solution containing monomers and dilute sulfuric acid. Initiation of copolymerization of the monomers dissolved in a small amount of dimethylacetamide is achieved by constant‐current electrolysis in the cathodic chamber of a three‐compartment electrolysis cell. Polymerization is initiated at the fiber surfaces; little polymer is formed in the cell solution. Electrocopolymerization is very consistent and rapid. The amount of polymer increases predictably with increasing comonomer concentration and current density. Using a 0.4 M (1 : 1) comonomer concentration, 0.0125 M sulfuric acid solution, and a current density of 20 mA/g, more than 60 wt % of copolymer coating per unit weight of graphite fibers is obtained within thirty minutes. Thermal gravimetric analysis showed the copolymer to be very stable at elevated temperatures and has initial and final decomposition temperatures of 430 and 520°C, respectively. The glass transition temperature measurement of the copolymer coatings was carried out by differential scanning calorimetry. A single glass transition temperature was obtained of about 210°C for most samples. The glass transition temperature of the copolymers did not change significantly with changing comonomer feed composition. Functional group and compositional analysis of the copolymer was done by FTIR spectroscopy. The copolymer composition remained relatively the same for copolymers made from different styrene/3‐carboxyphenyl maleimide feed composition, confirming a strong tendency toward alternation for the system.
Characterization of thermosetting polymer mortars
Authors: Vipulanandan C. 
Published: April 2003

AbstractThe behavior of epoxy and polyester mortars were studied under various curing conditions, temperatures, and strain rates. The effect of curing temperatures on the compressive stress–strain relationships of polymers and polymer mortars were also investigated. The properties of interest of the two polymer mortars cured under optimum conditions are the compressive strength, splitting tensile strength, compressive modulus, and compressive stress–strain relationship. The compressive strength of polymer mortars are related to the testing temperature and logarithmic strain rate. The compressive modulus and splitting tensile strength of polymer mortars are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress–strain behavior of epoxy and polyester polymer mortars.
13C CP/MAS NMR study on alkali cellulose
Authors: Yokota Hiromu , Sei Toshiya , Horii Fumitaka , Kitamaru Ryozo 
Published: April 2003

AbstractThe phase transition from cellulose to alkali cellulose (Na‐Cell) and the phase structure of Na‐Cell have been investigated by CP/MAS 13CNMR spectroscopy. It has been found from the 13CNMR spectra that both crystalline and noncrystalline components of cellulose decrease in resonance intensities in the transition process from cellulose to Na‐Cell I, suggesting that the noncrystalline and the crystalline regions of cellulose are converted to Na‐Cell simultaneously. The conversion model is considered as follows: The crystalline part imposes some restriction on the swelling of the noncrystalline part of cellulose, but the conversion of both parts to Na‐Cell may be possible when the swelling prevails in the whole microfibril as a result of the penetration of the alkaline solution into the crystalline part. Secondly, the 13C spin‐lattice relaxation times (T1) have been measured to elucidate the phase structure of Na‐Cell. Though two T1 values are obtained for each carbon of Na‐Cell except for C6 carbon, Na‐Cell has a homogeneous solid structure which is composed of the crystalline regions with a small heterogeneity.
Threshold tear strength of carbon black filled rubber vulcanizates
Authors: Bhowmick Anil K. , Neogi Chanchal , Basu S. P. 
Published: April 2003

AbstractThreshold tear strength of unfilled and filled Natural Rubber (NR) and Styrene‐butadiene Rubber (SBR) vulcanizates has been determined. Carbon black (N‐220, N‐375, N‐330, N‐550, and N‐660) and china clay are used as fillers. Threshold tear strength varies from 80 J/m2 to 1200 J/m2. Threshold tear strength is found to be dependent on filler loading, nature of filler, and small strain modulus. The results are explained with the help of strain energy density, tear tip diameter, and the excess energy required to stress the many bonds before breaking one of them.
A highly fluorinated epoxy resin: Post‐curing and transition behavior
Authors: Twardowski T. E. , Geil P. H. 
Published: April 2003

AbstractThe post‐curing and transition behavior of a highly fluorinated epoxy resin system was characterized. The material was found to have low temperature transitions similar to those found in DGEBA. The cure was discovered to be inhibited by the presence of CO2. The glass transition was broad and near room temperature, resulting in rapid aging characteristics.
Rheokinetic changes during polyurea reactions in solution
Authors: Wang K. J. , Hsu T. J. , Lee L. James 
Published: April 2003

AbstractThe viscosity rise and conversion profile of polyurea reaction in solution were measured using a Haake viscometer and an FTIR, respectively. In a three‐component polyurea system, it was found that the liquid–solid transition is dominated by the microphase separation from the formation of hard segments. The formation of soft segments mainly contributes to the initial viscosity buildup. A series of experiments were carried out to study the effects of resin composition, solvent concentration, and reaction temperature on the viscosity rise and gelation of polyureas.
The ductile–brittle transition in macroscopic tensile tests on polyethersulfone
Authors: Plummer C. J. G. , Donald A. M. 
Published: April 2003

AbstractIn tensile tests of polyethersulfone it is found that, as the temperature is raised, samples of low molecular weight exhibit a ductile–brittle transition. Thus, this normally tough polymer becomes less so at evaluated temperatures. Ultimately as the temperature is raised to close to Tg, more ductile behavior returns as homogeneous deformation occurs. For high molecular weight samples, at the strain rates used (∽ 10−4 s−1) ductile behavior was found at all temperatures with a neck forming as deformation proceeds. These findings can be rationalized in terms of a disentanglement model for craze formation: crazing via a disentanglement mechanism will be favoured by low molecular weight and high temperature, thus allowing craze‐initiated fracture to intervene before shear deformation has taken place. A comparison is made both with earlier work on thin films of polyethersulfone and with a theoretical model.
Radiation‐induced grafting of regenerated cellulose hollow‐fiber membranes
Authors: Lim S. L. , Fane A. G. , Fell C. J. D. 
Published: April 2003

AbstractGamma ray radiation‐induced grafting was carried out on regenerated cellulose hollow‐fiber membranes as the substrate polymer and empolying a number of monomer and solvent systems. The monomers used include styrene, maleic acid, acrylonitrile, acrylamide, and acrylic acid. Characterization of the graft copolymers was done by measuring their tensile properties in terms of breaking loads and breaking extensions. Permeating properties of the modified membranes were also assessed by measuring the water flux of each membrane. Membranes grafted with styrene showed improved tensile and permeation properties, while co‐irradiation graftings using acrylamide and acrylic acid as monomer only showed improved tensile properties but not the permeation properties of virgin membranes. For a given monomer, the pre‐irradiation grafting technique generally produced membranes with lower water fluxes than those produced using co‐irradiation grafting.
Solid phase graft copolymerization: Effect of interfacial agent
Authors: Lee Sunggyu , Rengarajan Ramesh , Parameswaran Vetkav R. 
Published: April 2003

AbstractSolvents or interfacial agents have been used as media to perform various polymerization reactions. The selection of solvents to provide the appropriate medium for the reaction has opened up a totally new area for research. In the present study, three solvents, viz., toluene, decalin, and tetralin, were investigated in the preparation of polypropylene‐maleic anhydride copolymers by solid phase graft copolymerization. The graft level was quantitatively determined by wet chemical methods and qualitative confirmations were made by Fourier transform infrared spectroscopy. It was found that toluene and decalin increased the surface area for reaction by swelling the polymer. The graft level increased with an increase in concentration of toluene and decalin. In the case of tetralin, the graft level decreased as the concentration of the solvent in the reactant mixture increased. It was experimentally observed that unlike toluene and decalin, tetralin did not cause swelling of the polymer at the reaction conditions. Therefore, the surface area available for reaction would be less when tetralin is used. Moreover, since tetralin dissolves the polymer rather than causing it to swell, the contact area for the reaction is further diminished by the formation of a monomolecular layer of solvent insulating the monomer from the polypropylene.
Characterization of polymer blends and alloys by constrained profile‐analysis of X‐ray diffraction scans
Authors: Murthy N. S. , Minor H. , Akkapeddi M. K. , Buskirk B. Van 
Published: April 2003

AbstractThe composition of polymer blends and alloys and the crystallinity and crystallite size/perfection of each of the components are determined by X‐ray diffraction (XRD) methods. A profile‐fitting procedure is used to resolve the XRD scan into crystalline and amorphous peaks corresponding to each of the polymers. The procedure uses templates derived from the XRD scans of the homopolymers as constraints. The usefulness of this method for studying the influence of blending and grafting is illustrated by analyzing the data from two‐component blends with and without the graft copolymer compatibilizer.
Surface‐active agents based on propoxylated lignosulfonate
Authors: Hornof V. , Hombek R. 
Published: April 2003

AbstractA commercial lignosulfonate was modified by the addition of propylene oxide. The products obtained had a degree of propoxylation ranging from 19% to 49%. The modified lignosulfonates retained high solubility in water and high salinity tolerance, while their interfacial activity increased dramatically in comparison with the original lignosulfonate. Aqueous solutions of propoxylated lignosulfonates exhibited very low interfacial tensions (down to 10−1−10−2mN/m) against both a pure hydrocarbon (isooctane) and a crude oil (Lloydminster crude).
A mechanistic interpretation of the zero order release from pendent chain‐linked glassy and swollen hydrogels
Authors: Shah S. S. , Kulkarni M. G. , Mashelkar R. A. 
Published: April 2003

AbstractZero order release of active ingredients, physically dispersed in the glassy hydrogels has been ascribed in the past to the case II transport of the penetrant medium into the glassy matrix (phase erosion). Surface erosion of the polymer by dissolution has also been shown to result in the zero order release of the dispersed/dissolved active ingredient. This communication reports the zero order release of the pendent chain‐linked p‐nitro benzoic acid and 2,4‐dinitro benzoic acid from glassy as well as swollen hydrogel matrices. The results have been elucidated on the basis of increase in the diffusivity of the active ingredient released by hydrolysis and the concomitant increase in the degree of swelling of the polymer matrix. This is the first reported finding of zero order release of an active ingredient from the matrix device as a result of bulk erosion.
Preparation of ABS (acrylonitrile/butadiene/styrene) latexes using hydroperoxide redox initiators
Authors: Daniels E. S. , Dimonie V. L. , El‐Aasser M. S. , Vanderhoff J. W. 
Published: April 2003

AbstractThe 80/20 (w/w) azeotropic styrene/acrylonitrile mixture was copolymerized at 35, 50, and 70°C in crosslinked polybutadiene seed latexes of varying particle size (range 113–242 nm) using the t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 redox initiator. Other initiators used for comparison were: (1) ammonium persulfate at 70°C; (2) ammonium persulfate/sodium bisulfite redox initiator at 35 and 50°C; (3) oil‐soluble, 2,2'‐azobis(2,4‐dimethylvaleronitrile) at 50°C. The following polymerization parameters were varied systematically: (1) polybutadiene seed latex particle size; (2) monomer/polymer swelling ratio; (3) polymerization temperature; (4) type and concentration of initiator; and (5) mode (and duration) of initiator addition. The following parameters were determined: (1) polymer yield (final conversion); (2) variation of conversion with time; (3) morphology of the latex particles; (4) amount of coagulum; and (5) fraction of styrene/acrylonitrile monomer mixture grafted to the polybutadiene seed latex (defined here as grafting efficiency). For polymerizations using the t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 redox initiator, the rates of polymerization were faster, the grafting efficiencies were greater, and the amounts of coagulum were greater at 70°C than at 50 or 35°C. The rates of polymerization were decreased by decreasing the concentration of redox initiator or adding it incrementally. A 1.00/1.00/0.08 (w/w) t‐butyl or cumene hydroperoxide/sodium formaldehyde sulfoxylate dihydrate/EDTA‐chelated Fe+2 ratio gave reasonable polymerization rates at 35 and 50°C, and a 0.48/1.00/0.07 ratio, at 70°C. The latexes were stabilized during polymerization with 3% (based on seed solids) nonionic Igepal CO‐990 at 35°C, and 6% at 50 and 70°C. The grafting efficiency increased with decreasing particle size of the polybutadiene seed latex and decreasing monomer/polymer ratio. The rate of polymerization increased with decreasing monomer/polymer ratio. The monomer/polymer ratio also affected the morphology of the particles; higher values gave inclusions of poly(styrene‐co‐acrylonitrile) in the polybutadiene particles. There were no significant differences in polymerization kinetics or grafting efficiency between the t‐butyl and cumene hydroperoxides.
Multiphase materials with lignin. VIII. Interpenetrating polymer networks from polyurethanes and polymethyl methacrylate
Authors: Kelley Stephen S. , Ward Thomas C. , Glasser Wolfgang G. 
Published: April 2003

AbstractSeveral types of interpenetrating polymer networks (IPNs) from polyurethane/polymethyl methacrylate (LPU/PMMA) on the basis of lignin were prepared. All composites were judged to possess two phase morphology. The composition and the presence of crosslinking were found to influence the thermal and mechanical properties of the solvent‐cast films. The mechanical properties were assessed by dynamic mechanical analysis and by tensile testing, and they were found to vary consistently with composition and the presence of crosslinks. The modulus behavior of the different IPNs could be explained by models which accounted for either dual phase continuity or phase inversion.
Radiation grafting of MMA onto PVC films
Authors: Hegazy El‐Sayed A. , Ebaid A. R. , El‐Sharabasy S. A. , Mousa A. M. , Hassan A. Y. 
Published: April 2003

AbstractAn approach to the problem of producing poly(vinyl chloride) (PVC) graft copolymer exhibiting good mechanical properties and electrical resistance that suits its uses as an electrical insulator has been investigated. Graft copolymerization of methyl methacrylate (MMA) onto PVC using γ‐radiation as initiator has been studied. PVC was chemically modified, and the effect of the change in its chemical and physical structure on its properties was investigated. In this grafting system, different solvents were tried and it was found that the most suitable diluent for the grafting of MMA onto PVC films is methanol. An appreciable improvement in tensile properties of the graft copolymer was achieved. The most suitable degree of grafting, concerning electrical insulation efficiency, was found to be near 80%. Gel determination in the graft copolymer was carried out, and a crosslinked network structure was formed. Increasing the crosslinking content in the graft copolymer leads to a decrease in the extent of swelling due to the less diffusivity of the solutions through such network structure.
An improved kinetic model for the autocatalytic curing of styrene‐based thermoset resins
Authors: Lam P. W. K. , Plaumann H. P. , Tran T. 
Published: April 2003

AbstractThe cure behavior of styrene‐based thermosets such as orthophthalic polyester, isophthalic polyester, and vinyl ester resins is characterized using both isothermal and dynamic differential scanning calorimetry (DSC) techniques. In the conventional autocatalyzed kinetic model, it is assumed that the isothermal cure reaction of a thermoset goes to completion, which usually leads to a poor fit with the DSC kinetic data. It appears from the conversion‐time profiles that the cure reaction reached a plateau value (αu) less than unity. This is not unexpected, as the molecular mobility of the resin system decreases as the network cures. In this work, we have refined the model to remove this restrictive assumption by taking the total ultimate conversion (αu) into account in the computation. This improved model permits us a better prediction of the course of the cure reaction of the styrene‐based thermosets under isothermal and dynamic conditions. In addition, the cure kinetics of the three thermoset resins are studied and compared on the basis of several kinetic parameters including conversion, cure rate, reaction rate constant, heat of cure reaction, half‐life, and Arrhenius parameters. The reactivity of these resins when arranged in ascending order is found to be: vinyl ester < orthophthalic polyester < isoththalic polyester.
Synthesis and water absorbility of base‐hydrolyzed starch‐g‐poly(acrylonitrile‐co‐sodium allylsulfonate)
Authors: Kejun Yao , Benlian Wang 
Published: April 2003

AbstractGrafting of mixed vinyl monomers, acrylonitrile (AN) and sodium allylsulfonate (SAS), onto starch was carried out in aqueous, gelatinized corn starch by using ceric ammonium nitrate (CAN) as an initiator at 30°C under a nitrogen atmosphere. Conversion (%) and percent graft (%) were determined as a function of (1) molar ratios of feed composition, (2) concentration of CAN, (3) HNO3 concentration, and (4) reaction temperature. The monomer, SAS, is found to decrease percent graft of mixed monomers onto starch. The graft copolymer, starch‐g‐poly(AN‐co‐SAS), can be hydrolyzed by varying amounts of aqueous NaOH at 80–100°C to obtain base‐hydrolyzed starch‐g‐poly(AN‐co‐SAS). The hydrolyzed product is an excellent water absorbent, which absorbs 1900 times its weight of deionized water. Water retention reached over 90% at 10 kg/cm2, and the toleration of electrolyte (synthetic urine) attained was better than that of hydrolyzed starch‐g‐polyacrylonitrile (H‐SPAN).
Gravimetric measurements of steady‐state moisture uptake in spin‐coated polyimide films
Authors: Pranjoto Hartono , Denton Denice D. 
Published: April 2003

AbstractPolyimide (PI) is an insulating polymer that is finding increased use in the semiconductor industry as an intermetal dielectric, passivation coating, and planarization layer. It has a low dielectric constant (3.5 at audio frequencies) and can be processed at temperatures below 450°C. These features make PI attractive to the integrated circuit industry. One disadvantage of this material is that, like most polymers, it is hygroscopic. Moisture can lead to such reliability problems in integrated circuits as increased insulator conductivity, loss of adhesion, and corrosion. It is important to quantify the moisture uptake in polyimide so that the reliability implications of its use can be fully understood. In this study, the steady‐state moisture uptake of the model PI pyromellitic dianhydride‐oxydianiline (PMDA‐ODA) is reported. The moisture uptake is measured using a Cahn 1000 Microbalance with a 1‐μg resolution. The samples are prepared by spin‐coating one or more layers of the precursor polyamic acid onto 2‐in silicon substrates. The moisture uptake in these polymers is found to be linearly related to ambient relative humidity, and the maximum moisture uptake by weight is 3.2%. The moisture uptake in PI is also shown to be a bulk absorption rather than a surface adsorption phenomenon.
Crystallization, tensile, and impact behavior of polypropylene/polybutadiene blend
Authors: Gupta A. K. , Ratnam B. K. 
Published: April 2003

AbstractA blend of isotactic polypropylene (PP) and polybutadiene (PBu), in the composition range 5–35 wt % PBu content, prepared by mixing in a two‐roll mill, is studied for crystallization, tensile, and impact behavior. Variations in crystallization behavior and the resulting morphology and structure are observed in both differential scanning calorimetry (DSC) and X‐ray diffraction measurements on this blend as a function of blend composition. Impact and tensile properties are studied in the entire blend composition range. Analysis of tensile properties data in terms of the various theoretical models is attempted to obtain better insight into the interphase adhesion and stress concentration effect in this blend. The effects of blend composition on the state of dispersion and morphology of dispersed phase droplets and correlation of tensile properties with the crystallization parameters of PP component are also presented.
Arylidene polymers III. A new route for the synthesis of conjugated polymers and copolymers of arylidenecycloalkanones, characterization, and some molecular orbital studies of its model
Authors: Abd‐Alla Mohamed A. , El‐Shahawy Anwar S. 
Published: April 2003

AbstractA new class of polyconjugated polymers, namely poly(2,5‐arylidenecyclopentanone) and poly(2,6‐arylidenecyclohexanone) has been obtained by condensation of cyclopentanone or cyclohexanone with terephthalaldehyde using alcoholic potassium hydroxide as a catalyst. Copolymerization of the corresponding monomers was also carried out. To characterize these polymers model compounds were prepared from cyclopentanone or cyclohexanone and benzaldehyde. The structures of the model compounds were elucidated by IR, NMR, and elemental analyses. DSC measurements, thermogravimetric, and X‐ray analyses. From the SCF‐CI calculations, the 2,5‐dibenzylidenecyclopentanone, as a model compound, has the trans form. Furthermore, the charge densities of this model, its anionic and cationic forms, as well as the ionization potential and the electron affinity have been calculated.