bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the synthesis of fiber‐forming block copolymers of polyacrylonitrile and poly(ethylene oxide)
Authors: Wódka Tadeusz 
Published: April 2003

AbstractModified PEO (MW 6000) containing xanthate groups was used for the synthesis of block copolymers of PAN and PEO. Principal parameters affecting the synthesis were examined. To confirm the segmental structure of the obtained products, precipitation fractionation, gel permeation chromatography, infrared, and 1H nuclear magnetic resonance methods were used. The fiber‐forming properties were investigated by means of rheological examination of concentrated solutions of PAN–PEO and confirmed by spinning the fibers under laboratory conditions. The physical and mechanical properties of the fibers were also determined.
The lithographic effect of electron beam on poly(methyl methacrylate) in a scanning electron microscope: Minimization of line width by the dose and beam current
Authors: Muchová M. , Pelzbauer Z. 
Published: April 2003

AbstractThe lithographic effect of electron beam in line exposures in scanning electron microscopy (SEM) on poly(methyl methacrylate) (PMMA) was evaluated using the line width in a film deposited on a silicium substrate and from the line profiles in a PMMA plate. It was found that the effect of the dose on dimensions of the exposed structures in line exposures is not unambiguous, in contrast to area exposures, but that at constant dose and beam width the line dimensions increase with beam current. Sensitivity in line exposures (line sensitivity) is smaller than in area exposures (area sensitivity). The effect of beam current on the line width increases with decreasing dose; at doses close to line sensitivity it is the strongest. The increasing effect of a beam on the polymer with increasing current at constant dose is explained through the increasing range of thermal degradation due to exposure. A qualitative explanation is based on simplified calculations of the thermal conditions in the resist film during and after the exposure.
Wilkinson's salt: A flame retardant for poly(methyl methacrylate)
Authors: Sirdesai Sunil J. , Wilkie Charles A. 
Published: April 2003

AbstractPoly(methyl methacrylate) reacts with RhCI(PPh3)3 at 260°C in a sealed tube to produce a material which is insoluble in common solvents. The infrared spectrum and CP/MAS 13C‐NMR spectrum indicate the presence of anhydrides. Differential scanning calorimetry shows that the transition temperature has increased by 15°C. Thermogravimetric analysis indicates that 25% of the material is not volatilized at 600°C. The oxygen index of the mixture of the rhodium compound with PMMA increases from 14 to 20 (bottom ignition).
Sorption of organic liquids and vapors by rigid PVC
Authors: Berens Alan R. 
Published: April 2003

AbstractThe effects of activity and solvent strength of a number of organic penetrants upon their sorption kinetics and equilibria in poly(vinyl chloride) have been studied by gravimetric vapor and liquid sorption experiments at 30°C. For each solvent, the relation of equilibrium sorption to activity is well approximated by the Flory–Huggins equation with a characteristic value of the interaction parameter χ. The glass transition temperature Tg is depressed in direct proportion to the volume fraction of solvent absorbed; the composition corresponding to a Tg of 30°C, Cg (30°C), is in the range of 0.22–0.30 volume fraction for several common solvents. The form of the sorption kinetics varies with the ratio of the equilibrium sorption to Cg, and thus depends on the combined effects of χ, solvent activity, and plasticizing action. When the equilibrium sorption is less than about Cg/2, kinetics are Fickian, with the very low diffusivities typical of the glassy state; for sorption values between Cg/2 and Cg, anomalous kinetics are observed; and when the sorption is greater than Cg, transport in thin PVC films follows Case II kinetics. At high sorption levels, increasing film thickness produces a shift of the kinetics toward Fickian form with apparent diffusivity values typical of rubbery polymers.
Microporous clay membrance materials for reverse osmosis applications. I. Performance characteristics from osmotic studies
Authors: Adhikari M. , Ghosh S. K. 
Published: April 2003

AbstractFired clay membranes were prepared from montmorillonite clay and also by incorporating protein (lysozyme) and nylon (copolymer of 6‐amino caproic acid) to clay followed by firing these membranes at different temperatures for different durations of time. Osmotic behaviors of the membranes were studied, and the results were correlated to the porosity determined by scanning electron microscope. Reverse osmosis parameters, namely, the reflection coefficient, solute permeability, and rejection coefficient, of the membranes were determined from osmosis experiments. Rejection coefficients as determined from reverse osmosis were compared with those obtained from osmosis experiments.
The crystallization and transition behavior of poly(vinylidene fluoride)/copoly(chlorotriofluorethylene‐vinylidene fluoride) blends
Authors: Siegmann A. , Cohen G. , Baraam Z. 
Published: April 2003

AbstractThermal analysis of solution precipitated blends of two crystallizable polymers, poly(vinylidene fluoride) (PVDF) and copoly(chlorotrifluorethylene‐vinylidene fluoride) (copoly(CTFE‐VDF)), has been carried out to study the transition temperatures, crystallinity, and crystallization rates. PVDF crystallizes over the whole blend composition either during precipitation from solution or upon cooling from the melt. The high degree of crystallinity attained, higher than in PVDF by itself, suggests the occurrence of partial PVDF‐copolymer cocrystallization. The melt crystallization temperature, decreasing with cooling rate, is lower in PVDF‐rich blends than for lean blends. However, the heat of crystallization increases with cooling rate, suggesting that the crystal composition depends on crystallization rate. No significant melting temperature depression due to blending was observed. However, the blends glass transition (Tg) changes linearly with composition, but less than expected by any mixing rule applicable to compatible systems. Annealing of the blends above Tg results in an additional crystalline phase consisting mainly of the copolymer. The amount of these crystals increases with PVDF content, due to partial cocrystallization and kinetic effects. The addition of the copolymer to PVDF results in a volume‐filling spherulitic structure consisting of spherulites which decrease in size with increasing copolymer content.
Impact thermoplastics: Combined role of rubbery phase volume and particle size on toughening efficiency
Authors: Cigna G. , Lomellini P. , Merlotti M. 
Published: April 2003

AbstractA relationship has been found for OSA (olefin‐acrylonitrile‐styrene) polymers between normalized Izod impact strength (ΔI/N) or yield stress (Δσy/N) with mean particle radius. These normalized functions (which analytically include radius and rubbery phase volume) are representative of the toughening effect of a single particle with respect to the styrene‐acrylonitrile (SAN) rigid matrix. ΔI/N and Δσy/N increase exponentially as a function of the radius. This approach, for Izod, was also applied to HIPS and toughened nylon reported in the literature and similar results were obtained. In the case of nylon, however, the ΔI/N values are split in two different curves related to the tough‐brittle transition described in that literature. Referring to OSA, three samples (with the largest radii more than 0.22 μm) fail in a brittle manner and do not fit the curve of ΔI/N: they fit, however, that of Δσy/N. Further work must be done in order to investigate a decisive role either of interfacial adhesion (eventual lack for these three materials) or of tough‐brittle transition mentioned before for shear‐yielding deforming materials. In fact, OSA has behavior intermediate between that of nylon and HIPS which deforms by crazing.
The crystallization of a copoly(chlorotrifluorethylene‐vinylidene fluoride) from the amorphous rubbery state
Authors: Siegmann A. , Cohen G. , Baraam Z. 
Published: April 2003

AbstractA random copoly(chlorotrifluorethylene‐vinylidene fluoride) in the ratio of 3 : 1 was annealed at the temperature range of Tg < T < Tm. The copolymer slowly crystallizes, attaining a rather low ultimate degree of crystallinity, depending on the annealing temperature, in the form of randomly distributed ribbonlike lamellae. The crystallites' melting temperatures are much lower than those of the corresponding homopolymers, increasing with annealing temperature and time. The crystallization kinetics, analyzed using the Avrami equation, indicates the formation of small, low‐ordered crystallites. The crystallization process results in a dramatic increase in the elastic modulus at T > Tg. Annealing of stretched samples results in oriented crystallization at much higher rates than in the unstretched material, without markedly affecting the ultimate degree of crystallinity. The oriented crystallites, distributed in an isotropic amorphous matrix, exhibit lower thermal stability than the corresponding unoriented crystals. Their melting temperatures increase with annealing time; however, they decrease with the extent of stretching, suggesting a strong kinetic effect on the crystallites' degree of order.
Investigations on the curing of epoxy resins with hexahydrophthalic anhydride
Authors: Steinmann Bettina 
Published: April 2003

AbstractThe bifunctional epoxides bisphenol A diglycidyl ether (BADGE) and hexahydrophthalic diglycidyl ester (HHDGE) as well as the monoepoxides phenyl glycidyl ether (PGE) and cyclohexane carboxylic acid glycidyl ester (CHGE) were cured with hexahydrophthalic anhydride (HHPA) in the presence of benzyldimethylamine (BDMA) or 1‐methylimidazole (1‐MI) as catalysts at 100–140°C. Investigations of the curing kinetics gave sigmoidal‐shaped curves with marked induction periods. IR analysis of the cured products revealed that the propagation proceeds not only by the esterification reaction of epoxide with anhydride but also by chain anhydride formation by the reaction of carboxylate with anhydride groups. 13C‐NMR investigations of the soluble polymers showed that most of the peaks resulting from double bonds could not be assigned to structures formed by initiation reactions that had previously been proposed for the anhydride curing of epoxides. In analogy to a postulated mechanism for the decarboxylation condensation of HHPA alone in the presence of tertiary amines, it is proposed that an isomerization product of HHPA is one of the molecules that initiate the curing reaction.
An approximate method for the determination of polymer–polymer interaction parameters of incompatible polymers in solution
Authors: Narasimhan Venkataraman , Huang Robert Y. M. , Burns Charles M. 
Published: April 2003

AbstractA method is developed, based on Scott's equations for ternary systems of two polymers and a mutual solvent, for the calculation of values of the polymer–polymer interaction parameter, χ23, for systems in which both polymer–solvent interaction parameters χ12 and χ13 are not known a priori. Equilibrium phase studies were carried out on ternary systems of polystyrene, polybutadiene, and tetrahydrofuran or toluene at 23°C and 1 atm. Typical interaction parameter values (χ23) calculated by this new method were compared with the values of χ23 determined earlier using standard equations and known χ12 values for these systems, and were found to agree very well. It is concluded that the technique presented in this article can be used for mixed polymer systems in good mutual solvents where neither polymer–solvent interaction parameter is known, for determining an approximate value of the χ23 parameter alone.
Network structure and properties of imidazole‐cured epoxy novolac adhesives
Authors: Madsen Patricia A. , Foister Robert T. 
Published: April 2003

AbstractThe structural characteristics of four epoxy adhesives, obtained by crosslinking an epoxy novolac with various levels of a substituted imidazole curing agent, were investigated and correlated with thermal and mechanical properties. Variations in network structure were characterized by measuring crosslink densities and by qualitatively assessing glassy state free volume from densities and coefficients of thermal expansion. Differential scanning calorimetry was used to obtain glass transition temperatures, and dynamic mechanical thermal analysis was used to follow primary (alpha) and secondary (beta) transitions. Bulk behavior was characterized by tensile modulus, strength, and toughness, together with compressive modulus and yield strength. The effect of sub‐Tg aging on compressive yield strength was investigated as well. As the level of imidazole increased, crosslink density, and hence network packing efficiency and free volume, decreased. For fully cured networks, both the glass and the alpha transition temperatures increased with crosslink density. Calculated activation enthalpies and entropies indicated significant degrees of network cooperativity in the alpha transitions, particularly for the more highly crosslinked systems. Beta transition temperatures, however, were found to be independent of crosslink density. Bulk properties generally showed a dependence both on crosslink density and free volume. Yield stress, for example, was highest for the network with lowest crosslink density and free volume. Volume relaxation associated with physical aging also caused yield stress to increase.
Porous substances immobilizing enzymes with polymer matrix
Authors: Kumakura Minoru , Kaetsu Isao 
Published: April 2003

AbstractThe preparation of porous substances immobilizing enzymes with polymer matrix having various properties have been studied by radiation polymerization method. The enzyme (cellulase) was immobilized on the surface parts of porous substances such as activated carbon, molecular sieve, silica gel, and coating with hydrophilic and hydrophobic monomers. As substrate of enzyme reaction, lignocellulosic wastes such as chaff pretreated by radiation irradiation (100 Mrad) were used. The enzyme activity of the immobilized enzyme substances was markedly affected by hydrophilicity of monomer and the copolymerization of methoxypoly(ethyle glycol) methacrylate (75%) and poly(ethylene glycol) dimethacrylate (25%) monomer gave the most highest enzyme activity. The immobilized enzyme substances was able to hydrolyze chaff pretreated by radiation irradiation.
Sorption behavior of water vapor into polyelectrolyte complex of poly(acrylic acid)/poly(4‐vinylpyridine)
Authors: Hirai Yoshiyuki , Nakajima Toshinari 
Published: April 2003

AbstractThe sorption of water vapor into the polyelectrolyte complex of poly(acrylic acid)/poly(4‐vinylpyridine) has been investigated. The sorption isotherm was evaluated on the basis of various theories; BET equation, Flory–Huggins interaction parameter χ1, and cluster function G11/v1. The behavior of the BET plot, χ1, and G11/v1 was considered in terms of the structure of the complex, while the crosslink density and charge density were determined from the carbonyl absorption in IR spectra. The reasonable conclusion drawn from the available data is as follows. The interaction of water with specific polymer sites plays an important role in the sorption. The sorbed water plasticizes this material, and it enables the expansion of the network. The large amounts of water incorporated by the expansion cannot be dispersed homogeneously in the network, and indicate clustering tendency.
Dynamic‐mechanical relaxations in high and low density polyethylenes. Effects of irradiation and annealing
Authors: Greus Amparo Ribes , Calleja Richardo Diaz 
Published: April 2003

AbstractA study of the dynamic‐mechanical relaxation spectrum in a series of commercial high and low density polyethylenes (Dow Chemical), irradiated as well as unirradiated, and subjected to different annealing process, has been performed. The effect of 20‐Mrad dose of irradiation on the chemical structure has been analyzed and an increase in the number of aldehyde, ketone, and transvinylene groups and a decrease in the number of vinyl and vinylidene groups has been observed. The dynamic‐mechanical spectrum of irradiated and unirradiated high and low density polyethylenes contains the γII‐, γI‐, β‐, αI‐, αII‐, and αIII‐ relaxations, in order of increasing temperature. It has been observed that γ‐irradiation followed by annealing modified the intensity and the position of relaxations in these polyethylenes.
Rubber‐modified epoxies: Interfacial tension and morphology
Authors: Sohn John E. , Emerson John A. , Thompson Patrick A. , Koberstein Jeffrey T. 
Published: April 2003

AbstractThe interfacial tension between carbomethoxy‐terminated butadiene–acrylonitrile copolymers and an epoxy resin as a function of temperature and copolymer composition is investigated. Using a digital image processing technique, the shape of a pendant drop of the epoxy in the copolymer is determined. Analysis of the drop shape is performed by profile discrimination and subsequent robust shape analysis. The data are used to examine the relationship between interfacial tension and particle size of the dispersed copolymer‐rich phase in rubber‐modified epoxy resins, that are immiscible in the uncured state.
The thermal shrinkage of the drawing poly(ethylene isophthalate terephthalate) copolyester films
Authors: Hsiue Ging‐Ho , Yeh Tuu‐Sheng , Chang Shuya 
Published: April 2003

AbstractThe objective of this study is to use the copolymerization method to improve the thermal shrinkage property of poly(ethylene terephthalate) (PET), so that the resultant copolyester can be used for the application of thermal shrinkage packing materials. The poly(ethylene isophthalate terephthalate) (PEIT) copolyester films were prepared and studied. The thermal shrinkage rate of PET films and the thermal shrinkage rate of the copolyester films were measured by using a thermomechanical analyzer (TMA). The thermal shrinkage of copolyester was found to be dependent on such factors as composition, molecular weight, and draw temperature. The highest thermal shrinkage was obtained when the copolymer contained 40 mol % of ethylene isophthalate. Its shrinkage ratio and shrinkage rate were consistently 1.3 and 2.4 times those of PET. The increase of molecular weight and decrease of drawing temperature resulted in the increase of the thermal shrinkage. The best drawing temperature range was between glass transition temperature and soft temperature of the copolymer. The relationship of shrinkage rate and temperature indicate that the shrinkage mechanism of the copolyester belongs to two‐step thermal shrinkage.
Polymer–filler interactions in hydroxy‐terminated polybutadiene–ammonium perchlorate system in the presence of a bonding agent
Authors: Kishore Kaushal , Rajalingam Ponswamy 
Published: April 2003

AbstractBonding between ammonium perchlorate (AP) and hydroxy‐terminated polybutadiene (HTPB), constituting a nonreinforcing filler system, has been studied in the presence of a unique bonding agent (BA)–a switter ion molecule, 2,4‐dinitrophenylhydrazone derivative of 1,1′‐bisacetylferrocene (DNPHD AF). Extensive conjugation and a permanent ionic character makes the DNPHD AF to bond strongly with the ionic oxidizer AP. Through its terminal OH group, HTPH bonds with the NO2 groups of DNPHD AF. Bonding sites in the molecules have been located from IR studies and from the first‐order rate constant measurements of the bonding of DNPHD AF and other model BAs with HTPB and AP. The bonding ability of DNPHD AF is further evidenced from SEM micrographs.
Fluorescence polarization study of the curing process of epoxide with aminimide
Authors: Ikeda Tomiki , Inubushi Shinzo , Tazuke Shigeo 
Published: April 2003

AbstractThe curing process of epoxide (Epikote 828, EK) with aminimide (trimethylamine valerimide, TMAV) was studied by a fluorescence polarization method. Two types of probe molecules were used: One was perylene (PE), which was just physically incorporated into the curing mixture and termed as the “extrinsic” probe, and the other was fluorescent product(s) formed during curing of EK with TMAV, which was termed as the “intrinsic” probe. Extraction experiments revealed that the “intrinsic” probe was covalently incorporated into the crosslinked matrix. No emission was observed for the “intrinsic” probe before heating, but its intensity increased with curing at 150°C. Fluorescence anisotropy (r) of both EK/TMAV/PE and EK/TMAV systems increased monotonically with curing time at the initial stage and then remained nearly constant. This means that at the early stage of curing the network becomes rigid enough to restrict rotational diffusion of the probe molecules. Calculated r values for the “extrinsic” probe alone were lower than observed r values of the “intrinsic” probe, which was well explained in terms of the mode of incorporation of the two types of the probe molecules into the matrix.
Graft copolymerization with a new class of acidic peroxo salts as initiator. V. Grafting of methyl methacrylate onto jute fiber using potassium monopersulfate catalyzed by Fe(II)
Authors: Samal Rajani K. , Samantaray Himansu S. , Samal Rabi N. 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate (MMA) onto jute fibers was studied in an aqueous solution using a new class of acidic peroxo salt, potassium monopersulfate, as initiator, under the catalytic influence of Fe(II) under nitrogen atmosphere. The grafting reaction was influenced by the reaction time, temperature, and concentrations of monomer, initiator, and jute fibers. The grafting reactions have also been studied in the presence of various salts and solvents. The maximum grafting percent (385.4%) has been observed at 35°C for the concentration of monomer (1.4082M), initiator (12.9 × 10−3M), catalyst (2.5 × 10−4M), and solvent (acetic acid) composition of (40:60) for a reaction time of 6 h. From the experimental results a suitable mechanism for the graft initiation and termination has been put forth. The graft copolymers have been characterized, and their improved properties such as tensil strength tested.
Engineering plastics from lignin. XVI. Starlike macromers with propylene oxide
Authors: Oliveira Willer De , Glasser Wolfgang G. 
Published: April 2003

AbstractStarlike macromers were prepared from hydroxypropyl organosolv lignin by reaction with propylene oxide, and they were analyzed by a combination of conventional analysis techniques. The average number of arms per macromer was controlled by partial capping with an alkoxy group; and the average length of arms by the degree of chain extension with propylene oxide. Analysis methods included treatment with hydriodic acid followed by gas chromatographic separation of alkyl iodides (HI/GC), UV spectroscopy, H‐NMR spectroscopy, and thermal analysis. The results were consistent with a hypothetical pentameric model structure having between two and six radiating arms, each with a length of between 1 and 4 propylene oxide units. The UV method was best qualified to determine degree of chain extension, while HI/GC was best suited for analyzing average number of arms per macromer fragment. The synthesis and analysis of starlike macromers from lignin is viewed as an important stepping stone for the formulation of lignin‐based engineering plastics and multiphase materials.