bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition metal chelates as accelerators for epoxy resin systems—studies with cobalt (III) acetylacetonate
Authors: Reddy P. V. , Thiagarajan R. , Ratra M. C. , Gowda N. M. Nanje 
Published: April 2003

AbstractCobalt(III)acetylacetonate serves as an accelerator for anhydride curable epoxy resin system and the rate of curing is found to increase with enhanced concentrations of the metal chelate. There is also an appreciable reduction in the cure gel time. Kinetic studies based on thermal analytical techniques reveal that the overall curing process follows first order kinetics. Based on the kinetic results a cure schedule has been proposed. It is also observed that the electrical, mechanical, and thermal properties of the cured epoxy system are not altered by the presence of the metal chelate at the concentration studied.
The role of extractives during vacuum pyrolysis of wood
Authors: Roy Christian , Pakdel Hooshang , Brouillard Dominique 
Published: April 2003

AbstractVacuum pyrolysis of wood, extractive‐free wood, holocellulose, and Avicel was conducted and their oil yields were compared. Formic and acetic acids and levoglucosan contents of all the oil products were determined. Molecular beam mass spectrometry analysis of wood and extractive‐free wood and their pyrolysis oils was performed. CO2and CO, the main pyrolysis gases, were measured for each pyrolysis experiment. The role of extractives and the modification in wood cellulosic structure, which occurred during wood extraction treatment process, were investigated. Extractives, lignin, and orientation of the cellulosic fibers all significantly influenced the production of pyrolysis oils and formic acid. Lignin and extractives exhibited an inhibiting effect for the production of acetic acid and levoglucosan, respectively. CO2and CO yields were affected by the presence of extractives and by the cellulosic fiber orientation.
Epoxy‐pretreated asbestos composites: Solution based versus interfacial polymerization pretreatment process
Authors: Papaspyrides C. D. , Duvis T. 
Published: April 2003

AbstractEpoxy‐resin‐based composites filled with treated asbestos fibers were made. The asbestos, of chrysotile variety, was coated by impregnation in poly(hexamethylene adipamide) solution and the results of testing the tensile properties of the asbestos/polyamide/epoxy composite system are presented. The interest was focused on the influence of the asbestos content in the composite together with that of the polyamide content deposited on asbestos. No satisfactory reinforcing effect was found, especially when comparing with previous studies on coating the chrysotile by in situ interfacial polymerization. Nevertheless, a qualitative model was proposed to correlate the effect of the different phases contained in the composite with the experimental behavior encountered.
Theoretical estimations of diffusion coefficients
Authors: Huang Robert Y. M. , Rhim Ji‐Won 
Published: April 2003

AbstractA model calculating the diffusion coefficients of liquids in polymeric membranes from the diffusion coefficients at zero concentration was developed. This model is based on Fujita's volume theory and considers crystallinity in the polymer and is tested by using available data in the literature, i.e., n‐hexane–polyethylene and benzene–polyethylene systems. The calculated diffusion coefficients were simulated by calculating the pure liquid permeabilities in a pervaporation system. When comparing the predicted pure liquid permeabilities with the experimental values, these calculated values were found to be in fairly good agreement.
Synthesis and fundamental structural analysis of composite PVC latices
Authors: Omi Shinzo , Shiiyama Eisuke , Aita Kazuyoshi , Matsumoto Masatoshi , Iso Mamoru , Sakaya Mitsuro , Nakano Akira , Imazawa Yasuta 
Published: April 2003

AbstractSyntheses of various combinations of composite particles were carried out employing PVC‐based latices, PVC, PVC–VAc and PVC–VD, as seed particles. Monomers for seed polymerization were chosen so that the solubility in water and the compatibility with seed polymer may influence the features of products. MMA, whose coverage improves the flow characteristics of PVC plastisols to a great extent, was most investigated along with MMA‐ST, BMA, and ST. Smaller monomerpolymer feed ratio (M/P), smaller seed size, and the employment of monomers sparsely soluble in water were the key factors in preventing the nucleation of secondary particles during the seed polymerization. A quantitative correlation to evaluate how effectively monomer is converted for the formation of composite particles was proposed. Analyses by means of the electron microscopy (TEM and SEM), GPC, DSC, and TLC strongly anticipated the development of IPN structure and the formation of graft linkage between PVC–VAc core and PMMA.
Polysulfone hollow fiber membranes spun from aliphatic acid (C2—C4): N‐methylpyrrolidone complexes—structure determination by oxygen plasma ablation
Authors: Fritzsche A. K. , Cruse C. A. , Kesting R. E. , Murphy M. K. 
Published: April 2003

AbstractPolysulfone hollow fiber membranes with increased free volumes as reflected by elevated glass transition temperatures can be obtained from a spectrum of Lewis acid : N‐methylpyrrolidone (NMP) complexes provided that the complex is readily dissociated by water. The upper limit of the candidate Lewis acid for suitable complexes is an acceptor number between 49.1 (propionic acid) and 52.9 (acetic acid). Although the enhanced free volume yields an increase permeability with maintenance of selectivity, a knowledge of the structure and morphology of both the active separating layer and the substructure is needed to understand the performance of the membrane. Oxygen plasma ablation experiments have shown that the active separating layer of these membranes decreases in the order NMP/FA > acetic acid : NMP > propionic acid : NMP, butyric acid : NMP, and isobutyric acid : NMP with the differences among the last three being too small to resolve by the current experiment. Also, the surface and internal pore size and internal porosity appeared to increase in the order NMP/FA < acetic acid : NMP < propionic acid : NMP < isobutyric acid : NMP < butyric acid : NMP.
Grafting onto isotactic polypropylene. III. Gamma rays induced graft copolymerization of water soluble vinyl monomers
Authors: Mehta I. K. , Kumar Sunil , Chauhan G. S. , Misra B. N. 
Published: April 2003

AbstractGraft copolymerization of water soluble vinyl monomers such as acrylic acid and acrylamide onto isotactic polypropylene by the pre‐irradiation method has been studied. Grafting was carried out in a water and water‐methanol solvent system. The percentage of grafting has been determined as a function of (i), total dose (ii) concentration of monomers, (iii) reaction time, and (iv) the composition and amount of water‐methanol solvent system. Water was found to be the best solvent for affording maximum grafting. The grafted samples were characterized by spectroscopic and thermogravimetric methods. Acrylic acid was found to be more reactive than acrylamide towards graft copolymerization.
The effect of compounding ingredients on microbial degradation of vulcanized natural rubber
Authors: Tsuchii Akio , Hayashi Kouji , Hironiwa Tadashi , Matsunaka Hiroshi , Takeda Kiyoshi 
Published: April 2003

AbstractA series of natural rubber vulcanizates containing varied amounts of sulfur and an accelerator (N‐cyclohexyl‐2‐benzothiazyl sulfenamide, CBS) were prepared and their resistance to attack by a strain of Nocardia, capable of utilizing natural rubber as carbon substrate, was examined. The higher the content of sulfur or CBS, the less the weight loss of the vulcanizates after microbial attack. In this system of curing without a filler, the rate of microbial degradation was suggested to depend on the cross‐link density estimated from the swelling. Addition of calcium carbonate as a filler did not affect the microbial degradation, and in some cases slightly enhanced it. Addition of carbon black, however, made the vulcanizate apparently more resistant to microbial attack. The specimens with HAF grade carbon black loading were more resistant than those with SRF grade.
Synthesis and characterization of conjugates of poly(α‐amino acids) and manganese (III) protoporphyrin IX as relaxation enhancement agents for MRI
Authors: Spaltro Suree M. , Foster Natalie 
Published: April 2003

AbstractPolymers are finding increasing use in medicine, and conjugates of paramagnetic species and polymers are now being studied as relaxation enhancement agents to improve contrast in magnetic resonance imaging. To assess the potential of such agents, the enhancement of proton relaxation by paramagnetic species bound to macromolecules has been observed for four conjugates of amino acid polymers and manganese (III) protoporphyrin IX. The conjugates all differ in their abilities to enhance the relaxation of water protons in solution; values of relaxation rates range from 3.2 to 9.1 s−1 mM−1. The rotational correlation times and volumes of the kinetic units within the macromolecules have been determined by fluorescence depolarization in an effort to understand the range of relaxation rates observed for the conjugates. The metalloporphyrins bound to the polymers all have very similar dynamic characteristics.
Aromatic copolyimide membranes for high temperature gas separations: H2/CH4, H2/N2, and O2/N2
Authors: Buys H. C. W. M. , van Elven A. , Jansen A. E. , Tinnemans A. H. A. 
Published: April 2003

AbstractA series of high‐molecular weight condensation polyimides prepared from pyromellitic dianhydride (PMDA) or 3,3,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) with 4,4′‐oxydianiline (ODA) and/or 1,5‐diaminonaphthalene (NA), and a series of high‐molecular weight condensation poly(amide–imides) prepared from trimellitic anhydride acid chloride (TMAC) with ODA and/or NA were evaluated to determine, in the temperature region 50–250°C, the effect of polymer molecular structure on the permeability and ideal permselectivity of hydrogen, oxygen, nitrogen, and methane. Replacement of ODA with NA generally decreases the permeability of each gas but it increases the permselectivity, which is explained by suppression of both the packing disruption effect and intrasegmental mobility of the amine segments. In general, the overall lower permeation values for the TMAC series of polyimides are much lower than the BTDA‐derived series, being the highest for the PMDA‐derived series. Permeation data were used to calculate the performance of a hollow fiber module on an industrial scale. It is shown that hydrogen can be efficiently recovered (> 90%) with a purity of at least 95% from ammonia synthesis off‐gas with a feed concentration of 61 mol % of hydrogen.
Flame retardancy effect of crosslinking of lignocellulose materials
Authors: S̆imkovic Ivan , Pastýr Jan , Csomorová Katarína , Balog Karol , Micko M. M. 
Published: April 2003

AbstractDynamic and isothermal thermogravimetry (TG) was used for the study of flame retardancy effects caused by crosslinking of lignocellulose materials. This effect was also checked with the limited oxygen index (LOI) method. It was found that dynamic TG measurements run to 400°C could indicate the decrease of flame retardancy effect when lower residues are observed for samples measured in oxidative in comparison to inert environments. The isothermal TG data of initial reactions are not suitable for the prediction of flame retardancy effects. Epichlorhydrin (E) is a suitable chemical for the flame retardancy of wood. The addition of polyethyleneimine (PEI) decreases the flame retardancy of wood. On the other hand xylan crosslinked with E gives lower LOI values than the xylan crosslinked in the presence of PEI.
Novel rheological model for the gelation kinetics of ionic polysaccharides
Authors: Lapasin Romano , Pricl Sabrina , Paoletti Sergio , Zanetti Flavio 
Published: April 2003

AbstractHomogeneous networks of an ionic polysaccharide (namely pectate) in the presence of divalent ions were prepared in situ by proper procedure and the kinetics of the gel formation was studied by means of a coaxial cylinder rheometer in oscillatory flow conditions. The stress response was expanded in a Fourier series and the variation of the components of the fundamental harmonic with time during the gelation process were examined. A model is proposed for the correlation between kinetic parameters such as the concentration of the species active during the gel formation and the rheological parameters that can be experimentally determined, like G′ and G′′. Considerations are developed concerning the mechanism that governs the gelation process under dynamic conditions.
Environmental effects on latex paint coatings. I. Base polymer degradation
Authors: Patil D. , Gilbert R. D. , Fornes R. E. 
Published: April 2003

AbstractFilms of the base polymer used in a latex paint have been exposed to various combinations of UV/SO2/H2O/air. The polymer is primarily a terpolymer of butyl acrylate, vinyl acetate, and vinyl chloride. Reported here are results from dynamic mechanical analysis (Tg), sol‐gel analysis, intrinsic viscosity and contact angle measurements. Exposure without the presence of UV and causes virtually no change in the properties of the films. In the presence of UV and clean air containing O2. there is evidence of both chain scission and crosslinking. When films are exposed to combinations of either UV/SO2 or UV/SO2H2O, a dramatic increase in the rate of change in the properties is observed, indicating a synergistic interaction between UV and SO2. The gel fraction increases from about 20% for the control to about 65% in samples exposed to UV/SO2 or UV/SO2/H2O for as little as 24 h. In the latter exposed samples, there is a corresponding precipitous drop in the intrinsic viscosity of the soluble fraction, a significant increase in the surface polarity of the films, and a large increase in the Tg. Reaction mechanisms for changes resulting from the various exposure conditions are proposed.
Organic polymer analysis by laser ionization mass spectrometry and pattern recognition techniques
Authors: Di Brozolo Filippo Radicati , Odom Robert W. , Harrington Peter de B. , Voorhees Kent J. 
Published: April 2003

AbstractResults obtained by combining pattern recognition techniques with the organic microanalysis capability of laser ionization mass spectrometry (LIMS) for identifying and classifying the mass spectra produced from 19 different polymer formulations are reported. The data demonstrates that the LIMS mass spectra of many polymers are sufficiently unique to permit accurate classification of different polymers. The results obtained also suggest that pattern recognition procedures combined with laser microprobe analyses could provide a routine and reliable method of performing microanalytical characterization of unknown polymers.
GPC studies on the cationic polymerization of cardanol initiated by borontrifluoridediethyletherate
Authors: Antony Rosy , Pillai C. K. S. , Scariah K. J. 
Published: April 2003

AbstractThe cationic polymerization of cardanol using borontrifluoridediethyletherate as initiator has been investigated by gel permeation chromatographic techniques. The molecular weight and molecular weight distribution of the polymer at different temperatures and various initiator concentrations were studied, and the polymerization conditions have been optimized as 140°C with an initiator concentration of 1%. The reaction was found to follow first‐order kinetics with respect to the monomer. The activation energy and rate constants for the system have also been evaluated. The polymer has been characterized by IR, 1H and 13C‐NMR spectra.
Comparison of the properties of thermotropic liquid crystalline copolyesters containing different disymmetrical units
Authors: Kim H. D. , Paul D. R. 
Published: April 2003

AbstractThe effect of dissymetrical units on the properties of thermotropic liquid crystalline copolyesters based on hydroxybenzoic acid (HBA), terephthalate) acid (TPA), and poly(ethylene terephthalate) (PET) units was examined. The dissymmetrical units employed included 2,7‐dihydroxynaphthalene (2,7‐DHN),1,4‐dihydroxynaphthalene (1,4‐DHN), and bromo‐hydroquinone (Br‐HQ). All of these polymers exhibited turbid melts. The flexible PET units lower the melting and/or stick temperature, and between 10 to 20 mol % is a critical level to achieve values in the range of 250°C or lower. The copolyesters based on 2,7‐DHN have the highest glass transition temperatures and maintain stiffness to the highest temperatures. The properties of each series of copolyesters are discussed in terms of the efficiency of molecular packing. The effects of chemical and physical inhomogeneity are emphasized.
Polyglycol modified poly(ethylene ether carbonate) polyols by molecular weight advancement
Authors: Harris Robert F. 
Published: April 2003

AbstractPoly(ethylene ether carbonate) polyols can be modified by chemical reactions with polyglycol modifiers under conditions of elevated temperatures and reduced pressures, where diethylene glycol is removed as distillate. Molecular weight builds in a predictable manner and can be controlled by the amount of distillate removed. A reaction pathway for this transformation is proposed. It is important that the modifier be stable to reaction conditions and have a higher boiling point than diethylene glycol. The process has been characterized by following the distillate formation and composition as a function of reactor temperature and product molecular weight build. The product has been characterized by molecular weight, CO2 content, carbon–13 NMR and viscosity/temperature relationships. Carbon–13 NMR of the carbonyl and methyl regions of the spectra are particularly useful for following the chemical changes. A new family of modified poly(ethylene ether carbonate) polyols has been prepared which was not available with prior technology. The modification procedure permits the control of properties such as modifier type and content, molecular weight, CO2 content, viscosity, Tg, density, etc., in the resultant polyol. Since poly(ethylene ether carbonate) polyols have predominantly polyester polyol properties, modification with polyether polyols can be used to adjust properties. These polyols are useful in polyurethane applications.
A durability index in the weathering of low‐density polyethylene (LDPE) films
Authors: Gonzalez A. , De Saja J. A. , Requejo A. , Barahona F. J. 
Published: April 2003

AbstractDegradation resulting from weathering in low‐density polyethylene (LDPE) films used in agricultural applications was investigated by a series of mechanical and spectroscopic characterization techniques. An easy, nondestructive, and comparatively sensitive test for measuring the durability of these films based on microhardness indentations is presented.
Dicumyl peroxide‐modified cellulose/LLDPE composites
Authors: Sapieha S. , Allard P. , Zang Y. H. 
Published: April 2003

AbstractThe present study reports results on the processing and mechanical properties of composites modified by the addition of dicumyl peroxide (DCP). The addition of minute amounts of peroxide to the cellulose/polymer system during processing has been shown to significantly improve the physical properties of composites. SEM micrographs of fracture surfaces of the peroxide modified composites reveal direct grafting of polyethylene onto cellulose fibers. The existence of a critical peroxide concentration indicates that the grafting reactions terminate when cellulose surfaces are no longer accessible. Possible mechanisms involved are discussed.
Interaction of some highly aggressive solvents and effect of temperature on the transport characteristics of polyurethane
Authors: Aminabhavi T. M. , Aithal U. S. 
Published: April 2003

AbstractA number of highly interacting liquids have been used as penetrants to study their transport characteristics into a commercial polyurethane membrane. The penetrant‐polyurethane interaction is strongly dependent on the nature of the interacting molecules. With tetrahydrofuran, dioxane, cyclohexanol, acetophenone, and benzyl alcohol the polymer swells greatly even at room temperature, and in such cases, sorption experiments were not carried out at higher temperatures. In a few other cases like pyridine, aniline, etc., thea polymer loses its shape and physical integrity leading to chemical degradation reactions. Some of the otherwise normally behaving liquids like n‐butanol, 1,4‐dichlorobutane, anisole, toluene, chlorobenzene, and nitrobenzene did not reach equilibrium at high temperatures (70–90°C) even after prolonged exposure, making it difficult to interpret the sorption data. The results of this study may be useful to make an overall assessment about the application of polyurethane under extreme service conditions. Furthermore, concentration‐independent diffusion coefficients have been calculated for those penetrant—polymer systems which exhibited the least amount of swelling. For highly swelling liquids, the transport mechanism deviates from the normal Fickian mode and diffusion coefficients for such systems have not been obtained.
Magnetic field effect on photocrosslinking reaction of directly excited azidomethylated polystyrene
Authors: Morita Hiroshi , Uchino Noriaki 
Published: April 2003

AbstractGel fractions of thin films of poly(styrene‐co‐vinylbenzyl azide) (AZMS) irradiated with a low pressure mercury lamp were measured in the absence and in the presence of an external magnetic field. By the application of a magnetic field of 0.089 T, the gel fraction of AZMS decreases, and the efficiency of photocrosslink formation decreases by ≈︁ 20%, in contrast to the case of sensitized photocrosslinking of AZMS where the efficiency increases by the application of a magnetic field. Based on the photocrosslinking mechanism of directly excited AZMS, it is concluded that the singlet nitrene which is produced from the singlet excited AZMS abstracts a hydrogen atom from the AZMS polymer to form the singlet radical pair, and that the magnetic field decreases the singlet–triplet intersystem crossing rate of the radical pair.
Thermal behavior and cured products of mixtures of two different bismaleimides
Authors: Nagai Akira , Takahashi Akio , Suzuki Masao , Katagiri Junichi , Mukoh Akio 
Published: April 2003

AbstractThe thermal behavior of a new Bismaleimide, 2,2‐bis[4‐(4‐maleimidophenoxy)phenyl]propane (BBMI) and its mixtures with a conventional monomer, bis(4‐maleimidophenyl)methane (BMI) were investigated by differential scanning calorimetry. The melting point of BBMI was 142°C, lower than that of BMI, although its molecular weight is about twice that of BMI. Each of these bismaleimides and their mixtures showed a melting point when heating, but did not have a distinct freezing point when cooling because of vitrification. The unobserved freezing curve was estimated by calculation based on Schröder's equation using melting point and molar heats of fusion in both bismaleimides. The cured product of BBMI has thermal stability as good as that of BMI. Moreover, the cured product of BBMI has a high flexurai strength and a high flexural elongation owing to the introduction of flexible ether bonds and long phenoxy groups within the monomer structure.
Synthesis and properties of new tetrafunctional epoxy resins containing oxyethylene units
Authors: Iijima Takao , Hiraoka Hideki , Tomoi Masao , Kakiuchi Hiroshi 
Published: April 2003

AbstractTetraglycidyl ethers of 2,2′,2″,2‴[sulfonyl bis(4,1‐phenylenenitrilo)] tetrakisethanol and 2,2′,2″,2‴[methylene bis(4,1‐phenylenenitrilo)]tetrakisethanol were synthesized and characterized. Curing reactivities of these new epoxy resins are investigated by differential scanning analysis. The mechanical, thermal, and dynamic mechanical properties of these resins cured with p,p'‐diaminodiphenylsulfone were examined and compared to those fo the conventional tetrafunctional epoxy resin (MY‐720). These new epoxy resins have the advantages of being easier to handle, having higher curing reactivities, and giving cured resins with higher toughness, compared with MY‐720 resin.