bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on modified phenolic resin. I. Modification with homopolymer prepared from p‐hydroxyphenylmaleimide
Authors: Matsumoto A. , Hasegawa K. , Fukuda A. , Otsuki K. 
Published: April 2003

AbstractWe studied the improvement of heat resistance and mechanical properties of phenolic resin modified with polymers prepared from p‐hydroxyphenylmaleimide (HPMI). Homopolymers of HPMI and copolymers of HPMI with some vinyl monomers were synthesized and Mn Tg and thermal decomposition temperature of them were measured by GPC, DSC, and TG, respectively. The miscibility of homopolymer with novolac was examined by DSC. It was found that the homopolymer had good heat resistance and good miscibility with novolac. Molding compounds were prepared by hot roll‐kneading the mixtures of novolac, the homopolymer, hexamethylenetetramine, and glass fiber. It was found that molded test pieces had good heat resistance.
Zinc–Borate complex as flame‐retardant filler
Authors: Agrawal J. P. , Gupta D. C. , Khare Yogesh , Satpute R. S. 
Published: April 2003

AbstractWater‐insoluble complexes have been prepared by reaction of boric acid, pentaerythritol, and metal salts i.e., acetates of zinc, cadmium, mercury, copper, nickel, cobalt, and manganese. The composition of these complexes has been established by determining metal content and by elemental analysis, and structural aspects have been studied by far‐IR spectra. The heat‐resistance data indicate that the zinc–borate complex is better than other metal‐borate complexes, and, therefore, it has been selected for detailed study. The effect of 10‐60 parts of zinc‐borate complex on novel unsaturated polyester‐7 (II) in respect of gel time, exotherm peak temperature, tensile strength, % elongation, nitroglycerine absorption, and flame retardance has been studied, and results have been discussed. Further, the zinc–borate complex also gives a synergistic effect in combination with antimony trioxide similar to other metal oxide fillers.
Development of potentially degradable materials for marine applications. II. Polypropylene‐starch blends
Authors: Gonsalves K. E. , Patel S. H. , Chen X. 
Published: April 2003

AbstractThe effect of exposure of unstabilized polypropylene‐starch blends, with or without a metal catalyst (e.g., cobalt (III) acetylacetonate), autooxidant (e.g., fatty acid), and a metal containing plasticizer (e.g., aluminum stearate) to the marine environment was studied for about six weeks at two different locations in New Jersey. Starch tends to absorb water. Unstabilized polypropylene degrades significantly during processin in air, as indicated by melt index values. Thus, for blends of unstabilized polypropylene‐starch (no additives), prepared under controlled conditions and exposed to plain seawater, there seems to be no microbial activity or chemical degradation, as indicated by no surface erosion and practically no change in molecular weight and tensile properties. However, for unstabilized polypropylene starch blends containing metal catalyst, auto‐oxidant, or plasticizer exposed under soft mud, surface erosion due to microbial activity is evident. In addition, chemical degradation due to the presence of degradative additives has been confirmed, as observed by a decrease in molecular weight and tensile properties. Changes in thermal characteristics of these blends after exposure to the marine environment have been studied.
Wet spinning of solid polyamic acid fibers
Authors: Dorogy William E. , St. Clair Anne K. 
Published: April 2003

AbstractRecent research at the NASA Langley Research Center has involved the production of polyamic acid fibers from resins derived from the reaction of 3,3′,4,4′‐benzophenonetetra‐carboxylic dianhydride and 3,3′‐diaminobenzophenone or 4,4′‐oxydianiline in N,N‐dimethylacetamide. Resins were extruded into aqueous solutions of ethylene glycol, ethanol, or N,N‐dimethylacetamide in order to induce filament formation. These filaments were then washed in water and dried using air or vacuum ovens. Fractured fiber ends were examined using an optical or scanning electron microscope for the presence of macropores, termed voids. Coagulation bath concentration and composition, resin inherent viscosity, resin % solids, and filament diameter were studied to determine their effect on the production of solid core fibers.
The thermal oxidative degradation of an ethylene–tetrafluoroethylene‐copolymer‐based electrical wire insulation
Authors: Morelli John J. , Fry Charles G. , Grayson Michael A. , Lind Arthur C. , Wolf Clarence J. 
Published: April 2003

AbstractA multidisciplinary spectroscopic evaluation of a commercial wire insulation based on a cross‐linked copolymer of ethylene and tetrafluoroethylene (X‐ETFE) was conducted to determine the chemical changes taking place during thermal aging. These studies provided insight into the roles of the various additives, such as triallylisocyanurate (TAIC) and antimony oxide, in the formulated X‐ETFE insulation. During irradiation processing, a large fraction of the TAIC is converted to a cross‐linked isocyanurate moiety; the unconverted TAIC is released during aging. Thermal aging of the X‐ETFE wire insulations was performed in air at 200°C for up to 5 months and resulted in oxidation of the base ETFE, loss of unreacted TAIC, and a small amount of dehydrofluorination. The antimony oxide serves the multiple roles of flame retardant and scavenger for the pyrolytically generated hydrogen fluoride.
Low‐pressure polymerization of ethylene. II
Authors: Pandya M. V. , Lata K. V. 
Published: April 2003

AbstractThis paper presents the kinetic study of polymerization of ethylene with VOCl3 and aluminum alkyls such as Et3Al and Et2AlCl. The effect of various parameters like the [Al]/[V] ratio, catalyst concentration, reaction time, temperature, solvents, and additives on rate of the reaction, yield, and molecular weight is reported. Each of these parameters has a remarkable effect on the yield and the rate of polymerization for both catalyst systems. Triethylamine is found to increase the catalyst efficiency and the rate. It is also observed that aliphatic hydrocarbons acted as a better polymerization medium than did the aromatic ones.
Polyurethane membranes from polyether and polyester diols for gas fractionation
Authors: Pegoraro M. , Zanderighi L. , Penati A. , Severini F. , Bianchi F. , Cao Nanyun , Sisto R. , Valentini C. 
Published: April 2003

AbstractPolyurethane prepolymers were prepared in ethylacetate from TDI and poly(oxypropilene)glicols) (PE‐PU) or poly(tetramethyleneglycoladipate)diols (PES‐PU) of different molecular weights (M). Homogeneous membranes were prepared by spreading the pre‐polymer solution added with a three, four or pentafunctional crosslinking agent, in the presence of stannous octoate as a catalyst. On increasing M, the PUs Tg decreases regularly in the range +30 to −47°C. PU's are amorphous with the exception of PES‐PU obtained from highest M polyester diols. Permeability P, diffusivity D, solubility coefficient S of N2, O2, CO2, CH4, CO were measured at T=35°C (>Tg).P, D, S do not depend on the crosslinker functionality, but mainly on M. P and D in PE‐PU are linear function of T‐Tg while in PES‐PU the function is not linear. Gas solubility fulfills in general the regular solution theory. P, D, S of water vapor is also given. Permeability decreases in the order H2O>CO2 > O2 > CH4 > CO > N2. Some practical application based on particular selectivities is suggested.
Peculiarities of phase and supermolecular structure of graft copolymers of polycaproamide with poly(methacrylic acid)
Authors: Rŭbtsov A. E. , Matv̆eev V. V. , Chălykh A. E. , Smirnova N. V. , Gabrielyan G. A. , Gal'Braikh L. S. 
Published: April 2003

AbstractThe structure of graft copolymers of PCA with PMAA obtained by the methods of chemically initiated liquid‐phase grafting polymerization has been investigated with the use of electron microscopy, electron‐probe microanalysis, and X‐ray radiography. The concentration profiles of the graft copolymer distribution along the fiber cross section and diffusion coefficients of the monomer solutions correlated with the kinetics of the graft layer penetration inside the polymeric matrix have been determined. The concentration profile of the graft polymer distribution has been shown to have drops down to the zero level. Grafting proceeds both in the amorphous regions and on the surface of imperfect crystals. The structure of the graft layer, in which the segregated chains of graft PMAA constitutes the dispersed medium and the PCA inclusions represent the dispersed phase, has been found to be heterogeneous.
Kinetics and mechanism of the thermal decomposition of potassium persulphate ions in aqueous solutions at 50°C in the presence of nitrogen gas and methacrylonitrile monomer
Authors: Guchhait Sukumar , Banerjee Monoranjan , Konar Ranajit Singha 
Published: April 2003

AbstractThe initial rate of persulphate (I) decomposition at 50°C in the presence of nitrogen and methacrylonitrile (MAN) in an unbuffered aqueous solution (pH 4–7) may be written as:

in the concentration ranges of persulphate (I) (0.25–2.50) × 10−2 (m/dm3) and of (MAN) 0.18–0.36 (m/dm3). During the reaction, a white substance (polymethacrylonitrile) separates out in the colloidal state or in the precipitate form from the medium depending on the ionic strength of the medium. The pH of the medium was found to decrease rapidly and continuously with time in the absence of methacrylonitrile, but it decreased slowly and continuously with time in the presence of the monomer, MAN. If an additional quantity of MAN is injected late in a run, the rate of persulphate decomposition is further accelerated in a given run. However, the rate of persulphate decomposition is found to decrease continuously in the presence of MAN with time, i.e., as the monomer is converted to polymer. It is suggested that MAN accelerates the decomposition of persulphate ions, due to the following reactions in the aqueous phase:

and

where (Mj˙)w is a‐water soluble oligomeric or polymeric (j = 1–10) free radical. The estimated values of k5 and k10 are 1.05 × 10−5 and 1.14 × 103 (in dm3/m/s), respectively.
Structure effect on water diffusion and hygroscopic stress in polyimide films
Authors: Jou Jwo‐Huei , Huang Rita , Huang Peir‐Teh , Shen Wen‐Ping 
Published: April 2003

AbstractA bending‐beam technique has been used to in situ monitor the diffusion of water in various polyimide films. The polyimides studied are pyromellitic dianhydride‐4.4′‐oxydianiline (PMDA–ODA), pyromellitic dianhydride‐p‐phenylenediamine (PMDA–PDA), and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride‐p‐phenylenediamine (BPDA–PDA), and their blends and random copolymers. The diffusion of water in these films obeys Fick's law. In PMDA–ODA, the mean diffusion constant is 5.2 ± 0.4 × 10−9 (cm2/s) for thicknesses ranging from 6.7 to 27.3 μm. In PMDA–PDA, it is 2.0 ± 0.4 × 10−9 (cm2/s) for thicknesses ranging from 7.3 to 20.0 μm, and in BPDA–PDA, 0.27 ± 0.02 × 10−9 (cm2/s) for thicknesses ranging from 4.8 to 21.0 μm. In the blends and random copolymer with 50 wt % PMDA–ODA and 50 wt % PMDA–PDA, the diffusion constants are slightly smaller than those in the pure PMDA–ODA, but much larger than in the pure PMDA–PDA. On the contrary, in those with 50 wt % BPDA–PDA and 50 wt % PMDA–PDA, the diffusion constants are much smaller than those in the pure PMDA–PDA, but slightly larger than in the pure BPDA–PDA. These diffusion constants are primarily affected by the chemical structure of the imide molecule. The morphology, such as crystallinity, of the films has played a secondary factor. Hygroscopic stresses due to water uptake in all the studied films increase as the film thickness increases. It can be attributed to that the film orientation decreases with the increase of thickness.
A dispersed anisotropic phase as the origin of the weak‐gel properties of aqueous xanthan gum
Authors: Carnali J. O. 
Published: April 2003

AbstractXanthan gum is a water‐soluble, extracellular polysaccharide that has gained widespread commercial use because of its strong pseudoplasticity and tolerance to high ionic strength. It possesses a rigid, rodlike structure and has been reported to form weak gels at concentrations on the order of 0.5%. The nature of these weak gels has been explored using creep measurements and dynamic mechanical spectroscopy. The usual weak gel symptoms are found in 0.02N KCl at xanthan levels exceeding 0.8% and include deviations from the Cox‐Merz rule (η* > η), onset of weak power‐law dependence of the loss and storage moduli, and appearance of unusually long relaxation times. We have also detected an apparent yield stress for concentrations beyond 0.8%. However, concentration‐independent relaxation times and a slip/stick behavior during extended flow runs also marked the weak gel region and suggested sample heterogeneity. This condition was confirmed by optical studies that showed samples in this region to consist of a nematic liquid crystalline phase dispersed in an isotropic phase. The conclusion is made that the unusual rheological behavior of xanthan can be traced to the occurrence of this phase separation. Possible mechanisms for the formation of the anisotropic phase are also discussed.
Grafting. IV. Graft tercopolymers as antifouling resin
Authors: Deb P. C. , Sankholkar S. C. 
Published: April 2003

AbstractA graft tercopolymer CLR‐g‐(MMA–TBTMA) based on chlorinated rubber as the backbone and binary copolymer of methyl methacrylate and tributyltin methacrylate as grafted chains has been synthesized. This graft copolymer has been used for the formulation of controlled‐release antifouling paints, and leaching rate behavior of toxin from such paints has been studied. The data have been compared with those obtained using controlled‐release antifouling paint based on linear chain copolymer of methyl methacrylate and tributyltin methacrylate. The paint based on grafted copolymer is characterized by having a lower leaching rate and reduced time for attainment of steady‐state leaching. Raft exposure studies indicate longer antifouling life compared to that of linear chain copolymer‐based paint both having the same dry paint film thickness.
Drag‐reduction efficiency, shear stability, and biodegradation resistance of carboxymethyl cellulose‐based and starch‐based graft copolymers
Authors: Deshmukh S. R. , Sudhakar K. , Singh R. P. 
Published: April 2003

AbstractGraft copolymers of carboxymethyl cellulose and starch with polyacrylamide have been synthesized by grafting acrylamide onto carboxymethyl cellulose and starch, respectively, using a ceric‐ion‐initiated solution polymerization technique. These graft copolymers have been tested for their drag‐reduction effectiveness, shear stability, and biodegradability. It has been shown that grafting enhances the drag‐reduction effectiveness and shear stability and also that these factors are very much dependent on the length and number of grafts in the molecule. None of the graft copolymer solutions shows any microbial degradation up to 10 days.
Effect of oxidized carbon black on the mechanical properties and molecular motions of natural rubber studied by pulse NMR
Authors: Asai Shigeo , Kaneki Hiromune , Sumita Masao , Miyasaka Keizo 
Published: April 2003

AbstractThe mechanical properties such as elastic modulus and stress‐relaxation and spin‐spin relaxation time T2 from pulse NMR were measured for surface‐oxidized carbon‐black‐filled natural rubber. The extent of reinforcement increased with CB volume percent in the range of 0–30%. At a given CB percent, this quantity increased by surface oxidation of fillers and decreasing filler size. From pulse NMR experiment, it was found that there were three components in rubber molecules which have different values for T2. Stress‐relaxation time and elastic moduli fitted one master curve against effective volume, fraction which is the sum of filler and bound rubber fraction. It was found that the distance between particle surfaces is the most important factor influencing reinforcing properties of filled polymers.
Effect of stirring on morphology and properties in a catalyst cured epoxy system
Authors: Wu Ching‐Shiun 
Published: April 2003

AbstractThis article describes the effect of stirring on epoxy network morphology and physical properties. Several different mechanical stirrer speeds, from 45 rpm to 800 rpm, were employed for the mixing of diglycidyl ether of bisphenol A resin with 2‐ethyl‐4‐methyl imidazole catalytic curing agent. The investigation indicated that the glass transition temperature, room temperature density, low temperature relaxation, tensile mechanical properties in the rubbery state, and nodular morphology are significantly affected by the stirrer speed used. Transmission electron microscopy has revealed that the extent of homogeneity for the dispersion of nodule domain in the low crosslinking matrix improved with increasing stirrer speed. However, an optimum stirrer speed condition is needed for achieving the most homogeneous system. In addition, it is shown that the room temperature tensile mechanical properties are independent of the mixing condition. This independence is ascribed to the fact that the glassy state mechanical properties are closely related to the intermolecular forces rather than to the network structure.
Photoelectronic properties of iodine‐incorporated poly(N‐vinylcarbazole) films
Authors: Hu J. , Kao K. C. 
Published: April 2003

AbstractIodine was incorporated into poly(N‐vinylcarbazole) (PVK) films by exposing the films to saturated iodine vapor at 100°C for 10 h. The content of iodine in the films was 2.3% by weight. The films were stable at room temperature. The infrared spectra indicate that no chemical reaction has taken place during the incorporation process. The dark conductivity of these films is about two orders of magnitude greater than that of pure PVK films. Carriers can be photogenerated in the films by light illumination from the UV region to the entire visible region. The most significant feature of these films is that the photoconductivity has a peak at the photon energy of 1.8eV. This is attributed to the charge transfer from the carbazole to I2. The results of thermally stimulated currents (TSC) indicate that there are deep traps in pure PVK films, but after iodine incorporation, these deep traps disappear or are replaced by a large quantity of shallow traps.
Preparation and properties of UV‐autocurable BTDA‐based epoxy‐multiacrylate resins. Effects of the degree of polymerization and the epoxy type
Authors: Chiang Wen‐Yen , Chan Shao‐Ching 
Published: April 2003

AbstractA series of UV‐autocurable epoxy‐multiacrylate resins was synthesized, and the effects of degree of polymerization (DP) and epoxy type on their properties were investigated. These autocurable multiacrylate resins possess good pot life and are cured rapidly when exposed to ultraviolet (UV) without the addition of photoinitiator or photosensitizer. The curing rate of the autocurable resins was probably dependent on the number of abstractable hydrogen in epoxy resins. Stress‐strain, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) were used to characterize the properties of cured multiacrylate resins. Increased crosslinking density of cured films improved tensile properties. Increasing the molar ratio of epoxy resin in the multiacrylate resins was found to decrease the effective acrylate concentration of resins and to depress crosslinking density of cured resins, which also resulted in an increased elongation at break but a decreased Young's modulus and breaking strength. Furthermore, the different structures of epoxy resins were used to give wide range properties of cured epoxy‐multiacrylate resins with a glass transition temperature (Tg range from 74 to 102°C. The film properties of the multiacrylate resins coated on steel plates were also investigated.
Gas transport in halogen‐containing aromatic polycarbonates
Authors: Hellums M. W. , Koros W. J. , Husk G. R. , Paul D. R. 
Published: April 2003

AbstractThe gas permeability and permselectivity of a series of halogen‐containing polycarbonates are discussed in terms of the fundamental solubility and diffusivity factors. These materials have structural features that hinder interchain packing and intrachain rotational mobility. Both diffusion and solubility coefficients are higher in materials with higher fractional free volumes. Diffusivity selectivities tend to increase with increasing restriction of intrachain torsional mobility. The materials with four bromine atoms substituted on the phenyl rings ortho to the carbonate linkages display a significantly increased diffusivity selectivity relative to conventional polycarbonate. This improvement in the ability of the polymer matrix to discriminate between gas molecules of different sizes is due to a reduction in intrachain torsional mobility. The reduction in chain mobility is indicated by higher glass transition and higher sub‐Tg transition temperatures in the bromine‐substituted materials. The materials with hexafluoroisopropylidene moieties have high fractional free volumes and exhibit a very significant increase in permeability relative to conventional bisphenol‐A polycarbonate. The material with both the hexafluoro and the tetrabromo substitutions displays significant simultaneous increases in permeability and permselectivity relative to conventional polycarbonate.
Polymer aqyeous solutions as quenching media. I. Polyvinylpyrrolidone
Authors: Louai Abderrahim , Pollet Gilbert , Francois Jeanne , Moreaux Francois 
Published: April 2003

AbstractThe cooling power of aqueous solutions of polyvinylpyrrolidone are studied with a silver standard sample by using two apparatuses quench with injection and quench with agitation. The dependences of the cooling rates at each temperature on polymer concentration and solution viscosity are established and empirical laws of variation are given.
The use of crossflow to improve nonwoven melt‐blown fibers
Authors: Milligan M. W. , Lu F. , Buntin R. R. , Wadsworth L. C. 
Published: April 2003

AbstractA stream of unheated crossflow air has been used to make finer melt‐blown fibers. Not only are smaller average fiber diameters obtained, but the variation in fiber diameter is smaller. The use of this technique can allow the production of melt‐blown nonwovens, which have finer fibers and more uniform webs. Since unheated air is used in the crossflow jet, the fiber enhancement in terms of finer, stronger fibers can be achieved with an energy savings by substituting unheated crossflow air for a portion of the primary air.
Tensile properties of polypropylene/kaolin composites
Authors: Maiti S. N. , Lopez B. H. 
Published: April 2003

AbstractTensile properties of isotactic polypropylene filled with particulate kaolin fillers were evaluated in the composition range 0–60 wt % kaolin. Tensile modulus increased with filler concentration while breaking elongation and tensile strength decreased. The modulus increase was attributed to the restriction on the molecular mobility of the polymer imposed by kaolin particles. The decrease in elongation was also an effect of this restriction coupled with interference to stress transfer by the filler particles. Generation of discontinuity in the composite structure through formation of stress concentration points accounted for the tensile strength decrease. Morphology studies by SEM also indicated the introduction of stress concentration points by the presence of bare and nonadherent kaolin particles and their agglomerates with sharp edges in these composites.