bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of comonomers on thermal degradation of polyacrylonitrile
Authors: Gupta D. C. , Agrawal J. P. , Sharma R. C. 
Published: April 2003

AbstractThe thermal degradation of polyacrylonitrile and copolymers of acrylonitrile (AN) with each of vinylacetate (VAC), methallyl sulfonate sodium salt (MASS), and 2‐acrylamido 2‐methyl propane sulfonate sodium salt (2‐AMPSS) i.e., P(AN–VAC), P(AN–MASS), P(AN–AMPSS), and P(AN–VAC–MASS), has been investigated using the technique of thermogravimetry and differential scanning calorimetry (DSC). The initial decomposition temperature (IDT) and integral procedural decomposition temperature (IPDT) for all the copolymers are less than that for polyacrylonitrile irrespective of the nature of the vinyl comonomers. TGA thermograms indicate faster rate of degradation in copolymers compared to polyacrylonitrile. Variation in the glass transition temperature is correlated to the polarity of the functional groups in the polyacrylonitrile copolymers.
Reuse of plastics recovered from solid wastes. Thermal and morphological studies from HDPE/LDPE blends
Authors: Laguna O. , Collar E. P. , Taranco J. 
Published: April 2003

AbstractIn this work a few observations are made about some microstructural aspects from HDPE and LDPE homopolymers and their blends as virgin materials and also from urban plastic wastes. Micrographs were taken by SEM. Micrographs corresponding to the fracture surface from specimens tested in an impact test clearly show different microstructural features due to polymer which is more than 50%. Parts were injection molded. On the other hand, a discussion is given about crystallization behavior of those materials obtained by DSC. For all blends the same results have been found, i.e., two peaks owing to each of the two polymers which are present in the blends.
Mechanism of gas transport in plasma treated glassy polymer films
Authors: Sada E. , Kumazawa H. , Xu P. , Kiyohara T. 
Published: April 2003

AbstractThe effect of oxygen‐ and Ar‐plasma treatment on glassy polysulfone and polyimide films upon the gas diffusion process was investigated in the permeation of CO2 and H2. The plasma treatment apparently induced a reduction of only the diffusivity of Henry's law population, while the diffusion coefficient of the Langmuir population was not altered by plasma treatment. The oxygen‐ and Ar‐plasma treatment on polysulfone films is favorable for permselectivity of H2 relative to CO2. Such a surface modification of polyimide films appears to be ineffective for improvement of permselectivity of H2.
Synthesis of copolymers of N,N‐dimethyl acrylamide and methacrylate esters and their surface tensions
Authors: Weinert Raymond J. , Piirma I. 
Published: April 2003

AbstractA systematic study of the preparation of N,N‐dimethylacrylamide (NDMA)/methacrylic ester statistical copolymers was conducted. The methacrylic ester comonomers used in the copolymerizations were ethyl, n‐butyl, n‐hexyl, n‐octyl, n‐dodecyl, n‐hexadecyl, and n‐octadecyl methacrylates. It was found that the NDMA copolymers could be prepared in three molecular weight regions 1.0 × 104, 2.0 × 105, and greater than 1.0 × 106 ([η] in water at 30°C of 0.1, 0.6, and greater than 1.5 dL/g, respectively). The molecular weights of the copolymers were dependent on the solvent employed in the polymerizations and on the presence of chain transfer agent (t‐dodecyl mercaptan). All copolymer compositional analyses were made by 400 MHz 1H‐NMR spectroscopy. The NDMA/methacrylic ester copolymers decreased the surface tension of water in the order: C4 = C6 > C8 > C12 > C16 > C2 = C18 > P(NDMA), from lowest surface tension (35 dyn/cm) to highest surface tension (59 dyn/cm).
Determination of Mark–Houwink–Sakurada equation for phenolic resins and estimation of their molecular conformation in acetone solution
Authors: Sue Haruaki , Ueno Eizaburo , Nakamoto Yoshiaki , Ishida Shin‐Ichiro 
Published: April 2003

AbstractThe effects of the molecular structure of phenolic resins on the Mark–Houwink–Sakurada (MHS) equation and the conformation in acetone solution were studied. The exponent in the MHS equation was remarkably less than that for linear polymers such as vinyl polymers, cellulose derivatives, and so on. As the cause, the branching and the hydrogen bonding between hydroxyl groups of the neighboring phenolic nuclei were considered. Several kinds of phenol‐p‐cresol and phenol‐p‐tert‐butylphenol cocondensation resins whose composition differs from one another were synthesized. Despite the difference in the degree of branching, the exponent in the MHS equation for each was approximately equal. On the other hand, the exponent for o‐cresol novolak, which was rich in ortho‐para methylene linkages was larger than the all‐ortho novolak and p‐cresol novolak, which were rich in ortho–ortho methylene linkages. Methylation of the phenolic hydroxyl group increased the value of the exponent. From these results, it became obvious that while the hydrogen bonding lowered the exponent in the MHS equation due to molecular conformation compaction in acetone solution, the molecular branching had little effect on the exponent α.
Pulsed NMR study of elastomeric block copolymer under deformation
Authors: Fukumori Kenzo , Kurauchi Toshio , Kamigaito Osami 
Published: April 2003

AbstractDeformation behavior of an elastomeric styrene–butadiene–styrene block copolymer (SBS) is studied by pulsed NMR techniques, and is related to lifetime distributions and the change of the microstructure in the stress relaxation process. By the measurement of spin–spin relaxation time, it is found that polybutadiene (PB) chains in the vicinity of polystyrene (PS) domains come to be in more constrained conformations with stretching than those remote from the domains mainly through the intramolecular interactions, followed by the enlargement of the constrained regions, which reflects the roles of both crosslinks and filler particles in crosslinked rubbers. In the stress relaxation process, however, the mean lifetime for SBS at the critical strain is longer than that at lower strain in contrast with the results for the crosslinked rubbers. It is estimated that the differences between the failure behaviors of SBS and those of the conventional crosslinked rubbers may be mainly caused by the characteristic change of the microstructure (the disruption of the weak interconnections between the spherical PS domains with high energy dissipation) in SBS on deformation, associated with the limited extensibility of the PB chains between the adjacent PS domains. It becomes clear that the pulsed NMR method complements the mechanical measurements with a more precise information on the heterogeneity in the rubbery polymers under deformation.
Blends of polyamide 6 with bisphenol‐A polycarbonate. I. Thermal properties and compatibility aspects
Authors: Gattiglia Ercole , Turturro Antonio , Pedemonte Enrico 
Published: April 2003

AbstractBlends of polyamide 6 (PA6) and polycarbonate (PC) have been investigated, over a full range of composition, to check interactions between them. SEM observations show that the mixtures are characterized by domains of clearly segregated homophases and voids between the two polymers. DSC and DMTA data indicate the presence of two Tg' s, corresponding to two separate phases, with the Tg of the PC phase decreasing on increasing the PA6 amount. Moreover, the crystallization kinetics of PA6 is slightly showed down by the PC. Chemical reactions between the two polymers are supposed to give rise to low molar mass compounds, as shown by GPC; these species plasticize the PC and partially dissolve into the molten polyamide, causing decrease of PC Tg and reduction of overall crystallization rate of PA6. Apparent influence of PC on melting temperature and enthalpy of PA6 is also discussed.
Influence of mold filling rate and gate geometry on the modulus of high pressure injection‐molded polyethylene
Authors: Boldizar A. , Kubát J. , Rigdahl M. 
Published: April 2003

AbstractHigh pressure injection molding of HDPE with relatively high molecular weight is known to give products with significantly increased modulus and strength. The extent of this improvement is reduced when the thickness of the molded sample increases. The present paper is an account of experiments with varying mold filling rates and gate geometries. After choosing proper gating and then optimizing the filling rate, thick samples with tensile moduli previously characteristic of thinner samples have been obtained. The modulus data are supplemented by measurements of the melting point of the normal and high‐strength HDPE structures at different locations in the molded test bars. Corresponding crystallinity data are also included. The structure of the samples appears to provide some guidance in interpreting the observed modulus variations.
Fractionation of a polydisperse polymer using an antisolvent. Application of continuous thermodynamics
Authors: Wu Albert H. , Prausnitz John M. 
Published: April 2003

AbstractContinuous thermodynamics is used to calculate liquid‐liquid equilibria in a ternary system containing polydisperse polymer, one good solvent and one poor solvent (antisolvent). The polymer has a semiinfinite molecular‐weight distribution which can be described by a gamma distribution. From Flory‐Huggins theory, the logarithm of the distribution ratio of the polymer is a linear function of the molecular weight. Because the distribution of polymer between the two liquid phases is very sensitive to the choice of binary Flory parameters. The Flory parameters must be fitted to the ternary data. Results are given for the system benzene, ethanol, and polydisperse polystyrene.
Hexavalent chromium interaction with chitosan
Authors: Udaybhaskar P. , Iyengar Leela , Rao A. V. S. Prabhakara 
Published: April 2003

AbstractChitosan prepared from fresh water crab shells was used for hexavalent chromium removal. Kinetic studies indicated a rapid removal of chromium from aqueous solutions. The first‐order rate constant for chromium removal was calculated to be 1.92 h−1. Sorption isothermal data could be interpreted by the Langmuir relationship. Drastic decrease in chromium removal was observed with the increase in pH. Sorption was almost 90% at pH 3 at an initial chromium concentration of 5 mg/L and reduced to 10% at pH 7 and above. Presence of electrolytes and chloride significantly affected the chromium removal, indicating the electrostatic attraction as the main removal mechanism. Regeneration of the sorbent with alkali was not very effective as only 60–65% of sorbed chromium could be recovered.
High‐strength poly(L‐lactide) fibers by a dry‐spinning/hot‐drawing process. I. Influence of the ambient temperature on the dry‐spinning process
Authors: Postema A. R. , Luiten A. H. , Pennings A. J. 
Published: April 2003

AbstractIn this paper the influence of the ambient temperature of the spinline during dry spinning of PLLA solutions has been discussed. Variation of this ambient temperature induced variation of the extrudate swell of the spinline, affected by the rate of solidification of the PLLA. By way of phase separation, porous filaments were achieved in which the morphology depended on the applied ambient temperature. Hot drawing of these filaments led to tensile strengths varying between 1.1 and 2.2 GPa. An optimal tensile strength of 2.2 GPa was achieved by hot drawing of a filament which was spun into a surrounding of 25°C.
Interfacial adsorption and crystallization of polycarbonate in carbon fiber composites
Authors: Brady Richard L. , Porter Roger S. 
Published: April 2003

AbstractA polycarbonate (PC)/carbon fiber (CF) composite system has been examined with regard to interfacial adsorption and crystallization by altering times and temperatures of annealing. Times up to 180 min and temperatures of 245, 275, and 300°C have been investigated. Tranverse tensile, tranverse toughness, and scanning electron microscopy results on unidirectional, continuous‐fiber composites indicate improved fiber/matrix adhesion at longer times and higher temperatures of annealing. Improvements in transverse toughness and transverse tensile strength of a factor of two is achieved. The data indicate that primarily adsorption rather than secondary interfacial crystallization is the likely mechanism for increased adhension. Isothermal transverse toughness values have been found to fit well to a Langmuir‐type expression. The temperature dependence of adsorption as measured by transverse toughness is described well by an Arrhenius equation. The dependence of transverse toughness on PC molecular weights from Mw = 26,600 to 39,800 was found to be large, with higher molecular weights adsorbing more effectively.
Reactive extrusion of poly(vinyl chloride) compounds with polyethylene and with ethylene‐vinyl acetate copolymers
Authors: Van Ballegooie Peter , Rudin Alfred 
Published: April 2003

AbstractThe mechanical properties of poly(vinyl chloride)/polyethylene blends can be improved by a reactive extrusion process in the presence of an organic peroxide and a coupling agent. With a judicious loading of dibenzoyl peroxide and triallyl isocyanurate coupling agent, such blends generally exhibit significantly greater ultimate tensile strengths and dynamic moduli. The nature of the sample posttreatment after compression molding is shown to have a major impact upon the relative magnitude of these differences. Evidence is also presented to suggest that such improvements result from a superior physical interlocking between blend components, rather than through the formation of co‐crosslinked graft segments (which would, presumably, impart a compatibilization effect). Similar extrusion trials with a poly(vinyl chloride)/poly(ethylene‐stat‐vinyl acetate) mixture revealed a general worsening of material properties with increasing dibenzoyl peroxide levels. These observations can be rationalized by examination of the degradation reactions that likely occur in these reacting systems.
Grafting of polyacrylamide on to guar gum using K2S2O8 ascorbic acid redox system
Authors: Bajpai U. D. N. , Jain Alka , Rai Sandeep 
Published: April 2003

AbstractThe grafting of polyacrylamide on to guar gum in aqueous medium initiated by the potassium persulfate/ascorbic acid redox system has been studied gravimetrically at the temperature 35 ± 0.2°C in the presence of atmospheric oxygen and Ag+ ions. The rate of grafting was found to increase with temperature, concentration of redox components, acrylamide, and guar gum. But at higher concentration of guar gum, the rate of grafting was found to decrease. A mechanism for grafting and suitable rate expression have been suggested.
Plasma‐modified nylon 4 membranes for reverse osmosis desalination
Authors: Lai J. Y. , Chao Y. C. 
Published: April 2003

AbstractThe effects of maturation time of casting solution and annealing conditions on reverse osmosis (RO) properties of nylon 4 membranes are studied. The effects of plasma treatment conditions, such as supply power, treatment time, and gases used in reactor, on the water contact angle, surface energy, water flux, and salt rejection of nylon 4 membranes are considered. The best results of 4.86 × 10−5 g/cm2 s of water flux with 74.2% of salt rejection for 1 wt % NaCl aqueous feed solution can be obtained in the conditions of plasma treatment for 80 W–3 min in a reactor with O2 on 25 wt % formic acid–4 h annealing nylon 4 membranes. The hydrophilic monomers, such as 1‐vinyl‐2‐pyrrolidone (VP), 2‐hydroxyethyl methacrylate (HEMA), and acrylic acid (AA), are plasma deposited onto the chemical and/or plasma etched nylon 4 membranes to improve the salt rejection without decrease in water flux. The salt rejection of 90.9% and water flux of 3.64 × 10−5 g/cm2 s of the deposited membrane are obtained in the conditions of depositing AA monomer onto the substrate membrane which was previously treated with annealing followed with plasma etching.
Fundamental modeling in anionic polymerization processes
Authors: Chang C. C. , Miller J. W. , Schorr G. R. 
Published: April 2003

AbstractThe anionic solution polymerization of butadiene was studied employing both batch and continuous reactor operations with n‐butyllithium (n‐BuLi) initiator, tetramethylethylenediamine (TMEDA) modifier, and hexane solvent. A model was proposed that described the kinetics as a function of both the fully modified and unmodified regressed rate data. Using the proposed kinetic model, the conversion, vinyl structure, and heterogeneity index of polymers produced for a series of continuous runs were successfully predicted. The model was used to simulate several process configurations.
Interpenetrating hydrogel networks. I. The gelatin–polyacrylamide system
Authors: Chatterji Prabha R. 
Published: April 2003

AbstractIn situ polymerization of acrylamide–bisacrylamide mixture in concentrated aqueous gelatin solutions followed by the subsequent crosslinking of gelatin itself with glutaraldehyde yields interpenetrating hydrogel networks. The surface morphology, swelling, and thermal behavior of the samples of different composition were investigated. The swelling characteristics of the hydrogel could be manipulated by varying gelating and acrylamide ratio.
Copolymerization of acrylic esters with ethyl α‐cyanocinnamate
Authors: Angelovici Mose M. , Kohn David H. 
Published: April 2003

AbstractThe copolymers of ethyl α‐cyanocinnamate with methyl, ethyl, and butyl acrylate were prepared in toluene solution with benzoyl peroxide as initiator. The copolymerization parameters were determined and the alfrey–Price Q and e values were calculated. The influence of the comonomer on some of the basic properties of the copolymers, like intrinsic viscosity, solubility, and glass transition temperature, was studied in comparison with the corresponding homopolyacrylates.
Solution viscosities of ethylene–propylene copolymers in oils
Authors: Rubin Isaac D. , Sen Ashish 
Published: April 2003

AbstractViscosities were obtained on oil solutions of ethylene‐propylene copolymers with 58‐80 mol% ethylene. For amorphous copolymers, intrinsic viscosities and equivalent hydrodynamic volumes showed little variation from −10 to 50°C. They decreased precipitously at low temperature for a partially crystalline copolymer with 80 mol% ethylene. The data can be explained by postulating that more ethylene and resulting crystallinity lead to ordered domains in solution at low temperatures, giving rise to additional contraction of the copolymer above that expected for a totally amorphous material.
A comparative study on the effect of aging on mechanical properties of LLDPE–glass fiber, mica, and wood fiber composites
Authors: Raj R. G. , Kokta B. V. , Daneault C. 
Published: April 2003

AbstractLinear low density polyethylene (LLDPE) was reinforced with wood fiber, glass fiber, and mica. The effect of aging on mechanical properties of the composites was examined under different conditions: (i) exposure at 105°C for 7 days; (ii) immersion in boiling water for 4 h. Samples containing glass fibers showed by far the best results with regard to tensile strength, elongation, and fracture energy. LLDPE filled with mica produced poor results compared to wood fiber composites. Dimensional stability of LLDPE–wood fiber composites, after boiling water treatment, was inferior to mica and glass fiber composites.
Characterization of oxidized LDPE by solid state fluorescence spectra
Authors: Konar J. , Ghosh R. 
Published: April 2003

AbstractThe fluoresence excitation and emission spectra of commercial LDPE and oxidized LDPEs using phase transferred permanganate as oxidant have been examined using solid state fluorescence spectra. The luminescent impurity species present in commercial polyethylene is found to be olefinic dione. LDPE has an emmission spectra at 330–345 nm and excitation spectra at 235 and 300–310 nm. The emission spectra of oxidized LDPEs contain two main peaks, one at 290–300 nm and the other at 330–345 nm. A comparison of the emission spectra of LDPE blends with the reference compounds, viz., stearic acid and stearone, with those of the oxidized LDPEs proves the presence of “saturated” keto groups (carbonyl in the main chain not conjugated with C = C) in oxidized LDPEs. This also enables us to find out quantitatively the amount of the keto groups present. The estimates thus obtained tally with the results of FT‐IR measurements and follow the increasing order of the stability constant of the permanganate ionpair in benzene.
Epoxy–amine oligmer production
Authors: Cuadrado T. R. , Macgregor J. F. , Hamielec A. E. 
Published: April 2003

AbstractThe production of an adduct epoxy‐polytheramine with free epoxy groups is anlyzed. Diffrential scanning caloriemetry (DSC), infrared spectroscopy (IR), titration of functional groups, and gel permeation chromatography (GPC) were used to study the reaction of bisphenol A diglycidyl ether (DER 332) with an aliphatic hindered polyether‐amine (Jeffamine D‐2000). The general kinetic model derieved by Riccardi and Williams1 is extended to generate equations for nonstoichiometric epoxy‐amine systems. The parameter N, which gives the reactivity ratio between the secondary and primary amine groups, was obtained from a linear regression obtained at various temperature levels. the activation energies of the epoxy amine reaction catalyzed by OH groups and the noncatalytic one were determined. According to experimental evidence, the etherfication reaction may be neglected. From dynamic experiments in DSC a heat of reaction of 25 kcal/eq was obtained. The weight average molecular weight of different epoxy‐amine oligomers with high ratio of epoxy‐amine were compared with those theoretically predicted using an statistical structural model (SSM). This model utilizes a kinetic scheme and a recursive method to determine statistical parameters and it was applie before to phenolic resins 2,3 epoxy‐amine systems.4 Depending on the required ologomer characteristics, the best production policy can be established using he data supplied in this report.
Aqueous polymerization of methyl methacrylate catalyzed by corundum of different particle sizes
Authors: Moustafa A. B. , Abdel‐Latif Z. H. , Amer L. I. 
Published: April 2003

AbstractThe aqueous polymerization of MMA in the absence and presence of corundum of different particle sizes was studied, and the effect of corundum on the conversion of monomer to polymer, as well as on the obtained average molecular weights, rate of flow (Rf) values, and activation energy, was also given.
Evaluation of disbondings and measurement of Poisson's ratio for plastic composites using holographic interferometry
Authors: Kimoto Masaki , Nagata Itsuo , Minowa Akio , Moriwaki Kousuke , Watanabe Toshiaki 
Published: April 2003

AbstractDisbondings and Poisson's ratio were examined for several plastics composite plates using holographic interferometry. The displacement at the disbondings could be detected below submicrometer order. The value of Poisson's ratio strongly depended upon orientation and type of fiber and laminate construction.
Copolymerization of cis‐butenedioic acid with sodium methallylsulfonate in an aqueous solution
Authors: Kejun Yao , Zenquan Qin , Chuanyao Ye 
Published: April 2003

AbstractWater‐soluble copolymers of cis‐butenedioic acid (MA) with sodium methallylsulfonate (SMAS) were prepared in aqueous solution using potassium persulfate (KPS) as the initiator. The effects of reaction conditions (e.g., monomer concentration, initiator concentration, monomer fractions and pH, reaction temperature and times, etc.) on the copolymerization were also studied. The results showed that higher conversion could be obtained under suitable conditions (see Figs. 1–5). The copolymers were characterized by IR and NMR spectroscopy. The ratios of infrared absorbances at 1585 cm−1 (carboxyl absorption) and 1048 cm−1 (sulfonic group absorption) were used to de‐termine the composition of poly(MA‐co‐SMAS). The reactivity ratios were calculated by Kelen–Tudos method and Fineman–Ross method. Both the chemical analysis and the scanning electron micrographs showed that the copolymer has an excellent antiscaling effect on calcium carbonate.