bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of fibers on the crystallization of poly(phenylene sulfide)
Authors: Desio Glenn P. , Rebenfeld Ludwig 
Published: April 2003

AbstractThe isothermal crystallization of unreinforced poly(phenylene sulfide) (PPS) and PPS filled with glass, carbon, and aramid fibers was studied by differential scanning calorimetry. The Avrami exponent and rate constant are reported, but the crystallization half‐times were used to compare the effects of different fibers on the rate of PPS crystallization. The aramid and carbon fibers decreased the crystallization half‐time with the aramid fiber having the most pronounced effect. The glass fibers affected the crystallization half‐time only at the higher crystallization temperatures. The aramid filled PPS exhibited anomalous degree of crystallinity behavior in that the degree of crystallinity passed through a minimum as a function of temperature. The other systems all exhibited increasing degree of crystallinity with increasing crystallization temperature. Finally, the Avrami plot for the aramid filled PPS is not linear, and the data are fitted better with two linear regions indicating that two types of crystallization processes may be present.
Kinetic study of ethylene polymerization by highly active silica supported TiCL4/MgCl2 catalysts
Authors: Kim Il , Kim Jae Ha , Woo Seong Ihl 
Published: April 2003

AbstractThe kinetics of ethylene polymerization with TiCl4/MgCl2/SiO2 has been investigated in the range of temperatures between 40 and 90°C and in the range of ethylene pressures between 4 and 12.4 kg/cm2. The role of MgCl2 was discussed from the dependence of the Mg/Ti ratio on the catalytic activity. The polymerzation rate was first order with respect to the monomer concentration and the dependence of the polymerization rate on the concentration of Al(C2H5)3 could be described by the Langmuir–Hinshelwood mechanism. The dependence of initial rate and the time to reach the maximum polymerization rate on the concentration of Al(C2H5)3 was also discussed. Polymerization rates as a function of the polymerization temperature showed a maximum and the activation energy was 11.8 kcal/mol between 50 and 80°C. The polymerization rate decreased with the increase of hydrogen partial pressure. The active site concentration (C*) was 1.9 × 10−2 mol/mol Ti by the inhibition method with carbon monoxide.
Oxygen permeability of teflon–PFA tubing
Authors: Giacobbe F. W. 
Published: April 2003

AbstractThe permeability coefficient for oxygen diffusing through a sample of Teflon‐PFA tubing was determined experimentally. The source of the diffusing oxygen was ambient temperature air surrounding a coiled length of the PFA tubing. High pressure nitrogen was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing high pressure nitrogen was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent nitrogen were determined as a function of varying nitrogen flow rates, at nitrogen gas pressures of 4.4 and 7.8 atm (absolute), within the tubing bore. All measurements were also carried out at ambient temperatures of 21 ± 1°C. In addition, a theoretically related graphical method of evaluating the experimental data was developed and subsequently employed to actually determine the oxygen permeability coefficient for this system.
Vapor phase photografting on low‐density polyethylene film in binary monomer systems
Authors: Kubota Hitoshi , Yoshino Nobuyuki , Ogiwara Yoshitaka 
Published: April 2003

AbstractVapor phase photografting of monomer mixtures on low‐density polyethylene film, on which benzoyl peroxide is coated, was investigated at 60°C using various vinyl, allyl, and solid monomers. Styrene (St) itself was difficult to graft on the film substrate, but the combinations of St with vinyl monomers such as acrylonitrile (AN), glycidyl methacrylate (GMA), acrylic acid, and methacrylic acid led to the accelerated grafting, affording a maximum percent grafting at an certain monomer ratio. The same combination effect was observed for AN–N‐vinyl pyrrolidone and –GMA monomer mixtures. The monomer combinations such as allyl aldehyde–St and allyl alcohol–maleic anhydride were useful for performing the grafting of allyl monomers effectively. Maleic anhydride and maleimide as solid monomers were also possible to introduce into the film substrate by means of the monomer combination, where St, N‐vinyl pyrrolidone, vinyl ethers, and benzyl methacrylate were available as comonomers. Thus, the monomer combinations affording an accelerating effect on grafting may be monomer pairs rich in an alternative copolymerizability, suggesting that monomer reactivity ratio controls a major factor for the combination effect. It was confirmed from IR study on grafted films that both monomer components are introduced in the film substrate as the grafted chain component.
Modeling of poly(ethylene terephthalate) reactors. IX. Solid state polycondensation process
Authors: Ravindranath K. , Mashelkar R. A. 
Published: April 2003

AbstractA mathematical model for simulation of industrial process of solid state polycondensation of poly(ethylene terephthalate) (PET) has been developed. The model eliminates errors evident in the earlier models by proper formulation. The model results have been validated by experimental data in the literature. It enables prediction of the influence of particle shape, size, temperature, etc. on the polycondensation process correctly in all different regimes of operation, apart from bringing out the importance of gas‐side resistance, influence of carrier gas, etc. for the first time.
Fluorescent properties of polymer–rare earth ion complexes. II. Poly(acrylic acid‐co‐acrylamide)–rare earth ion complexes
Authors: Lu Hong , Li Gao‐Fen , Fang Shi‐Bi , Jiang Ying‐Yan 
Published: April 2003

AbstractPoly(acrylic acid‐co‐acrylamide) with uniform composition was synthesized from acrylic acid and acrylamide by azeotropic copolymerization. The fluorescent properties of the copolymer–Eu3+ or −Tb3+ complexes were investigated. It was found that the fluorescence intensity of the complexes is dependent on the composition of the copolymer. Fluorescence lifetime measurement indicates that Eu3+ or Tb3+ exists in the complexes in at least two coordination forms, and the difference of the nature or relative quantity of the coordination forms varies with the composition of the copolymer. The fluorescence lifetime of Eu3+ or Tb3+ in the complexes is also dependent on the composition of the copolymer. It was also found that intramacromolecular hybrid coordination of oxygen containing and nitrogen containing coordination groups makes Eu3+ or Tb3+ fluoresce more strongly than intermacromolecular hybrid coordination of the two types of coordination groups does.
Chemical toughening of epoxies. I. Structural modification of epoxy resins by reaction with hydroxy‐terminated poly(butadiene‐co‐acrylonitrile)
Authors: Sankaran S. , Chanda Manas 
Published: April 2003

AbstractIn an attempt to toughen the epoxy resin matrix for fiber‐reinforced composite applications, a chemical modification procedure of a commercially available bisphenol‐A‐based epoxy resin using reactive liquid rubber HTBN [hydroxy‐terminated poly(butadiene‐co‐acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed.
Chemical toughening of epoxies. II. Mechanical, thermal, and microscopic studies of epoxies toughened with hydroxyl‐terminated poly(butadiene‐co‐acrylonitrile)
Authors: Sankaran S. , Chanda Manas 
Published: April 2003

AbstractDiglycidyl ether–bisphenol‐A‐based epoxies toughened with various levels (0–12%) of chemically reacted liquid rubber, hydroxyl‐terminated poly(butadiene‐co‐acrylonitrile) (HTBN) were studied for some of the mechanical and thermal properties. Although the ultimate tensile strength showed a continuous decrease with increasing rubber content, the toughness as measured by the area under the stress‐vs.‐strain curve and flexural strength reach a maximum around an optimum rubber concentration of 3% before decreasing. Tensile modulus was found to increase for concentrations below 6%. The glass transition temperature Tg as measured by DTA showed no variation for the toughened formulations. The TGA showed no variations in the pattern of decomposition. The weight losses for the toughened epoxies at elevated temperatures compare well with that of the neat epoxy. Scanning electron microscopy revealed the presence of a dual phase morphology with the spherical rubber particles precipitating out in the cured resin with diameter varying between 0.33 and 6.3 μm. In contrast, a physically blended rubber–epoxy showed much less effect towards toughening with the precipitated rubber particles of much bigger diameter (0.6–21.3 μm).
Blends of low density polyethylene/plasticized poly(vinyl chloride): The rheological, morphological, and mechanical characterization
Authors: Mikkonen Raija , Savolainen Antti 
Published: April 2003

AbstractAn experimental study was conducted to investigate the rheological, morphological, and mechanical properties of a heterogeneous polymer blend system consisting of low density polyethylene (LDPE) and plasticized poly(vinyl chloride) (PVC). The components were mixed using a single‐screw extruder, which was equipped with a special measuring head for the determination of rheological quantities. The morphology of blends was examined by scanning electron microscopy. Die swell was determined by photography. The velocity of ultrasound through the polymer melt was also measured. The dependencies of viscosity, die swell, and ultrasonic velocity on blend composition were qualitatively similar, exhibiting a minimum at about 70 wt % PVC. The morphology of the blend system at this blending ratio was different from morphologies of the other blends. Tensile properties of blends, except elongation at break, were not significantly inferior to those of the LDPE component.
Correlation of mechanical and acoustical properties of plasticized epoxy polymers
Authors: Prassianakis J. N. 
Published: April 2003

AbstractIn the present experimental work the influence of the percentage of plasticizer on the mechanical and acoustical properties of the plasticized epoxy polymers was studied. The velocity cl of the longitudinal waves and the acoustic attenuation coefficient α were evaluated from the acoustical properties. Also the influence of curing time of plasticized epoxy polymers on the acoustical properties, cl and α, was examined and it was found out that these quantities tend to their limiting values when the polymerization is completed. Furthermore, the determined acoustical properties are correlated with the corresponding mechanical properties for the same materials, which were also considered in earlier papers. So, a simple and quick experimental nondestructive technique is provided for the evaluation of the elastic properties, as well as of the epoxy polymers composition, by determining the velocity cl of the longitudinal waves only.
Effects of core‐shell latex morphology on film forming behavior
Authors: Devon Michael J. , Gardon John L. , Roberts Glen , Rudin Alfred 
Published: April 2003

AbstractA series of core‐and‐shell latex particles were made from methyl methacrylate/butyl acrylate copolymers. All latexes were almost monodisperse in particle size. The polymer hardness was varied by changing the methyl methacrylate/butyl acrylate ratio between the limits of 40/60 and 60/40 parts by weight. The minimum film temperatures(MFTs) of these particles were expected to vary with core and shell characteristics in the following order: soft/hard > medium/medium > hard/soft. In fact, this order was observed only if the shell thickness was greater than a certain minimum value that depends on the diameter of the core polymer. Thinner, softer shells on harder cores may require higher drying temperatures than thicker shells with the same composition because the former are required to deform more to produce void‐free films.
Aqueous polymerization on clay surfaces. IV. Effects of hydrogen–montmorillonite, monomer concentrations, and temperature on the polymerization of methyl methacrylate
Authors: Bhattacharya J. , Talapatra S. , Saha S. K. , Guhaniyogi S. C. 
Published: April 2003

AbstractThe polymerization of methyl methacrylate in aqueous montmorillonite suspension with thiourea was studied. The polymerization initiated on the montmorillonite surface following the adsorption of thiourea and the monomer. A 20% increase in the basal spacings of the clay mineral was observed. A large fraction of the polymer was nonextractable and was found to be thermally more stable than the extractables. The rate of the polymerization increased with increasing amounts of clay, thiourea, and followed one‐half order on the latter. The apparent energy of activation (Ea) of the system was characteristic of redox free radical polymerization.
Properties of positive resists. III. The dissolution behavior of poly(methyl methacrylate‐co‐maleic anhydride)
Authors: Drummond Rashmi K. , Boydston Gail L. , Peppas Nikolaos A. 
Published: April 2003

AbstractThe dissolution characteristics of model positive resists were investigated through the use of various copolymers of methyl methacrylate and maleic anhydride. Dissolution in methyl ethyl ketone was found to be dependent on the radiation dose and on the composition of the copolymers. The Lee–Peppas dissolution model was used to calculate important parameters of this dissolution process. It was shown that the overall dissolution rate was initially controlled by the swelling process whereas the true disentanglement/dissolution process predominated during the latter portion of the overall phenomenon. In addition, the thickness of the formed gel layer was a function of the square root of time.
Poly(styrene‐co‐acrolein) latex particles: Copolymerization and characteristics
Authors: Yan Changhong , Zhang Xianming , Sun Zonghua , Kitano Hiromi , Ise Norio 
Published: April 2003

AbstractReactive microspheres suitable for binding proteins were prepared using emulsifier‐free emulsion copolymerizations of styrene (St) and acrolein (AL) with various molar ratios of monomers St and AL. A maximum polymerization rate was obtained when the molar ratio of the monomers was 1 : 1. The diameter of the latex particles increased with increase in the amount of monomer AL. The amounts of aldehyde groups on the latex particle surfaces were determined by conductometric titration. The binding capacity of the copolymer latexes with spacer molecules was also examined.
Dielectric relaxation properties in polypropylene–polyurethane composites
Authors: Bánhegyi G. , Karasz F. E. , Petrović Z. S. 
Published: April 2003

AbstractAC dielectric relaxation properties of polypropylene/polyurethane composites have been studied. The segmented polyurethane (PUR) component contained a poly(propylene oxide) soft segment, and a diphenyl methane diisocyanate/butanediol hard segment. The molecular weight of the soft segment, the concentration of the latter in the polyurethane phase, and the PUR content of the blends were changed systematically. It was observed that the polypropylene is phase‐separated with respect to both PUR segments and that the dielectric relaxation properties are determined largely by the PUR component. Two transitions attributable to the glass transitions of the soft and hard phases, respectively, were observed. The soft segment transition temperature decreases with increasing molecular weight of the latter. The transition temperatures are somewhat dependent on the PUR content in the blend, indicating some interaction between the phases. Model calculations show that these shifts and some intensity anomalies are not due simply to the existence of a heterogeneous structure. The ohmic interfacial relaxation process does not play an important role in the temperature and frequency range studied.
Ink adhesion on corona‐treated polyethylene studied by chemical derivatization of surface functional groups
Authors: Lanauze J. A. , Myers D. L. 
Published: April 2003

AbstractCorona discharge (CD) treated polyethylene films were examined using X‐ray photoelectron spectroscopy (XPS) and a variety of chemical derivatization techniques. The composition of the CD‐treated surfaces were found to be relatively unaffected by aging at temperatures between 70 and 80°F. Ink adhesion testing of films treated under progressively more serve conditions indicated the efficiency of adhesion varied directly with the severity of treatment. Derivatization of CDtreated polyethylene films with pentaflurophenylhydrazine (PFPH) resulted in the formation of a stable hydrazone complex. The PFPH complex extends the detection limit for enolizable carbonyl groups ca. eight‐fold and provides relative quantitation of the number of these groups on variously treated polyethylenes. Formation of the hydrazone complex destroyed ink adhesion, indicating that the complex had blocked the site responsible for chemical bonding to the ink. Adhesion of water‐soluble printing inks to CD‐treated polyethylene is a direct consequence of hydrogen bonding between enolic hydroxyls on the polymer surface and carbonyl groups of the ink.
Studies on impact modification of polystyrene (PS) by ethylene–propylene–diene (EPDM) rubber and its graft copolymers. II. PS/EPDM‐g‐(styrene‐co‐methylmethacrylate) blends
Authors: Shaw S. , Singh R. P. 
Published: April 2003

AbstractThe toughness of a polymer blend is one of the major factors deciding its practical application. An impact modified polystyrene (PS) is usually a multiphase system consisting of the thermoplastics and an elastomeric component. The heterogeneous character of such a system and the interfacial adhesion between the components determine its impact strength. The graft copolymer of ethlene–propylene–diene (5‐ethylidene‐2‐norbornene) rubber with styrene and methylmethacrylate is synthesized, characterized, and blended with polystyrene to improve its impact strength. It is observed that there is improvement in impact strength with the subsequent decrease of tensile strength. The improved impact strength has been discussed in terms of morphology, compatibility, and interfacial adhesion of graft copolymers with PS matrix.
Infrared spectroscopic and dielectric studies of swollen cellulose
Authors: Nada A. M. A. , Shabaka A. A. , Yousef M. A. , Abd‐El‐Nour K. N. 
Published: April 2003

AbstractInfrared spectra of treated cotton linters and bleached cotton stalk pulp with different concentrations of ethylene diamine and zinc chloride solution are studied. The structural changes brought about by these treatments have been studied from infrared spectral diagrams. It is found that the crystallinity index calculated from the infrared spectral data of these treated pulps decreases with increasing concentration of ethylene diamine and zinc chloride. The decrease in the crystallinity index (Crl) of the treated pulp with zinc chloride is higher than in case of treatment with ethylene diamine (EDA). The detectable frequency change at the hydrogen bonded OH of cotton linters by treatment with zinc chloride and ethylene diamine reflects the contributions of this bond in the swollen pulp. The dielectric study of these treated pulps confirmed the molecular structural changes determined from IR spectroscopic study.
The effect of coagulant on the structure and properties of poly(p‐phenylene benzobisthiazole) fibers [PBZT]
Authors: Rakas M. A. , Farris R. J. 
Published: April 2003

AbstractFibers spun from anisotropic solutions of a lyotropic rigid‐rod polymer, poly(para‐phenylene benzobisthiazole) [PBZT], were coagulated into homogeneous nonsolvents including a solution of 18% iodine/82% ethanol, ethanol, and water. The effect of these coagulants on the structure and mechanical properties of the PBZT fibers was studied. Structural and mechanical studies were performed on as‐spun fibers. Wide‐angle X‐ray diffraction techniques have shown that fibers coagulated in the presence of iodine anions had d‐spacings that were unique, as well as d‐spacings that were characteristic of PBZT or iodine anions. Tensile and shear properties were highest in a fiber having a spin/draw ratio of 3 which contained 19.5% iodine species by weight. For these fibers, an average tensile strength of 2.2 GPa and a torsional modulus of 1.14 GPa was recorded. For fibers having this spin/draw ratio, and undergoing no post‐processing heat treatment or tension drying, these values are much higher than would be expected.
Studies on the role of organophosphites in polyester blends: I. 31P nuclear magnetic resonance spectroscopy
Authors: Carduner K. R. , Carter R. O. , Cheung M.‐F. , Golovoy A. , Van Oene H. 
Published: April 2003

AbstractThe utility of 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) for the identification of organophosphite polymer additives, their hydrolysis products, and for the determination of their concentration is demonstrated for bis‐(2,4‐di‐t‐butylphenyl) pentaerythritol diphosphite (BTBP) in polycarbonate. This additive undergoes a complex process of hydrolysis that leds to the formation of at least three new phosphous species. High‐resolution solution 31P NMR is used to help in the identification of the products of the stailizer chemistry.
Synthesis and characterization of oxyethylene containing polyamide‐imides
Authors: Avadhani C. V. , Wadgaonkar P. P. , Vernekar S. P. 
Published: April 2003

AbstractTwo nonlinear dihydrazides, namely 1,2‐bis(3‐hydrazinocarbonylphenoxy)ethane and bis[2(3‐hydrazinocarbonylphenoxy)ethyl] ether, were synthesized by the acylation reaction of hydrazine hydrate with the corresponding aromatic esters and were characterized by IR, 13C‐NMR, and mass spectroscopy. These dihydrazides were each polycondensed with dianhydrides, benzophenonetetracarboxylic dianhydride (BTDA), and pyromellitic dianhydride (PMDA) to obtain poly(amic acid) with ηinh 0.60–0.85 dL/g in dimethylacetamide solution. These poly(amic acid)s were soluble in polar aprotic solvents like dimethylacetamide (DMAc), dimethyl formamide (DMF) and could be cast into transparent, tough, and flexible films that were cyclodehydrated to obtain amorphous, thermally stable polyamide‐imides. The polymers were characterized by IR spectroscopy, X‐ray diffraction, and thermogravimetric analysis.
Permeation of mixed gases in glassy polymer membranes
Authors: Sada E. , Kumazawa H. , Xu P. , Wang S.‐T 
Published: April 2003

AbstractSteady‐state permeation rates for pure CO2 and CH4 and the binary mixture through homogeneous dense polysulfone and polycarbonate membranes have been measured at 40°C and upstream pressures up to 26 atm. The pressure dependence of the mean permeability coefficients for CO2 and CH4 for all of the systems was simulated equally well in terms of the dual‐mode mobility models driven by gradients of chemical potential and concentration. The dual‐mode sorption and transport parameters used for evaluation of the mobility models are only those determined from sorption and permeation runs for a single gas. The approximate solution for the mean permeability coefficient of each component in a binary mixture was derived on the basis of the same mobility model driven by gradients of chemical potential. The deviation of approximate solutions from numerical ones remains less than 0.3%.