bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fatigue crack propagation in microlayer composites of polycarbonate and poly(styrene–acrylonitrile)
Authors: Ma M. , Im J. , Hiltner A. , Baer E. 
Published: April 2003

AbstractThe effect of layer thickness on fatigue crack propagation (FCP) in microlayer composites of polycarbonate (PC) and styrene–acrylonitrile copolymer (SAN) has been studied. Variation in layer thickness was achieved by increasing the number of layers from 49 to 776 while keeping the overall sheet thickness and composition the same. It was found that the 776 layer composite had a larger number of fatigue cycles from crack initiation to fracture, a longer stable crack length and higher value of critical strain energy release rate J1C. Microscopic characterization of the damage zone and resulting fracture surface revealed a transition from SAN crazing to shear deformation as layer thickness decreased from 18 to 1 μm; the resulting plastic deformation and ductile fracture of the 776 layer composite was responsible for the enhanced FCP resistance. The ductile fracture mechanism produced a measurable temperature rise at the crack tip that revealed the stop–start nature of crack propagation.
Studies on impact modification of polystyrene (PS) by ethylene–propylene–diene (EPDM) rubber and its graft copolymers. III. PS/EPDM‐g‐(styrene‐co‐maleic anhydride) blends and its relative performance
Authors: Shaw S. , Singh R. P. 
Published: April 2003

AbstractThe graft copolymer of ethylene–propylene–diene (5‐ethylidene‐2‐norbornene) rubber with styrene and maleic anhydride is synthesized, characterized, and blended with polystyrene. The tensile and the impact behaviors of the blends were investigated. The relative performance of EPDM‐g‐(styrene‐co‐maleic anhydride) as impact modifier for polystyrene has been evaluated.
Water‐soluble sulfonated amino‐formaldehyde resins. V. Effect of reaction condition on molecular weight distribution
Authors: Lahalih S. M. , Hovakeemian G. 
Published: April 2003

AbstractThe effect of reaction conditions of sulfonated urea‐melamine formaldehyde on molecular weight distribution was studied. It was found that the molecular weight distribution of these materials is influenced by the percent of urea to melamine in the mixture, the concentration of the reaction mixture, the pH and the time of reaction of the low pH condensation step, and finally, the reaction time during the high pH condensation and rearrangement step. Weight average molecular weights increased as percent melamine to urea, concentration of reaction mixture, the alkalinity of the third step, and the reaction time of the fourth step increased. The weight average molecular weight decreased as the reaction time of the third step decreased. The reaction variables influenced the fraction of the high molecular weight species that, in turn, influenced these materials performance. Finally, it appeared that the final product contained separate sulfonated urea formaldehyde and sulfonated melamine formaldehyde components in addition to sulfonated urea‐melamine formaldehyde polycondensates.
Pseudosteady states in semicontinuous emulsion copolymerization
Authors: Dimitratos J. , El‐Aasser M. S. , Georgakis C. , Klein A. 
Published: April 2003

AbstractThe appearance of pseudo‐steady states in semicontinuous emulsion copolymerization is studied. Different correlations between the monomer feed rate and the polymerization reaction rate proposed in the literature for homopolymerization systems can be derived from a unified view as presented in this work. The theoretical analysis for copolymerization systems predicts that the individual consumption rates of both monomers involved assume a constant value if the monomer addition rates are kept constant. Different cases for either fixed radical concentration or seeded polymerization with water‐soluble or sparingly water‐soluble monomers are considered. The assumptions and results of the analysis are tested against experimental data from the seeded copolymerization of vinyl acetate/n‐butyl acrylate.
Polyimides and polyamide–imides containing arylene sulfone ether linkages
Authors: Idage S. B. , Idage B. B. , Gunjikar V. G. , Vernekar S. P. 
Published: April 2003

AbstractPolyimides and polyamide–imides containing arylene sulfone ether linkages were synthesized from 4,4′‐bis(4‐isocyanatophenoxy) diphenylsufone (SPI), 4,4′‐bis(3‐isocyanatophenoxy) diphenylsulfone (SMI), pyromellitic dianhydride (PMDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and trimellitic anhydride (TMA) using one‐step method. The diisocyanates SPI and SMI were synthesized from 4,4′‐bis (4‐carboxyphenoxy) diphenylsulfone (SPA) and 4,4′‐bis(3‐carboxyphenoxy) diphenylsulfone (SMA) by a Weinstock‐modified curtius rearrangement method. All the polycondensation reactions were carried out in N‐methyl‐2‐pyrrolidone (NMP) and the polymers obtained were characterized by infrared spectroscopy, solution viscosity, elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction.
Effect of γ‐irradiation and temperature on the structure of metal‐chloride‐treated poly(vinyl alcohol)
Authors: Rabie S. M. , Abdel‐Hakeem Nagwa , Moharram M. A. 
Published: April 2003

AbstractThe infrared and ultraviolet spectra of poly(vinyl alcohol)(PVA) treated with ferric chloride and zinc chloride were recorded. Careful examination of the infrared spectra revealed that these treatments cause significant changes in the crystallinity of PVA, particularly in the case of the treatment with ZnCl2. The results showed that exposure of untreated and FeCl3‐treated PVA to 12 or 28 Mrds results in no observable changes in their ultraviolet and infrared spectral features, whereas exposure of ZnCl2‐treated PVA at the same dosages, results in the appearance of an absorption band at 1595cm‐1 corresponding to β‐diketone groups. It was also found that γ‐irradiation of ZnCl2‐treated PVA produces a remarkable change in its crystallinity. Moreover, the effect of heat on the spectral features of the ZnCl2‐treated PVA was discussed. It was found that the treatment of PVA with ZnCl2 helps in oxidative degradation of PVA.
Synthesis and characterization of thermo‐sensitive polymeric beads
Authors: Abe Takashi , Egawa Hiroaki , Ito Hiroshi , Nitta Atsuhiko 
Published: April 2003

AbstractThermo‐sensitive polymeric beads were synthesized by inverse suspension polymerization of aqueous monomer solution containing N‐acryloylpyrrolidine (APR) and N,N′‐methylenebisacryl‐amide (MBA : crosslinking agent). The polymerization conditions such as dispersion medium, dispersing agent, monomer, and initiator concentration were investigated. Fine spherical gels with diameter of 50–500μm were obtained in high yield. The swelling volume of these gels in water continually decreased by raising atmospheric temperature and vice versa. The degree of swelling increased for the gels synthesized with lower degree of crosslinking or with lower monomer concentration at polymerization. The degree of swelling was high in water and alcohols, but the gels swelled even in nonpolar organic solvents, although the degree of swelling was low. The pore radius distribution of the gels was determined by aqueous size exclusion chromatographic method to investigate relations between pore characteristics of the gels and polymerization conditions. Monomer concentration had large effect on pore size, porosity, and pore volume of the gels. On the other hand, degree of crosslinking had little effect on these pore characteristics.
Cure kinetics of epoxy/anhydride thermosetting matrix systems
Authors: Woo E. M. , Seferis J. C. 
Published: April 2003

AbstractThe kinetics of bisphenol‐A diglycidyl ether epoxy (DGEBA) cured with trimellitic anhydride (TMA) were studied using differential scanning calorimetry (DSC) and FT‐IR under isothermal temperatures in the range of 100–200°C. The effects of an onium salt catalyst and styrene monomer (a reactive diluent additive) on cure kinetics of the DGEBA/TMA resin systems were also investigated. For the uncatalyzed DGEBA/TMA system, the reaction was found to be second order up to a fractional conversion of 0.8, where a diffusion‐limited reaction regime was observed as the matrix gelled. The apparent activation energy was calculated to be 11.3 kcal/mol. The cure reaction of the catalyzed DGEBA/TMA system was found to be second order up to a fractional conversion of 0.3 and first order thereafter. The apparent activation energy of the catalyzed resin system was calculated to be 12.3 kcal/mol. In the FT‐IR investigation, it was discovered that the KBr powder catalyzed the cure reaction. Additionally, the styrene component in the styrene‐DGEBA/TMA resin system polymerized independently in the later stage of the cure reaction of the epoxy component. Therefore, the styrene monomer had little effect on the kinetics of cure reaction of the epoxy system.
Polybutadiene grafting and crosslinking in high‐impact polystyrene bulk thermal process
Authors: Peng Fred M. 
Published: April 2003

AbstractThe grafting and the crosslinking of polybutadiene during the bulk thermal polymerization of high‐impact polystyrene were studied. The kinetic equations for these two reactions were derived by the use of the moments of the distribution functions. This kinetic model indicates that both the density of grafting and the degree of crosslinking increase with the increasing temperature of polymerization and, most significantly, with the increasing conversion of styrene.
Processing‐morphology‐property relationships in epoxy resins containing an organometallic cobalt complex
Authors: Mijović Jovan 
Published: April 2003

AbstractAn investigation was carried out into the effect of an organometallic complex, cobalt (III) acetylacetonate, on curing, morphology, and mechanical properties of several epoxy resins. Differential scanning calorimetry, electron microscopy, and a series of mechanical measurements were performed on bifunctional and terafunctional formulations. The addition of cobalt (III) acetylacetonate did not cause drastic changes in any of the systems investigated, although a slight effect on cure kinetics, Young's modulus, and fracture‐surface morphology was noted. Also, there was no effect on the impact strength or the critical stress intensity factor of any of our formulations.
Low pressure polymerization of propylene: Kinetics
Authors: Pandya M. V. , Lata K. V. 
Published: April 2003

AbstractKinetic studies on low pressure polymerization of propylene using the catalyst system VOCl3 + AIEt3 and Et2AlCl are reported. Effect of various parameters such as the [Al]/[V] ratio, catalyst concentration, reaction time, temerature, solvents, and additives on rate of the reaction, yield, and % conversion were studied. Each of these parameters had a profound effect on the yield and rate of the reaction for both the systems. Triethylamine was found to increase the yield and the rate of polymerization. We also found that aliphatic hydrocarbons acted as a better polymerization medium than aromatic ones.
Dynamic mechanical characterization of tire cord dip films
Authors: Das B. , Girgis M. M. 
Published: April 2003

AbstractVarious dip films with different amounts of F/R resins, polybutadiene latex, styrene/butadiene/vinyl pyridine terpolymer latex, and/or with carboxylated butadiene latex were prepared on a Teflon‐coated hot plate by spraying the properly formulated dip mixes using a Binks air gun. These dip films were cured at 300°F in hot air oven between two Teflon plates. A DDV‐IIC Rheovibron instrument was used to measure elastic modulus (E′), loss modulus (E″), and tan δ (E′′/E′) of different dip films. Dip films with higher F/R resin (11 vs. 7%) concentration gave higher tan δ values which peaked between −20 and −30°C. Films with higher resin concentrations were also found stiffer (higher E′), if all other ingredients of the films were identical. Dip films, where more than 40% of the film ingredient was polybutadiene, showed a phase‐separated glass transition temperature for polybutadiene between −60 and −90°C. Films, with 40% polybutadiene and 7.0% F/R resin and the rest of the ingredients being styrene/butadiene/vinyl pyridine and other additives such as wax, silanes, etc., gave two distinct glass transition temperatures: one between −60 and −80°C for polybutadiene and the other for complex between F/R resin and vinyl pyridine around −20 and −30°C. Tire cords coated with dip mixtures of lower tan δ values in the −20 to +20°C range gave better fatigue performance in the Gristmill tire test at room temperature. Tire cords coated with dip mixtures containing 40% polybutadiene and 7.0% F/R resin exhibited phase separated two distinct glass transition peaks in the temperature ranges of −60–−90°C and −20–−30°C. Films of the above formulations showed low modulus and high elongations. Cords coated with the above dip mixtures gave good fatigue performance in the Firestone cold wheel test at −50°C. It so happens that, in this temperature range of −30–−60°C, the above phase‐separated dip films go through a minimum damping value and, therefore, give superior tire performance.
Graft copolymerization by iniferter method; structural analyses of graft copolymer by glass transition temperature
Authors: Yamashita K. , Ito K. , Tsuboi H. , Takahama S. , Tsuda K. , Otsu T. 
Published: April 2003

AbstractSince 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC) polymer easily cleaves at the C—S bond and generates benzyl radical, graft copolymerization of methyl methacrylate (MMA) or 4‐vinylpyridine (VPy) onto VBDC polymer is easily performed by UV irradiation. The structural analyses of the graft copolymers are performed through glass transition temperature measurements. The graft copolymers of MMA have one Tg and VPy graft copolymers have two Tg's arising from the main and side chains. It becomes clear that the mode of side chains propagation is significantly different for each of the second monomers used.
Effect of prevulcanisation of natural rubber latex on the chemical and physical properties of latex thread
Authors: Peethambaran N. R. , George Tessy K. 
Published: April 2003

AbstractThe effect of prevulcanisation on the processing properties and network structure of a series of latex compounds containing conventional and efficient vulcanisation (E.V. systems) systems for the manufacture of latex thread was evaluated. Prevulcanisation was effected at 70°C and the extent of crosslinks formed and compound viscosity at various periods of heating were studied. It is observed that the vulcanisation systems studied have a profound effect on the extent of crosslink formation during prevulcanisation. The network structure of the vulcanisate was also studied and found that polysulphidic content is high as the extent of prevulcanisation of the latex compound increases. Latex threads were also prepared from typical latex compounds which were prevulcanised to different degrees and their chemical and physical properties were evaluated. It is observed that the extent of prevulcanisation affects the aged and unaged physical properties of latex threads.
Pilot plant synthesis of methacrylate copolymer precursors to nonlinear optical materials
Authors: Katz H. E. , Bohrer M. P. , Mixon D. A. , Alonzo J. , Markham J. , Sohn J. E. , Cox D. I. 
Published: April 2003

AbstractThe copolymerization of methacrylates with methacrylates containing anilino side chains was investigated. Azobis(isobutyronitrile) was a better initiator than benzoyl peroxide. Continuous feed of initiator was advantageous compared to adding the initiator all at once. The reaction was scaled up using a 10‐L reactor, ultimately yielding hundreds of grams of the desired copolymers, which are valuable precursors to polymeric dyes used in nonlinear optical studies.
Polyurethanes from aromatic bischlorformates
Authors: Morgan Paul W. 
Published: April 2003

AbstractLinear polyurethanes, having high molecular weight, were prepared by interfacial polycondensation from halogen substituted aromatic bischloroformates and aliphatic diamines, piperazines, and aromatic diamines. Examples of specific intermediates are hexamethylenediamine, piperazine, homopiperazine (see formula), m‐phenylendiamine, and the bischloroformates of 2,2‐bis (4‐hy‐droxy‐3,5‐dichlorophenyl) propane, 2,2‐bis(4‐hydroxy‐3,5‐dibromophenyl) propane, and 2,2‐bis(4‐hydroxyphenyl) hexafluoropropane:
magnified imageIn comparison with corresponding unhalogenated polyurethanes, the polymers from this study, particularly those based on piperazines, had high glass transition and softening temperatures. Polyurethanes in this class, like most ring‐containing polyurethanes, do not have sufficient thermal stability at their high melting points for easy melt for easy melt forming. They were more soluble in a variety of common solvents and had excellent resistance to ultraviolet light. Surprisingly, the irregularity introduced into the polymer chain by the use of such intermediates as homopiperazine (formula above) or 2‐methylpiperazine did not inhibit crystallization. On the other hand the symmetry provided by trans‐2,5‐dimethylpiperazine greatly reduced solubility in many solvents. Several polyamides and a polyurea from homopiperazine are included.
Influence of the matrix thickness on radiation‐induced grafting of styrene onto poly(ethylene terephthalate) films and nuclear membranes
Authors: Zhitariuk N. I. , Zagorets P. A. , Kuznetsov V. I. 
Published: April 2003

AbstractRadiation‐induced graft polymerization of styrene onto poly(ethylene terephthalate) (PET) nuclear membranes and films was performed by various methods, viz., preirradiation in air and in a vacuum. The grafting yield obtained via the preirradiation in a vacuum was considerably higher than that obtained under the same conditions by preirradiation in air. The higher the average distance between pores is, the higher the grafting yield. But when grafting is performed onto both the membranes with average distance between pores and films with different thickness, the grafting yield passes through the maximum as the thickness increases. When the average distance between the pore walls of a membrane is equal to the film thickness, the grafting rate onto the film is higher than that onto the membrane. This is attributed to growth of the termination rates both the active sites within the polymeric matrix and the growing macroradicals during graft polymerization. Both the processes proceed at the phase boundary. The boundary area increases as a result of chemical treatment in the course of nuclear membrane manufacturing. The values of the characteristic parameter α and the critical thickness for styrene grafting onto nuclear membranes and films have been obtained.
Synthesis and characterization of some polyaniline–organic acceptor complexes
Authors: Khor S. H. , Neoh K. G. , Kang E. T. 
Published: April 2003

AbstractThe charge transfer (CT) interactions between polyemeraldine (PEM) and six organic electron acceptors were studied. The complexing ability of the acceptors, based on the maximum attainable electrical conductivity of the resulting complex, could be arranged in the following ascending order:tetrachloro‐p‐benzoquinone (p‐chloranil), tetrafluoro‐p‐benzoquinone (p‐fluoranil), tetrabromo‐o‐benzoquinone (o‐bromanil), 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ), tetrachloro‐o‐benzoquinone (o‐chloranil), and tetracyanoethylene (TCNE). Conductivity in the order of 10‐1 S/cm was achieved in the PEM/TCNE complex. The complexes were also characterized by infrared (IR) absorption spectroscopy, thermogravimetric (TG) analysis, and X‐ray photoelectron spectroscopy (XPS). In most complexes, the CT interactions have proceeded further than the formation of pure molecular complexes. However, the mechanism of CT interaction was found to be analogous to that of protonation of PEM by protonic acids.
Fibers from polyurethanes based on halogen‐substituted bisphenols
Authors: Morgan Paul W. 
Published: April 2003

AbstractFibers were prepared on an experimental scale by wet and dry spining from eight, nonelastomeric polyurethanes based on halogen‐substituted bisphenols. The fibers had properties suited to clothing textile uses. They were examined primarily for their potential in wash and wear fabrics. The fibers had moderate water absorption, low shrinkage in hot water, modest lowering of tensile properties under wet conditions, high tensile and work recoveries, and good stability to ultraviolet light. The polyurethanes from piperazines and 2,2‐bis (4‐hydroxy‐3,5‐dichlorophenyl) propane bischloroformate had unusually high thermal transitions and good solubility combined with ease of orientation and crystallization in fiber form. Fibers from the 2‐methylpiperazine and homopiperazine urethanes were converted to fabrics. These fabrics exhibited a silklike handle, good wash wrinkle recovery, resistance to soil and bleach, stability to ironing at 200°C, and very low flammability.
Curing kinetics of polyurethane reactions
Authors: Chern Chorng‐Shyan 
Published: April 2003

AbstractThe curing reactions of polyurethane resins are accelerated by electron donors (e.g., hydroxyl group) and electron accepting materials (e.g., carboxyl group and dibutyltin dilaurate). As the critical extent of reaction is reached, a three‐dimensional cross‐linked network is formed. Afterwards, most of the reactive functional groups are attached to the cross‐linked network. The mobilities of these reactive functional groups are seriously restricted and the curing reactions become diffusion controlled. This could lead to incomplete extent of reaction. Based on elementary reaction mechanisms a kinetic model is developed. The concept of diffusion‐limited reactions is used to describe the phenomenon of limiting extent of reaction. Changes in free volume are related to changes in the rate constants with extent of reaction. When the model is applied to experimental data available in the literature, agreement between the model predictions and experimental data is reasonably good.
Dynamic mechanical properties of low‐density and linear low‐density polyethylenes. Influence of molecular segregation
Authors: Orozco J. A. Gonzalez , Rego J. M. , Katime Issa 
Published: April 2003

AbstractThe dynamic mechanical properties of different low‐density and linear low‐density polyethylenes have been measured as a function of crystallization conditions. The mechanical results have been explained accounting for molecular segregation as well as reorganization capacity of the crystallizable segments during isothermal thickening. The presence of a high amount of segregated material does not allow detection of any relationship between crystallization conditions and mechanical relaxations for three of the four samples. The average values of the resonance relaxation temperatures and the relaxation strengths are dependent on branch content and branch type.
High‐performance thermoplastic toughened BMI matrix system. II. Interface study
Authors: Liao Yih‐Tyan , Lin Chen‐Ron , Liu Wen‐Liang 
Published: April 2003

AbstractBis‐maleimide (BMI) has recently attracted condsiderable attention as an important matrix resin for high‐performance composites, due to its outstanding high‐temperature performance. First‐generation BMI is too brittle for primary strauture. Our toughening approach began by dissolving PEI (polyetherimide) into compatible dially compound (Matrimid 5292 B, Ciba Geigy) prior to coreaction with BMI resin. In this note, the toughness and interface properties were investigated for the toughened matrix system.