bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of polyamic acids on interfacial shear strength in carbon fiber/aromatic thermoplastics
Authors: Chuang S. L. , Chu Ning‐Jo , Whang W. T. 
Published: April 2003

AbstractCarbon fiber surfaces were coated in various thickness with polyamic acids (PAA) prepared from (1) benzophenone tetracarboxylic dianhydride (BTDA) and 4,4'‐diaminodiphenyl ether (ODA), (2) BTDA and 4,4'‐diaminodiphenyl sulfone (DAS), and (3) BTDA and ODA modified with bisaminopropyldisilane, designated as PAA‐1, PAA‐2 and PAA‐3 respectively. The treated carbon fiber, with or without imidization, was embedded in thermoplastic polyetheretherketone (PEEK), polyetherimide (PEI), polyethersulfone (PES), polysulfone (PSF), and polyphenylsulfide (PPS) by the microbond method, and the interfacial shear strength was measured by pulling out the fiber from the embedded resin. Maximum increments in interfacial bonding strength from 24% to 35% were obtained from PAA‐1 in PEEK in PEI, PAA‐2 in PEEK, PEI, PSF, and PPS, and PAA‐3 in PEEK and PES. Imidization of PAA‐1 and PAA‐2 before resin application reduced their bonding capability. A linear relationship between the length of the embedded fiber and debonding load was found in the case of PEEK, PEI, and PSF; scattered results were obtained in the case of PES and PPS. Inadequate specimen annealing was believed to be the cause for PES, Brittle fracture appeared to occur in the case of PPS.
Effects of gamma‐ray irradiation on the change of characteristics of polyurethane
Authors: Shintani Hideharu , Kikuchi Hiroshi , Nakamura Akitada 
Published: April 2003

AbstractInvestigations have been carried out on gamma‐ray irradiated thermoplastic polyurethane (PU). The change of molecular weight as a result of irradiation and the change of absorbance of samples eluted daily by methanol extraction were determined. GPC patterns, tensile strength, and residual amount of radicals based on chemiluminescence were also measured. PU chain‐extended with 1,4‐butanediol (BU) showed degradation, while PU without chain‐extended with BU (linear PU) showed mainly crosslinking by gamma‐ray irradiation. G values were 1.1 (degradation) and 0.2 (crosslinking). A linear relationship between the irradiation dose and the residual radical amount was found. There was no significant difference in molecular weight as determined immediately following irradiation with analysis 6 months after irradiation. The influence of the amount of residual radical on the changes in the characteristics of PU was not significant. The elution of PU oligomers (n = 1–10) was confirmed from the GPC pattern of methanol extract. The changes in tensile strength correlated well with the changes in molecular weight. Sequential daily methanol extract analysis showed that elution occurred semilogarithmically. Methanol extract at an early stage is more toxic due to abundant elution of lower molecular weight compound.
Fibers from flexible liquid crystal main‐chain polymers. I. Polymers based on 4,4′‐dihydroxy‐2,2′‐dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides
Authors: Blumstein A. , Lin C. H. , Mithal A. K. , Tayebi A. 
Published: April 2003

AbstractThe anisotropic properties of thermotropic liquid crystalline polymers are paramount to the development of highly oriented and extended polymer chains in a fiber spinning process. Fibers from liquid crystalline polymers were spun above the mesophase transition temperature. Linear thermotropic liquid crystalline polymers based on 4,4′‐dihydroxy‐2,2′‐dimethylazoxybenzene and alkyl dicarboxylic acids and alkyl dihalides have been previously studied by different techniques and their conformational properties are well established. In this work the mechanical properties of fibers based on such polymers were studied. High values of tenacity and tensile moduli were obtained. These values increase with molecular mass, but decrease with the length of the flexible spacer moiety. The spinning temperature is also an important parameter.
Effect of cooling rate and shear‐induced crystallization on the pressure–specific volume–temperature diagram of isotactic polypropylene
Authors: Fleischmann E. , Koppelmann J. 
Published: April 2003

AbstractRectangular plates were injection molded with isotactic polypropylene. At a pressure of 1300 bar the mold was sealed mechanically in the gate. After the injection and compression phase the internal pressure decay has been calculated using the pressure–specific volume–temperature diagram and compared with measurements. The calculation method is described. The pvT diagram determined on stationary melt at a low cooling rate yields no good approximations of the measured values. It is shown which modifications of the pvT diagram are necessary to obtain a better description of the melt behavior under injection molding conditions. At the end of the cooling phase, the calculated pressure differs from the measured pressure. The reason is the volume change of the mold caused by the high internal pressure.
Epoxy resins based on aromatic glycidylamines. I. Analysis of N,N‐diglycidylaniline by GPC and HPLC
Authors: Podzimek S̆. , Dobás̆ I. , S̆vestka S̆. , Horálek J. , Tkaczyk M. , Kubín M. 
Published: April 2003

AbstractN,N‐bis(2,3‐epoxypropyl) aniline (N,N‐diglycidylaniline, DGA) and an intermediate of its synthesis, N,N‐bis(2‐hydroxy‐3‐chloropropyl) aniline (N,N‐dichlorohydrin of aniline, DCHA), were analyzed by GPC and HPLC. The main impurities were isolated by semipreparative HPLC and their structure was identified by mass, IR, and NMR spectroscopy. Attention was also paid to the mechanism underlying the formation of these impurities.
The use of RuO4 in studies of polymer blends by scanning electron microscopy
Authors: Ohlsson Bertil , Törnell Bertil 
Published: April 2003

AbstractFlat samples of blends of PP and SEBS were contrasted with ruthenium tetroxide and studied in a scanning electron microscope provided with a detector for back‐scattered electrons. The images showed the SEBS phase as bright areas with dark dots and the PP phase as dark. The dots in the bright SEBS areas corresponded to the unstained EB‐domains of the triblock SEBS polymer. The technique used provided BSE images of high resolution. This is a consequence of the intrinsic electrical conductivity conferred to the sample surface by the ruthenium species deposited there during staining. Treatment with ruthenium tetroxide vapor conferred electrical conductivity to the stained areas, which explains the high resolution obtained with the present technique.
Synthetic sequence effects in polyurethane–poly(n‐butyl methacrylate) mixtures: Grafting and mechanical properties
Authors: Fox R. B. , Armistead J. P. , Roland C. M. , Moonay D. J. 
Published: April 2003

AbstractMorphology, stress–strain properties, and grafting have been investigated in highly phase‐separated polyurethane (PU)‐poly(n‐butyl methacrylate) (PBMA) mixtures as a function of the sequence of formation of the components, both linear (l) and crosslinked (x), in the presence of each other. In the range of 0.3–0.7 weight fraction of PU, a morphology of PBMA particles in a PU matrix results. Particle size depends on matrix viscosity at the time of PBMA formation, decreasing as viscosity increases. The PBMA (l) particles are spherical; PBMA (x) particles are irregular in shape when formed in a fluid medium but tend to become spherical as the delay time before the onset of their formation is increased. Grafting, decreasing with increasing delay time, is observed between PBMA (l) particles and the PU (x) or PU (l) matrix. The grafting results from transesterification between BMA and the polyol precursors to the PU. Two families of mechanical properties are found, depending generally more on particle shape than size. Systematic trends of property values through a series of samples of constant composition, but increasing delay times, are observed with greater variation in the series with PBMA (x) particles; the trends are explainable in terms of matrix immobilization by the particles.
Melt flow index values and molecular weight distributions of commercial thermoplastics
Authors: Bremner T. , Rudin A. , Cook D. G. 
Published: April 2003

AbstractThe traditional melt index test (ASTM D 1238) is widely used in the plastics industry to characterize polymer processability. The data from this measurement must be interpreted cautiously, however, because polymers are usually processed under conditions that are far removed from those of the melt index test. In this study, melt index (MI) values from a series of polystyrene, polypropylene, linear low‐density polyethylenes (butene and octene copolymers), and high‐density polyethylenes were measured and related to molecular weight distributions of these materials. It was found that a simple relationship between 1/MI versus M̄xw (where x = 3.4–3.7) was followed for the linear polymers with similar polydispersities. For branched polymers, the best correlation was that of ‐ln(MI) versus ln(M̄v). A general relation for shear modifiable polymers like polyethylenes cannot be obtained unless the rheological state of the material can also be defined.
Effect of corona discharge treatment on cellulose prepared from beech wood
Authors: Uehara Tohru , Sakata Isao 
Published: April 2003

AbstractCellulose prepared from beech wood (Fagus crenata Blume) was treated in a corona discharge. The chemical changes produced by the treatment were investigated by use of infrared spectrum, Schiff's reaction, adsorption of methylene blue and Orange II, and intrinsic viscosity. Infrared absorption bands at 1382 and 1715 cm−1 were formed. The color reaction with Schiff's reagent indicated that the 1715 cm−1 absorption was due to the aldehyde group and not to the carboxyl group. The intrinsic viscosity was decreased by the air corona treatment, but was not affected by nitrogen corona treatment. The adsorption of methylene blue was not increased by corona treatment, indicating that no acidic groups were formed. Adsorption of Orange II indicated that some basic groups were formed by the nitrogen corona after a long treatment time. Low molecular weight fractions showing the 1382 cm−1 infrared absorption band were formed by corona treatment. These fractions were removed from cellulose by washing with water, and they increased with an increase in the treatment time. The absorption band at 1382 cm−1 was assigned to the symmetric carbon‐hydrogen bending of methyl group.
Bead–spring macromolecules that perturb the solvent
Authors: Grisafi S. 
Published: April 2003

AbstractA dispersion force based interaction between the solvent and the beads of a bead‐spring model macromolecule is used to couple the motion of the solvent and polymer in dilute solution flows. The polymer exerts a force on the solvent equal and opposite to the force that the solvent exerts on it. The friction coefficient approximation of the Rouse‐Zimm theories is eliminated. Both the solvent and polymer are subject to ensemble averaging over their respective phase space. A constitutive equation for the polymer stress is presented. By appropriate selection of the interaction potential between the solvent and the polymer, any normal stress difference can be predicted.
The effect of biaxial orientation and crystallinity on the long‐term creep behavior of poly(ethylene terephthalate) films below glass transition temperature
Authors: Cakmak M. , Wang Y. D. 
Published: April 2003

AbstractThe use of thin polymeric films in applications such as flexible circuit boards and dish membrane solar collectors has been gaining popularity. In these and many other applications the films are used under constant loading conditions which subjects them to long‐term creep. In this paper, we present detailed experimental tensile creep results on unoriented films of varying crystallinities and unequal and equal biaxially oriented poly(ethylene terephthalate) (PET) films. The results indicate that the increasc of crystallinity, stretch ratios, and annealing causes reduction in longterm creep strains. Unequal biaxially stretched films exhibited in‐plane anisotropy in their tensile creep behavior. In these films the lowest creep strains are observed in the direction along which the film stretched to the highest stretch ratio.
Heterogeneous polymerization of methyl methacrylate in absence and presence of surface modified cuprous oxide
Authors: Moustafa A. B. , Aboul‐Wafa O. , Radwan F. M. , Emam A. 
Published: April 2003

AbstractThe heterogenous polymerization of methyl methacrylate in the presence of cuprous oxide was studied. Adsorption measurements of stearic acid from benzene solution onto the surface of Cu2O were carried out. The specific surface area of cuprous oxide as obtained from the extrapolation to the concentration of monolayer surface coverage in the adsorption isotherm was compared with that evaluated from the BET‐equation. Sedimentation volume and sedimentation rate of the variably surface modified Cu2O samples were determined. It was found that the surface modification of Cu2O enhances its catalytic effect in the heterogenous polymerization of methyl methacrylate up to monolayer surface coverage. The viscosity average molecular weights M̄v of the respective polymers as well as the apparent activation energy of the polymerization process were correlated with the reaction parameters.
Thermal shock resistance of plastic IC package
Authors: Kojima Yoshitsugu , Ohta Takashi , Matsushita Mitsumasa , Takahara Minoru , Kurauchi Toshio 
Published: April 2003

AbstractDual‐in‐line packages (DIPs) were formed from epoxy molding compounds with various physical properties using a transfer molding machine. The compounds were prepared by changing kinds and amounts of additives and addition methods. The thermal shock test was carried out by the following procedures. The plastic package was soaked alternately in liquid nitrogen (−196°C) and in liquid solder (250°C) in the cycle of 140 s. The packages were intermittently subjected to optical microscopic inspection for crack initiation. The median life to crack initiation is defined to be the number of the cycles when half of the specimens exhibited crack initiation. Glass transition temperature, coefficient of linear expansion, and flexural modulus were measured to calculate thermal stress in plastic packages. According to the linear fracture mechanics, the following expression was obtained among the median life N, thermal stress σt and strength σb. N =/σ We found the linear relation between logarithm of Nσ and logarithm of σb/σ t for various packages, and obtained that the value of C and m are estimated as 3 × 104 MPa2 and 5.5, respectively. Therefore, the median life can be predicted from the glass transition temperature, coefficient of linear expansion, flexural modulus, and strength of plastic materials for packages.
Modification of transport properties of ion exchange membrane. XI. Electrodialytic properties of cation exchange membranes having polyethyleneimine layer fixed by acid–amide bonding
Authors: Sata Toshikatsu , Izuo Ryuji 
Published: April 2003

AbstractFor the purpose of preparing the monovalent cation permselective membrane for electrodialysis, the membrane having—SO2Cl groups reacted with the polyethyleneimine to form a cationic polyelectrolyte layer on the membrane surface by using the acid–amide bonding. Reaction conditions, i.e., reaction temperature, concentration of the polyethyleneimine solution and the addition of tertiary amines to the polyethyleneimine solution, were all examined in detail. As a result, all the different kinds of polyethyleneimines were effective in obtaining the monovalent cation permselective membrane if the correct reaction conditions were selected. The durability of the monovalent cation permselectivity was evaluated in a continuous electrodialytic concentration of sea water. The monovalent cation permselectivity decreased gradually during the electrodialysis in the cation exchange membrane with the polyethyleneimine layer. Therefore, the cation exchange membrane with the cationic polyelectrolyte layer was further treated with crosslinking reagents, i.e., form aldehyde–hydrochloric acid, epichlorohydrin, etc. or other alkylating reagents. The monovalent cation permselectivity of the treated membranes was almost constant for two months. The crosslinking reaction of polyethyleneimine was more effective than alkylation in maintaining the high permselectivity constantly.
Self‐curing epoxy compounds
Authors: Mikroyannidis John A. 
Published: April 2003

AbstractA new series including eight structurally different self‐curing epoxy compounds bearing azomethine linkages were synthesized, characterized and polymerized. 4‐(2,3‐Epoxypropoxy)‐benzaldehyde (EPB) or 2,3‐epoxypropyl glyoxylate monohydrate (EPG), prepared by reacting 4‐hydroxybenzaldehyde or glyoxylic acid monohydrate, respectively, with excess of epichlorohydrin in the presence of benzyltrimethylammonium bromide as catalyst, were used as starting materials. EPB or EPG reacted with an equimolar amount of a substituted aromatic amine (4‐aminobenzoic acid, 5‐aminoisophthalic acid, 4‐aminophenol, or 1,4‐phenylene‐diamine) to afford the epoxy compounds. They were characterized by IR and 1H‐NMR spectroscopy. Their thermal polymerization was investigated by DTA. The thermal stabilities of cured resins were evaluated by dynamic TGA and isothermal gravimetric analysis (IGA). The polymers of the epoxy compounds derived from EPB were stable up to 225–298°C in N2 and afforded anaerobic char yield of 57–62% at 800°C.
Viscosity of aqueous solutions of polysaccharides and their carboxylate derivatives
Authors: Nomura Hiroyasu , Koda Shinobu , Hattori Futoshi 
Published: April 2003

AbstractThe viscosities of aqueous solutions of methyl cellulose, dextran, and their carboxymethyl derivatives were measured as functions of molecular weight and concentration. Furthermore, effects of ionic group and added salt on the viscosity of aqueous solutions of carboxymethyl derivatives were investigated. The viscosities of dextran and carboxymethyl dextran solutions did not show any shear stress dependence, but those of methyl and carboxymethyl cellulose solutions strongly depended on shear stress even at low concentrations. The results were discussed on the basis of the points of molecular structure and hydration and ionic interaction of a polymer chain in solutions.
Physicochemical changes in stabilized, orientated polypropylene films during the initial stages of thermal oxidation
Authors: Horrocks A. Richard , D'souza Jennifer A. 
Published: April 2003

AbstractOrientated, stabilized, isotactic polypropylene films have been oven‐aged at 130°C for times shorter than required for their embrittlement. The structural changes occurring during this induction period have been studied using tensile tensiometric, density, thermal analytical (DTA and TGA), and infrared spectrophotometric techniques. After an initially rapid annealing, films show similar time‐dependent changes in tensile, density‐derived crystalline and thermogravimetric behaviors. Comparison with vacuum‐aged sample properties shows that these changes reflect the effects of oxidative attack of polypropylene chains. Infrared examination shows that, even after the longest aging times studied and close to the induction period for embrittlement, the presence of oxidized chain groups is only just discernible. Oven aging reduces post‐fusion oxidative onset and maximum mass loss temperatures determined by TGA. Kinetic analysis demonstrates that the apparent activation energies and Arrhenius factors are reduced during aging as the post‐fusion oxidation mechanism becomes more complex. The results suggest that, during the induction period, changes in both physical and chemical structural features of orientated polypropylene occur which have possible importance in determining the lifetime of the polymer in use.
Polystyrene/Polycarbonate/Polystyrene‐block‐Polycaprolactone blends. Emulsification and mechanical performance
Authors: McKay Ian D. 
Published: April 2003

AbstractTwo polystyrene–polycaprolactone diblock copolymers, of differing molecular weights, have been extrusion‐blended with polystyrene and polycarbonate. The morphologies of the resultant blends were studied using differential scanning calorimetry and scanning electron microscopy. In all compositions studied, the polystyrene and polycarbonate phases exhibited discrete glass transitions indicative of the immiscibility of these components. However, addition of the copolymer increased the extent of dispersion of the homopolymer components within one another quite effectively. Blend specimens were tested with respect to tensile, flexural, impact, thermal, and flow characteristics to probe the effects of morphology and composition on these factors. In general, the blends were rigid, brittle materials with thermal characteristics in the range between those of the polystyrene and polycarbonate components. Addition of polystyrene‐block‐polycaprolactone polymer to the blends resulted in increased brittleness, reduced thermal performance, maintenance of rigidity, and improved flow.
Studies on the synthesis of a methacrylate‐based dental restorative resin
Authors: Sheela M. S. , Selvy K. Tamare , Krishnan V. Kalliyana , Pal S. N. 
Published: April 2003

AbstractThe synthesis of bisphenol A–glycidyl methacrylate (BIS–GMA), the resin component in most dental composite restorative materials, catalyzed by different tertiary amine accelerators such as N,N′‐dimethyl‐p‐toluidine (DMPT), N,N′‐dimethylamino phenethyl alcohol (DMAPEA), and N,N′‐dimethylamino ethyl methacrylate (DMAEMA) is reported in this work. The effect of varying concentrations of accelerators and the reaction conditions of the synthesis as a function of time is studied in detail. The kinetics of the reaction between epoxide and carboxyl group during the formation of BIS–GMA is monitored using infrared (IR) and chemical techniques. The reaction is found to follow first‐order and zero‐order kinetics with respect to epoxide and acid, respectively. The degree of epoxide and acid conversion has been calculated as a function of time. The percentages of various isomers, formed under different reaction conditions have been reported. Characterization procedures for BIS–GMA have been developed.
Rubber‐modified epoxies. II. Influence of the cure schedule and rubber concentration on the generated morphology
Authors: Verchere D. , Pascault J. P. , Sautereau H. , Moschiar S. M. , Riccardi C. C. , Williams R. J. J. 
Published: April 2003

AbstractThe morphology of a system consisting of a bisphenol A diglycidylether (DGEBA) based epoxy, cured with a cycloaliphatic diamine (4,4′‐diamino‐3,3′‐dimethyldicyclohexylmethane, 3DCM), in the presence of an epoxy‐terminated butadience‐acrylonitrile random copolymer (ETBN), was studied as a function of the cure schedule and the initial rubber concentration. Scanning (SEM) and transmission (TEM) electron microscopy, differential scanning calorimetry (DSC) and dynamic mechanical analysis were used to characterize the generated morphology. SEM results were not affected by the type of mechanical test and strain rate. Trends observed for the particle size distribution, the volume fraction of dispersed phase, the concentration of dispersed phase particles and the composition of both phases as a function of polymerization temperature and rubber concentration, were discussed. A correlation between the viscosity at the cloud point and the average size of dispersed phase particles was found for different systems, independently of the cure temperature and the initial rubber amount.