bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study on the synthesis of perfluorovinyl‐sulfonic functional monomer and its copolymerization with tetrafluoroethylene
Authors: Kostov G. K. , Kotov St. V. , Ivanov G. D. , Todorova D. 
Published: April 2003

AbstractTetrafiuoroethylene (TFE) and hexafluoropropylene (HFP) were subjected to reactions with freshly distilled sulfur trioxide to obtain 1‐fluorosulfonyldifluoro‐acetylfluoride (FSDFAF, yield 65–70%) and pentafluoro‐2‐propenylfluorosulfate (PPFS, yield up to 50%). A subsequent reaction of FSDFAF with PPFS under anhydrous conditions led to a preparation of 2‐(1‐pentafluoro‐2‐propenyloxy)tetrafluoroethanesulfonyl fluoride (PPOTESF, yield 40–41%) whose structure was proved by both infrared (IR) spectroscopy and nuclear magnetic resonance (19F NMR). TFE was copolymerized with PPOTESF in bulk by using a free radical initiator of the hydrocarbon type at a temperature of 50°C. Various TFE/PPOTESF mole ratios were employed and the presence of sulfonyl fluoride (SO2F) functional groups in the copolymers was proven by IR spectroscopy. The copolymers were subjected to alkaline hydrolysis and the SO2F content was found not to exceed 0.70–0.80 mEq/g with polymer yields in the range of 11–31%. The reactivity ratios r1 and r2 related to TFE and PPOTESF, respectively, were determined by using the Fineman‐Ross method. A random distribution of PPOTESF units along the polymeric chain, consisting mainly of TFE fragments, was found to exist. The copolymers had melting temperatures 40–45°C lower than polytetrafluoroethylene and were thermally stable to 305–315°C. © 1993 John Wiley & Sons, Inc.
Preparation and characterization of aromatic polyimides and related copolymers
Authors: Li Shaohua , Karasz Frank E. 
Published: April 2003

AbstractCopolyimides containing BTDA‐3DDS and BTDA‐4ODA units have been synthesized by solution imidization methods. The copolyimides have high Tg's (267–283°C) and high decomposition temperatures (540–575°C; nitrogen); both properties are dependent on composition. Those copolymides with low concentrations of BTDA‐4ODA are generally soluble in organic solvents, whereas those copolyimides with higher BTDA‐4ODA content are only partially soluble or insoluble. However, all the copolyimides prepared can be compression molded. It has also been found that segmental motion above Tg is heavily suppressed in the BTDA‐4ODA homopolymer relative to that in the BTDA‐3DDS homopolymer. This reduction in molecular motion may severely hinder the solubility and fusibility of the BTDA‐4ODA homopolymer. © 1993 John Wiley & Sons, Inc.
Kinetic analysis of high‐resolution TGA variable heating rate data
Authors: Salin I. M. , Seferis J. C. 
Published: April 2003

AbstractIsothermal and constant heating rate thermogravimetric analysis (TGA) experiments have been performed for examining decomposition of polymers and composites. In practice, low heating rates are necessary to obtain good resolution under nonisothermal conditions thus increasing the time required for experiments. A novel TGA mode, high‐resolution TGA (Hi‐ResTM TGA), provides a means to remarkably increase the resolution while often decreasing the time required for experiments. In this variable heating rate mode of Hi‐ResTMTGA, the heating rate is continuously and dynamically varied to maximize resolution. Thus, traditional methods cannot be directly utilized to determine kinetic parameters. Accordingly, in this work, variable heating rate experiments were run on ethylene‐vinylacetate (EVA) copolymer, poly(ether ether ketone) (PEEK), and carbon‐fiber‐reinforced bismaleimide (BMI), whose kinetics have been quantitatively described with traditional isothermal and nonisothermal experiments. Comparison of the different techniques led to the development of a simplified method by which the activation energy, preexponential factor, and reaction order can be extracted from variable heating rate TGA experiments. The technique, based on the principle that maximum weight loss rate is observed at minimum heating rate, gave kinetic results that were in excellent agreement with values that have been determined by traditional isothermal and dynamic experiments. © 1993 John Wiley & Sons, Inc.
Studies on fiber formation of thermotropic copolyesters
Authors: Mehta Sanjay , Deopura B. L. 
Published: April 2003

AbstractThermotropic copolyesters PET/60 PHB and PET/80 PHB fibers are melt spun at different extrusion temperatures and at different draw‐down ratios. The flow behavior of PET/60 PHB is studied at different temperatures and shear rates. The melt of (PET/60 PHB) at temperatures above 265°C exhibit low viscosity and low activation energy of flow. The modulus and strength for both PET/60 PHB and PET/80 PHB fibers increase with the increase in extrusion temperature and draw‐down ratio in the ranges studied. High birefringence, indicating the presence of mesophase is observed between 265 and 300°C on a hot stage polarizing microscope. X‐ray diffraction patterns show that the molecular orientation increased with increasing draw‐down ratio. Scanning electron microscopy of these fibers shows a well‐developed highly oriented fibrillar structure. Superior mechanical performance of fibers spun at around 275°C are attributed to the presence of nematic mesophase in the polymer melt. © 1993 John Wiley & Sons, Inc.
Wavelength sensitivity of the photodegradation of poly(methyl methacrylate)
Authors: Mitsuoka Takuya , Torikai Ayako , Fueki Kenji 
Published: April 2003

AbstractPoly(methyl methacrylate) (PMMA) was photolyzed with monochromatic light of wavelengths 260, 280, 300, 320, 400, and 500 nm in vacuo by the use of the Okazaki Large Spectrograph. UV spectral changes, the quantum yields of main‐chain scission (ϕcs), and effects of wavelength were investigated. UV spectral changes around 280 nm were observed with irradiation at 260 nm. The ϕcs has a maximum value in case of irradiation with 300 nm light. It turned out that photodegradation of PMMA took place by irradiation of 260–320 nm light but did not by irradiation with the light longer wavelength than 340 nm. The average values of ϕcs obtained in this work were 0.84 × 10−4, 1.06 × 10−4, 4.21 × 10−4, 1.23 × 10−4, 0, and 0 for irradiations at 260, 280, 300, 320, 400, and 500 nm, respectively. It was found that the photo‐induced side‐chain scission initiates the main‐chain scission of PMMA by irradiation of 260 and 280 nm light. © 1993 John Wiley & Sons, Inc.
Surface and interfacial FTIR spectroscopic studies of latexes. IV. The effect of surfactant structure on the copolymer–surfactant interactions
Authors: Thorstenson Timothy A. , Urban Marek W. 
Published: April 2003

AbstractThe interactions between sodium dodecylbenzene sulfonate (SDBS) and the components of an ethyl acrylate/methacrylic acid (EA/MAA) copolymer latex were examined and the influences of using D2O as the synthetic suspension medium were investigated. Whereas it is found that D2O has no detectable influence on the fully coalesced latex films, the film coalescence conditions are shown to significantly affect the nature of surfactant interactions within the film matrix. When films are prepared and stored under controllable low atmospheric water‐vapor concentrations, hydrogen‐bonding interactions between the surfactant SO3−Na+ groups and the copolymer acid functionality dominate. However, coalescence and storage of the films under higher relative humidity conditions results in a displacement of these interactions in favor of the hydrated form of the surfactant. It is also shown that the presence of an aromatic ring adjacent to the surfactant sulfonate group exerts an influence on the nature of the SO3− ··· HOOC interactions within the copolymer matrix. Relative to sodium dioctyl sulfosuccinate (SDOSS), the aromatic group near hydrophilic end of SDBS increases the strength of the SO bond in the presence of acid interactions. © 1993 John Wiley & Sons, Inc.
Laser‐irradiation effect on poly(vinyl alcohol) films doped with nanometer‐sized CdS particles: Ablation and third‐harmonic generation
Authors: Nosaka Yoshio , Tanaka Kazunori , Fujii Nobuyuki 
Published: April 2003

AbstractUltrasmall CdS particles, whose average size was controlled by thiols to range from 2 to 4 nm, were embedded in poly(vinyl alcohol) films. Shift of the fluorescence peak associates with the shift of the absorption threshold of the films, and the fluorescence intensity increases with the decrease in the size of CdS. Laser ablation at 308 nm was investigated by monitoring the emission spectra. Third‐harmonic generation was measured for various sizes of CdS particles, and the optical nonlinearity in the nonresonance region was found to remain almost constant in the diameter range studied. © 1993 John Wiley & Sons, Inc.
Cyclohexanone oxime‐blocked polyisocyanates
Authors: Kothandaraman H. , Thangavel R. 
Published: April 2003

AbstractCyclohexanone oxime‐blocked isophorone diisocyanate and cyclohexanone oxime‐blocked toluene diisocyanate were synthesized and analyzed by infrared spectra, nuclear magnetic resonance spectra, elemental analysis, etc. Decomposition temperatures of the blocked isocyanates were determined by thermogravimetry. The solubilities of blocked isocyanates in various polyols were tested. © 1993 John Wiley & Sons, Inc.
Fracture toughness of high‐impact polystyrene based on threej‐integral methods
Authors: Lee Chang‐Bing , Lu Ming‐Luen , Chang Feng‐Chih 
Published: April 2003

AbstractThreeJ‐integral methods and their modified versions have been used to characterize the fracture toughness of high‐impact polystyrene (HIPS) with different thicknesses. TheJcvalues obtained were highest from the E813–87 method, followed by the E813–81 method, then by the hysteresis method. The hysteresis method based on the steep rising of hysteresis energy under constant displacement‐controlled loading inJcdetermination has many advantages over the ASTM E813–81 or the E813–87 method. The requirement of crack growth length measurements is no longer necessary and the controversial issue on the crack blunting line can also be avoided. The E813–87 method resulted in significantly higherJcvalues for polymers, but the modified version of E813–87, by moving the offset line from the original 0.2 to 0.1 mm, resulted in comparableJcvalues. Since crazes as the main failure mechanism for HIPS, well‐defined crack blunting does not expect to occur and theJcobtained by the original E813–81 based on the theoretically predicted blunting line is indeed slightly higher. The modified version of E813–81 by neglecting the blunting line inJcdetermination is believed to be more reasonable for HIPS. The nature of polymers will determine whether the crack tip will be blunted, partially blunted, or not blunted. ASTM E813–81 is appropriate for those polymers with a well‐defined blunted crack tip (such as elastomer‐modified polycarbonate), whereas the modified version of ASTM E813–81 seems better for those polymers with craze as the main failure mechanism (such as HIPS). Experimental results indicated that this hysteresis method is able to inherently adjust the crack blunting effect and therefore can be applied to any type of ductile polymer. © 1993 John Wiley & Sons, Inc.
Structural, mechanical, and thermal properties of extruded sheets of a liquid crystalline copolyester
Authors: Kyotani Mutsumasa , Kaito Akira , Nakayama Kazuo 
Published: April 2003

AbstractStructural, Mechanical, and thermal properties of extruded sheets of a liquid crystalline copolyester containing p‐hydroxybenzoic acid and 2‐hydroxynaphthoic acid were investigated using X‐ray diffraction measurements, differential scanning calorimetry, rheovibron measurements, and scanning electron microscopic observation. The extruded sheets of the thermotropic copolyester are composed of layered structures containing skin and core layers. A skin layer comprises fine fibrils oriented almost parallel to the extrusion direction. A core layer contains poorly oriented thicker fibrils or platelike structures. The orientation function of sheets and their tensile dynamic modulus parallel to the extrusion direction increase with increasing draw‐down ratio of the sheet. Annealing of the sheet caused the increases in the temperature and the heat of crystal—mesophase transition, the heat‐resistance to the mechanical tensiles properties, and the inherent viscosity of the polymer. The effect of annealing on the structural properties of the extruded sheet was discussed. © 1993 John Wiley & Sons, Inc.
The crystallization kinetics of filled poly(ethylene terephthalate)
Authors: Cheng Sen , Shanks Robert A. 
Published: April 2003

AbstractThe crystallization kinetics of poly(ethylene terephthalate) was measured under isothermal conditions by DSC in the presence of various fillers and with varying filler concentrations. The fillers used were carbon, titanium dioxide, glass fiber, and calcium carbonate. The kinetics was calculated using the slope of the crystallization vs. time plot, the times for 10% and 50% reduced crystallization, and the Avrami equation. Activation energies were determined from measurements under different isothermal temperatures. The fillers caused athermal nucleation to be inhibited as shown by the increased values of the Avrami exponent, n. Interactions between the polyester and filler were interpreted to reduce the mobility of the polymer in the melt. This decreased the rate of crystallization and increased its activation energy. The order of the filler effect in reducing crystallization was the following: no filler < carbon < titanium dioxide < glass fiber < calcium carbonate. The concentrations of filler were above those typically used for nucleation and more in the range expected for reinforcement or dilution of the polymer. © 1993 John Wiley & Sons, Inc.
The effects of high‐energy radiation on the surface chemistry of polystyrene: A mechanistic study
Authors: Onyiriuka E. C. 
Published: April 2003

AbstractIrradiation of polystyrene by 15 Mrad gamma or exposure to a 254 nm ultraviolet (UV) light source leads to surface oxidation of the polymer to depths greater than 10 nm as opposed to ∼ 3 nm depth offered by either plasma or corona‐discharge treatment. Oxidation increases linearly with UV irradiation time. More carboxyl (OCO) acid functionality, which increases with depth, was detected for UV‐treated polymer. With 3 Mrad gamma irradiation, only hydroxyl (CC) groups were detected by XPS as the surface‐oxidized species. ADXPS, GPC, and static SIMS data suggest that chain scission is the dominant degradation mechanism for polystyrene exposed to high gamma and UV radiation, respectively. © 1993 John Wiley & Sons, Inc.
Surface modification of epoxy resin with fluorine‐containing methacrylic ester copolymers
Authors: Kasemura T. , Oshibe Y. , Uozumi H. , Kawai S. , Yamada Y. , Ohmura H. , Yamamoto T. 
Published: April 2003

AbstractTo improve oil and water repellency, fluorine‐containing block copolymers, which were composed of methyl methacrylate (MMA), glycidyl methacrylate (GMA), and 1H, 1H, 2H, 2H‐heptadecafluorodecyl acrylate (PFA), were blended with an epoxy resin. It was expected that a glycidyl group would mesh with the epoxy resin by primary bonding, and the low surface energy fluorocarbon segment would absorb and orient to the exterior to fluorinate the surface. X‐ray photoelectron spectroscopy, contact angle, and peel strength of pressure‐sensitive adhesives for modified epoxy resin surface were determined. The amount of fluorine obtained via angular‐dependent ESCA investigation in the modified resin surfaces increased with the shallowing of the sampling depth. With increasing modifier content, the amount of fluorine in the modified resin surface layer increased, and the critical surface tension of modified resin surfaces and the peel strength of a silicone pressuresensitive adhesive affixed to the modified epoxy resin, decreased. A considerable amount of fluorine in the resin surface modified with GMA‐containing block copolymers remained after Soxhlet extraction, whereas in the surface modified with copolymer without GMA, more fluorine was extracted. It was extracted. It was shown that these copolymers were good surface modifiers to improve oil and water repellency. © 1993 John Wiley & Sons, Inc.
Application of SIMS in polymers and lignocellulosic materials
Authors: Hua Xujun , Kaliaguine Serge , Kokta Bohuslav V. 
Published: April 2003

AbstractSecondary Ion Mass Spectrometry (SIMS), a new surface analysis technique, has begun to be applied to the studies of organic macromolecule surface either for chemical imaging and functional group analysis or for the determination of molecular weight distribution. The instrumental conditions that are critical for obtaining a meaningful spectrum are discussed for polymers which have properties similar to lignocellulosic materials, i.e., they are thermally fragile and electrically insulating. Examples are given for qualitative and quantitative analyses. Possible uses of SIMS for characterization of lignocellulosic materials are suggested. © 1993 John Wiley & Sons, Inc.
Measurements of craze velocities in polystyrene‐polybutadiene blends
Authors: Spiegelberg Stephen H. , Argon Ali S. , Cohen Robert E. 
Published: April 2003

AbstractNormally brittle polystyrene (PS) can be toughened effectively by the inclusion of a few weight percent of low molecular weight polybutadiene (PB). The PB, which can be made to phase separate into submicron sized, randomly dispersed pools, locally plasticizes the glassy phase in the vicinity of a growing craze; the resulting reduction in craze flow stress and increased craze velocity lead to significant enhancement of toughness when strain rates are below approximately 10−1 s−1. Craze velocities were measured in PS containing 1 to 5 wt % of a low molecular weight PB (2300 g/mol). The results were compared to a version of the interface convolution mechanism for craze growth that has been modified to account for the localized plasticization effect of the low molecular weight diluent. Addition of 5 wt % PB led to craze velocities that are three orders of magnitude larger than observed for pure PS. The model deviated significantly from the experimental data at the higher and of the PB concentration range studied here, but it did exhibit the general form of the observed dependence of craze velocity on PB content. © 1993 John Wiley & Sons, Inc.
Catalytic grafting: A new technique for polymer‐fiber composites. III. Polyethylene‐plasma‐treated KevlarTM fibers composites: Analysis of the fiber surface
Authors: Wang Qi , Kaliaguine Serge , Ait‐Kadi Abdellatif 
Published: April 2003

AbstractIn this article, plasma‐treated KevlarTM fiber‐polyethylene composites prepared by the catalytic grafting technique were studied. The reactive groups COOH, OH, NH2 generated on the Kevlar fiber surface by oxygen plasma treatment were used to chemically anchor Ziegler‐Natta catalyst, which was then followed by ethylene polymerization on the fiber surface. The surface structure of the Kevlar fibers, untreated or treated by oxygen plasma, catalyst grafted, or ethylene polymerized, was characterized by X‐ray photoelectron spectroscopy (XPS), attenuated total reflection (ATR), and scanning electron microscopy (SEM). The morphology, interfacial behavior, and mechanical properties of the high‐density polyethylene (HDPE) composites reinforced by either catalytic grafted or ungrafted Kevlar fibers were investigated by means of differential scanning calorimetry (DSC), polarized light optical microscopy, tensile testing, and SEM. Special attention was devoted to the tensile properties of the composites in the direction transverse to the fibers. The experimental results show that oxygen plasma treatment increases the reactive site concentration on the fiber surface significantly and that the composites reinforced by catalytically grafted Kevlar fibers exhibit higher tensile strength both parallel and transverse to the fibers. The improved interfacial adhesion is attributed to the interfacial chemical bonding established by catalytic grafting. © 1993 John Wiley & Sons, Inc.
The transverse elastic modulus of fiber‐reinforced composites as defined by the concept of interphase
Authors: Sideridis E. 
Published: April 2003

AbstractA theoretical expression for the prediction of the transverse elastic modulus in fiber‐reinforced composites was developed. The concept of interphase between fibers and matrix was used for the development of the model. This model considers that the composite material consists of three phases, that is, the fiber, the matrix, and the interphase. The latter is the part of the polymer matrix lying at the close vicinity of the fiber surface. In the present investigation it was assumed that the interphase is inhomogeneous in nature with continuously varying mechanical properties. Different laws of variation of its elastic modulus and Poisson ratio were taken into account in order to define the overall modulus of the composite. Thermal analysis method was used for the estimation of the thickness of the interphase. The results obtained were compared with the respective values of other models as well as with experimental data. © 1993 John Wiley & Sons, Inc.
pH‐sensitivity of hydrogels based on complex forming chitosan: Polyether interpenetrating polymer network
Authors: Yao Kang De , Peng Tao , Goosen M. F. A. , Min Ji Mei , He Yu Yin 
Published: April 2003

AbstractThis article deals with a novel, semi‐interpenetrating polymer network (semi‐IPN), composed of crosslinked chitosan (cr‐CS) with glutaraldehyde (GA) and polyether. The pH responsibility of swelling data shows that swelling reaches a maximum at pH = 3.19 and a minimum at pH = 13. The concentration of chitosan acetic acid solution, the amount of crosslinking agent, and polyether, have effects on the swelling behavior of the network. Stimulating‐response of the semi‐IPN, induced by abrupt changes of pH between 1 and 13, is discussed as well. © 1993 John Wiley & Sons, Inc.
A kinetic study of the hydrolytic degradation of polyethylene terephthalate at high temperatures
Authors: Campanelli John R. , Kamal M. R. , Cooper D. G. 
Published: April 2003

AbstractThe hydrolytic depolymerization of molten PET in excess water was studied using a 2 L stirred pressure reactor at temperatures of 250, 265, and 280°C. Rate constants for hydrolysis are calculated from the initial rate data. At initial water: PET charge ratios (w/w) exceeding 5.1, essentially complete depolymerization to monomer is possible at 265°C. At lower water: PET initial charges, an equilibrium is established. The equilibrium constants are calculated for 2 g water/g PET at three temperatures. A kinetic model is proposed to describe the hydrolysis reaction. The model is shown to fit experimental data and to yield good predictions for the equilibrium concentration of carboxyl groups. Carboxyl‐group concentrations are measured using an end‐group analysis technique. Potentiometric titrations are carried out in one of two solvent systems, dimethylphenol:chloroform or dimethylsulfoxide, depending on the extent of hydrolysis. © 1993 John Wiley & Sons, Inc.