bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cure kinetics of a flexible aromatic dicyanate with schiff base structure
Authors: Wang Ying‐Hung , Hong Yeng‐Long , Hong Jin‐Long 
Published: April 2003

AbstractPolycyclotrimerization of a flexible aromatic dicyanate with a Schiff base structure was studied by means of differential scanning calorimetry (DSC). The study on dynamic DSC evaluated an apparent activation energy (Ea) of 75.8 kJ/mol and autocatalytic first‐order kinetics with rate expression Af(α) = 1.96 X 105 (1 + 4.39 α) (1 ‐ α) min−1. The kinetic feature can be explained by a proposed mechanism consisting of hydroxyl‐catalyzed and autocatalytic paths. The lower value of Ea compared with other aromatic dicyanates is due to the electron‐withdrawing linkage of the inherent imine (—CHN) structure. The kinetic feature is affected by the content of the residual impurities (e.g., phenols or absorbed water) in the corresponding sample. © 1995 John Wiley & Sons, Inc.
Studies on thermodynamic compatibility of nitrile rubber and polybutadiene by inverse gas chromatography
Authors: Tripathi V. S. , Lal Darshan , Sen A. K. 
Published: April 2003

AbstractInverse gas chromatography technique has been used to study the thermodynamic compatibility of the industrially important elastomers polybutadiene (BR) and polybutadiene copolymerised with acrylonitrile (NBR). The NBR used in this study had nitrile contents of 18 and 34%. The ratio of BR/NBR in blends varied between 1 and 0.25 in both cases and retention volume of twelve probes was measured at 80°C. The Flory‐Huggins interaction parameter X′23, computed using a standard procedure, and also the interaction parameter B23 showed that BR and NBR are incompatible in all compositions and that incompatibility increases with nitrile content. © 1995 John Wiley & Sons, Inc.
Correlation between microstructure and physical properties in styrene–ethylene copolymers
Authors: D'Aniello Concetta , De Candia Francesco , Oliva Leone , Vittoria Vittoria 
Published: April 2003

AbstractThe structural organization and the physical properties of a new copolymer styrene–ethylene have been analyzed. The composition was 80% of ethylene units, corresponding to 52% in weight, with a distribution of styrene units in the chain implying the absence of styrene–styrene sequences. The length of the polyethylene chains, limited by the insertion of the phenyl group, is not sufficient to allow good crystallization, and in fact the copolymer shows a very low crystailinity, of the order of 5–10%, and a broad melting range, with a peak centered at 120°C. The small crystalline domains are segregated into an amorphous matrix, producing a thermoplastic elastomer. The mechanical properties at large deformation were analyzed at different temperatures. The copolymer shows good elastic properties, in terms of deformation reversibility as well as of energy dissipation in the hysteresis cycles. Also the stress level and the elastic recovery are very good, if compared with others thermoplastic elastomers. © 1995 John Wiley & Sons, Inc.
Synthesis of chiral polymers having camphanediol moieties and their applications on the optical resolution of some racemates
Authors: Liu Jui‐Hsiang , Tsai Fu‐Ren , Lai Yuh‐Chung 
Published: April 2003

AbstractOptically active exo‐exo‐2,3‐camphanediol (CPO) (3) was synthesized from (+)‐camphor. Chiral polymers poly(CPO‐co‐TDI) (6) and poly(CPO‐co‐IPDI) (7) were synthesized by the step polymerization of chiral compound CPO (3) with toluene‐2,4‐diisocyanate (TDI) and isophorone diisocyanate (IPDI). To investigate the stereo structure of the chiral polymers, two kinds of model compounds, exo‐exo‐2,3‐di[(phenylamido)oxy]camphane (4) and exo‐exo‐2,3‐di[(propylamido)oxy]camphane (5), related to polymers (6) and (7) were synthesized. Chiroptical characteristics and stereo structures of the chiral polymers were investigated using a circular dichroic spectrometer. The results obtained in this investigation suggest that the chiral polymers (6) and (7) have no one‐handed helix conformation. The optical resolution ability as chiral adsorbent for HPLC of the chiral polymers was investigated. It was found that chiral polymers (6) and (7) are effective for the optical resolution of some racemates. © 1995 John Wiley & Sons, Inc.
In vitro monocyte adhesion and activation on modified FEP copolymer surfaces
Authors: Azeez A. , Yun J. , DeFife K. , Colton E. , Cahallan L. , Verhoeven M. , Cahallan P. , Anderson J. M. , Hiltner A. 
Published: April 2003

AbstractThe functional group content and the ionic state of functional groups present on a series of surface modified poly(tetrafluoroethylene/hexafluoropropylene) (FEP) copolymers were characterized by electron spectroscopy for chemical analysis (ESCA), contact angle, and attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR). Additionally, after a protein was preadsorbed on these surfaces, in vitro cell (monocyte) adhesion and activation were analyzed. The two proteins in this study were fibrinogen and immunoglobulin‐G (IgG). Four modified FEP surfaces were prepared with increasing concentration of carboxyl groups relative to amide groups; ESCA was used to quantify the functional group content. To characterize the ionic state of the functional groups at physiological pH (7.1), the ATR‐FTIR spectra were collected at various pH levels. Collectively, the contact angle, ESCA, and ATR‐FTIR results suggested that the amide groups were unprotonated and the carboxyl groups were ionized at the physiological pH. The results from the in vitro studies showed that on the fibrinogen preadsorbed surfaces, monocyte adhesion was higher and monocyte activation was lower on the three surfaces that contained carboxyl groups compared to the FEP surface that had only amide groups. Conversely, the results indicated that the surface chemistry had no significant effect on monocyte adhesion or activation on the IgG preadsorbed surfaces. © 1995 John Wiley & Sons, Inc.
Blends of isotactic and atactic poly(lactide). I. Effects of mixing ratio of isomers on crystallization of blends from melt
Authors: Tsuji Hideto , Ikada Yoshito 
Published: April 2003

AbstractPoly(L‐lactide) (PLLA) and poly(DL‐lactide) (PDLLA) blends were crystallized from the melt and their crystallization behaviors and morphologies were investigated using differential scanning calorimetry and polarizing microscopy. PLLA could crystallize from the melt in the presence of PDLLA when the PLLA content in the blend (XPLLA) was higher than 0.2. Spherulites were formed when XPLLA was between 0.6 and 1. The radius of the spherulites formed in the presence of PDLLA was larger than that of nonblended PLLA, probably because the coexisting PDLLA reduced the density of nuclei for the spherulites. Small crystallite assemblies were formed when XPLLA was between 0.2 and 0.5, and grew spherically from the nuclei when XPLLA was 0.5. Isotactic PLLA and atactic PDLLA seem to be miscible prior to crystallization, but PDLLA will be trapped between the lamellae of the spherulites or spherulitic assemblies during crystallization. PDLLA delayed the induction for crystallization of the blends. In spite of different morphology, the melting temperature and crystallinity of PLLA remained virtually constant when annealing was conducted for 600 min at XPLLA between 0.5 and 1. © 1995 John Wiley & Sons, Inc.
Surface properties of fluorinated polyimides exposed to VUV and atomic oxygen
Authors: Rasoul Firas A. , Hill David J. T. , Forsythe John S. , O'Donnell James H. , George Graeme A. , Pomery Peter J. , Young Philip R. , Connell John W. 
Published: April 2003

AbstractThe effect of atomic oxygen flux and VUV radiation alone and in combination on the surface of fluorinated polyimide films was studied using XPS spectroscopy. Exposure of fluorinated polyimides to VUV radiation alone caused no observable damage to the polymer surface, while an atomic oxygen flux resulted in substantial oxidation of the surface. On the other hand, exposure to VUV radiation and atomic oxygen in combination caused extensive oxidation of the polymer surface after only 2 min of exposure. The amount of oxidized carbon on the polymer surface indicated that there is aromatic ring‐opening oxidation. The changes in the O1s/C1s, N1s/C1s, and F1s/C1s ratios suggested that an ablative degradation process is highly favorable. A synergistic effect of VUV radiation in the presence of atomic oxygen is clearly evidenced from the XPS study. The atomic oxygen could be considered as the main factor in the degradation process of fluorinated polyimide films exposed to a low earth orbit environment. © 1995 John Wiley & Sons, Inc.
Some properties of aqueous solutions of poly[(maleic acid)‐alt‐(p‐sulfostyrene, styrene)]
Authors: Jarm V. , Kovaĉ‐filipović M. , Ŝegudović N. 
Published: April 2003

AbstractBy sulfonation of poly[(maleic anhydride)‐alt‐styrene] in mild conditions (SO3/triethylphosphate, 298 K) a series of poly[(maleic acid)‐alt‐(p‐sulfostyrene, styrene)] have been prepared having the same average chain length but various content of p‐sulfostyrene units (from 18 to 83 mol %). A behavior of diluted aqueous solutions of two polyelectrolyte series (polyacids and Na‐salts) has been compared, using viscosimetric, conductometric, and potentiometric measurements, and taking into consideration the degree of sulfonation and the kind of counterions (H+, Na+). Although the values of intrinsic viscosities [η] and equivalent conductivities λ of two copolymer series belong to two different ranges, in polyacid series they increase with increasing the degree of sulfonation, while in Na‐salt series they decrease. According to the potentiometric titration and reduced viscosity data, the intensity of conformational chain transitions of sulfonated polycids also decreases with increasing the degree of sulfonation. The noticed effects are related to structural characteristics of functional copolymers, gradual increase of a charge density along the chains, lower mobility of the Na‐salts, and to a diminished hydrophobicity of styrene units due to sulfonation. © 1995 John Wiley & Sons, Inc.
Studies on co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyester: Thermomechanical and thermodynamic properties
Authors: Shinn Ted‐Hong , Lin Chen‐Chong 
Published: April 2003

AbstractA series of co[poly(ethylene terephthalate‐p‐oxybenzoate)] thermotropic copolyesters were prepared by the copolymerization of poly(ethylene terephthalate) (PET) as moiety (II) and p‐acetoxybenzoic acid (POB) as moiety (I). The polymeric products obtained were subjected to solid‐state polymerization. Characterization of the copolyesters by thermomechanical analysis shows that properties such as the coefficient of thermal expansion, transition temperature, and maximum softening rate temperature varied directly as a function of composition as well as did solid‐state polymerization time. All thermomechanical data were found to increase with the solid‐state polymerization time due to the increase in the degree of polymerization and the effect of annealing. The coefficient of thermal expansion behaves in a manner that is interpretable by the crystalline state of the copolyester. The relationship between the free‐volume fraction and thermodynamic properties is further correlated for a more comprehensive discussion on its molecular arrangements. © 1995 John Wiley & Sons, Inc.
Micellar effect on the polymerization. III. kinetics of polymerization of acrylonitrile initiated by Ce(IV)–glucose system in presence of cationic micelles
Authors: Panda A. , Singh B. C. 
Published: April 2003

AbstractThe micellar effect on the kinetics of ceric ion‐initiated polymerization of acrylonitrile (AN) in the presence of glucose was studied in the temperature range 40‐50°C. The effects of concentration of the metal ion, monomer, sulfuric acid, substrate (glucose), emulsifier, some inorganic salt, and organic solvent on the rate of polymerization (Rp) were also investigated. The remarkable features of the investigation involve the enhancement of Rp in the presence of a micelle, the derivation of the rate expression for the above system along with the calculation of activation energy, and prediction of optimum conditions. Comparison of the rates for a micellar medium with those for the aqueous medium indicates that cationic micelles exert an accelerating influence on the rates of polymerization. © 1995 John Wiley & Sons, Inc.
Potassium permanganate/thioureadioxide redox system‐induced grafting of methacrylic acid onto loomstate cotton fabric
Authors: Abdel‐Hafiz S. A. 
Published: April 2003

AbstractGraft polymerization of methacrylic acid (MAA) to loomstate cotton fabric using the KMnO4/thioureadioxide system as the initiator was studied under different polymerization conditions. The polymerization reaction was assessed with respect to graft yield, homopolymer, total conversion, and graft efficiency. The magnitude of each of these characteristics was found to depend upon parameters such as concentrations of KMnO4, thioureadioxide, and MAA as well as liquor ratio, reaction time, and temperature of polymerization. Based on a detailed investigation of these parameters, the optimal condition for grafting is KMnO4 0.045 g/L, thioureadioxide 0.03 g/L, material to liquor ratio 1 : 30, MAA 100% (owf), temperature 80°C, and time 60 min. A reaction mechanism for the polymerization reaction is also reported. © 1995 John Wiley & Sons, Inc.
Recognition of amino acids by membrane potential and circular dichroism of immobilized albumin membranes
Authors: Hara Mariko , Higuchi Masahiro , Minoura Norihiko , Higuchi Akon 
Published: April 2003

AbstractThe shifts in membrane potential, caused by the injection of some amino acids into a permeation cell, were measured using immobilized serum albumin membranes at isoelectric points of the amino acids. The effective fixed charge density was estimated to decrease after the injection of alamine, phenylalanine, and tryptophan and to increase after the injection of serine. The change in the fixed charge density originated from the conformational change of the immobilized albumin membranes induced by the binding between the albumin and amino acids in the membranes, since the conformational change of the immobilized albumin membranes induced by the binding of the amino acids to the serum albumin was observed from circular dichroism measurements. There was found, however, some discrepancy between the conformational change of the serum albumin in the albumin membranes detected by the membrane potential measurements and the circular dichroism measurements. This is explained by the fact that the circular dichroism measurements detect the increase or decrease in the α‐helix, β sheet, and random coil contents; however, they do not always contribute to the detection of the change in the charge density due to the presence of the amino acid in the albumin membranes. © 1995 John Wiley & Sons, Inc.
Solubility parameters of polymers from swelling measurements at 60°C
Authors: Chee K. K. 
Published: April 2003

AbstractThe swelling behavior of the networks of natural rubber, an epoxidized natural rubber, low‐density polyethylene, polystyrene, and poly(methyl methacrylate) are studied in six classes of solvents at 60°C. The data of the swelling coefficient are successfully treated by a modified version of the empirical equation proposed by Gee, as to determine the solubility parameter of a polymer, δ2. It is found that increasing the temperature would decrease the δ2's of these polymers with a common rate of 0.02 (J/mL)1/2/K. A semiempirical model is proposed to rationalize the present finding satisfactorily. © 1995 John Wiley & Sons, Inc.
Production of polystyrene particles via aerosolization
Authors: Norasetthekul Somchintana , Gadalla Ahmed M. , Ploehn Harry J. 
Published: April 2003

AbstractAerosolization of polystyrene solutions followed by drying in a tubular furnace produced submicron‐sized polystyrene particles. Characterization using x‐ray diffraction, scanning electron microscopy (SEM), and infrared spectroscopy (FT‐IR) revealed that the particles were amorphous, spherical, and free of residual solvent. The average particle size and size distribution varied with furnace temperature, the initial polystyrene solution concentration, and solvent type. The particles' BET‐based specific surface area depended upon these parameters as well as the carrier gas flow rate. Analysis of the competing rates of convection, solvent evaporation, droplet collisions, and polymer diffusion help to rationalize the results. The dependence of the solvent evaporation rate on temperature controls the particle diameter, but droplet coalescence cannot be ignored. Long residence times and high furnace temperatures softened the particles; after filtration, polymer diffusion between solid particles produced visual evidence of partial coalescence. © 1995 John Wiley & Sons, Inc.
pH‐induced swelling kinetics of polyelectrolyte hydrogels
Authors: Chu Y. , Varanasi P. P. , McGlade M. J. , Varanasi S. 
Published: April 2003

AbstractThrough swelling experiments on polyelectrolyte (HEMA/DMA) hydrogels, pH‐induced swelling kinetics is found to be best described by a diffusion–mechanical relaxation incorporated model. The theory of equilibrium swelling is quantitatively combined into the model of swelling kinetics. By doing so, the advantage is taken of applying relatively more matured knowledge of gel swelling thermodynamics to predict less knowledgeable dynamic behavior of gels. © 1995 John Wiley & Sons, Inc.
FRP composites based on different types of glass fibers and matrix resins: A comparative study
Authors: Ghosh Premamoy , Bose Nripati Ranjan 
Published: April 2003

AbstractFlexural properties, impact energy, heat deflection temperature, and resistance to thermal and hydrothermal degradation of composites based on E‐glass and N‐glass fibers as the reinforcing agents, and epoxy, unsaturated polyester, phenolic, and epoxy‐phenolic resin systems as the matrix materials were studied and compared. As a reinforcing agent E‐glass fiber is superior to N‐glass fiber, particularly with respect to development of flexural strength and modulus, impact strength, and thermal resistance; N‐glass fiber, however, imparts to the composites substantially higher resistance to hydrothermal degradation under boiling conditions in different chemical environments. For use of both E‐glass and N‐glass fibers as reinforcing agents, the general order of resistance to hydrothermal degradation for the composites based on different matrix resins is epoxy > phenolic > unsaturated polyester resin. Incorporation of a low dose of a rubbery polymer, such as styrene butadiene rubber (0.1–0.2%) and liquid polybutadiene (0.5–0.75%), in unsaturated polyester resin as the matrix resin measurably enhances impact energy of the composite. © 1995 John Wiley & Sons, Inc.
Adhesion promotion at high temperature for epoxy resin or polyimide onto metal by a two‐component coupling system of polybenzimidazole and 4‐aminophenyl disulfide
Authors: Xue Gi , Wang Yongxia , Chen Yiyuan , Tsai Shingsan , Jiang Lusha 
Published: April 2003

AbstractA two‐component coupling agent layer consisting of polybenzimidazole and 4 aminophenyl disulfide showed better anticorrosive performance and higher adhesive strength for copper and resins than did each single component even at high temperature. © 1995 John Wiley & Sons, Inc.
Preparation of poly(vinylidene fluoride)–polypyrrole composite films by electrochemical synthesis and their properties
Authors: Bhat N. V. , Geetha P. , Pawde Sunita , Nallathambi R. 
Published: April 2003

AbstractComposite films of poly(vinylidenc fluoride–polypyrrole (PVDF–PPy) were prepared by electrochemical polymerization of pyrrole on a very thin PVDF matrix film (∼ 0.5 μm). The polymerization was carried out in aqueous media using stainless steel, coated with PVDF matrix, as a working electrode, and p‐toluene sulfonate (PTS), as a dopant. The films were prepared at different voltages for different durations of time in order to optimize the conditions of composite formation. The resulting films were characterized by studying IR spectra, conductivity, SEM, XRD, and tensile strength measurements. The mechanical properties of the composites were found to have improved, while the conductivity remained more or less same as that of pure PPy. © 1995 John Wiley & Sons, Inc.
Structure of poly(ε‐caprolactam) obtained in anionic bulk polymerization
Authors: Mateva R. , Delev O. , Kaschcieva E. 
Published: April 2003

AbstractThe nascent structures of poly(ε‐caprolactam) (N6), obtained during anionic polymerization in bulk in the presence of different additives, were investigated. The experimental data show that both the type and the quantity of activator influence significantly the process of polymerization as well as the chemical and the physical structures of N6. By means of WAXD, DSC, IR, light and transmission microscopy (TEM), and electron microdiffraction (ED) the changes in the morphological and the crystal structure were followed. The observed alterations in the physical structures of N6 samples are explained on the base of changes in the chemical structure and mobility of the polymer chains. © 1995 John Wiley & Sons, Inc.
Accurate description of intrinsic viscosity changes under polymer degradation: Narrow schulz distributions
Authors: Shyichuk A. V. 
Published: April 2003

AbstractFor the Shulz distributions with weight—polydispersity from 1.4 to 2.0, the following equation is correct: ln [η] = ln [η]0 − a{ln P0 + DD − ln[PF − P0) × exp(−1.2 × DD)]}. Here, P0 and PF are viscosity–polydispersities of the initial molecular weight distribution (MWD) and the Flory distribution, respectively; a is the Mark–Houwink exponent; and DD = ln(Mn0/Mn). For more narrow MWDs, the complicated equation is required: ln [η] = ln[η]0 − a{ln P0 + DD − ln[PF − (PF − P0 × exp(−0.9 × DD − 0.28 × DD2)]}. The inaccuracy of these equations is less than 1.5%. © 1995 John Wiley & Sons, Inc.
Radiography of rabbit articular cartilage with diffraction‐enhanced imaging
Authors: Muehleman Carol , Chapman L. Dean , Kuettner Klaus E. , Rieff Joel , Mollenhauer Juergen A. , Massuda Koichi , Zhong Zhong 
Published: April 2003

AbstractArticular cartilage of synovial joints is not visible with conventional X‐ray imaging. Hence, the gradual degeneration and destruction of articular cartilage, which is characteristic of degenerative joint diseases, is only detected at a late stage when the cartilage is lost and the joint space that it once occupied narrows. The development of an X‐ray imaging technique that could detect both the degenerative cartilage and bone features of joint diseases is of special interest. Here we show, for the first time, that a high‐contrast imaging technique, diffraction‐enhanced X‐ray imaging (DEI), allows the visualization of articular cartilage of both disarticulated and articulated rabbit knee joints. Furthermore, a single cartilage lesion can be visualized within an intact joint. The results suggest that DEI has the potential to be of use in the study of cartilage degeneration. Anat Rec Part A 272A:392–397, 2003. © 2003 Wiley‐Liss, Inc.