bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellulose‐based fibers from liquid crystalline solutions. III. Processing and morphology of cellulose and cellulose hexanoate esters
Authors: Davé Vipul , Glasser Wolfgang G. 
Published: April 2003

AbstractCellulose and a cellulose hexanoate ester (DS 0.69) exhibited liquid crystalline behavior in dimethylacetamide/lithium chloride and dimethylacetamide, respectively. The experimentally observed critical volume fraction (Vcp) of cellulose was lower than that predicted by Flory's theory, whereas the experimental and theoretical values of Vcp were within 70% of prediction for cellulose hexanoate. The Vcp value obtained for cellulose hexanoate was lower than that previously reported for cellulose acetate butyrate with a maximum degree of butyration (CAB‐3). This indicates that bulky substituents may lower Vcp values. Fibers were spun from isotropic and anisotropic solutions of cellulose and cellulose hexanoate by a dry jet/wet spinning method. There was an increase in mechanical properties through the isotropic to anisotropic transition with moduli reaching 152 g/d (20.8 GPa) for cellulose fibers. The formation of cellulose fibers with high modulus at large extrusion rates and large takeup speeds (draw ratio) is explained with molecular organization prior to coagulation. This unexpected enhancement is attributed to the air gap that exists in the dry jet/wet spinning process. Similar improvements were not observed for cellulose hexanoate fibers. This is explained with incomplete development of liquid crystalline structure at the solution concentrations from which the fibers were spun. © 1993 John Wiley & Sons, Inc.
Photocross‐linking of low‐density polyethylene. I. Kinetics and reaction parameters
Authors: Qu Bao Jun , Rånby Bengt 
Published: April 2003

AbstractThe kinetic characteristics and the reaction conditions of photocross‐linking of low‐density polyethylene (LDPE) in the melt have been studied using benzophenone (BP) and its derivatives such as 4‐chlorobenzophenone (4‐CBP) as photoinitiator and triallyl cyanurate (TAC) as cross‐linker. The efficiency of the photoinitiated cross‐linking system LDPEBP‐TAC and various factors affecting the cross‐linking process, such as photoinitiator and cross‐linker and their concentrations, irradiation time, temperature, and atmosphere, and UV light intensity were examined extensively by determining gel content, IR, and UV spectra. It has been found (i) that LDPE samples of 2–3 mm thickness are easily cross‐linked to a gel content of about 70% with a UV‐irradiation time of about 15 s under optimum conditions; (ii) that the photoinitiating system of a suitable initiator combined with a multifunctional cross‐linker such as 4‐CBP–TAC can enhance the efficiency of photocross‐linking reactions, especially by increasing the initial rate of cross‐linking; (iii) that photocross‐linking of LDPE should be carried out in the melt, which increases the penetration of UV light by decreasing the scattering by crystallites, and (iv) that the rate of cross‐linking is proportional to the square of the light intensity. An increase in light intensity can decrease the concentration of photoinitiator required to reach a certain rate of cross‐linking. The photocross‐linking of polyethylene is promising for industrial applications. © 1993 John Wiley & Sons, Inc.
The elastic and plastic mechanical responses of microcellular foams
Authors: Ozkul M. H. , Mark J. E. , Aubert J. H. 
Published: April 2003

AbstractMicrocellular foams were prepared by the thermally induced phase‐separation technique, which yields materials having very small cell dimensions (0.1–20μm). The polymers employed were isotactic polystyrene, polyacrylonitrile, poly(4‐methyl‐1‐pentene), polyurethane, and Lycra® and the resulting foams all had densities in the range 0.04–0.27 g cm−3. Values of Young's modulus and the collapse stress for these foams were measured and compared with predictions for conventional foams containing defects. Also investigated were plastic deformations, some time‐dependent behavior, and Poisson's ratio. © 1993 John Wiley & Sons, Inc.
Sorption and diffusion of organic esters into fluoropolymer membranes
Authors: Aminabhavi Tejraj M. , Munnolli Ravindra S. , Stahl William M. , Gangal Subhas V. 
Published: April 2003

AbstractA sorption gravimetric technique has been used to estimate the diffusion and thermodynamic parameters of four different VITON fluoropolymers in the presence of five ester molecules. Diffusion parameters have been obtained by assuming the Fickian transport and their concentration dependencies are studied. Fluorine contents of the fluoropolymers have significant effects on the membrane transport characteristics. © 1993 John Wiley & Sons, Inc.
Water‐soluble polymers. I. Synthesis of N‐succinimido (N) thiocarbonyl acrylamide and its polymerization: Grafting of this monomer and acrylamide onto poly(vinyl alcohol)
Authors: Devarajan R. , Arunachalam V. , Jayakumar E. , Selvi P. 
Published: April 2003

AbstractA new monomer, N‐succinimido (N) thiocarbonyl acrylamide is formed when succinic anhydride, thiourea, and acryloyl chloride are condensed in mole proportions at low temperatures. The monomer is polymerized and graft copolymerized onto poly(vinyl alcohol) using a potassium bromate‐thiourea redox system. Acrylamide is also similarly grafted to poly(vinyl alcohol) using the same initiator system. Grafting efficiencies of the monomers are determined from the elemental analyses data of the graft copolymers. Thermal behavior of the polymers are derived from the DSC thermograms of the polymers. © 1993 John Wiley & Sons, Inc.
Microhardness as a thermally activated process: Indentation time dependence for an amorphous copolyester
Authors: Lorenzo V. , Benavente R. , Pérez E. , Bello A. , Pereña J. M. 
Published: April 2003

AbstractVickers microharness, MH, measurements have been performed on samples of a plasticized amorphous copolyterephthalate with different diluent contents. The dependence of MH on contact time is explained in terms of the Eyring equation and it has been found that the activation volume increases abruptly in the vicinity of the glass transition. © 1993 John Wiley & Sons, Inc.
HPLC and 13C‐NMR study of carboxymethyl‐β‐(1 → 6)‐D‐gluco‐β‐(1 → 3)‐D‐glucan derived from saccharomyces cerevisiae
Authors: S̆oltés Ladislav , Alföldi Juraj , S̆andula Jozef 
Published: April 2003

AbstractSodium salt of carboxymethyl‐β‐(1 → 6)‐D‐gluco‐β‐(1 → 3)‐D‐glucan (CMG‐Na) was prepared from β‐D‐glucan isolated from baker's yeast (Saccharomyces cerevisiae). Three samples, Fractions I, II, and III, were further separated from the crude CMG‐Na derivative. For the physicochemical characterization of the separated fractions, the methods of high‐performance liquid chromatography (HPLC) in the size‐exclusion mode and carbon−13 nuclear magnetic resonance (13C‐NMR) spectroscopy were applied. The HPLC method revealed that the molecular weights, Mn, Mw, and Mz averages, of Fraction II were 9.71 × 104, 2.27 × 105, and 3.59 × 105 Da, respectively, whereas those of Fraction III were 1.52 × 104, 2.13 × 104, and 3.57 × 104 Da, respectively. The 13C‐NMR spectra of Fraction II showed a ratio of 3 : 1 for β−(1 → 3) / β−(1 → 6), whereas for Fraction III, the content of β‐(1 → 3) units was smaller. © 1993 John Wiley & Sons, Inc.
Separability of SO2 from SO2/N2 mixture through sulfoxide‐modified poly(vinyl alcohol) and cellulose membranes
Authors: Imai Kiyokazu , Shiomi Tomoo , Tezuka Yasuyuki , Itamochi Hiroko , Miya Masamitsu 
Published: April 2003

AbstractSeparability of SO2 from mixtures of SO2 and N2 gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t‐butyl, and phenyl vinyl sulfoxides. Of these sulfoxide‐modified polymers, the phenyl vinyl sulfoxide‐modified PVA membranes were found to give the best separation of SO2. In the phenyl vinyl sulfoxide modified PVA membranes, the permeability coefficient of SO2 increased with sulfoxide content while separability of SO2 was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO2 was about 170 at this sulfoxide content. © 1993 John Wiley & Sons, Inc.
Rate and extent of supercritical fluid extraction of additives from polypropylene: Diffusion, solubility, and matrix effects
Authors: Cotton N. J. , Bartle K. D. , Clifford A. A. , Dowle C. J. 
Published: April 2003

AbstractAnalytical extraction of additives from polymers using a supercritical fluid (SFE) is a promising alternative to liquid extraction. Factors affecting SFE with carbon dioxide of Irgafos 168 and Irganox 1010 from commercial polypropylene have been studied, with analysis of extracts by capillary supercritical fluid chromatography (SFC). A diffusion limited extraction model was investigated by measuring the rate of SFE as a function of pressure, particle size, flow rate, and temperature. The rate of extraction was found to fit the sum of exponential decays; results were also consistent with an extrapolation procedure to obtain the total mass of additive without exhaustive extraction. Derived diffusion coefficients for the additive in polypropylene differed from literature values by approximately two orders of magnitude apparently because of swelling of the polymer by sorbed carbon dioxide. The variation of extraction rate with pressure and flow rate confirmed the solubility limitation of proposed model. The rate of extraction increased between 20 and 140°C, then fell away at higher temperatures with the onset of melting. © 1993 John Wiley & Sons, Inc.
Study on the kinetics of lignin methylolation
Authors: Peng W. , Riedl B. , Barry A. O. 
Published: April 2003

AbstractThe kinetics of lignin (ammonium‐based lignosulfonate and sodium‐based lignosulfonate) methylolation were studied in solution by monitoring the rate of disappearance of form‐aldehyde and by using differential scanning calorimetry (DSC) techniques under an iso‐thermal program, at 20, 40, 50, and 60°C, respectively. The kinetic parameters obtained from these two methods agree with each other. The results show that the degree of lignin methylolation depends on the number and availability of reactive sites per C9 unit of lignin. Lignin methylolation has a lower activation energy and a lower preexponential factor than that of phenol methylolation. Lignins took a shorter time to reach complete methylolation than did phenol at the low temperatures used here. © 1993 John Wiley & Sons, Inc.
Solid‐State NMR characterization of a superactive supported ziegler–natta catalyst
Authors: Vizzini James C. , Shi J.‐F. , Chien James C. W. 
Published: April 2003

AbstractThe formation of CH‐type catalysts has been investigated by high‐resolution and solid‐state NMR. These catalysts are prepared from a soluble MgCl2 and 2‐ethyl‐1‐hexanol adduct (MgCl2·3EH) by reaction with phthalic anhydride (PA) to form dioctylphthalate (DOP) and then with TiCl4 in the presence of di‐i‐butylphthalate (BP). In the model systems MgCl2·3EH/PA, MgCl2/BP, and MgCl2/TiCl4/BP, the ester is complexed with MgCl2 and /or TiCl4 in two or more states. Only single‐ester CO and OCH2 resonances are seen in TiCl4/BP, probably due to exchange of ester coordinations. CH‐catalysts prepared by three different procedures exhibit a single mode of bonding for the ester. The chemical shift values are consistent for ester complexed with MgCl2. The most active and stereoselective catalyst has the most shielded chemical shift values for the CO and —OCH2— carbons, shortest TH1 and TH1p, and longest TCH relaxation times. These parameters change monotonically with the decrease of activity and stereoselectivity of the catalyst preparation. © 1993 John Wiley & Sons, Inc.
Transport and dielectric properties of poly(ethylene terephthalate) as determined via electrochemical techniques
Authors: Kloppers M. J. , Bellucci F. , Latanision R. M. , Brennan J. E. 
Published: April 2003

AbstractThe electrochemical impedance spectroscopy (EIS) technique was used to evaluate the water transport (diffusion and equilibrium water uptake) and the dielectric properties of free‐standing poly(ethylene terephthalate) (PET) membranes at 40°C. Permeability and diffusion coefficients were also obtained using the Payne cup method and the MacBain quartz spring balance to assess the reliability of the EIS method when compared to other techniques. In addition, an electromigration (dc) technique was used to estimate the NaCl diffusion coefficient across PET films. Results obtained indicate that PET is highly permeable to water and much less permeable to salt. The water diffusion coefficient, D, varies from 2.11× 10−9 to 9.97× 10−9 cm2s−1 for thicknesses between 22 and 205μm, whereas the equilibrium water uptake, W, varies from 0.54 to 0.95 wt % for the same given range of thicknesses. The average calculated dielectric constant of the free‐standing PET films is 3.6. An estimate of the NaCl diffusion coefficient, Ds, is 9.34× 10−14 cm2s−1. Transport properties results obtained via the electrochemical technique are in reasonable agreement with those obtained with the classical gravimetric method. © 1993 John Wiley & Sons, Inc.
Modification of polythioesters from bis (4‐mercaptophenyl) ether with adipoly, sebacoyl, and isophthaloyl chlorides with the use of 2,2‐bis (4‐hydroxyphenyl) propane
Authors: Podkościelny Wawrzyniec , Wdowicka Danuta 
Published: April 2003

AbstractModification of polythioesters obtained by interfacial polycondensation bis (4‐mercapto‐phenyl) ether and adipoyl, sebacoyl, or isophthaloyl chlorides with the use of 2,2‐bis (4‐hydroxyphenyl) propane (bisphenol A) has been described. Polycondensates with 10, 50, or 90% molar of bisphenol A in relation to dithiol were obtained under the same conditions as those established earlier as optimal for synthesis of polythioesters from dithiol and adipoyl, sebacoyl, or isophthaloyl chlorides. The structure of all the polycocondensates was determined by infrared spectra and X‐ray analysis. Thermal and some mechanical and electrical properties for polycocondensates containing 50% molar bisphenol A in relation to dithiol were defined. © 1993 John Wiley & Sons, Inc.
Effects of mean stress and frequency on fatigue crack propagation in rubber‐toughened polycarbonate/copolyester blends
Authors: Moskala Eric J. 
Published: April 2003

AbstractThe effects of an impact modifier, mean stress level, and test frequency on the fatigue crack propagation rate in a miscible amorphous blend of polycarbonate and a copolyester were investigated. Experiments were performed on a servohydraulic testing machine, in load control, using a sinusoidal waveform. The addition of a small amount of impact modifier improved the fatigue resistance of the blend. Fatigue crack propagation rate, da/dN, at any value of crack tip stress intensity factor range, ΔK, in the impact modified blend, was more than a factor of 20 lower than that in the untoughened blend. Significantly more plastic deformation occurred on the fracture surface of the toughened blend than on that of the untoughened blend. The effect of mean stress level on da/dN was determined by varying the minimum‐to‐maximum stress ration, R, from 0.1 to 0.5. Plots of log (da/dN) vs. δK showed that the fatigue crack propagation rate was unaffected by R and, consequently, the mean stress level. The effect of frequency on da/dN was determined by varying the frequency from 0.25 to 25 Hz. The fatigue resistance of the untoughened blend was not affected by test frequency, whereas the fatigue resistance of the toughened blend increased with increasing frequency. Hysteretic heating at the crack tip was minimal at the highest frequency. The frequency sensitivity of the toughened blend was explained in terms of creep‐assisted crack growth. © 1993 John Wiley & Sons, Inc.
Viscosities of ethylene–propylene–diene terpolymer blends in oil
Authors: Rubin Isaac D. , Kapuscinski Maria M. 
Published: April 2003

AbstractViscosities were obtained on oil solutions of two ethylene–propylene–diene terpolymers (EPDMs) and their blends. For the amorphous terpolymer with 59 mol% ethylene, intrinsic viscosities were constant between–10 and 40°C. The viscosities decreased rapidly at low temperature for blends of this material with as little as 20 wt % of a slightly crystalline EPDM with 79 mol% ethylene. Dynamic viscosity measurements on 1.0% solutions of blends likewise gave considerably smaller values at low temperature than measurements on an amorphous EPDM of similar molecular weight. The data are in agreement with the view that longer ethylene sequences that crystallize in the bulk polymer can organize in oil into ordered domains that interfere less with flow than the disordered amorphous polymer regions. © 1993 John Wiley & Sons, Inc.
Characterization and radical polymerization of (E‐CE)C/AA mesomorphic solutions
Authors: Jiang S. H. , Huang Y. 
Published: April 2003

AbstractEthyl–cyanoethyl cellulose (E–CE)C/poly (acrylic acid) (PAA) composites were prepared by polymerizing acrylic acid (AA) in (E–CE) C/AA cholesteric liquid crystalline solutions. The morphology and structure and the compatibility of composites prepared in different conditions were studied by small‐angle light scattering (SALS), differential scanning calorimetry (DSC), X‐ray spectrometry, polarizing microscopy, and electron microscopy. Ho‐mogeneous composites with the cholesteric structure could be obtained by photopolymerization. During the photopolymerization, however, the morphology of the liquid crystalline domains became crylindric and the axial direction of the cylindric domain was at an angle of about 45° to the layers of the ordered molecular chains. The polymerization initiated by azobisisobutyronitrile (AIBN) resulted in the phase separation. The morphology of the liquid crystalline domains was maintained although the cholesteric structure of the composite was partly destroyed. © 1993 John Wiley & Sons, Inc.
Flame‐retardant EPM compositions for cable insulation, containing Br‐N‐S fire retardants
Authors: Karaivanova M. S. , Gjurova K. M. 
Published: April 2003

AbstractThe influence of ammomnium salts of oligomeric Br‐N‐containing sulphonic acids and some inorganic fire retardants on the physico‐mechanical properties, flammability characteristics, and thermooxidative degradation of EPM compositions for insulation of ship cables has been studied. The ternary system consisting of bromosulphaminic acid bromonitrosulphonic acid and antimony trioxide in 6.6 : 3.4 : 4–5 mass ratio has been found to exhibit an addictive effect on the fire retardancy. A correlation between the flammability characteristics and some thermal properties of EPM compositions has also been established. The organic fire retardants of certain concentrations in EPM compositions have been found to exhibit a positive plasticizing performance. © 1993 John Wiley & Sons, Inc.
Thermal shock test of IC packages sealed with epoxy molding compounds filled with irregular‐shaped silica particles
Authors: Nakamura Yoshinobu , Yamaguchi Miho , Tanaka Atsushi , Okubo Masayoshi 
Published: April 2003

AbstractThe effect of the filler silica particle size on the properties of integrated circuits (IC) packages sealed with an epoxy molding compound was studied. For this purpose, two kinds of epoxy molding compounds filled with irregular‐shaped silica particles having mean sizes of (A) 16 μm and (B) 5 μm were prepared. The fracture toughness (Kc) of cured A was higher than that of cured B, but the flexural strength of cured A was lower than that of cured B, i.e., cured A and B had opposite physical properties. The thermal shock test was carried out in which IC packages were repeatedly dipped alternately in −65 and 150°C liquids and package cracking was observed. The thermal shock property of the IC package sealed with A was superior to that sealed with B. There was a good relationship between the thermal shock test property and Kc value. © 1993 John Wiley & Sons, Inc.
Exudation processes in hydrogenated bisphenol‐a‐based epoxy coatings: Spectroscopic study
Authors: He Mingbo , Urban Marek W. , Bauer Ronald S. 
Published: April 2003

AbstractSurfaces of hydrogenated bisphenol‐A (DGEHBPA)‐based epoxy resins cross‐linked with polyamide based on dimer fatty acid and triethylenetetramine coatings were studied using ATR FTIR spectroscopy. These studies illustrate that for nonpigmented coatings the surface species resulting from the coatings' exposure to ambient conditions generate noncross‐linked epoxies, whereas for pigmented coatings, polyamide is the primary surface component. The presence of these species is attributed to the adsorption on pigment particles and small, yet significant amounts in nonstoichiometry changes introduced into the system during formulation. © 1993 John Wiley & Sons, Inc.
The role of crystallization kinetics in the development of the structure and properties of polypropylene filaments
Authors: Lu F. M. , Spruiell J. E. 
Published: April 2003

AbstractThe processing, structure, and properties of filaments melt spun from three polypropylenes with similar rheology but substantially different crystallization kinetics were studied. The crystallization kinetics of the homopolymer was increased by the addition of a nucleating agent, whereas slower crystallization kinetics was obtained through a small amount of random copolymerization with ethylene. The relative crystallization kinetics of these three polymers was examined under quiescent conditions using differential scanning calorimetry. The technique of on‐line diameter and birefringence measurement was used to show the characteristics of the on‐line crystallization of the different resins. It was found that changing the quiescent crystallization kinetics by either the addition of a nucleating agent or through copolymerization with ethylene can produce profound effects on the structure and properties of polypropylene as‐spun filaments when they are spun under relatively low stress and low takeup velocity conditions. Higher takeup velocities and spinline stresses reduce the effect of differences in quiescent crystallization due to the influence of on‐line stress‐induced (molecular orientation‐enhanced) crystallization. © 1993 John Wiley & Sons, Inc.
Distribution of onium salt photoinitiators in a two‐phase epoxy system
Authors: Covert Kathleen L. , Russell David J. 
Published: April 2003

AbstractA phase‐separated epoxy blend containing a sulfonium salt cationic photoinitiator was studied. The onium salt was found to be preferentially soluble in one of the resins of the system. Scanning electron microscopy and microprobe analyses were done to determine the concentration distribution in the phases and the results compared to a model based on liquid extraction distribution coefficient behavior. Finally, the photolithographic behavior of various blends of the epoxy resins is discussed and the results compared to the behavior predicted by the photoinitiator distribution. © 1993 John Wiley & Sons, Inc.
Epoxy polymerization initiated by BF3–amine complexes. I. Synthesis and characterization of BF3–amine complexes and BF3–amine complexes dissolved in γ–butyrolactone
Authors: Chabanne Philippe , Tighzert Lan , Pascault Jean‐Pierre , Bonnetot Bernard 
Published: April 2003

AbstractWith the aim of identifying the species responsible for initiating epoxy homopolymerization, several BF3–amine complexes were synthesized. Their characterization was accomplished by several spectroscopic techniques, notably by 11B‐NMR. In these polymerizations, the active species appears to be the R–NHBF salt and not the BF3–amine complex. The interactions between BF3–amine complexes and the γ–butyrolactone were also studied by FTIR. © 1993 John Wiley & Sons, Inc.