bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and properties of cationic membranes obtained by radiation grafting of methacrylic acid onto PTFE films
Authors: Hegazy El‐Sayed A. , Taher N. H. , Kamal H. 
Published: April 2003

AbstractCationic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly(tetrafluoroethylene) (PTFE) films followed by alkaline treatment to confer ionic character in the graft copolymer. The complete inhibition of homopolymerization of MAA by using ammonium ferreous sulfate (Mohr's salt) failed. However, the addition of 0.5 wt % FeCl3 to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. It was found that the graft polymerization proceeded successfully in presence of methanol/water mixture (30/70 wt %), and much higher degrees of grafting were obtained as compared with those in the presence of other diluents used here. The influence of irradiation atmosphere (air, N2 gas, and vacuum) on the grafting process was investigated. The dependence of the grafting rate on MAA concentration was found to be of orders 2.9 and 0.72 in the presence of 0.5 wt % Mohr's salt or 0.5 wt % FeCl3, respectively. This grafting system proceeds by the front mechanism. Investigation of mechanical properties, electrical conductivity, and swelling behavior of the grafted films revealed that such a copolymer could be acceptable in practical use as a cation‐exchange membrane.
Electron beam effects on polymers. II. Surface modification of bis‐GMA substrates by functionalized siloxane oligomers
Authors: Kim Ha‐Chul , Song Joo H. , Wilkes Garth L. , Smith Steve D. , McGrath James E. 
Published: April 2003

AbstractSurface modification of polymer films via electron beam irradiation was studied using the methacrylic acid derivative of the diglycidyl ether of bisphenol A, commonly called bis‐GMA, as a curable substrate. Functionalized polydimethylsiloxane (PDMS) oligomers were utilized as surface modifiers. Considerable changes in the wetting characteristics were observed for the siloxane modified bis‐GMA surfaces by critical surface tension measurement. For dosages up to 5 Mrads, the dosage level strongly affects the critical surface tension of the polymer. This result implies differences in the concentration of the attached PDMS oligomers to the bis‐GMA substrate. The methacrylate‐terminated PDMS was observed to be more effective in lowering the critical surface tension than a similar vinyl‐terminated PDMS. Higher molecular weight and multifunctional PDMS coatings resulted in somewhat lower critical surface tensions in the dosage range applied in this study. The surface thickness of the functionalized PDMS coatings which were bonded to the substrate surface depended on the molecular weight of the surface modifiers as obtained by XPS analysis. Peel tests of the uncoated and PDMS coated bis‐GMA clearly resulted in agreement with the critical surface tension data. Chemical inertness and poor wettability of PDMS provided the PDMS coatings with enhanced resistance to chemical degradation caused by a 24‐h exposure to aqueous nitric and acetic acid.
Molecular weight distribution of poly(ethylene adipate) and its changes caused by aging
Authors: Kaštánek Alois , Dufka Oldřich , Dosoudilová Ivana 
Published: April 2003

AbstractPrecipitation fractionations of poly(ethylene adipate) were carried out by nonsolvent addition methods using chloroform as solvent and petroleum ether as nonsolvent. Seventy‐five grams of the polyester was fractionated into 10 fractions by stepwise method and 35 g of the former was fractionated into nine fractions by triangle method. Number‐average molecular weights were determined by ebullioscopic measurements with chloroform as solvent. Acid, hydroxyl, and saponification numbers were determined by analytical methods. It was proved that poly(ethylene adipate) contained considerable quantity of cyclic molecules (ca. 23 mol %). The molecular weight distribution curves of linear molecules constructed from the results of polyester fractionations were found to differ rather from distribution expected from the theory of kinetics of polycondensation and statistical theory. This discrepancy may be explained by higher reactivity of functional groups belonging to shorter molecular chains. It was found out that the aged poly(ethylene adipate) hydrolyzed to a great extent and practically contains no cyclic molecules. Molecular weight distribution of the aged poly(ethylene adipate) determined by GPC is very near to the theoretical “most probable distribution” derived for polycondensates.
Copolymerization of sulfur dioxide with some alkenoic acids
Authors: Tsonis C. P. , Ali Sk. A. , Wazeer M. I. M. , Abdennabi A. M. 
Published: April 2003

AbstractThe copolymerization of sulfur dioxide with some alkenoic acids such as acrylic, 3‐butenoic, 4‐pentenoic, and 10‐undecenoic acid was carried out using organic and aqueous media in the presence of (CH3)3 COOH/SO2 redox system. Elemental analysis, IR, and 13C‐NMR revealed that the copolymers synthesized from the acrylic acid/SO2 system were of variable composition in organic media, but only polyacrylic acid homopolymer was formed in the presence of water. The other three alkenoic acid/SO2 systems gave always polysulfone copolymers of alternating structure regardless of the experimental conditions employed. Thermal analysis (TGA and DTA) of selected samples gave Tg in the 73–101°C, range Tm between 160 and 228°C, and the total weight loss in air from 31 to 97%. Flammability decreased as the S:C mole ratio increased. NMR shows that the complexation of SO2 with the CC part of all alkenoic acids is low.
Dielectric properties of segmented polytetramethyleneoxide‐based polyurethanes
Authors: Petrović Zoran S. , Koco Ferenc , Horvath Laslo , Dulić Nesto 
Published: April 2003

AbstractThree series of segmented polyurethanes, based on polytetramethylene oxide (PTMO) soft segments, having molecular weights of 650, 1000, and 2000 and MDI/butane diol hard segments, were synthesized and their dielectric properties examined. The effect of the soft segment length, soft segment concentration (ssc) as structural variables, and frequency and temperature as experimental variables, on relative permittivity and tan δ, were examined. The results were discussed in terms of the structural parameters such as the degree of phase separation and soft segment phase state. It was found that both soft segment length and ssc strongly affect dielectric behavior.
Synthesis and thermal self‐crosslinking reaction of copolymers from 2,3‐epoxypropyl methacrylate and p‐substituted phenyl methacrylates
Authors: Nishikubo Tadatomi , Saita Seiji , Uchida Noritsugu 
Published: April 2003

AbstractCopolymers of 2,3‐expoxypropyl (glycidyl) methacrylate (GMA) with various phenyl methacrylates such as 4‐nitrophenyl methacrylate (NPMA), 4‐chlorophenyl methacrylate (CPMA), or phenyl methacrylate (PMA), and other monomers such as methyl methacrylate (MMA), ethyl acrylate (EA), or styrene (ST) were synthesized by radical copolymerization, and then thermal self‐crosslinking reactions of the obtained copolymers were carried out using various catalysts such as quarternary ammonium salts, tert‐amines, or the crown ether/potassium salt systems at 100–150°C. Although the copolymer of GMA–NPMA–MMA does not produce any gel products without catalyst upon heating at 110°C for 5 h, this copolymer gives gel products in 82% yield using 10 mol% of tetrabutylammonium bromide as a catalyst under the same conditions. The rate of gel production of the copolymer of NPMA is faster than those of copolymers of CPMA and PMA. The rate of the gel production of the copolymer of GMA–NPMA–EA is also faster than those of copolymers of MMA and ST. Furthermore, it was found that the rate of gel production of the copolymer was strongly affected by the kind of catalyst, the catalyst concentration, and the reaction temperature.
Preparation, characterization, and properties of polylactide (PLA)–poly(ethylene glycol) (PEG) copolymers: A potential drug carrier
Authors: Zhu K. J. , Xiangzhou Lin , Shilin Yang 
Published: April 2003

AbstractPolylactide (PLA)‐poly(ethylene glycol) (PEG) copolymers were synthesized from polyethylene glycol and D,L‐lactide using low toxic stannous octoate as catalyst at 180°C by bulk polymerization. The copolymers were characterized by GPC, IR, and 13C‐NMR. A full assignment NMR spectrum is presented. The physical, drug release, and biodegradable properties in vitro of PLA–PEG copolymers were investigated. The result indicates that the rates of drug release and biodegradation could be tailored by adjusting polymer composition. This amorphous material might be used as a drug carrier in medical applications.
Aromatic polyesters. I. Synthesis and characterization of poly(4,4′‐thiodiphenyl phthalate)s
Authors: Nayak Sasmita , Banthia Ajit K. , Banerjee P. C. 
Published: April 2003

AbstractPoly(4,4′‐thiodiphenyl phthalates) (iso/tere) have been synthesized using both low temperature step‐growth and phase‐transfer catalyzed polymerization techniques. These polymers were characterized using conventional techniques like elemental analysis, solubility characteristics, X‐ray diffraction, infrared, and proton nuclear magnetic resonance spectroscopy. 4,4′‐Thiodiphenyl dibenzoate was used as a model compound.
Effect of flame‐retardant treatment on the thermal behavior of some tropical timbers
Authors: Garba Bashiru , Eboatu N. A. 
Published: April 2003

AbstractPotassium aluminium sulfate, hereafter referred to as alum, was used as a flame retardant for some Nigerian timbers. It was observed that flame spread rate and after‐glow time were drastically reduced. Thermogravimetric analysis shows that alum functions as a flame retardant (FR) by a complex process that entails the dehydration, condensed phase, and the vapor phase mechanisms.
New thermoplastic elastomers of rubbery polyisobutylene and glassy cyclopolyisoprene segments
Authors: Kaszás Gabor , Puskás Judit E. , Kennedy Joseph P. 
Published: April 2003

AbstractNew thermoplastic elastomers (TPEs) consisting of a central rubbery polyisobutylene (PIB) and glassy outer cyclopolyisoprene (cy‐PIP) segments have been prepared by living carbocationic polymerization by sequential monomer addition. First the homopolymerization of isobutylene (IB) and isoprene (IP) have been investigated. The living polymerization of isobutylene initiated by the p‐dicumyl methoxy (p‐DiCumOMe)/TiCl4 system in CH3Cl/n‐C6H14 mixtures at −80°C gave living ⊕PIB⊕ dications of desired molecular weights. The polymerization of IP induced by cumyl acetate (CumOAc)/TiCl4 or cumyl methyl ether (CumOMe)/TiCl4 systems in the same solvent at −40°C readily yielded gel‐free off‐white powders comprising trans‐1,4‐PIP units and cy‐PIP sequences. The polymerization most likely proceeds by trans‐1,4‐PIP ⊕ cations that undergo inter/intramolecular alkylation and cyclization leading to branched multiblocks. Block copolymers were synthesized by the addition of IP to charges containing ⊕PIB⊕ dications of different molecular weights. Under select conditions pure (tr‐1,4‐PIP)‐b‐PIB‐b‐(tr‐1,4‐PIP) triblocks with relatively short tr‐1,4‐PIP sequences have been obtained. Extended reaction times result in multiblocks; most likely ⊕ (tr‐1,4‐PIP)‐b‐PIB‐b‐(tr‐1,4‐PIP) ⊕ dications induce alkylation and cyclization of PIP sequences. The extent of alkylation can be regulated by the viscosity of the medium (molecular weight and/or concentration of the PIB midblock). The rate of IP incorporation decelerates after an initial fast polymerization; however, it can be accelerated by adding fresh Lewis acid to the system. Although tr‐1,4‐PIP endblocks of linear triblocks can be completely cyclized by acid treatment to saturated products, multiblocks cannot, probably because of their branched structure. Transmission electron microscopy of multiblocks shows phase separation with PIB (95–70 mol%) the continuous phase (Tg = −73°C) and cy‐PIP blocks (5–30 mol %) the discrete phase. The Tg of the cy‐PIP domain is in the range 95–190°C and it is affected by the extent of cyclization and/or the length of the cy‐PIP sequence. The new multiblock TPEs are soluble in organic solvents and can be melt‐processed above ∼ 140°C. A multiblock TPE film containing 15 mol % glassy cy‐PIP block and 85 mol % rubbery PIB block of M̄n = 55,500 cast from CCl4 exhibited to MPa tensile strength [120 MPa engineering strength (sigma true)] and 1200% elongation. The completely cyclized linear triblock shows higher Tg (≡ 180°C) but, due to its low cy‐PIP content, exhibits unsatisfactory tensile properties.
Porous bead aliphatic–aromatic methacrylate copolymers. VII. TG, DTA, DSC, and inverse gas chromatography studies
Authors: Wójcik Anna B. 
Published: April 2003

AbstractThe thermal behavior of porous bead methyl methacrylate–di(methacryloyloxymethyl)naphthalene (DMN) copolymers was investigated by TG, DTA, and DSC measurements as well as the inverse gas chromatography method using several different molecular probes. TG and DTA results proved copolymer stability up to 250°C. The retention diagrams for all probes used showed the temperature transitions among which one corresponds to glassy transition of amorphous PMMA. The other features observed on the retention diagrams correspond to a segmental mobility of weakly crosslinked copolymer parts.
The influence of relative humidity on polyarylate hydrolysis
Authors: Golovoy A. , Zinbo M. 
Published: April 2003

AbstractThe influence of relative humidity (RH), between 55 and 100%, on the rate of hydrolytic degradation of polyarylate was investigated at 100°C. The equilibrium water sorption in weight percent, C∞, was determined to be C∞ = 0.0043 X (RH)1.2. For specimens 0.32 cm thick, it takes about 24 h to reach 0.9C∞ at 100°C. The decrease in molecular weight (M̄w) due to the hydrolytic attack of water was linear with time, suggesting a zero‐order process with respect to M̄w. The rate of decrease was found to be proportional to C∞. A 30% decrease in M̄w was observed after 21 days at 55% RH and 100°C and, at that point, the material has become brittle.
Copolyesters. III. Thermal degradation of poly(butylene terephthalate‐co‐adipate)s
Authors: Chang Shinn‐Jen , Chen Mei‐Sui , Chang R. S. , Chen Shu‐Mei , Tsai Hong‐Bing 
Published: April 2003

AbstractThe copolyesters of poly(butylene terephthalate) and poly(butylene adipate) were prepared by melt polycondensation of 1,4‐butanediol, terephthalic acid, and adipic acid. The thermal stability was important for their use a shot melt adhesives. The thermal degradation of these copolysters and homopolyesters was determined through TGA, change of acid number, IR, GPC, and NMR analyses. It was found that the thermal stability of the copolysters in oxygen decreased as the content of butylene adipate increased at temperature above and below Tm. Thermal degradation occured in oxygen even at temperature lower than Tm, so that degradation would also occur at room temperature in air and embrittlement was found for these copolysters for long term service.
Copolyesters. IV. Copolyesters of polycaprolactone and poly(butylene terephthalate)
Authors: Tsai Hong‐Bing , Kuo Wen‐Faa , Chen Mei‐Sui , Chang Nien‐Shi , Chen Shu‐Mei , Chang Shinn‐Jen 
Published: April 2003

AbstractThe copolyesters of poly(butylene terephthalate) and polycaprolactone were prepared by melt polycondensation. The charged form of the caprolactone unit was either caprolactone or polycaprolactonediol. The chemical structure of the copolyesters was investigated by proton NMR. It was found that the content of the caprolactone unit in copolyesters was lower than the charged value. The copolyesters prepared from both caprolactone and polycaprolactonediol were found to be random copolymers. Tm, Tg, and crystallinity of the copolyesters decreased as the content of caprolactone unit increased due to the copolymerization effect. The tensile strength, modulus, and hardness decreased as the content of caprolactone unit increased, which was consistent with the trend of crystallinity.
Stretching of PET films under constant load. I. Kinetics of deformation
Authors: Le Bourvellec G. , Beautemps J. , Jarry J. P. 
Published: April 2003

AbstractThe deformation of amorphous and isotropic polyester film is studied using a device which simulates on a laboratory scale the continuous stretching between rolls by a drawing under constant load. The kinetics of deformation is compared to the kinetics involved in a conventional drawing at constant speed of elongation. The results of drawing under constant load are applied to the industrial case of stretching between rolls.
A formation of compatible poly(vinyl alcohol)/alumina gel composite and its properties
Authors: Suzuki Fumio , Onozato Kenji , Kurokawa Yohichi 
Published: April 2003

AbstractA formation of poly(vinyl alcohol) (PVA)/alumina gel composite was investigated with a viewpoint of compatibility of the composite. An alumina sol was prepared from aluminium iso‐propoxide (Al(iPro)3). The alkoxide was hydrolyzed and the resultant hydrate was peptized to a clear sol with acetic acid. The composite were transparent in whole content of alumina. The effects of dispersed alumina on the sorption of water and mechanical properties of composite were examined. The composites containing PVA 40–50% are flexible. They are folded in various forms and can be drawn five times the initial length in humid state. The residues obtained by calcination to remove PVA at 600°C keep its original form and transparency.
Curing of epoxy resins with in situ‐generated substituted ureas
Authors: Fasce D. P. , Galante M. J. , Williams R. J. J. 
Published: April 2003

AbstractAn epoxy resin based on bisphenol‐A diglycidylether (DGEBA) was cured with a substituted urea generated in situ from the reaction of piperidine with an equivalent amount of toluenediisocyanate (TDI). Curing at 100°C or higher temperatures, during 24 h, led to a complete conversion of epoxy groups and the appearance of aliphatic ethers and oxazolidone rings as revealed by IR spectra. The epoxy conversion was proportional to the oxazolidone concentration. The reaction heat was (−ΔH) = 61 kJ/eq. The maximum Tg was 102°C, e.g., the same value as the one obtained with piperidine alone. Thus, the cure with the substituted urea leads to a similar network but has the following advantages: increase in the latency of the initial formulation, absence of secondary amine volatilization (reproducible curing schedule), and decrease in the reaction heat per epoxy equivalent.
Sorption behavior and crystallinity of jute fiber at higher alkali treatments
Authors: Reddy S. S. , Bhaduri S. K. 
Published: April 2003

AbstractMoisture regain of jute fiber was studied at different alkali concentrations and temperatures. It was found that the moisture regain increased up to 4.5N alkali treatment and then leveled off. Variation in swelling temperature had no significant effect on moisture regain. Amorphous fraction calculated from Valentine's equation using sorption ratio was compared with infrared crystallinity. The accessibility was increased with decreasing crystallinity in alkali‐treated jute fiber, where as in cyanoethylated jute fiber it increased with increasing the degree of cyanoethylation.
High performance size‐exclusion chromatography of anionic polymers in aqueous solutions
Authors: Malfait Tony , Slootmaekers Dirk , Van Cauwelaert Frans 
Published: April 2003

AbstractThe applicability of high performance size‐exclusion chromatography was tested for anionic polymers with a new type of column. It was found that a solvent salt concentration of 0.1M and an elevated temperature (60°C) prevented adsorption of the polystyrene sulfonate standards on the column packing. The calibration curve and the effect of the concentration on the retention volume remained, however, colum‐dependent. We concluded also that the use of the column was restricted to the linear range of the calibration curve and to concentrations below 1 mg mL−1 for the highest molecular weight standards. The influence of the flow rate (below 1 mL min−1) on the retention volume was negligible. The main cause of errors when the universal calibration technique is used originated in the experimental determination of the intrinsic viscosities of the standards. The combination of the errors on the viscosity and on the experimentally determined retention volume easily introduced an error of 15% on the determined molecular weight of the sulfated polysaccharide k‐carrageenan. The use of the universal calibration method for an exact molecular weight determination of anionic natural polymers is therefore still questionable.
Film diffusion effects in nylon 6,6 polymerization
Authors: Steppan D. D. , Doherty M. F. , Malone M. F. 
Published: April 2003

AbstractAn unsteady reaction–diffusion model has been developed to represent the polymerization of a nylon 6,6 prepolymer in a stationary film. A realistic kinetic and equilibrium description is incorporated by the use of apparent rate and equilibrium constants that are composition dependent. The model is suitable for evaluating the effect(s) of changes in throughput (film thickness), temperature, and catalyst activity on the performance of an idealized film reactor. The model is characterized by a single dimensionless parameter, the Thiele modulus. The composition‐dependent kinetic constants are important for accurate prediction of molecular weight evolution in the film. Below a threshold value of the Thiele modulus, molecular weight generation is reaction‐controlled, while above another threshold value it is diffusion‐controlled.
Elastic behavior of natural rubber filled vulcanizates
Authors: Kontou E. , Spathis G. 
Published: April 2003

AbstractThe reinforcement effect of carbon black and, the effect of accelerator‐to‐sulfur ratio variation on the elastic behavior of natural rubber vulcanizates have been studied. The Mooney–Rivlin relation was used to describe the behavior of the rubber matrix, and values of constants c1 and c2 have been evaluated with the use of the strain‐amplification factor. The stress softening of the vulcanizates tested has also been examined.
Modification of gel‐drawn poly(vinyl alcohol) fibers with formaldehyde
Authors: Grubb David T. , Kearney F. Rich 
Published: April 2003

AbstractPoly(vinyl alcohol) fibers which were drawn from dried gels were chemically treated with formaldehyde to induce crosslinking in the amorphous phase. The room temperature storage modulus decreased early in the treatment, to an almost constant value of 50–60% of the initial modulus of the fiber. This behavior was independent of the concentration of formaldehyde used. The modulus at low temperature was also reduced, and no Tg peak could be seen in heavily treated fibers. The modulus above the original Tg, 70°C, was much less affected. The crystallinity determined by DSC fell by one third as the room temperature modulus decreased, and X‐ray diffraction indicated a reduction in the crystal length along the chain direction at the same time. Thus, under the conditions of treatment used, the loss of properties due to destruction of crystals outweighs the stiffening and reduced water sensitivity of the crosslinked amorphous phase.
Reaction of aromatic amines with epoxidized natural rubber latex
Authors: Perera M. C. S. 
Published: April 2003

AbstractSince oxidizability of raw rubber is adversely affected by epoxidation, an attempt was made to bind an amine antioxidant to the rubber molecule through the oxirane group. Effective binding was observed only if the latex is neutralized before addition of the amine. Of the three amines used, 4‐amino‐para‐phenyl diamine (pAA) reacted faster than meta‐nitro‐aniline (mNA), where as N‐isopropyl‐N′‐phenyl‐para‐phenyl diamine (IPPD) was the least reactive. Crosslinking was observed with the primary amine, while, with higher epoxy contents, cyclization products were also formed. mNA had little effect on oxidation resistance once it was bound.