bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Surface 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

Precipitation 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

The 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

Three 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

Copolymers 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

Polylactide (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

Poly(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

Potassium 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

New 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

The 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

The 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

The 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

The 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

The 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

A 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

An 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

Moisture 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

The 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

An 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

The 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

Poly(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

Since 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.
Diffusion–adsorption problems in macromolecular systems: New techniques for parameter estimation
Authors: Ravetkar D. D. , Ambeskar V. D. , Mashelkar R. A.
Published: April 2003

It has been shown that the techniques used for estimation of diffusion–adsorption parameters in the past have certain basic flaws. New and efficient techniques for parameter estimation have been proposed. These have many advantages such as using the full concentration‐time profile (rather than part of it), time saving, etc. The validity of these techniques has been demonstrated by the analysis of the data generated in our laboratory on adsorption of polyacrylamide and also the data on adsorption of dyes on chitin reported in the literature.
Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters. II. Presence of quaternary ammonium salt in the alkali‐bath
Authors: Datye Keshav V. , Palan Bharat H.
Published: April 2003

Influence of alkyl (C12–C14)‐dimethyl‐benzyl ammonium chloride in the solution of sodium hydroxide on the hydrolysis of poly(ethylene terephthalate) (PET), anionically modified poly(ethylene terephthalate) copolyster (CDP), and block polymer of poly(ethylene terephthalate)‐poly(ethylene glycol) (EDP), has been studied under a variety of proportions, concentrations, time and temperature of reaction, M : L ratio, etc. Mechanical properties of treated polymeric materials are evaluated. Hydrolysis of two polymers in the same bath is compared with that in separate baths.
Suspension polymerization of styrene with circular loop reactor
Authors: Tanaka Masato , Hosogai Kazuhiko
Published: April 2003

A circular loop reactor was devised and applied to the suspension polymerization of styrene. The transient droplet diameter distribution and the final particle size distribution are measured by changing widely the impeller speed, the dispersed phase volume fraction, and the stabilizer concentration. The effects of these conditions on the size distribution and mean size of the final polymer particle are investigated. An expression correlating the mean particle size with the operating conditions is derived. The circular loop reactor is found to be superior to the production of the polymer particle of uniform size.
Influence of silica reinforcement upon the glass transition behavior of acrylic polymers
Authors: Reid Charles G. , Greenberg Alan R.
Published: April 2003

The glass transition temperatures (Tg) of poly(acrylic acid), poly(methyl acrylate), and poly(ethyl acrylate) filled with submicron particulate silicas and silicates have been measured by dynamic mechanical spectroscopy and differential scanning calorimetry. The peak temperatures of the damping factor (tan δ) and the dynamic shear loss modulus (G″) were shifted by an amount which depended upon the quantity and type of filler added to each polymer. The temperatures corresponding to the step discontinuity of specific heat also shifted, but to a lesser extent than those measured mechanically. The degree of Tg shift per unit of volumetric filler addition increased with polymer pendant group polarity for both measurement methods. Utilizing a Tg‐crosslinking analogue, a model was developed that related positive Tg shifts to polymeric segmental adsorption onto filler surfaces. This model also incorporated negative contributions to the Tg shift from energy storage mechanisms arising from particle–particle interactions, as well as corrections due to effective surface area available for polymer adsorption.
Radiation‐initiated graft copolymerization of individual monomer and comonomer onto polyethylene and polytetrafluoroethylene films
Authors: Hegazy El‐Sayed A. , Taher N. H. , Ebaid A. R. , Rabie Abdel‐Gawad , Kamal H.
Published: April 2003

Preparation and some properties of the graft copolymers obtained by radiation‐induced graft polymerization of methacrylic acid (MAA) and (acrylonitrile/MAA) comonomer onto polyethylene and polytetrafluoroethylene films, were investigated. The effect of reaction conditions, solvent, monomer, and inhibitor concentration, comonomer composition, and comonomer concentration, on the graft copolymerization process was studied. The grafting process was enhanced in the presence of comonomer (AN/MAA) as compared with individual grafting of MAA or acrylonitrile (AN). The optimum comonomer composition, at which the highest grafting yield was obtained, was found to be (80/20) wt % of (AN/MAA) comonomer. The graft copolymerization of (AN/MAA) comonomer was enhanced in presence of AN due to its higher polarity strength. The electrical and swelling properties of the graft copolymers were greatly affected by the contents of PAN and PMAA graft chains. Mechanical properties of the graft copolymers were significantly changed with the grafting yield.
Preparation of microporous membranes from cation exchange membranes prepared by the paste method
Authors: Mizutani Yukio , Kusumoto Koshi , Nishimura Masakatsu , Nishimura Toshihiko , Asada Eiji
Published: April 2003

A microporous membrane is prepared by treating the cation exchange membrane (Fe+++ form) with an H2O2 aqueous solution. The cation exchange membrane is prepared by the paste method: the base membrane is prepared beforehand and then sulfonated. The preparative conditions of the base membrane were studied in connection with the characteristics of the resultant microporous membrane. Furthermore, the availability of the microporous membrane for ultrafiltration was studied by using an aqueous solution of a bovine hemoglobin.
Physical aging in poly(methyl methacrylate) / poly(styrene‐co‐acrylonitrile) blends. I. Stress relaxation
Authors: Mijovic Jovan , Devine Steven T. , Ho Tai
Published: April 2003

An investigation was carried out on the effect of physical aging on viscoelastic properties of compatible polymer blends. Poly(methyl methacrylate) (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were chosen for this study. Blends of six different ratios of PMMA and SAN were physically aged at different times and temperatures and then subjected to stress–relaxation tests at small strains. It was found that the shape of the stress‐relaxation curve does not change with a change in blend composition, aging temperature, or aging time. A single “master curve” is presented, to which all data may be fit using 0.408 for the exponential parameter of the Williams‐Watts equation. In creating the master curve, all data are shifted horizontally in time only. For a given set of experimental conditions, the relaxation time τ may be expressed in terms of blend composition, aging temperature, and aging time.
The effect of physical aging on long‐term properties of poly‐ether‐ketone (PEEK) and PEEK‐based composites
Authors: D'Amore A. , Cocchini F. , Pompo A. , Apicella A. , Nicolais L.
Published: April 2003

The viscoelastic properties of the amorphous and semicrystalline PEEK and of a PEEK‐based composite (APC2) have been analyzed as a function of the aging time and related free volume relaxation, at temperatures close to the glass transition temperature. The effect of thermal treatments (physical aging) on the polymer amorphous phase of the three systems is presented. Creep tests approaching the “zero stress” were performed on samples subjected to different thermal histories. The presence of a second phase, namely crystallites and fibers, determines a loss of the mobility of the polymeric amorphous chains and consequently a decrease of the rate of free volume relaxation.
Influence of the pressure profile inside a dense membrane on the rate of permeation
Authors: Van der Waal M. J.
Published: April 2003

Lee1 showed that molecular transport in all isothermal membrane processes, based on dense layers, can be described with one single general equation, including only measurable conditions from outside of the membrane. Following arguments given by Paul2 for homogeneous rubber membranes, Lee assumed the pressure everywhere inside the membrane to be equal to the feed side pressure. In this paper the question is stated whether this assumption always holds for very thin and/or nonhomogeneous membranes like asymmetric membranes made of semicrystalline polymers. A study based on less stringent assumptions of the pressure profile inside the membrane is performed. The results show that in most cases this pressure profile does not play a major role in the permeation process.
Characterization of methacrylonitrile‐grafted silk fibers
Authors: Tsukada Masuhiro , Shiozaki Hideki
Published: April 2003

The structure and physical properties of silk fibroin fibers graft‐polymerized with methacrylonitrile (MAN) were analyzed in relation to the weight gain on the basis of the results of tensile properties as well as of thermal analysis and X‐ray diffractometry. The solubility of the specimen in NaOH solution and the moisture absorption decreased slightly with the duration of the MAN treatment. However, the polymerizing treatment with MAN did not affect significantly the tensile properties, i.e., strength and elongation at break of the original fibers. The position of the endothermic peak attributed to the thermal decomposition of the silk fibroin shifted to higher temperatures when the weight gain exceeded 25%, and a constant value at 328°C was obtained above a weight gain of 40%. Wide‐range X‐ray diffraction diagram of silk fibers with a weight gain of 10% showed diffraction maxima at the equator corresponding to the molecule oriented crystal structure of the silk fiber, in addition to the spots on a series of hyperbolic arcs arranged symmetrically at about the equator, which are associated with the crystalline form of the MAN polymer copolymerized in the specimen. Crystalline structure of the silk fiber remained unchanged essentially regardless of MAN treatment.
Optimization of a batch polymerization reactor at the final stage of conversion. II. Molecular weight constraint
Authors: O'Driscoll K. F. , Ponnuswamy S. R.
Published: April 2003

A mathematical model for the free radical batch solution polymerization of methyl methacrylate that takes depropagation into account was developed. This model was then used to derive optimal temperature and initiator concentration policies to reduce residual monomer concentration to desired levels, producing at the same time a polymer with the desired number average molecular weight. An objective function was formulated to take account of the cost of the initiator with respect to the cost of time of reaction. It was observed that when the cost of initiator increased, optimal initiator concentration decreased whereas optimal temperature increased. Finally temperature reached a limiting value above which polymer with desired number average molecular weight could not be produced. These results give insight into the factors that determine the policies that could be employed in optimizing the operation of a reactor.
FT‐IR studies of polymer blends containing an oligo(isophthalate‐co‐fumarate of diethylene glycol) and different epoxy prepolymers
Authors: Suspene L. , Lam T. M. , Pascault J. P.
Published: April 2003

Miscibility of one unsaturated polyester (UP) with different epoxy prepolymers have been examined. Thermodynamic interaction parameters have been calculated. Calorimetric and clarity measurements indicate formation of miscible blends. This is in good agreement with the theoretical predictions excepted those with the 3‐dimensional solubility parameter. Fourier transform infrared (FT‐IR) studies are presented. The ability of acid solvent to associate with ester group have been used to determine the shift of the carbonyl stretching frequency. Similar shift has been found in UP/DGEBA blends and is attributed to specific interactions between these two types of oligomers.
Graft polymerization of methyl methacrylate on flavin mononucleotide by tetravalent cerium ion and an application of obtained polymer to dye transfer printing
Authors: Enmanji Koe
Published: April 2003

The polymerization mechanism of methyl methacrylate (MMA) with flavin mononucleotide (FMN) and cerium nitrate was investigated. The effect of the polymer grafted to FMN on the color fastness to light of some dyes were also investigated. Poly(methyl methacrylate) (PMMA) was produced with FMN, cerium nitrate, and MMA in the presence of water above 40°C. The conversion of PMMA is proportional to the reaction time up to 2 h in this system. It is also proportional to the first order of concentration of FMN and Ce(IV). Activation energy of the polymerization reaction was estimated to be 29.3 kJ mol−1 by the investigation of the temperature dependence of conversion. Purified polymer in acetone has the absorption peak at the same wavelength as FMN aqueous solution. The color fastness to light of Methylene Blue and anthraquinone dye were improved in the presence of the obtained polymer. Heat stability of the printed image which is made by transferring anthraquinone dye did not decrease by use of obtained polymer to recording layer of the medium in dye transfer printing system.
Alcoholysis of copolymers of vinyl acetate with itaconic acid
Authors: Kotzeva L. , Mateva R.
Published: April 2003

We studied alcoholysis of vinyl acetate and itaconic acid (up to 8.5 mol %) copolymers. We obtained the copolymers both by single and continuous addition of the second comoner, and carried out the alcoholysis in methanol and methanol‐gasoline medium at temperature 30°C using sodium hydroxide as catalyst. We established that the presence of itaconic sequences in the vinyl acetate polymer chain in an amount of 1.5–2 mol % causes significant reduction in the viscosity of methanol solutions without greatly affecting the molecular weight of the copolymer. The alcoholysis of random copolymers, containing not more than 4 mol % itaconic sequences takes place at a higher rate. The vinyl acetate‐vinyl alcohol copolymer, containing groups of itaconic acid has better surface activity. This is more clearly expressed in the case of random copolymers.
Comparative study of orientation in hot‐drawn poly(ethylene terephthalate) by means of refractive index and microhardness measurements
Authors: Lorenzo V. , Pereña J. M.
Published: April 2003

Refractive index and microhardness of drawn samples of poly(ethylene terephthalate) were measured by means of an Abbé refractometer and a microindentation hardness equipment. The optical and mechanical anisotropies determined from these measurements were compared with the birefringences obtained by using compensators and fitted to the affine deformation scheme, showing that microhardness anisotropy is a suitable technique for studying the overall orientation in polymers.
Impedance characteristics of parchment supported inorganic precipitate membranes
Authors: Beg M. N. , Altaf I.
Published: April 2003

The impedance characteristics of parchment‐supported inorganic precipitate model membranes have been analyzed in order to understand the mechanism of ionic diffusion through biomembranes. The observed values of membrane capacitance and resistance were found to be dependent on the concentration of bathing electrolyte and applied oscillator frequency. The change in membrane capacitance and resistance values with the change in electrolyte concentration and oscillator frequency has been interpreted in terms of changes produced in the electrical double layer at the membrane–solution interface. The values of interfacial double layer capacitance derived by the equations of Armstrong and Longer were found to be different due to the presence of polarising charge and other structural details of membrane matrix. Different model‐equivalent electrical circuits have been analyzed using the experimental data. The complex impedance spectra have been found to deviate from the theoretical predictions at low frequencies due to nonhomogenous and rough surface of the membrane.
Synthesis of casein‐g‐poly(methyl acrylate). II
Authors: Mohan D. , Radhakrishnan Ganga , Rajadurai S.
Published: April 2003

The synthesis of casein‐g‐poly(methyl acrylate) was studied using the potassium peroxydisulfate–ascorbic acid redox system. The effect of synthetic variables has been investigated in the light of rates of conversion of monomer, graft copolymerization and homopolymerization, percent grafting, and grafting efficiency. The results are compared with the system initiated by pure potassium peroxydisulfate alone.
Processing of polymer latex emulsion: Batch coagulation
Authors: Ghosh Anup K. , Lindt J. Thomas
Published: April 2003

A small‐scale batch experiment has been developed to establish processing conditions for latex coagulation in an extruder environment—characterized by the prevailing flow field, temperature, and pressure. Our experiments have shown that the most effective processing means to control the particle size distribution and also the particle morphology is the coagulation temperature. The changes in hydrodynamics, introduced by variations in the channel depth and rotor speed, affect the average particle size to a lesser degree. The morphology of the coagulated particles and their size distribution have been found to play an important role in the latex dewatering process. By coagulating well above the glass transition temperature(s) of the polymer, an order of magnitude drop in the specific surface area of the coagulated particles has been observed.
Linear polythioesters. XV. Products of interfacial polycondensation of 1,4‐dimercapto‐tetramethylbenzene with some aliphatic and aromatic acid dichlorides
Authors: Podkościelny Wawrzyniec , Kowalewska Wanda
Published: April 2003

New polythioesters by interfacial polycondensation of 1,4‐dimercaptomethyl–tetramethylbenzene with oxalyl, succinyl, adipoyl, suberoyl, sebacoyl, and isomeric phthaloyl dichlorides were obtained. To define the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: type of organic phase, concentration of hydrogen chloride acceptor, the quantitative ratio of aqueous to organic phase, molar ratio of reagents rate of acid chloride addition, contribution of benzyltriethylammonium chloride as a catalyst, and the temperature of the reaction. Thorough studies were carried out only for polycondensation of the dithiol with adipoyl, sebacoyl, and isophthaloyl chlorides. The structure of polythioesters obtained under the model conditions was determined by elementary analysis and infrared spectra. Initial decomposition temperature, mass loss in percentage at the same temperature, maximum rate of decomposition, and mass loss percentage at 100–400°C were defined from the curves of thermogravimetric analysis. Chemical resistance of the polythioesters was determined by treatment with some organic solvents, mineral acids (concentrated and 10%) and sodium hydroxide (10% and 50%). The molecular weight was not measured because of the low solubility of the polythioesters.
Grafting. III. Copolymerization of methyl methacrylate and methacrylic acid
Authors: Sankholkar S. , Deb P. C.
Published: April 2003

The method of graft copolymerization of methyl methacrylate on halogen‐containing polymer has been utilized for grafting of methyl methacrylate–methacrylic acid monomer pair onto poly(vinyl chloride) and chlorinated rubber. Substantial grafting could be obtained by using the method reported earlier. However, the compositions of the grafted chains are found to deviate appreciably from the compositions calculated from r1 and r2 values reported in literature. The reactivity ratios for this pair of monomers have been therefore evaluated using azobisisobutyronitrile and n‐butane thiol–dimethyl sulfoxide as initiators. The anomalies of the grafted chain compositions have been discussed and an explanation presented on preferential solvation.
Annealing effects on the viscoelastic anomaly between the β and γ processes for as‐polymerized polytetrafluoroethylene
Authors: Takenaga Mitsuru , Yamagata Kyozo , Kasai Akinari , Ariyama Takashi
Published: April 2003

The viscoelastic anomaly found at 208 K for as‐polymerized polytetrafluoroethylene (PTFE) is investigated on the basis of thermal treatment dependence of mechanical spectra. The loss intensity and relaxation strength of the anomaly tend to decrease at annealing temperatures much lower than the melting point. The structural region relevant to the anomaly can be rearranged in more ordered states on annealing; accordingly, the loss peak of the crystalline dispersion is intesified, although that of the amorphous γ‐relaxation remains nearly unchanged. The anomaly originates from the intermediate or paracrystalline regions, many of which are included in the virgin samples; segmental motions like local mode relaxation are considered.
Pressure effects in polymer melt rheology
Authors: Driscoll Paul D. , Bogue Donald C.
Published: April 2003

Wide ranges of pressure and temperature are encountered in polymer processing operations, as, for example, in injection molding. While the temperature dependence of viscosity has been widely studied, the pressure dependence has not. The present work focuses on the measurement of the melt viscosity of polystyrene at high pressures (up to 124 MPa or 18,000 psi) and high shear rates (1–100 s−1) at 180°C. The apparatus was a capillary rheometer with the downstream chamber being held at a high back pressure by means of a needle valve. The data so obtained were combined with zero shear viscosity data from the literature; and then correlated with a shear‐dependent rheological model of the authors, using a shift factor suggested by Utracki (based on the Simha–Somcynsky equation of state). The final correlation calls for making both the elastic modulus and the time constant dependent on pressure, with the modulus being the dominant factor at high shear rates.
Photomodification of polymer surface by utilizing photoinitiated amino‐groups formation–effects of comonomers on the dyeing of irradiated polymer surface
Authors: Song Kyoung‐Hun , Iwamoto Akiko , Tsunooka Masahiro , Tanaka Makoto
Published: April 2003

Photomodifications of polymer surface are investigated from the viewpoint of dyeing of the irradiated polymer surface. For this purpose, several kinds of acryloyl acetophenone oxime (AAPO) copolymers are prepared. As the other monomer components, methyl methacrylate (MMA), styrene (St), 2,3‐epoxypropyl methacrylate (EPMA), 2‐hydroxyethyl methacrylate (HEMA), N‐vinyl pyrroridone (NVP), and n‐butyl methacrylate (BMA) are used. In the photolysis of acyloxyimino (AOI) groups in AAPO copolymers, alkylimino groups can be introduced very effectively, which can be easily transformed to ammonium groups by hydrolysis in an aqueous solution of HCI. The surface of AAPO copolymers becomes dyeable with an acid dye (Congo Red) by the irradiation followed by HCI treatment and the degree of dyeing of the surface depends on not only the contents of ammonium groups but also the physical properties of the other monomer components. Although the hydrophilic or polar monomer such as NVP, HEMA, and MMA are cooperative for dyeing, the hydrophobic monomer such as St decreases the function of ammonium groups for dyeing. Although the undecomposed AAPO components in AAPO–MMA do not affect the degree of dyeing up to 24.5 mol % of AAPO contents in AAPO–MMA copolymers, they show the inhibition effect for dyeing of AAPO(38.8)–MMA at an earlier stage in irradiation. Aromatic moieties in AAPO are thought to inhibit the dyeing.
Crystallinity in PPS–carbon composites: A study using diffuse reflection FT‐IR spectroscopy and differential scanning calorimetry
Authors: Cole K. C. , Noël D. , Hechler J.‐J. , Wilson D.
Published: April 2003

A method based on diffuse reflection Fourier transform infrared (FT‐IR) spectroscopy has been developed for determining the state of crystallinity in composite materials made from poly(phenylene sulfide) (PPS) reinforced with carbon fibers. Using this technique, good‐quality spectra can be obtained directly from the surface of prepreg or molded composite; thus the method is rapid and nondestructive. Several peaks in the spectrum are sensitive to the crystallinity and can be used for quantitative characterization purposes. The recommended indicator is the ratio of the heights of the peaks at 1075 and 1093 cm−1. Using a range of samples of varying crystallinity prepared by annealing amorphous prepreg, it has been shown that there is a very good correlation between this ratio and the enthalpy of crystallization as determined by differential scanning calorimetry. The effects of such annealing, as well as heating in air at high temperatures, have been investigated.
Thermal effects of heat‐resistant rubber blends. I. Joule heating effects in carbon black‐loaded NR/SBR blends
Authors: Hassan H. H. , Abdel‐Bary E. M. , Amin M. , El‐Mansy M. K. , Gouda M. E.
Published: April 2003

A heat‐resistant rubber blend of natural rubber NR and styrene butadiene rubber (SBR‐1502) was prepared according to the standard techniques. The rubber blend was loaded with different concentrations of LAMP black and general purpose furnace (GPF) black for obtaining conductive rubber composites. The obtained vulcanizates were subjected to electrical conductivity measurements over a wide range of temperature and electric field. It was found that all samples showed negative values of temperature coefficient of conductivity (TCC). The temperature developed inside the samples by the Joule heating effect was recorded as a function of time (T–t) at different values of the initial applied DC‐electric power. The T–t dependence was found to obey an exponentially growing function with a time constant (τ), which was found to be dependent on the concentrations as well as the type of carbon black and the value of the initial applied power. The current–voltage characteristics of the samples showed a negative resistance behavior after a characteristic voltage (V*). It was noticed that V* decreases as the carbon black concentration increases.