bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of solvent or hydrophilic polymer on the hydration melting behavior of polyacrylonitrile
Authors: Min Byung Ghyl , Son Tae Won , Kim Byoung Chul , Lee Chul Joo , Jo Won Ho
Published: April 2003

The effect of solvent, DMF, and hydrophilic polymer on the hydration melting behavior of Tae Kwang polyacrylonitrile‐based copolymer (T‐PAN) was investigated by DSC measurement. The melting temperature (Tm) of T‐PAN was sharply lowered by incorporating water under autogenous pressure, but leveled off above a critical water content: 23 wt %. However, an additional incorporation of DMF into the hydrated T‐PAN further lowered the Tm, even above the critical water content. On the other hand, addition of water‐soluble poly(acrylic acid), poly(vinyl alcohol), and poly(ethylene glycol) or water‐swellable starch to the hydrated PAN slightly raised the Tm. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of different mixtures of acrylic monomers on amylopectin. Swelling behavior
Authors: Castellano I. , Pascual B. , Vazquez B. , Goñi I. , Gurruchaga M.
Published: April 2003

Hydroxylic and nonhydroxylic acrylates—methyl acrylate (MA), ethyl acrylate (EA), butylacrylate (BA), hydroxypropyl methacrylate (HPMA), ethylenglycol dimethacrylate (EGDMA), and mixtures of HPMA–MA, HPMA–EA, HPMA–BA in a 50/50 feed composition—were grafted onto amylopectin with different amounts of crosslinking agent, EGDMA. Percent of total conversion, percent crude grafting, and influence of pH in water content were studied. In this sense it was only at pH 10 when a real variation in the water content could be seen. It was also proved that the highest values were obtained when one of the comonomers was EGDMA with a 34 mol% of the initial feed composition. © 1994 John Wiley & Sons, Inc.
Grafting cellulose acetate with styrene maleic anhydride random copolymers for improved dimensional stability of cellulose acetate
Authors: Nie Li , Narayan Ramani
Published: April 2003

Graft copolymers of cellulose acetate (CA, d.s.:2.45) with styrene maleic anhydride random copolymers (SMAs) were synthesized by reacting the hydroxyls on CA backbone with the anhydride on SMA. The formation of graft copolymers leads to compatibilized blends with microscopic phase domains under appropriate conditions. The grafting reaction was studied in detail. The uniform dispersion of SMA in the CA matrix brings new properties to the grafting reaction products. Tests from acetone‐cast films showed improved dimensional stability in comparison to cellulose acetate; i.e., in the presence of 50% SMA in the formulation, there is more than 50% reduction on the dimensional change as compared to CA. The dimensional stability of the grafting products is better or comparable to cellulose triacetate. There are, for the alloys, reduced moisture adsorption, improved tensile strength, tensile modulus, reduced elongation, as compared to cellulose acetate. © 1994 John Wiley & Sons, Inc.
Surface properties of a segmented polyurethane containing amphiphilic polymers as additives
Authors: Kober Maria , Wesslén Bengt
Published: April 2003

Two different types of amphiphilic polymers were used as surface‐modifying additives to a polyetherurethane, Pellethane 2363–75D, which has Tg close to room temperature. The additives used were a segmented polyetherurethane designated Pol C, and Pluronics PE6800 and PE9400, i.e., triblock copolymers of propylene oxide and ethylene oxide. Pol C was prepared from poly(ethylene glycol), methylene diphenylene diisocyanate, and a fatty acid monoglyceride. The properties of the blends were investigated in their unhydrated state and after water immersion at 23°C and 80°C. Surface composition, water absorption, and leakage of additives to the aqueous phase have been studied. From ESCA and contact angle measurements it was concluded that Pol C was enriched in the surface layer of the matrix material after water immersion at 80°C. The Pluronics showed less effects on the surface properties of the matrix material, probably because of their high water solubility. © 1994 John Wiley & Sons, Inc.
Prevaporation of water/alcohol mixtures through the PVA membranes containing cyclodextrin oligomer
Authors: Yamasaki Akihiro , Ogasawara Keiichi , Mizoguchi Kensaku
Published: April 2003

Prevaporation through the PVA membrame containing β‐cyclodextrin oligomer (PVA/CD membrane) was performed for the mixtures of water/ethanol, water/1‐propanol, and water/2‐propanol. At higher alcohol concentrations, the water selectivities were greatly increased by CD for all the mixtures, in the order of 2‐propanol/water>1‐propanol/water>ethanol/water. The water permeation rate was decreased by CD, and the alcohol permeation rate was decreased much more for each mixture. At lower alcohol concentrations, the water selectivity for 1‐propanol/water was slightly increased by CD, and that for 2‐propanol/water was scarcely affeted, whereas that for ethanol/water was greatly increased. The water permeation rate was increased by CD for each mixture, and the relative increases in the water rates for propanols/water were smaller than that for ethanol/water. The permeation rate of 1‐propanol as well as that of ethanol was decreased by CD, but the rate of 2‐propanol was was increased. These effects of CD can be explained in terms of the inclusion strength. © 1994 John Wiley & Sons, Inc.
Characterization of polyamide 6 made by reactive extrusion. II. Analysis of microstructure
Authors: Hornsby P. R. , Tung J. F.
Published: April 2003

Consideration is given to the characterization of microstructure in polyamide 6 prepared by polymerization of ϵ‐caprolactam in a corotating twin‐screw extruder. Results obtained by FTIR, WAXD, DSC, and DMTA are discussed in terms of the molecular mass of the polymer, the thermal history of the material, and the influence of residual monomer. © 1994 John Wiley & Sons, Inc.
A study of the degradation of polyethylene by high‐temperature dynamic light‐scattering
Authors: Wu Chi
Published: April 2003

After passing throught an extuder, a small amount of degradation normally occurs in the high molecular weight tial of a broadly distrubuted polymer sample. This small amount of degradation counld dramatically affect the polymer viscoelastic properties. It is difficult to detect this type of degradion by using convetional analytical methods, such as hightemperature size exculsion chr omatography. An investisgation of this thype of degradation in a broadly distributed polyethylene sample was accomplished by using high‐temperature dynamic light‐scattering (HTDLS). We have shown that the measured line‐width (or the tsranslatinal diffusion coefficient) distrubuiton in the HTDLS is proportional to Mα with α = 3. 580 ± 0.005 so that the HTDLS is a very sensitive techique for detecting a very small amount of degradation im the high molecular weight tail. Another advantage of using the HTDLS is that the study does not intoduce further stress or perturbation into the sample. In study, we also investigated the thermal degradation of the polyelthylene sample in trichlorobenzene at high temperatures. We found that the polyethylene sample after the extrusion undergoes a thermal degradation more easily. © 1994 John Wiley & Sons, Inc.
Effect of different cross‐linking systems on properties of highly saturated nitrile rubber compounds
Authors: Hernández L. González , González J. L. De Benito , Rueda L. Ibarra , Díaz A. Rodríguez
Published: April 2003

The peroxide curing of highly saturated nitrile rubber was analyzed. Reactions such as chain scission occurred that account for the drop in physical properties. The results are compared with an alternative cross‐linking that is currently being assessed. With a new curing agent the chain‐scission reaction was not present and the properties of the compounds were improved. Finally, an estimation of the free volume of the materials tested was attempted by using the WLF equation. © 1994 John Wiley & Sons, Inc.
Synthesis of graft poly(ester ether) by ring‐opening copolymerization of epoxy‐terminated poly(ethylene glycol) with lactones
Authors: Ikeda Isao , Horie Naofumi , Suzuki Kimihiro
Published: April 2003

The copolymerization of epoxy‐terminated poly(ethylene glycol methyl ether) (CH3PEG–epoxide) with lactones such as ϵ‐caprolactone (CL) was carried out to prepare the PEG graft poly(ester ether). The methanol‐insoluble part of the reaction product was considered to be the graft copolymer. The graft copolymer was prepared using potassium tert‐butoxide or sodium methoxide as a catalyst. The apparent number‐average molecular weight (M̄n) of the graft copolymers increased with an increase in CL concentration and a decrease in the dielectric constant of the solvents. ß‐Propiolactone (PL) and δ‐valerolactone (VL) were also copolymerized with CH3PEG–epoxide as well as was CL. The apparent composition of the graft copolymers (lactone units/CH3PEG) was greater than the feed ratio of the two monomers in all cases. On the other hand, the composition of copolymers prepared with the copolymerization of low molecular weight epoxides such as phenyl glycidyl ether with VL was almost consistent with the feed ratio of the two monomers. © 1994 John Wiley & Sons, Inc.
Room‐temperature kinetics of castor‐oil‐based polyurethane/poly(2‐hydroxyethyl methacrylate) interpenetrating polymer networks
Authors: Suthar Bhikhu , Jadav Kanak , Dave Mayank
Published: April 2003

The kinetics aspects of the formation of castor‐oil‐based polyurethane/poly(2‐hydroxyethyl methacrylate) interpenetrating polymer networks (IPNs) were studied. The effect of parameters such as the polyurethane content, the activator, and acrylic cross‐linker on the kinetics of formation of IPN networks was examined at room temperature. The formation of the individual networks, polyurethane, poly(2‐hydroxethyl methacrylate), and their IPNs, was studied by measuring the decrease of absorbance of characteristic absorption peak of each system using IR spectroscopy. © 1994 John Wiley & Sons, Inc.
Preparation and application of low‐molecular‐weight poly(vinyl chloride). V. Preparation and characteristics of blended poly(vinyl chloride) by two‐step suspension polymerization
Authors: Yamamoto Kikuo , Maehara Takashi , Mitani Katsuo , Mizutani Yukio
Published: April 2003

Poly(vinyl chloride) (PVC) with relatively broader molecular weight distribution (BMD‐PVC) was prepared by two‐step suspension polymerization: (1) preparation of poly(vinyl chloride) with relatively higher molecular weight (HMW‐PVC) and (2) successive preparation of poly(vinyl chloride) with relatively lower molecular weight (LMW‐PVC) in the presence of the resultant HMW‐PVC and 2‐mercaptoethanol as a chain transfer agent. Some properties of BMD‐PVC were investigated: fusion time, melt viscosity, discoloration time, tensile strength at yield, tensile modulus in tension, and elongation at break. © 1994 John Wiley & Sons, Inc.
Morphological implications of phase transitions in polymer solutions: Study of polyacrylonitrile‐based solutions
Authors: Akki Rashi , Desai P. , Abhiraman A. S.
Published: April 2003

Solution‐based processing of infusible polymers usually involves large quantities of undesirable solvents and transport‐limited morphological evolution that is often difficult to control. The present study constitutes a rational exploration of the phase transitions in polymer solutions to form the basis for new processes that would diminish the abovementioned problems and also identify appropriate mechanisms for controlled generation of useful morphologies. The fundamental concepts in this regard are exemplified through solutions of acrylonitrile‐based homopolymer and copolymers, with important inferences drawn regarding their potential implications for the formation of fibers, films, and membranes. Thermodynamic and kinetic manipulation of transitions such as liquid–liquid phase separation and crystallization is shown to be effective in controlled generation of morphologies ranging from microporous to dense. © 1994 John Wiley & Sons, Inc.
Surface properties for poly(perfluoroalkylethyl methacrylate)/poly(n‐alkyl methacrylate)s mixtures
Authors: Park In Jun , Lee Soo‐Bok , Choi Chang Kyun
Published: April 2003

A poly(perfluoroalkylethyl methacrylate) and a series of poly(n‐alkyl methacrylate)s such as poly(methyl methacrylate), poly(ethyl methacrylate), and poly(n‐butyl methacrylate) were prepared and used to investigate the surface properties of polymer mixtures containing a fluorinated homopolymer and a nonfluorinated homopolymer and the effect of the side‐chain length of poly(n‐alkyl methacrylate) on the surface free energy for the polymer mixtures. Contact angles were measured for the surfaces of polymer mixtures by varying the concentration of poly(perfluoroalkylethyl methacrylate). From the contact angle data, it can be inferred that most of the poly(perfluoroalkylethyl methacrylate) added to poly(n‐alkyl methacrylate)s is located in the outermost layer of polymer‐mixture surface. Surface free energies for the outermost surfaces of polymer mixtures were calculated from the contact angle data using Owen and Wendt's equation. The decrease in the surface free energy for the polymer mixture with the poly(perfluoroalkylethyl methacrylate) addition is more pronounced as the side‐chain length of poly(n‐alkyl methacrylate) decreases. Due to the steric effect of the side chain of poly(n‐alkyl methacrylate), the arrangement of the perfluoroalkylethyl group of poly(perfluoroalkylethyl methacrylate) to the air side is considerably hindered. The ESCA analysis of atomic compositions of the surface for the polymer mixture verified that poly(perfluoroalkylethyl methacrylate) is preferentially arranged and concentrates at the polymer mixture–air interface. The results of functional group compositions obtained by ESCA showed that the functional group composition of CF3 for the outermost layer has a more important effect on the surface free energy than that of CF2 and confirmed the hindrance of the arrangement of perfluoroalkylethyl group to the air side by the side chain of poly(n‐alkyl methacrylate). © 1994 John Wiley & Sons, Inc.
The permanence of UV absorbers in a rubber‐modified acrylic film by UV/visible spectrophotometry
Authors: Bonekamp J. E. , Maecker N. L.
Published: April 2003

A new analysis technique for UV/visible spectrophotometry is described. This technique is used to accurately determine the retention of several UV absorbers (UVAs) in a rubbermodified acrylic film during xenon arc accelerated weathering. The effects of reflectance, light scattering, and matrix absorbance are deconvoluted from the total apparent absorbance, resulting in an absorbance spectrum due to the UVA alone. All of the UVAs studied exhibit significant losses upon xenon arc exposure, which has important implications for the longterm durability of polymers that utilize these stabilizers. © 1994 John Wiley & Sons, Inc.
Permanence of polymer stabilizers in hostile environments
Authors: Bell B. , Beyer D. E. , Maecker N. L. , Papenfus R. R. , Priddy D. B.
Published: April 2003

Additives are commonly formulated into polymers to stabilize them against thermo‐oxidative and photo‐oxidative degradation. However, the additives themselves undergo degradation in the polymers, especially when the polymers are placed in hostile environments. This study focuses on the degradation of additives in chemical and photo‐oxidizing environments; i.e., spas and xenon arc, respectively. HPLC‐UV/vis, FT‐IR, and GC‐MS techniques were utilized to follow the degradation chemistry of the additives. The chemistry was determined for additive degradation by spa chemicals, but the degradation chemistry of benzotriazoles remains elusive due to the insolubility of the resinous degradation products. © 1994 John Wiley & Sons, Inc.
Polylactide. III. Fiber preparation by spinning in precipitant vapor
Authors: Horáček I. , Kalíšek V.
Published: April 2003

The mechanical properties and morphologies of poly(L‐lactide) (PLLA) fibers, prepared by spinning in different vapor precipitants and hot drawing afterward, were studied in relation to fiber in vitro degradability. Petrolether, methanol, and ethanol were employed as precipitants. PLLA was used as‐polymerized, i.e., with 10% of residual L‐lactide. The tensile strength, structure, and degradability of obtained fibers were mainly governed by the nonsolvent concentration in the vapor phase. Using methanol as the precipitant for the fiber preparation, total tensile strength loss was achieved during 12 wk of in vitro degradation. © 1994 John Wiley & Sons, Inc.
Aqueous dispersion of polyurethanes containing ionic and nonionic hydrophilic segments
Authors: Kim Byung Kyu , Lee Young Min
Published: April 2003

Aqueous polyurethane (PU) dispersions were prepared from isophorone diisocyanate (IPDI), polytetramethylene glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and dimethylol propionic acid (DMPA) as anionic center. The effects of the PEG/PTAd mixing ratio, type of polyether polyols, and hard segment content on the state of dispersion, surface, dynamic, and tensile properties of emulsion‐cast film were determined. With more incorporation of nonionic hydrophilic PEG, particle size of the emulsion and tensile strength of the emulsion‐cast film decreased, while the emulsion viscosity and elongation at break increased. Among ether type polyols, PTMG‐based PU generally showed superior mechanical properties. With increasing hard segment content, particle size, storage modulus (E′), and tensile strength increased. At the lowest hard segment content (36 wt %) tested in this experiment, soft segments crystallized and water swell decreased. © 1994 John Wiley & Sons, Inc.
Ion beam irradiation effect on gas permeation properties of polyimide films
Authors: Xu X. L. , Dolveck J. Y. , Boiteux G. , Escoubes M. , Monchanin M. , Dupin J. P. , Davenas J.
Published: April 2003

This study deals with the ion beam irradiation effect on gas permeation properties of polyimide films. 2 MeV α, 500 keV, and 170 keV N+ ions were used for modifying the membranes. It was found that there are two different effects according to the implantation dose. In the case of small‐dose irradiation, ion implantation causes a raise of permeability both for CH4 and H2. When the implantation dose reaches a more important level, the implanted membranes have at the same time high permselectivity for H2/CH4 and high permeability for H2. The relationships between the permeation properties and microstructure of the films are also discussed. © 1995 John Wiley & Sons, Inc.
Cross‐linked coatings by co‐reaction of isocyanate–methoxymethyl melamine systems
Authors: Ntsihlele E. S. , Pizzi A.
Published: April 2003

Two‐components methoxymethyl melamine/isocyanate and three‐components methoxymethyl melamine/isocyanate/polyol coating systems were studied. Methoxymethyl melamine was shown to react with isocyanate groups through the carbocation formed by splitting within the methoxymethyl group. In three‐components systems, methoxymethyl melamine/polyol and methoxymethyl melamine/isocyanate rections appear to occur, but not isocyanate/polyol reactions. This was ascribed to the release from the methoxymethyl melamine/polyol reaction of methanol which reacts more rapidly than the polyol with the isocyanate group. A blocked isocyanate was then used whereby the methoxymethyl melamine reacts at an earlier stage and urethane formation is delayed. Introducing the blocked isocyanate, however, required significant increase in cure temperature for the isocyanate/polyol reaction, narrowing the cure temperature window of the system. © 1995 John Wiley & Sons, Inc.
The effect of crystallization conditions on the properties of polyoxymethylene
Authors: Plummer C. J. G. , Menu P. , Cudré‐Mauroux N. , Kausch H.‐H.
Published: April 2003

Measurements using compact tension specimens machined from compression and injectionmolded plaques of polyoxymethylene show a systematic decrease in the plane‐strain critical stress intensity KIC for crack initiation with crystallization temperature and with molecular weight, but little change in the yield stress in plane strain compression tests. The variation in KIC with crystallization temperature has been accounted for in terms of the effective entanglement density in the damage zone ahead of the crack tip. The entanglement density is argued to decrease with increasing temperature owing to partial disentanglement of the polymer chains during lamellar folding. © 1995 John Wiley & Sons, Inc.
Strategies for supercritical CO2 fractionation of polydimethylsiloxane
Authors: Zhao X. , Watkins R. , Barton S. W.
Published: April 2003

The fractionation of polydimethylsiloxane (PDMS) using supercritical CO2 was studied to determine the parameters of pressure and temperature required to separate specific molecular weights. On a laboratory scale, we show that this fractionation method can quickly provide gram quantities of the polymer with a polydispersity of around 1.2 for molecular weights in excess of 200 kg/mol. This technique has obvious applications in the preparation of PDMS for surface‐related uses. © 1995 John Wiley & Sons, Inc.
Effect of silica filler on dynamic mechanical properties of lonic elastomer based on carboxylated nitrile rubber
Authors: Mandal U. K. , Tripathy D. K. , De S. K.
Published: April 2003

Variation of dynamic mechanical propeties like storage modulus (E′) and loss tangent (tan δ) with temperature show the presence of two transitions in the carboxylated nitrile rubber (XNBR) molded in the presence of zinc oxide (ZnO). The low‐temperature transition is due to the glass–rubber transition (Tg) of XNBR, and the high‐temperature transition is due to formation of ionic clusters. Incorporation of reinforcing silica filler makes the high temperature transition more prominent and high filler loading casues a shift of the transition temperature to the higer side. It is believed that the rubber–filler interaction in the cluster region causes striking changes in the variation of E′ and tan δ with a double‐strain amplitude (DSA). © 1995 John Wiley & Sons, Inc.
Characterization of microstructure and fracture behavior of polypropylene/elastomer blends containing small crystal in elastomeric phase
Authors: Nomura Takao , Nishio Takeyoshi , Iwanami Kunio , Yokomizo Katsuyuki , Kitano Kissho , Toki Shigeyuki
Published: April 2003

Fracture behavior of polypropylene (PP)/ethylene–propylene–rubber (EPR) blends containing small crystal in elastomeric phase was investigated. Various ethylene‐α‐olefin co‐polymers (ECP) were used as crystal components and put into the elastomer phase of the blends. The crystallite size was controlled by changing the composition of the ECP. From thermal analysis and electron microscopic analysis, it was found that the ECP having a smaller crystal had better affinity to EPR and thus the crystal was finely dispersed in the elastomeric phase. The ECP with large crystallite size had poorer affinity to EPR and tended to segregate in the elastomeric phase. Scratch resistance and tensile elongation of blends were measured and it was found that the small crystal drastically improved the above properties while the large crystal deteriorated them. The dispersed small crystal was thought to act as a crosslinking point in the elastomeric phase. The reinforcement of the elastomeric phase by such quasi‐crosslinking structure was the possible reason for the improvement of the mechanical properties of the blends. © 1995 John Wiley & Sons, Inc.
Deformation and fracture of urethane–methacrylate resins
Authors: Elleithy R. H. , Hiltner A. , Baer E. , Fraser I. M. , Orton M. L.
Published: April 2003

The tensile properties of three urethane–methacrylate resins that varied in the soft segment content of the urethane were characterized. The strain birefringence at a circular hole was observed during loading–unloading cycles to progressivley higher displacements. The shear strain distribution at the hole was calculated from the isochromatic fringe contours and compared with results from linear elastic analysis. When the onset of nonlinearity, and the subsequent appearance of residual strain at the root of the hole, were correlated with features of the macroscopic stress‐displacement curves, three regions of prefracture deformation were defined. A region of linear elastic behavior was observed at the lowest strains. The maximum shear strain at the linear limit was the same in all the resins, and appeared to correlate with the yield condition at the hole. When the shear strain at the hole exceeded about 2.8%, the fringe patterns started to deviate from the elastic prediction. However, strain was fully recoverable in this region as indicated by the absence of residual birefringence at the hole after unloading. This region of nonlinear, recoverable deformation extended to progressively higher strains as the amount of urethane soft segment increased. This feature was attributed to the network structure of the urethane–methacrylate resins. A region characterized by nonrecoverable deformation at the hole followed at higher strains; the urethane soft segment content had a major effect on the amount of permanent deformation sustained before fracture. The fracture surfaces exhibited features typical of brittle fracture without crazing. © 1995 John Wiley & Sons, Inc.
Preparation of amphiphilic membranes using photosensitive polymers and their applications on the enzyme electrode
Authors: Liu Jui‐Hsiang , Chung Yi‐Chang , Lin Ming‐Ter
Published: April 2003

To decrease the mass transfer resistance of oxygen permeation and to improve the response of the enzyme electrode, a series of hydrophilic–hydrophobic polyvinylcinnamate (PVCin) membranes were developed. The PVCins were synthesized from polyvinyl alcohol using various amounts of cinnamoyl chlorides in the presence of alkali. The amphiphilic membranes were prepared by using photosensitive PVCin and/or sensitizers that were used instead of the traditional Teflon–hydrophilic two‐layer membranes. The properties of photocrosslinking, water and oxygen permeability of the amphiphilic membranes, the calibration curves, and the characteristics of the enzyme electrode prepared by the amphiphilic membranes were investigated. © 1995 John Wiley & Sons, Inc.
Study of radical copolymerization of tetrafluoroethylene with ethylene in bulk
Authors: Kostov G. K. , Nikolov Al. T.
Published: April 2003

Radical copolymerization of tetrafluorethylene (TFE) with ethylene (E) by azo‐bis‐iso‐butyronitrile in the temperature interval 333–363 K, monomer pressure from 3.0 to 7.0 MPa at TFE/E molar ratio from 77/23 to 23/77 in bulk was carried out. The effect of reaction conditions on the yield, molecular weight, and polymer composition of copolymer synthesized was studied. White powdery alternating copolymers were obtained at TFE content in the monomer mixture from 65 to 85 mol %. Copolymerization rate R was described by the equation R = kM[ln] [Σ M]1.3 which was related to the heterophase character of the reaction. The reactivity ratio of TFE and E (0.067 ± 0.12 and 0.52 ± 0.18, respectively) and apparent activation energy Ea = 135 kJ/mol were found. The TFE and E block formation probabilities were calculated and compared with IR spectroscopy data. Melting point, entropy, and enthalpy of fusion of the entirely alternating copolymers were determined. Some of the basic properties of the alternating copolymers obtained were also studied. © 1995 John Wiley & Sons, Inc.
Electrical conduction in cellophane and polypyrrole composites and its use as an electrode in rechargeable batteries
Authors: Bhat N. V. , Yasmin S.
Published: April 2003

Electrical properties of cellophane and polypyrrole [cello + PPy] composite films were investigated by the two‐probe method. The electrical conduction of composite films was studied as a function of voltage, temperature, and percentage content of PPy in the composite films. An attempt was made to use the [cello + PPy] composite films as electrodes in rechargeable batteries. © 1995 John Wiley & Sons, Inc.
Synthesis and rheological behavior in aqueous solutions of poly(acrylamide‐co‐maleic acid)
Authors: Yao Ke‐Jun , Liu Feng‐Hui
Published: April 2003

Water‐soluble copolymers of acrylamide with maleic acid were synthesized in aqueous solution by using potassium persulfate with N,N,N′,N′‐tetramethyl ethylenediamine as initiator. The influences of synthetic variables on the copolymerization were investigated. The copolymers were characterized by IR and 1H‐NMR spectroscopy. The copolymeric composition was obtained by using 1H‐NMR method. The monomer reactivity ratios were calculated by the Kelen‐Tudos method and the values of r1 (AM) and r2 (MA) were determined to be 11.45 and 0.0129, respectively. The rheological behavior of aqueous solution of synthetic poly(acrylamide‐co‐maleic acid) was determined, and flowing activation energy E was calculated. © 1995 John Wiley & Sons, Inc.
Effect of some superplasticizers on the mechanical and physicochemical properties of blended cement pastes
Authors: El‐Hosiny F. I. , Gad E. A. M.
Published: April 2003

Blended cement pastes made of Portland cement and fine sand (known in Egypt as El‐Karnak cement) were made using a water–cement ratio of 0.25 by weight. Three pastes containing admixture (water‐soluble condensates) were also prepared using a water–cement ratio of 0.25 and condensate (superplasticizer) content of 0.25% by the weight of cement; the superplasticizers used are Na‐phenol sulfonate formaldehyde, Na‐polystyrene sulfonate, and Na‐ß‐naphthol sulfonate formaldehyde condensates. All pastes were cured for various time intervals within the range of 0.02–90 days. Compressive strength tests, hydration kinetics, X‐ray diffraction analysis, thermal analysis, and surface properties were studied and related as much as possible to the pore structure of the hardened pastes. © 1995 John Wiley & Sons, Inc.
Reactive extrusion of PP/natural rubber blends
Authors: Yoon Lee Keun , Choi Chi Hoon , Kim Byung Kyu
Published: April 2003

Reactive extrusion of polypropylene (PP)/natural rubber (NR) (90/10) blends was conducted in the presence of a peroxide [1,3‐bis(t‐butylperoxy)benzene] and coagent (trimethylolpropanetriacrylate, TMPTA). Effects of peroxide and coagent content were studied in terms of melt index (MI), melt viscosity, morphology, thermal, and mechanical properties. At a constant content of the coagent, melt viscosity increased at a low and decreased at a high content of the peroxide. On the other hand, melt viscosity increased monotonically with the coagent concentration at constant peroxide content. The increase and decrease of viscosity were interpreted in terms of crosslinking and chain scission of PP, which governed the rubber domain size and mechanical properties of the reactive blends. © 1995 John Wiley & Sons, Inc.
Role of bulky polysiloxanylalkyi methacrylates in oxygen‐permeable hydrogel materials
Authors: Lai Yu‐Chin
Published: April 2003

Polysiloxanylalkyl methacrylates, such as methacryloxypropyl tris(trimethylsiloxy)silane (TRIS), have been used extensively in rigid gas‐permeable contact lens materials due to their ability to produce high oxygen permeability in the resulting polymeric material. In this study, the role of TRIS was evaluated as a component in silicone hydrogel materials based on polysiloxane‐based prepolymers. It was found that it not only gave high oxygen permeability, but also gave hydrogels with better tear strength and lower modulus. These changes in properties are all favorable for applications such as oxygen‐permeable hydrogel lenses. © 1995 John Wiley & Sons, Inc.
Photoresponsive permeability of polyelectrolyte complex capsule membrane containing triphenylmethane leucohydroxide residues
Authors: Kono Kenji , Nishihara Yasuhiro , Takagishi Toru
Published: April 2003

To develop a functional capsule, which can be controlled to release materials entrapped in the inner aqueous space responding to light, partly crosslinked poly(acrylic acid)–poly‐ethylenimine complex capsules containing a copolymer of acrylic acid and bis[4‐(dimethylamino)phenyl](4‐vinylphenyl)methyl leucohydroxide as an additional membrane component with radii of ca. 3 mm have been prepared. The triphenylmethane derivative on the copolymer dissociated into an ion pair under ultraviolet light irradiation in the weak alkaline region. Permeation of p‐toluenesulfonate through the capsule membrane was enhanced significantly by the photoirradiation after a several minutes time lag under a weak alkaline condition. The photoinduced increase in permeability of the capsule was pH‐dependent. The maximum effect of light on the permeability was observed near pH 8, whereas less enhancement was observed above or below the pH value. When the irradiation of the light was stopped, permeation of the permeant decreased. The photoresponsive permeability change of the capsule membrane can be carried out reversibly. © 1995 John Wiley & Sons, Inc.
Development of an anisotropic conductive adhesive film (ACAF) from epoxy resins
Authors: Asai Shin'ichiro , Saruta Ueki , Tobita Masayuki , Takano Minoru , Miyashita Yasuo
Published: April 2003

A thermoset type anisotropic conductive adhesive film (ACAF), which electrically connects an ITO glass and a flex circuit both having conducting pattersn of less than 100 μm in pitch, has been developed. In this development, bisphenol A and bisphenol F epoxy resins were tested to formulate an ACAF with easy‐to‐handle tackiness, flexibility, and strenght. A curing agent that gives fast cure and long shelf‐life properties to the epoxy resin was also selected. The tensile stress–strain responses of obtained adhesive films were successfully used for determining the formulation. Good aftercure physical properties (electrical and mechanical) were obtained. Durability against high temperature and high humidity were also tested to confirm long‐term stability of the conduction of this ACAF. © 1995 John Wiley & Sons, Inc.
Positron annihilation lifetime study of vapor sorption in polypropylene and polytetrafluoroethylene
Authors: Sánchez Victor , López Rafael , Fucugauchi Luz Alicia , Ito Yasuo
Published: April 2003

Positron annihilation lifetime (PAL) spectra were measured for two different kinds of polymers: polypropylene (PP) and polytetrafluoroethylene (PTFE), during sorption of vapors of the following molecules: n‐hexane, cyclohexane, benzene, methyl methacrylate, acrylic acid, and water. The behavior of ortho‐positronium (o‐Ps) annihilation parameters: lifetime, τ3, and intensity, I3, can be explained by considering different sorption mechanisms in rubbery and glassy polymers. The mean size of the intermolecular‐space holes and the relative free‐volume fraction of PP and PTFE were estimated before and during the sorption process from the o‐Ps parameters obtained. Sorption of n‐hexane, cyclohexane, and benzene in both polymers affect the o‐Ps component in a systematic way, for PP τ3 and I3 tend to decrease, while in PTFE, τ3 stay almost constant and I3 diminishes. These effects are interpreted in relation to the different states of the polymers studied: rubbery for PP and glassy for PTFE. In case of methyl methacrylate molecules, the behavior of o‐Ps parameters was more complicated. For acrylic acid and water, their associated polarity provokes a diminution in I3, which is explained from the viewpoint of the spur model of positronium formation. Large changes in the mean size and the fraction of free volume, as well as their constant behavior in some cases, were interpreted to be due to positive or negative interactions, respectively, between vapor molecules and PP and PTFE, which could be correlated with the solvent‐interaction parameters calculated. © 1995 John Wiley & Sons, Inc.
Effect of morphology on mechanical and rheological properties of butyl acrylate–methyl methacrylate multiphase polymers
Authors: Canche‐Escamilla G. , Mendizabal E. , Hernandez‐Patiño M. J. , Arce‐Romero S. M. , Gonzalez‐Romero V. M.
Published: April 2003

Polymers of butyl acrylate–methyl methacrylate with different morphologies were synthesized by emulsion polymerization. Four types of polymers were obtained: copolymer, core–shell, three layer, and a core–shell with a copolymer layer of variable composition (gradient). The effect of the morphologies on the mechanical and rheological properties of these polymers was studied. It was found that when the same overall composition was used the properties of the polymer can be varied from those of rigid plastic to those of an elastomeric material. It was found that increasing the content of butyl acrylate (BA) improves the mechanical properties and the presence of a copolymer zone improves the impact resistance of the material. © 1995 John Wiley & Sons, Inc.
Thermal characterization of some products obtained by chemically modified poly(vinyl chloride) with phenol
Authors: Cascaval Constantin N. , Robilǎ Gabriela , Stoleriu Aurel
Published: April 2003

The chemical modification of poly(vinyl chloride) (PVC) in reaction with phenol, in the absence of a catalyst and at temperatures within the range of 60°C and the boiling temperature of phenol (180°C), led to the reaction products with the general structure of a vinyl chloride–vinyl phenol copolymer. The synthesized polyphenols were thermally characterized using the following experimental techniques: thermo–optical analysis (TOA), thermogravimetry (TG), derivative thermogravimetry (DTG), and pyrolysis in combination with gas chromatography (P–GC). The PVC samples modified with phenol show a thermal stability lower than the original PVC sample. The glass transition temperatures (Tgs) increase with increased degree of chlorine substitution. The main pyrolysis products of the modified PVC samples are hydrocarbons with low boiling points (C1–C4), benzene, toluene, naphthalene, indan, and phenol. The semiquantitative estimation of the pyrolysis products of the synthesized samples led to the conclusion that the following structural element types can be present, statistically distributed along the chain: vinyl chloride and vinyl phenol units, acetylenic and ethylenic units, and indan type structures. © 1995 John Wiley & Sons, Inc.
Selective crosslinking reaction in polymer blends. III. The effects of the crosslinking of dispersed EPDM particles on the impact behavior of PP/EPDM blends
Authors: Inoue Toshio , Suzuki Tokuhito
Published: April 2003

The selective dynamic crosslinking reaction by means of the N,N'‐m‐phenylene–bismaleimide/poly‐(2,2,4‐trimethyl‐1,2‐dihydroquinoline) system was carried out on PP/EPDM blends and its effect on the Izod impact strength (IIS) was investigated. Three series of PP/EPDM combinations were adopted to establish different morphologies. In each series, the EPDM wt % varied from 5 to 30 at 5 wt % intervals. The system crosslinked the EPDM particles selectively without PP degradation and change of morphology. Following the crosslinking, the IIS at 23, −10, and −30°C increased in all blends, and the critical EPDM wt % at 23°C necessary to cause the dramatic IIS increase was lowered. The increase in interfacial adhesion is considered to be the most important factor necessary for the improvement. The nucleation effect of the crosslinked particles and the decrease of crystallinity of the EPDM were also considered to contribute to the improvement in the IIS. Impact fracture energy absorption can thus be changed by adjusting the magnitude of the interfacial adhesion by the dynamic crosslinking even at essentially the same morphology. © 1995 John Wiley & Sons, Inc.
Effect of network structure on thermal and mechanical properties of biphenol‐type epoxy resins cured with phenols
Authors: Ochi M. , Tsuyuno N. , Sakaga K. , Nakanishi Y. , Murata Y.
Published: April 2003

In the biphenol‐type epoxy resin cured with catechol novolac (CN), a very weak glass transition and, thus, a very high rubbery modulus were observed. On the other hand, the glass transition was clearly observed in the system cured with phenol novolac (PN). This means that the micro‐Brownian motion of network chains is highly suppressed in the system cured with CN. The reason for this suppression of the chain motion in the CN‐cured system has been pursued from the viewpoint of the conformation of network chains. The disappearance of the glass transition in the biphenol‐type resin depends on the formation of the active hydrogens in the curing agents. Thus, it was suggested that the suppression of the micro‐Brownian motion is due to the orientation of the biphenyl groups in the network. Moreover, it has been shown that the mechanical and bonding strength at high temperature is considerably improved by the suppression of the network chain motion in the CN‐cured biphenol resin system. © 1995 John wiley & Sons, Inc.
Surface modification of polyimide films by graft copolymerization
Authors: Loh F. C. , Lau C. B. , Tan K. L. , Kang E. T.
Published: April 2003

Surface modifications of polyimide (PI) films by Ar‐plasma, O2‐plasma, and O3 pretreatment and by near‐UV light‐induced graft copolymerization with water‐soluable monomers, such as acrylamide (AAm), acrylic acid (AAc), and sodium salt of 4‐styrenesulfonic acid (NaSS), have been carried out. The angle‐resolved x‐ray photoelectron spectroscopy (XPS) results show that surface pretreatment results in the formation of peroxide species on the polymer film surfaces and leads to a substantial enhancement of the density of surface graft. The XPS results further suggest that in the case where substantial grafting has taken place, the grafted polymer either forms a surface layer uniformly intermixed with the substrate chains, or a graft‐rich surface layer in the case of sterically hindered migration of the graft. The resulting surface structures are further supported by dynamic water contact angle measurements. These surface structures are probably associated with the thermoset character of PI, as they differ from the stratified microstructures observed on most thermoplastic films after surface modification by graft copolymerization with hydrophilic monomers. © 1995 John Wiley & Sons, Inc.
Applications of magnetic resonance imaging to ion‐exchange resins
Authors: Wallner Anton S. , Ritchey William M.
Published: April 2003

Magnetic resonance imaging (MRI) was used to determine swollen resin morphology in cation–exchange beads. The study of the nonuuniformity of the swelling of cation–exchange beads [sulfonated styrene–divinylbenzene (SDVB) copolymers] is of interest because the exchange kinetics and other properties are expected to be strongly influenced by the swelling. MRI can replace current invasive and destructive methods for studying the morphology of these resins. Several types of ion–exchange resins were examined including beads which exhibit homogeneous swelling, heterogeneous swelling, and partially sulfonated beads. The variation in intensity observed is due to a variation in crosslink density, degree of sulfonation, composition, sulfone bridging, or a combination of these variables. Due to their small size, the beads were also imaged using a small coil insert. Results are compared to commercially available insert images in terms of signal‐to‐noise and experiment time. © 1995 John Wiley & Sons, Inc.
Effects of low‐profile additives on the curing reaction of unsaturated polyester resins
Authors: Sun B. , Yu T. L.
Published: April 2003

The effect of low‐profile additives (LPA), i.e., poly(vinyl acetate) (PVAC) and poly(methyl methacrylate) (PMMA), on the curing reaction of unsaturated polyester (UPE) resins was studied by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The curing reaction profiles were determined by DSC, while GPC was used to investigate the variation of the sizes of microgel particles during the early stage of curing reaction in UPE–styrene resins. The DSC experimental results indicated that the curing reaction rate decreased as the concentration of LPA increased. At a fixed LPA concentration, the curing reaction rate was slower for resins mixed with LPA possessing worse compatibility with UPE resins. During the early stage of curing reaction, the size and structure of the UPE microgels formation strongly depended on the concentration of LPA and also on the compatibility of the components in the curing system. The experimental results of this study revealed that the concentration of LPA and the compatibility of LPA with UPE resins had a strong influence on the polyester microgel formation and the curing behavior. © 1995 John Wiley & Sons, Inc.
Solvent effect on fluorescence lifetimes at swollen glassy–rubber interphase domains in blendlike particles
Authors: Pekcan Önder
Published: April 2003

Fluorescence of naphthalene (N) labeled to poly(methyl metracrylate) (PMMA) particles sterically stabilized by polyisobutylene (PIB) was studied by transient fluorescene method in iso–octane, hexadecane, and in powder from. When samples of dispersions are annealed above 60°C, their room temperature lifetimes increase, and when powder samples are so annealed, lifetimes decrease. Self‐quenching effects among N*/N pairs were eliminated to isolate unimolecular lifetimes. Low‐frequency intramolecular vibrations are found responsible for the temperature dependence of nonradiative transition of excited N molecules. Corresponding activation energies are measured and found to be between 2300 and 1100 cal/mol. Solvent effects on these activation energies are discussed. © 1995 John Wiley & Sons, Inc.
Surface behavior of dilute blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers
Authors: Gorelova M. M. , Pertsin A. J. , Volkov I. O. , Filimonova L. V. , Makarova L. I. , Zhdanov A. A.
Published: April 2003

X‐ray photoelectron spectroscopy is used to study the surface segregation of siloxane in blends of poly(vinyl chloride) with siloxane–urethane–ethyleneoxide oligomers. At high concentration of the oligomeric additive, the surface segregation of siloxane in the blends strongly depends on the molecular architecture of the additive: the segregation is much higher when the siloxane blocks are at the ends of the oligomeric chains. At low additive concentrations, the surface segregation of siloxane is governed solely by the siloxane concentration in the bulk. © 1995 John Wiley & Sons, Inc.
Graft‐interpenetrating polymer networks of polyurethane and bismaleimide
Authors: Hsieh K. H. , Hung W. Y. , Liao D. C. , Kao S. C.
Published: April 2003

Graft‐interpenetrating polymer networks (graft‐IPNs) of polyurethane (PU) and bismaleimide (BMI) were prepared by using a simultaneous polymerization technique. The effects of the PU molecular weight and the amounts of the PU on the mechanical properties, density, and morphology of the IPNs are discussed. The graft‐IPNs exhibited superior ultimate tensile strength and large improvement in flexural strength when the short soft segments of the PU were introduced. Better thermal stability of the IPNs was shown by increasing the BMI content. The heterogeneous and phase‐separated characteristics were found from the results of dynamic mechanical analysis. The maximum density was achieved by the graft‐IPNs structure when 33.3 wt % of PU with short soft chain length was added. The graft‐IPNs also showed heterogenous morphology in the micrographs when a large amount of PU was incorporated. © 1995 John Wiley & Sons, Inc.