bluuebunny/crossref_metadata_2025 huggingface dataset:
Polyacrylamide‐reactive styrene/unsaturated polyester microgel composites
Authors: Ruckenstein E. , Liang L.
Published: April 2003

Reactive microgels (RM) were prepared by the copolymerization of styrene and an unsaturated polyester in an emulsion of oil (styrene + unsaturated polyester) in water. The adsorption of the unsaturated polyester on the water–oil interface ensured the stability of the emulsion. Furthermore, polyacrylamide (PAAM) crosslinked with RM was obtained by suspending RM particles in an aqueous AAM solution and polymerizing the system at 70°C to obtain a PAAM–RM composite. The extraction experiments of the RM with dioxane and of the PAAM with water indicated the presence of small amounts of soluble PAAM homopolymers and negligible amounts of free RM, the materials being PAAM crosslinked by RM. The extent of swelling of these materials in water decreased with increasing weight ratio of RM/AAM and was independent of the composition of RM. When the final polymerization temperature was increased to 130°C, RM reacted not only with AAM to form a crosslinked polymer, but also with itself to form semi‐interpenetrating reactive polymer networks (SIRPN). The extent of swelling of PAAM–RM SIRPN in water was much lower than that of the PAAM–RM material. Membranes were also prepared by hot pressing at 200°C the PAAM–RM and PAAM–RM SIRPN composites. The swelling behavior of these membranes in water, acetone, tetrahydrofuran, acrylic acid, ethyl alcohol, and dioxane, as well as in the mixtures of ethyl alcohol–water, acetone–water, tetrahydrofuran–water, and acrylic acid–water, was investigated. © 1995 John Wiley & Sons, Inc.
Effects of orientation on the transport of d‐limonene in polypropylene
Authors: Moaddeb M. , Koros W. J.
Published: April 2003

Kinetics and equilibria of sorption and desorption of d‐limonene in three polypropylene films (unoriented polypropylene [UN], uniaxially oriented polypropylene [UA], and biaxially oriented polypropylene [BA]) were studied at 30°C and various penetrant activities. The weight percent uptake of a saturated vapor of limonene in UN, BA, and UA films ranged ranged from 12.5 to 19.0%. The kinetics of sorption of a saturated vapor of limonene in these polymers exhibits an increasing tendency toward Fickian transport as the degree of orientation increases, with the highly oriented BA approaching a Fickian response. As the penetrant activity is lowered, sorption kinetics tends to show a Fickian response more closely even for the UN and the UA films. Desorption of limonene from the three samples appears to be Fickian and considerably faster than sorption in the initial stages; however, the process decelarates after roughly half of the penetrant has desorbed. Subsequent exposure of the three oriented films to a saturated vapor of limonene resulted in identical sorption kinetics, suggesting the absence of crazing or other irreversible damage often associated with anomalous sorption in glassy polymers. These results illustrate that the concentration dependent anomalies in kinetics of sorption of a large penetrant such as limonene in the unoriented polypropylene film may be influenced by orientation to yield Fickian transport even at the highest external surface concentration. Thus, the orientation processes appear to affect large‐scale swelling‐induced relaxations to a larger degree than it does the diffusional processes which are dependent on smaller‐scale segmental motions. © 1995 John Wiley & Sons, Inc.
Copolymers of higher alkyl methacrylates with triallyl cyanurate
Authors: Ryttel Anna
Published: April 2003

Copolymers of higher methacrylates (propyl, pentyl, hexyl, cyclohexyl, heptyl, octyl, and dodecyl) with triallyl cyanurate were synthesized by free‐radical polymerization using benzoyl peroxide as initiator. The properties of the copolymers such as thermal stability, Tg, Vicat softening temperature, hardness, refractive indices nD, chemical stability, density, and shrinkage on polymerization were studied. The influence of the alcohol alkyl chain length in methacrylates and the content triallyl cyanurate in copolymers on their properties is discussed. © 1995 John Wiley & Sons, Inc.
Sequential crystallization kinetics of poly(p‐phenylene sulfide) doped with carbon or graphite particles
Authors: Chen Jen‐M. , Woo E. M.
Published: April 2003

Isothermal crystallization kinetics were investigated by differential scanning calorimetry (DSC) for poly(p‐phenylene sulfide) (PPS) doped with amorphous carbon or crystalline graphite particles. Both types of carbon forms have been found to affect the crystallization behavior of PPS to different extents. The crystalline graphite particles have a more pronounced effect on the overall rate as well as mechanisms of PPS crystallization than do the amorphous carbon particles. Relative contributions and competition from crystallizations of two different crystals in the later‐stage crystallization of PPS have been found to cause the phenomenon of deviation from linearity in the Avrami plots. A sequential crystallization model has been shown to describe well the crystallization behavior of the PPS doped with the particles. © 1995 John Wiley & Sons, Inc.
Preparation of glass‐fiber membranes grafted with poly(NIPAAm containing triphenylmethane leucocyanide) and permeation of solutes through the membranes
Authors: Kurihara Seiji , Yoshimura Kazuhiro , Ogata Tomonari , Nonaka Takamasa
Published: April 2003

Glass‐fiber membranes (GF membranes) grafted with poly(N‐isopropylacrylamide containing triphenylmethane leucocyanide) [poly(NIPAAm–LeCN)] were prepared. Ultraviolet irradiation of the GF membranes with poly(NIPAAm–LeCN) induced a change in the phase‐transition temperature of the poly(NIPAAm) segments. The changes in both the phase‐transition temperature of the poly(NIPAAm) segments and the permeation rate of solutes are discussed in relation to the dissociation of LeCN molecules. © 1995 John Wiley & Sons, Inc.
Flexibility improvement of epoxy resin by using polysiloxane–PGMA (MMA) composite particles
Authors: Tong Jiangdong , Bai Ruke , Pan Caiyuan , Goethals Eric J.
Published: April 2003

A study on the increase of the flexibility and decrease of the internal stress of cured epoxy resins by addition of polysiloxane rubber particles grafted with and without glycidyl methacrylate (GMA) or methyl methacrylate (MMA) is reported. Polysiloxane latex was obtained by cycling a mixture of polysiloxane containing a vinyl group and aSiH group, respectively, emulsifier, and water in a homogenizer. Graft polymerization of GMA (or MMA) on these rubber particles was performed in the latex under γ‐ray irradiation of 60Co. The rubber particles were used to improve the flexibility of the epoxy resin. The particles grafted with GMA showed a homogeneous distribution in the matrix, better inducing and terminating craze. Comparisons were made among the particles grafted with MMA and various MMAGMA or a series of GMA; the results indicated that the particles grafted with GMA (graft ratio = 10%) showed the greatest increase of elongation and decrease of internal stress. The factors influencing the toughness of the epoxy resin matrix are discussed. © 1995 John Wiley & Sons, Inc.
Survey of preparation techniques of monodispersed microspheres of glycidyl methacrylate and its derivatives
Authors: Hoshino Mitsutoshi , Arishima Koichi
Published: April 2003

This article describes the preparation of monodispersed microspheres of glycidyl methacrylate, 2‐hydroxyethyl methacrylate, and triethylene glycol dimethacrylate by radical polymerization. The initial stage of the polymerization reaction began in the liquid phase. As the polymerization proceeded, a nuclear polymer chain of microspheres was generated from soluble oligomeric radicals and then solidified from the liquid phase. The radius of the microspheres was controlled by polymerization parameters, such as monomer concentration, polymerization time, and the kind of polymerization solvent. A small number of thin platelike substances may be produced by the anisotropy of the two‐dimensional monomer added to the oligomeric radicals. The monodispersed microspheres were achieved through the use of the following: (1) a fluorinated tube in which the polymerization reaction proceeded; (2) a monomer concentration of about 1 mol/L; (3) a higher concentration of crosslinking regeant than used commercially; (4) the prevention of the occurrence of polymer microsphere aggregation; (5) pouring the solution mixtures into a large amount of cooled acetone after the polymerization reaction; and (6) the use of a low‐temperature purification process and centrifugation at low temperature. This article describes the mechanism of microsphere formation and growth by solution polymerization. © 1995 John Wiley & Sons, Inc.
Introduction of functional groups on polyethylene surfaces by a carbon dioxide plasma treatment
Authors: Terlingen Johannes G. A. , Gerritsen Hermina F. C. , Hoffman Allan S. , Feijen Jan
Published: April 2003

Poly(ethylene) (PE) films were treated with a carbon dioxide (CO2) plasma to study the formation of oxygen‐containing functional groups at the surface. Modified and nonmodified films were characterized by X‐ray photoelectron spectroscopy (XPS) and water contact angle measurements. During the CO2 plasma treatment, the PE surface is etched and oxidized, yielding films with a very hydrophilic surface. The oxygen incorporation at the surface is fast and can be described by a combination of a zero‐order incoraporation and a first‐order etching process. Several oxygen functionalities such as carboxylic acid (approximately 14% of the oxygen persent), ketone/aldehyde (25%), and hydroxyl/epoxide (5–9%) groups were introduced at the surface by the plasma treatment. This was shown by using derivatization reactions for specific functional groups followed by XPS analysis. The wettability of the plasma‐treated surface decreased when the films were stroed for prolonged periods of time in air. This aging process could not be completely reversed by immersion of the films in water. © 1995 John Wiley & Sons, Inc.
Synthesis of graft copolymers. Part I. Synthesis of macroinitiators
Authors: Morales Graciela , Castro Efraín , Kaluyzhnaya Elena , Guerrero‐Santos Ramiro
Published: April 2003

Thermal polymeric initiators, having pendant 1,2‐bis(trimethylsilyloxy)tetraphenylethane (or benzopinacolate) groups along the chain, have been prepared. First, the reactivity ratios of 4‐vinylbenzophenone (4VBP) and 4‐methacryloyloxybenzophenone (MOB) copolymers with styrene or methylmethacrylate were determined. Then the randomly containing 4VBP or MOB copolymers were transformed into polymeric initiators by duplication reaction of the attached benzophenone. Polymerization of MMA or St initiated by the resulting copolymers having pendant benzopinacolate groups was carried out yielding PMMA‐g‐PS and PS‐g‐PMMA. © 1995 John Wiley & Sons, Inc.
A simple neural network based model approach for nylon 66 fabrics used in safety restraint systems: A comparison of two training algorithms
Authors: Keshavaraj Ramesh , Tock Richard W. , Nusholtz Guy S.
Published: April 2003

Airbag technology relies on woven fabrics as the material of construction and particularly on knowledge pertaining to the fabric's permeability as a function of pressure drop, inflation temperature of the gas, fabric weave, fiber denier, and biaxial stress–strain relationships under biaxial conditions. While fabric permeability can be quantified by actual experimental measurements, the number and nonlinearity of the variables involved make the experiments time‐ and cost‐intensive. Moreover, interpolations within a given data set can yield questionable results. In this study, a very simple feed forward neural network architecture was used with a training rule involving a nonlinear optimization routine for updating weights of the proposed network. This training was compared to the training with an error‐back propagation routine. During this training, the ANN is introduced to data that contain the actual cause and effect patterns, with adjustments being made by changes in weighting factors until the errors in the output variables are minimized. Once trained, ANN can ascertain the essentials of the relationships and assimilate henceforth. In this study, after the initial training, the ANN was tested on additional data which were not part of the training processes. The predictions of the proposed trained network agreed very well with the new experimental data. On this basis, the proposed ANN model appears to be an effective tool for modeling airbag fabric behavior. This ANN model can assimilate relationships between different variables from the real‐world data and does not require extensive normalizing of the process data like a back‐propagation algorithm. Once trained, only fractions of a second are needed for information assimilation and output generation. This coupled with simplicity of use and accuracy of predictions from the real‐world data make this ANN model attractive for on‐line applications. © 1995 John Wiley & Sons, Inc.
Mechanism of radiation vulcanization of natural rubber latex sensitized by monoacrylates
Authors: Hill D. J. T. , O'Donnell J. H. , Perera M. C. S. , Pomery P. J. , Smetsers P.
Published: April 2003

The mechanism of radiation vulcanization of natural rubber with 2‐ethyl hexyl acrylate (2EHA) monomer was investigated using electron spin resonance spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The primary radicals formed in the arcylate molecule were found to abstract the allylic hydrogens of the polyisoprene. Crossliking may occur through the allylic radicals and/or main chain radicals formed on the polyacrylate. Acrylate was found to concentrate in the rigid regions of the crosslinked rubber indicating heterogeneity and a nonuniform distribution of the acrylate in the latex particles. The addition of the acrylate and the irradiation seems to effect the Brownian motion of the latex particles. Both the viscosity and the NMR peak widths are effected by the irradiation. Addition of 5% 2EHA increases the crosslinking by a factor of 3.6. The thermal stability of the rubber first increases with the dose in the presence of acrylate, but drops at higher doses due to peroxide formation. © 1995 John Wiley & Sons, Inc.
Synthesis, characterization, and thermotropic properties of side‐chain liquid crystalline polysiloxane polymers with an oligo(ethylene oxide) unit in the side chain
Authors: Chang‐Chien Guo‐Ping , Kuo Jen‐Feng
Published: April 2003

A series of new alkene and octenyloxy monomers containing 4′‐[oligo(ethylene oxide)] n monomethyl ether 4‐biphenyl ether carboxyl benzoate [MS3BDBEn] (n = to 3) and 1‐ (p‐methoxydiphenyl)–(carboxyl benzoate) [oligo(ethylene oxide)]n [MSm+2BEnDB] (m = 1, 6; n = 1 to 3) as end groups were synthesized. The molecular structure of the monomers was charaterized using nuclear magnetic resonance (NMR) spectroscopy. These monomers were grafted onto poly(methylhydrosiloxane)s (PMHS) by the platinun‐catalyzed hydrosilylation process. The thermal transition temeratures and mesophase textures of the monomers and the polysiloxane polymers have been determined by diffential scanning calorimetry (DSC) and by polarized optical microscopy. The effect of changes in chemical structure on the mesophase properties, glass transition temperature, isotropic temperature, and mesophase texture of the monomers and the polysiloxane polymers is discussed. Polymers PS3BDBEn showed smectic and nematic phases which were not analogous to their precursor nematic monomers MS3BDBEn. Both monomers MSm+2BEnDB and their polymeric homologous PSm+2BEnDB did not exhibit mesophase properties. This demonstrated that the polymer effect could not stabilize the mesophase obtained from mesogenic core which contained a flexible oligo(ethylene oxide) unit interconnecting aromatic group. © 1995 John Wiley & Sons, Inc.
Surface modification of calcium carbonate used for polypropylene blending with dimeric aluminates
Authors: Liao Kairong , Chen Xuexin , Zheng Chenmou
Published: April 2003

There kinds of dimeric aluminates (2DH‐306, 2DH‐324, and 2DH‐335) have been used for surface modification of calcium carbonate (CaCO3) particles. The dimeric aluminates were shown to have an appreciable coupling effect at the interfaces between the light calcium carbonate (L‐CaCO3) and polypropylene (PP) in the blends by mechanical property study and SEM observation. In the 2DH‐306 modified L‐CaCO3/PP (25/75) system, the impact strength exceeded that of the nonmodified system by more than 30 kJ/m2. X‐ray study showed that the dimeric aluminates had a synergistic effect with L‐CaCO3 on the formation of PP β‐crystal, which would exert an important influence on the elongation ratio at break for the L‐CaCO3/PP blends. © 1995 John Wiley & Sons, Inc.
Permeation of simple gases through plasma polymerized films from fluorine‐containing monomers
Authors: Oh Saejoong , Zeng Yuan , Koo Ja‐Kyung , Zurawsky W. P.
Published: April 2003

The permeation of several different permanent gases through plasma polymer membranes was studied. The plasma polymers were produced by a microwave discharge of various fluorine‐containing monomers. Plasma polymers made from fluorine‐rich monomers (F/C ≈ 1) yield films with the highest selectivities; those made from low fluorine content monomers show very little selectivity among the various gases. CO2 solubility is very high in the fluorine‐rich plasma polymers and gives rise to large CO2 to CH2 selectivities. © 1995 John Wiley & Sons, Inc.
Rubberwood–polymer composites based on diallyl phthalate and methyl methacrylate
Authors: Rozman H. D. , Kumar R. N. , Abusamah A.
Published: April 2003

Wood–polymer composites (WPC) of rubberwood (Hevea brasiliensis), were prepared by impregnating the wood with methyl methacrylate (MMA), and the combinations of MMA and diallyl phthalate (MMA/DAP). Polymerization was carried out by catalyst heat treatment. Impregnated samples showed significant improvements in compressive and impact strengths, hardness, and dimensional stability (toward water) over that the untreated rubberwood. © 1995 John Wiley & Sons, Inc.
Tetramethylthiuram disulfide and 2‐mercaptobenzothiazole as binary accelerators in sulfur vulcanization. I. Exchange reactions between the accelerators and sulfur in the absence of rubber
Authors: Giuliani B. V. M. K. , McGill W. J.
Published: April 2003

Exchange reactions between tetramethylthiuram disulfide, 2‐mercaptobenzothizole, and sulfur were studied by heating powdered mixes to vulcanization temperatures at a programmed rate in a DSC. The reaction was stopped at points along the thermal curve and the mixture was analyzed by HPLC. On dissolution, even unheated samples undergo a sulfide exchange reaction leading to a mixed accelerator, while polysulfides of the thiuram and mixed accelerator form in low concentrations. On heating, higher concentrations of these polysulfides are formed, particularly in the presence of elemental sulfur. Dimethyldithiocarbamic acid, formed in the exchange, influences the product spectrum if it remains trapped in the DSC pan. Tetramethylthiourea is formed only at elevated temperatures when dimethylamine, a degradation product of the acid, is trapped in the DSC pan. A series of reactions is proposed to explain the product spectrum obtained under different conditions. © 1995 John Wiley & Sons, Inc.
Carbon–polymer composite electrodes for redox cells
Authors: Haddadi‐Asl V. , Kazacos M. , Skyllas‐Kazacos M.
Published: April 2003

Conductive carbon–polymer composite electrodes for the vanadium redox flow battery were developed and their properties investigated. Conductive polymer composite materials were fabricated by mixing PVC, nylon 6, nylon 11, LDPE, and HDPE with conductive fillers. To overcome the deterioration in the mechanical properties of carbon–polymer composites with high carbon loading, a range of chemically resistant rubbers was blended into the composites. Electrical, mechanical, permeation, and electrochemical studies show that the HDPE composite is the best electrode matrix material for the vanadium redox battery. The performance of a vanadium redox flow cell employing the best composite electrode was also evaluated and voltage efficiencies as high as 88% were obtained with electrodes employing graphite felt active layers bonded to the carbon–polymer composite substrates. © 1995 John Wiley & Sons, Inc.
Synthesis of formaldehyde‐dibenzo‐18‐crown‐6 condensation resins containing phosphonic acid groups and their alkali‐metal cation sorption
Authors: Zhao Qiang , Bartsch Richard A.
Published: April 2003

Ion‐exchange resins are prepared by introducing phosphonic acid monoethyl ester or phosphonic acid groups into formaldehyde condensation poly(dibenzo‐18‐crown‐6) resin. The phosphonic acid ion‐exchange groups provide accessibility for metal cations, while the ion‐selective cyclic polyether binding site influences the selectivity. The selectivities and efficiencies for competitive alkali‐metal cation sorption from aqueous solutions by these crown ether‐containing phosphonic acid resins are strongly influenced by the pH of the aqueous solution, the identity of the phosphonic acid groups, and the molar ratio of ion‐exchange groups to crown ether units. © 1995 John Wiley & Sons, Inc.
Study of radical copolymerization of tetrafluoroethylene with ethylene in suspension
Authors: Kostov G. K. , Nikolov Al. T.
Published: April 2003

Radical copolymerization of tetrafluoroethylene (TFE) with ethylene (E) was initiated by 2,2′‐azo‐bis‐isobutyronitrile in batch and semibatch operation. The effect of reaction conditions (temperature, pressure, stirring speed, molar ratio of monomers, etc.) on copolymerization rate and copolymer molecular weight was studied. The highest reaction rate was observed at TFE content over 70 mol % and was found to be proportional to initiator concentration and total monomer content by powers of 0.9 and 1.54, respectively. These dependencies were attributed to the heterophase character of the copolymerization.

The monomer reactivity ratios and overall activation energy of the reaction were determined. The effect of the monomer composition on the distribution of monomer units in the copolymer chain was studied. Kinetic mechanism of the copolymerization was suggested.

Some of the basic physical properties and chemical resistance of the alternating copolymers synthesized were also determined. © 1995 John Wiley & Sons, Inc.
The effects of spinning conditions on the structure formation and the dimension of the hollow‐fiber membranes and their relationship with the permeability in dry–wet spinning technology
Authors: Kim Jeong‐Hoon , Park You‐In , Jegal Jonggeon , Lee Kew‐Ho
Published: April 2003

Hollow‐fiber membranes were prepared by dry–wet spinning under different spinning conditions. The used spinneret was tube‐in‐orfice type and the membrane material was polysulfone (Udel P‐3500). N‐methyl‐2‐pyrrolidinone (NMP) and water were used as solvent and coagulant, respectively. The concentration of the dope solution was 22 wt %. The effects of the three spinning factors—spinning height; extrusion rates of dope solution and inner coagulant; dimensions (inner diameter, outer diameter, and thickness) and permeation properties of the hollow‐fiber membranes—were studied. The results were as follows: With changes in the spinning factors, spinning velocity and falling time before the membrane entered the water (coagulant) were changed; consequently, the structures and the dimensions of the hollow‐fiber membranes varied with a certain tendency. The permeation properties of the hollow fibers were related very closely to the changes in the fibers' structures and dimensions. © 1995 John Wiley & Sons, Inc.
Influence of activation time on the properties of polyacrylonitrile‐based activated carbon hollow fiber
Authors: Yang Ming‐Chien , Yu Da‐Guang
Published: April 2003

Activated carbon hollow fiber (ACHF) was prepared from polyacrylonitrile (PAN) hollow fiber through carbonization in nitrogen and activation with carbon dioxide. The effect of the activation time on the pore size distribution and the surface structure of the resulted ACHF was investigated. The results show that increasing the activation time at 800°C can increase the number of pores and reduce the crystal size, the tensile strength, the modulus, and the elongation. © 1995 John Wiley & Sons, Inc.
A simple and efficient SEC/GPC linear calibration technique using broad‐range standards
Authors: Nwankwo Emeka O. , Abbott Scot D.
Published: April 2003

A simple method for calibrating high‐performance SEC/GPC systems is presented. This technique sequentially finds the correct slope, D2, by tracking the calculated polydisperity, P, using arbitrary calibration slopes from which the intercept, D1, is ultimately back‐calculated. The case of application and relative efficiency of this search technique are highlighted and discussed. Theoretical justification of the simple form of the convergence equation is presented using two distribution models—the Gaussian (pseudo‐Flory) and the sine (cosine) exponential models. © 1995 John Wiley & Sons, Inc.
Modification of PP/HDPE blends by PP‐PE sequential polymerization product
Authors: Zhu Wei , Zhang Xuequan , Huang Baotong , Feng Zhiliu
Published: April 2003

The morphology and mechanical properties of polypropylene/high‐density polyethylene (PP/HDPE) blends in a wide range of compositions modified by a sequential Ziegler‐Natta polymerization product (PP‐PE) have been investigated. PP‐PE contains multiple components such as PP, ethylene‐propylene copolymer (EPC), and high molecular weight polyethylene (HMWPE). The effects of PP‐PE on the mechanical properties and morphology of the PP/HDPE blends are the aggregative results of all its individual components. Addition of PP‐PE to the blends not only improved the tensile strength of the blends, but the elongation at break increased linearly while the moduli were nearly unchanged. Morphological studies show that the adhesion between the two phases in all the blends of different compositions is enhanced and the dispersed domain sizes of the blends are reduced monotonously with the increment of the content of PP‐PE. PP‐PE has been demonstrated to be a more effective compatibilizer than EPC. Based on these results, it can be concluded that the tensile strength of the blends most on the adhesion between the two phases and the elongation at break depends most on the domain size of the dispersed component. © 1995 John Wiley & Sons, Inc.
Evaluation of recycled PP/rubber/talc hybrids
Authors: Long Yu , Tiganis Bill E. , Shanks Robert A.
Published: April 2003

Mechanical properties of recycled PP/rubber/filler systems were studied and mechanisms were discussed on the basis of molar mass and molar mass distribution, morphologies, and thermal behavior. Characteristics of recycled PP/rubber/filler depend on degradation of PP and additional components. Recycling processes decreased impact strength, but it seemed not to affect tensile properties significantly. Aging with UV and moisture affected mechanical properties by some degree of PP chain scissions and ethylene chain crosslinking in EP rubber. Inorganic filler acted as a crack center and accelerated aging degradation. Paint decreased mechanical properties significantly by introducing stress concentrations. Recycle processing decreased the molar mass and increased the molar mass distribution of PP. Aging with UV decreased crystallization temperature and increased crystallization half‐time by decreasing nucleation. © 1995 John Wiley & Sons, Inc.
Effect of particle size on impact strength of polymer blends
Authors: Jiang Wei , Liang Haojun , Zhang Jilin , He Dayong , Jiang Bingzheng
Published: April 2003

The effect of particle size on impact strength of polymer blends with ductile fracture was studied. The results are in agreement with the experiments. © 1995 John Wiley & Sons, Inc.
Poly(styrene‐graft‐ethylene oxide) as a compatibilizer in polystyrene/polyamide blends
Authors: Jannasch Patric , Wesslén Bengt
Published: April 2003

Polystyrene (PS) blends containing a dispersed phase of either polyamide‐6 (PA‐6) or polyamide‐12 (PA‐12) were compatibilized by additions of 1, 3, or 5 wt % poly(styrene‐graft‐ethylene oxide). The graft copolymers were found to have a stabilizing effect on the domain sizes. Weight average radii of PA‐6 domains in compression molded samples were reduced by a factor of 5 with 3 wt % graft copolymer added. The corresponding size reduction for PA‐12 domains was by a factor of 3. Also, the domain sizes were more uniformly distributed in blends containing the graft copolymers. Thermal analysis of the blends revealed that compatibilization retarded the PA crystallization, with some PA crystallizing at the PS glass transition. This retarded crystallization is explained as a result of the domain size reduction and by the presence of graft copolymer at the interface. The graft copolymers had a toughening effect on the blends and the impact strength of a PS/PA‐12 blend was improved by 65% by adding 3 wt % of graft copolymer. Binary blends of the PA and poly(ethylene oxide) (PEO) were investigated in a separate study to verify miscibility of the graft copolymer side chains and the PA. Hydrogen bonding between PA‐6 and PEO was confirmed by IR spectroscopy and partial miscibility was indicated by melting point depressions. © 1995 John Wiley & Sons, Inc.
iPP/HDPE blends: Interactions at lower HDPE contents
Authors: Blom H. P. , Teh J. W. , Rudin A.
Published: April 2003

Mechanical and rheological properties of blends of polypropylene (PP) and linear polyethylene (PE) were studied, with particular attention to the effects of aging of such mixtures. These two olefin polymers are basically incompatible. In PP‐rich blends, addition of highdensity PE (HDPE) causes only a slight decrease in tensile properties and impact resistance of injection‐molded specimens. In all cases, annealed specimens have higher moduli and lower impact strength than as‐molded products. While none of these changes are very drastic, the addition of small amounts of HDPE was observed to result in a serious decrease of gate‐region impact resistance of thin‐walled moldings. Blends with 10–20% HDPE exhibited an unexpected interaction in tensile, thermal, and melt‐flow properties as well as in crystallization behavior. © 1995 John Wiley & Sons, Inc.
Studies of rigid poly(vinyl chloride) (PVC) compounds. I. Morphological characteristics of poly(vinyl chloride)/chlorinated polyethylene (PVC/CPE) blends
Authors: Chen C. H. , Wesson R. D. , Collier J. R. , Lo Y. W.
Published: April 2003

Chlorinated polyethylene (CPE) is a commonly used impact modifier of poly(vinyl chloride) (PVC). The major goal of this research was to understand the fundamental morphological aspects of PVC/CPE blends. Scanning electron microscopy (SEM) was used to image the surface structure of these blends, and both transmission electron microscopy (TEM) and scanning‐transmission electron microscopy (S‐TEM) were used to image the morphological boundaries of the blends. TEM imaging distinguishes the boundaries between PVC and CPE more clearly or better than does S‐TEM, but it is time‐consuming. However, some CPE particles are not observed in TEM because of inefficient staining. S‐TEM imaging is much faster and does not depend on staining for the imaging of the CPE phase. © 1995 John Wiley & Sons, Inc.
Studies on the formation of novel copolyesters containing naphthalene and aralkyloxy structures
Authors: Sun Y.‐M. , Wang C.‐S.
Published: April 2003

Copolyesters containing naphthalene structure were synthesized from bis(hydroxyethyl)naphthalate (BHEN) and various aralkyloxy diols. The starting bis(4‐(2‐hydroxyethoxy)aryl) compounds were derived from a nucleophilic substitution of various bisphenols with ethylene carbonate in the presence of potassium iodide (KI). Copolyesters having intrinsic viscosities of 0.50 to 0.60 dL/g were obtained by melt polycondensation in the presence of metallic catalysts. The effects of reaction temperature and time on the formation of copolyesters were investigated in order to obtain an optimum condition for copolyester manufacturing. The optimal reaction temperature and time were found to be 290 to 310°C and 90 to 120 min, respectively. Most of these copolyesters have better solubilities than polyethylene naphthalate (PEN) in aprotic solvents such as N‐methyl‐2‐pyrrolidone or m‐cresol. The thermal properties of the copolyesters were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Glass transition temperatures of these copolyesters were in the range of 90 to 141°C, and 10% weight loss values in nitrogen were all above 460°C. © 1995 John Wiley & Sons, Inc.
Influence of poly(arylether sulfone) molecular weight distribution on measures of global thermal stability
Authors: Broadbelt Linda J. , Klein Michael T. , Dean Barry D. , Andrews Stephen M.
Published: April 2003

The dependence of the thermal stability of high‐performance poly(arylether sulfones) (PAES) on the initial molecular weight distribution and backbone structure was assessed experimentally and through computer simulation. Reaction of PAES polymers resulted in the formation of an insoluble gel fraction and significant changes in weight and number average molecular weights of the sol fraction. A PAES with alternating ether and sulfone linkages formed a larger fraction of gel at a given reaction time than a PAES with the hydroquinone moiety. For a given chemical composition, more rapid molecular weight changes and gel fraction formation were observed for the polymer with the higher value of the initial weight average molecular weight. The growth of molecular weight was also faster for the polymer with the broader initial distribution. The simultaneous increase in Mw and decrease in Mn suggested the occurrence of two types of overall reactions: scission and addition. Simulation of these reactions using Monte Carlo kinetics allowed estimation of the range of probability for bond scission, R, of 0.5 < R < 0.8 capable of accounting for the observed experimental behavior. The dependence of the simulated molecular weight changes on the initial molecular weight distribution agreed qualitatively with the experimental trends. © 1995 John Wiley & Sons, Inc.
Crystallization of very low density copolymers of ethylene with α‐olefins
Authors: Minick J. , Moet A. , Hiltner A. , Baer E. , Chum S. P.
Published: April 2003

Differential scanning calorimetry (DSC) was used to analyze the crystal distribution in homogeneous ethylene–octene copolymers polymerized by the constrained geometry catalyst technology (CGCT). To minimize ambiguities from thermal history effects, copolymers were isothermally annealed at temperatures within the melting range. The cumulative crystallinity was related to the crystal distribution by the Gibbs–Thomson equation. The results provided a clear distinction between Type I copolymers (density less than 0.89 g/cc) and Type II copolymers (densities between 0.89 and 0.91 g/cc). The former had a singlecrystal population that was identified with the bundled crystals seen in transmission electron micrographs. In comparison, the latter had two crystal populations that correlated with lamellar crystals and bundled crystals. © 1995 John Wiley & Sons, Inc.
Melt polycondensation of poly(ethylene terephthalate) in a rotating disk reactor
Authors: Cheong Seong Ill , Choi Kyu Yong
Published: April 2003

A multicompartment model is proposed for a semibatch melt polycondensation of poly(ethylene terephthalate) in a rotating disk polymerization reactor and compared with laboratory experimental data. The reactor is a horizontal cylindrical vessel with a horizontal shaft on which multiple disks are mounted. The reactor is assumed to comprise N equal sized compartments and each compartment consists of a film phase on the rotating disk and a bulk phase in which disks are partially immersed. The effects of disk rotating speed, number of disks, reaction temperature, and pressure were investigated. It was observed that ethylene glycol is predominantly removed from thin polymer layers on the rotating disks and the enhanced interfacial area exerted by ethylene glycol bubbles accounts for about 30–50% of the total available interfacial mass transfer area. Although the rate of polymerization increases as more disks are used, the maximum number of disks in a reactor must be determined properly in order to prevent the formation of thick polymer films that result in a reduced specific interfacial area and reduced polymerization efficiency. At a fixed reaction pressure, the equilibrium conversion is reached but the rate of reaction can be further increased by increasing the reaction temperature. The results of the proposed multicompartment model are also compared with those predicted by a simple one‐parameter model. © 1995 John Wiley & Sons, Inc.
Membranes based on poly(styrene‐N‐phenylmaleimide)/poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends
Authors: Lokaj J. , Sikora A. , Pientka Z. , Bleha M.
Published: April 2003

Blend membranes were prepared by casting chloroform solutions of mixtures of styrene‐N‐phenylmaleimide copolymer containing ca. 10 mol % imide units with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO), and their phase behavior was evaluated. At a content of 20% PPO, the membranes were homogeneous; those having 40 or more % PPO exhibited phase separation. Membranes made of the parent polymers and their blends were tested in the pervaporation of aqueous ethanol solutions; permeabilities to oxygen, nitrogen, and carbon dioxide were also determined. The pervaporation characteristics and gas transport properties are discussed considering the interactions of polymer chains and the phase structure of the membranes. © 1995 John Wiley & Sons, Inc.
Practical aspects of polymerization of D,L‐Lactide initiated with tetraphenyltin
Authors: Mehta Sanjay , Raghuvanshi R. S. , Misra A. , Ganga S. , Talwar G. P.
Published: April 2003

Melt polymerization conditions for D,L‐Lactide initiated with tetraphenyltin were studied with regard to polymer molecular weight. The combined effect of time and temperature on polymer molecular weight and degree of conversion of D,L‐Lactide is described. Polymerization at constant initiator concentrations resulted in a narrow scattering of reproducible molecular weight values. The presence of air/moisture and other impurities during the melt polymerization most likely have a deterimental effect on molecular weight. After a short induction period the rather slow polymerization of D,L‐Lactide resulted in a maximal molecular weight followed by an almost constant value of molecular weight. © 1995 John Wiley & Sons, Inc.
Pervaporation separation of binary organic–aqueous liquid mixtures using crosslinked PVA membranes. III. Ethanol–water mixtures
Authors: Lee Kew‐Ho , Kim Hae‐Kyung , Rhim Ji‐Won
Published: April 2003

The application of the pervaporation process in biotechnology is rapidly growing. A two stage pervaporation process could be applied to the downstream processing of ethanol fermentation. In this paper, the second stage process—a water‐selective process—was investigated in detail using the crosslinked poly(vinyl alcohol) membranes with the low molecular weight of poly(acrylic acid) as the crosslinking agent. The ratio of poly(vinyl alcohol) and poly(acrylic acid) in the membrane was 90/10, 85/15, and 80/20 by weight. The prepared membranes were tested to separate the various compositions of the water–ethanol mixtures, specially 50/50 solution at 60°C and 30/70, 20/80, 10/90, and 4.4/95.6 solutions at 60, 70, and 75°C. For water: ethanol = 50 : 50 solution, the separation factor αw/e = 260 at 75°C was obtained by using a PVA/PAA = 80/20 membrane. The permeation rate and the separation factor at the azeotropic point of a water–ethanol mixture showed 30 g/m2/h and 5800 at 75°C, respectively, when a PVA/PAA = 80/20 membranes was used. © 1995 John Wiley & Sons, Inc.
Effect of simulated low earth orbit radiation on polyimides (UV degradation study)
Authors: Hill David J. T. , Rasoul Firas A. , Forsythe John S. , O'Donnell James H. , Pomery Peter J. , George Graeme A. , Young Philip R. , Connell John W.
Published: April 2003

UV degradation of polyimide films in air and vacuum were studied using UV‐visible, ESR, FTIR, and XPS spectroscopies. The UV‐visible spectra of polyimide films showed a blue shift in the absorption compared to Kapton. This behavior was attributed to the presence of bulky groups and kinks along the polymer chains which disrupt the formation of a charge‐transfer complex. The UV‐visible spectra showed also that UV irradiation of polyimides result extensively in surface degradation, leaving the bulk of the polymer intact. ESR spectra of polyimides irradiated in vacuum revealed the formation of stable carbon‐centered radicals which give a singlet ESR spectrum, while polyimides irradiated in air produced an asymmetric signal shifted to a lower magnetic field, with a higher g value and line width. This signal was attributed to oxygen‐centered radicals of peroxy and/or alkoxy type. The rate of radical formation in air was twofold higher than for vacuum irradiation and reached a plateau after a short time. This suggests a continuous depletion of radicals on the surface via an ablative degradation process. FTIR, XPS, and weight loss studies supported this postulate. An XPS study of the surface indicated a substantial increase in the surface oxidation after irradiation in air. The sharp increase in the CO binding energy peak relative to the CC peak was believed to be associated with an aromatic ring‐opening reaction. © 1995 John Wiley & Sons, Inc.
Viscoelastic properties and coating performance of water‐soluble acrylic copolymers crosslinked with melamine resin
Authors: Fukuda Tadanori
Published: April 2003

Acrylic copolymers with different amounts of carboxyl and hydroxyl groups for obtaining practical performance of melamine‐cured acrylic coatings was investigated. Property testing results indicated that glass transition temperature (Tg) and shear modulus increased, and molecular weight between crosslinks (Mc) decreased with the increase of hydroxyl and carboxyl number in the acrylic copolymers. The degree of crosslinks influenced the resistance to solvent and chemicals at a lower baking temperature. Compared with acrylic acid, itaconic acid as a carboxyl monomer was more effective in inducing a lower baking schedule. The water‐soluble acrylic copolymer, which is neutralized with triethylamine, consists of 20 wt % methylmethacrylate, 55 wt % buthylacrylate, 15 wt % hydroxyethyl methacrylate, and 10 wt % itaconic acid. The copolymer showed higher crosslinks when cured with methoxymethyl melamine formaldehyde resin under a relatively lower baking schedule at 135°C for 30 min. It also has excellent solvent and chemical resistance. This coating film has a Tg value of 39°C, modulus of 2 × 108 dyne/cm2 in the rubbery state, and Mc value of 464. Also the acrylic copolymer films with Mc < 900 have good properties for solvent, acid, and alkali resistance. © 1995 John Wiley & Sons, Inc.
Studies on swelling of cotton fibers in alkali metal hydroxides. IV. Influence of initial fiber properties and variations in fine structure on tensile behavior
Authors: Sreenivasan S. , Iyer P. Bhama , Patel G. S.
Published: April 2003

Nineteen varieties of cotton, covering a wide range of fiber properties like maturity, fineness, and strength uniformity ratio were swollen in 5N KOH and NaOH at room temperature (30 ± 1°C). Tensile and fine structural properties of the resultant samples were measured and their relationship with initial fiber properties was examined. A comparative evaluation of fiber properties of KOH swollen fibers with those swollen in NaOH revealed that, irrespective of variety, fibers swollen in the former reagent retain higher tenacity. It was further noted that fine structural parameters like crystallite orientation and amorphous content which influence tensile properties become modified differently while swelling in the two reagents. While changes in crystallite orientation were found to be less drastic during KOH swelling, unlike in NaOH, the reverse was found to be true with crystalline content. These changes in fine structure could more or less explain the variation in tensile properties of fibers swollen in these two reagents. © 1995 John Wiley & Sons, Inc.
Polymerization of 2‐dibutylamino‐1,3,5‐triazine‐4,6‐dithiol on wire during friction process
Authors: Mori Kunio , Ibashi Wataru , Hirahara Hidetoshi , Oishi Yoshiyuki , Katayama Masanari
Published: April 2003

2‐Dibutylamino‐1,3,5‐triazine‐4,6‐dithiol (DB) and a mixture of DB and triallylisocyanurate (TAIC) were used as a lubricant during steel wire drawing due to a dry process. DB gave a polymer film with 180 nm in thickness to wire surfaces during the wire drawing. The polymer film had a disulfide structure on the backbone and contained a small amount of DB monomer and olygomer. Molecular weight and polymer weight increased with the drawing rate. The mixture of DB and TAIC gave mainly a three‐dimensional polymer film with 225 nm in thickness to wire surfaces during drawing. The polymer film insoluble in THF had mono and disulfide structures and contained a small amount of linear polymer, DB, and TAIC. Such tribological polymerizations are estimated as follows: DB produces dithiyl radicals on a nascent surface formed during drawing and in the presence of oxygen and heat. The dithiyl radicals were polymerized by coupling with each other to give disulfide bonds or added to allyl groups in TAIC to give monosulfide bonds. It is concluded that this technique should be possible to use for unifying metal processing and surface treatment. © 1995 John Wiley & Sons, Inc.
Reduced number of intrinsic pulmonary nitrergic neurons in Fawn‐Hooded rats as compared to control rat strains
Authors: Van Genechten Jeroen , Brouns Inge , Scheuermann Dietrich W. , Timmermans Jean‐Pierre , Adriaensen Dirk
Published: April 2003

The Fawn‐Hooded rat (FHR) strain reveals a congenital predisposition to primary (idiopathic) pulmonary hypertension (PPH), and can therefore be regarded as an animal model in which to study possible mechanisms underlying an inherited susceptibility to pulmonary hypertension. Pulmonary hypertension can be induced in FHRs after a short exposure to mild hypoxia, presumably because of an altered peripheral oxygen sensitivity. Given the presence of pulmonary nitrergic neurons in rat lungs, the observed link between airway hypoxia and the expression of pulmonary neuronal nitric oxide synthase (nNOS), and the fact that nNOS appears to be involved in peripheral chemoreceptor sensitivity, we examined the intrinsic pulmonary nitrergic innervation in the FHR. In the present study the number of intrapulmonary nitrergic nerve cell bodies, detected by NADPH diaphorase (NADPHd) histochemistry, was quantified in the FHR and three control rat strains. Compared to the control rat strains, the FHR lungs revealed a highly significantly lower number of intrinsic nitrergic neurons, while no apparent differences were found in the number of enteric nitrergic neurons in the esophagus. In conclusion, the possible links between neuronal NO, hypersensitivity to airway hypoxia, and the development of PPH clearly deserve further investigation. Anat Rec Part A 272A:446–453, 2003. © 2003 Wiley‐Liss, Inc.