bluuebunny/crossref_metadata_2025 huggingface dataset:
Elimination of stress whitening in high‐molecular‐weight polyethylene
Authors: Lee Y. W. , Kung S. H.
Published: April 2003

High‐molecular‐weight polyethylene (HMWPE) sheets have been cold rolled biaxially to different reductions in thickness. After 40% or more reduction in thickness by cold rolling, the stress‐whitening phenomenon in HMWPE was eliminated. To find out the reason of elimination of stress whitening by cold rolling, different techniques were employed. The measurement of hardness, density, and strain distribution of the specimens were carried out for the study of the differences in mechanical and physical properties of the stress whitened and nonwhitened specimens. Recovery of density, hardness, and dimensions of the specimens due to heating were also studied. Differential scanning calorimetry (DSC) and polarized‐light microscopy were used to study the melting, and recrystallization behavior and scanning electron microscopy (SEM) were used to study the surface texture of the specimens. Based on the results of the different techniques employed, it is concluded that after cold rolling, especially biaxially rolled, due to the combined forces of compression and shear acting on the specimens from different directions, the macro‐and micro‐imperfections of the material may be eliminated to some extent. At 40% or more rolling reduction, the imperfections were largely eliminated; hence stress whitening did not occur.
Melt‐rheological properties of PP/EVA blend
Authors: Gupta A. K. , Ratnam B. K. , Srinivasan K. R.
Published: April 2003

This paper describes a study of melt‐rheological properties of the binary blend of isotactic polypropylene (PP) and ethylene–vinyl acetate copolymer (EVA) at varying blending ratios (from 0 to 40 wt % EVA content) and using three samples of EVA containing different vinyl acetate contents (VA %), viz. 9, 12, and 19%. Measurements made on a capillary rheometer at three different temperatures (210, 220, and 230°C) in a shear stress range of 104–106 Pa (shear rate 101–104 s−1) are presented and discussed for the effects of blend composition and shear stress on the flow curves, melt viscosity and melt elasticity. Morphology of the blend studied through scanning electron microscopy revealed distinct differences in size and number density of dispersed EVA droplets, which are discussed in terms of the variation of average size and number density of the dispersed EVA droplets as a function of blend composition and shear stress. Melt‐rheological properties and morphology of dispersion are correlated and found quite consistent.
Formation and structural characteristics of porous ethylene glycol dimethacrylate networks
Authors: Okay Oğuz , Gürün Çiğdem
Published: April 2003

The relationships between the synthesis conditions and the morphology of ethylene glycol dimethacrylate (EGDM) networks were investigated. EGDM networks were prepared by free‐radical polymerization in toluene as a diluent. The networks were characterized by swelling, porosity, and pendant vinyl group content measurements. The accessibility of pendant vinyls to low molecular weight compounds was tested using pyrrolidine as a model reactant. The results show that the polymerization of EGDM in toluene is accompanied by a phase separation in the system. The networks thus obtained are heterogeneous and exhibit an inhomogeneity in the porosity and swelling distributions. Both the weight swelling ratio and the pore volume of the networks increase with increasing monomer dilution. It was also found that the accessibility of pendant vinyls increases as the cross‐linking density of the network decreases or as its porosity increases. The results can be explained with the formation of highly cross‐linked microgels as the intermediates in the network formation processes. Two equations were derived to predict the equilibrium weight swelling ratio and the pore volume of heterogeneous networks. Satisfactory agreement of the results of measurements with the predictions of the equations was observed.
Crystallization of polymer melts under fast cooling. II. High‐purity iPP
Authors: Piccarolo S. , Saiu M. , Brucato V. , Titomanlio G.
Published: April 2003

Samples of a high‐purity isotactic polypropylene (iPP) were quenched from the melt so as to monitor cooling history. A continuous variation of morphology and crystal structure was obtained with cooling rate. This is discussed in relation to sample thermal history evidencing that cooling history relevant to quenched samples is in the neighborhood of 90°C. In particular the samples are essentially mesomorphic when at this temperature cooling rates larger than 80°C/s were adopted, while below a few tens of °C/s only α‐monocline form is obtained. Densities of quenched samples were compared with predictions of an isokinetic extrapolation of Avrami model of polymer crystallization kinetics.
Physical and surface properties of aqueous solutions of polyvinyl alcohols having an n‐alkylthio end group
Authors: Sato Toshiaki , Okaya Takuji
Published: April 2003

The polyvinyl alcohols (PVAs) having a n‐alkylthio end group of 10 through 16 carbon atoms were found to associate in the dilute aqueous solutions through hydrophobic interaction. From the apparent number‐average molecular weight with vapor pressure osmometer, the PVAs having an n‐dodecylthio and an n‐hexadecylthio group at one end were calculated to associate by about five and three molecules, respectively. The aqueous solutions of the PVA having an n‐dodecylthio group at one end showed much higher viscosity compared with the PVA having a hydroxyethylthio group at one end (HOCH2CH2S—PVA) in low concentration regions of below 10 wt % due to the association of the n‐dodecyl end group. Surface tensions of the aqueous solutions of the PVAs having an n‐alkylthio group at one end (n‐CnH2n+1S—PVA) showed almost the same value, which was slightly smaller than that of HOCH2CH2S—PVA, at 4 and 6 of carbon atoms, lowered with an increase in the number of carbon atoms above 8, showed minimum at 12 and then increased at 16 and 18. In the emulsion polymerization of vinyl acetate, n‐CnH2n+1S—PVAs of 10 through 18 carbon atoms acted effectively as a protective colloid.
Chemorheology on simultaneous IPN formation of epoxy resin and unsaturated polyester
Authors: Lin Mu‐Shih , Chang Reui‐Je
Published: April 2003

Study of the simultaneous interpenetrating polymer network (IPN) between diglycidyl ether of bisphenol‐A (DGEBA) and unsaturated polyester (UP) was carried out at ambient temperature. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the intermolecular H‐bonding and functional group changes. Viscosity changes due to H‐bonding and crosslinking were examined with a Brookfield viscometer. Gelation time was measured by a Techne gelation timer. Complexation between Co(II) (the promoter for UP cure) and diamine (the curing agent for DGEBA) was detected with UV‐visible spectrometer. Experimental evidence revealed that intermolecular interactions were observed in systems such as DGEBA/UP, DGEBA/diamine, Co(II)/diamine, DGEBA/uncured UP, and UP/uncured DGEBA. All such interactions had measurable effects on the curing behaviors for both networks, as were indicated by the viscosity changes and gelation time. The IPNs thus obtained were further characterized with rheometric dynamic spectroscopy (RDS) and differential scanning calorimetry (DSC). Partial compatibility between UP and DGEBA networks was evidenced from a main damping peak with a shoulder near glass transition temperature (Tg) for lower UP content; while at higher UP content, only a main damping peak near Tg was observed. DSC revealed a broad glass transition for all IPNs. The resultant IPN materials were all transparent. © 1992 John Wiley & Sons, Inc.
The interaction of poly(methyl methacrylate) and chromium chloride: Transfer of methyl groups from the ester to the main chain
Authors: Beer Rudolfo Scott , Wilkie Charles A. , Mittleman Martin L.
Published: April 2003

The interaction of transition‐metal halides with poly(methyl methacrylate) (PMMA) has been studied in the past and methyl halides are always observed as a product of the reaction. When CrCl3 is used as an additive for PMMA, only traces of methyl‐containing products are seen and these only at quite high temperatures. The principal volatile products consist of carbon dioxide, carbon monoxide, and monomer, while the nonvolatile residue contains a multitude of methylene and methine carbons. A mechanism is invoked by which the ester methyl is transferred to the polymer backbone in a concerted process.
Preparation and properties of liquid crystalline alkyd resin with para‐hydroxybenzoic acid mesogenic side chain
Authors: Chiang Wen‐Yen , Yan Chun‐Shyurng
Published: April 2003

Liquid crystalline (LC) alkyd resins with mesogenic side chains are prepared with the following three methods: (a) grafting p‐hydroxybenzoic acid (PHBA) to hydroxy‐terminated alkyd resin, (b) grafting PHBA to carboxyl‐terminated alkyd resin, and (c) grafting PHBA to an excess succinic anhydride‐modified alkyd resin. Dicyclohexylcarbodiimide (DCC) is employed to react with formed water in promoting esterification of PHBA with alkyd at room temperature. Pyridine is used as a solvent, and the catalytic amounts of p‐toluene‐sulfonic acid (p‐TSA) is added to suppress side reaction and to promote esterification. Grafting efficiency (% GE) is estimated to range from 70 to 95%. The character of liquid crystallinity is imparted only when at least two or more aromatic units of PHBA are connected to form the rodlike mesogenic side chain. At present, we have found that LC alkyd resins have the following merits: the polymer solution viscosity is reduced; the coating's dry‐to‐touch time is reduced; and the coating film is both hardened and toughened and has excellent resistance to water and acid. © 1992 John Wiley & Sons, Inc.
Properties of UV‐curable polyurethane acrylates for primary optical fiber coating
Authors: Kim Han Do , Kang Seung Gu , Ha Chang Sik
Published: April 2003

Studies have been made on the effects of the chemical structure of reactive urethane acrylate prepolymers and diluents (reactive monomers) and overall composition of the prepolymer/diluent on the properties of the UV‐curable polyurethane acrylates for primary optical fiber coating. We prepared several urethane acrylate prepolymers from two different isocyanates, 4,4′‐dicyclohexylmethane diisocyanate (HMDI) or isophorone diisocyanate (IPDI), and two different polyols, polybutadiene diol (PBD) or polypropylene oxide diol (PPG), and 2‐hydroxyethyl acrylate (HEA) with dibutyl tin dilaurate as a photoinitiator. UV‐curable coating materials were formulated from the prepolymers and 2,2‐dimethyl 2‐phenyl acetophenone as a photoinitiator with one of four different diluents such as 1‐vinyl 2‐pyrrolidone (VP), lauryl methacrylate (LMA), acrylic acid 2‐ethyl hexyl ester (AEHE), and acrylic acid n‐butyl ester (ABE). It was found that AEHE is the desirable diluent in the formulation of the primary fiber‐coating material. The desirable composition of PBD, when mixed PBD/PPG diols are used, should be about 50 wt % for optimum formulation. Most of the urethane acrylate prepolymers prepared in this study could be applied in the formulation of primary optical fiber coating and exhibited good properties of buffer functions, including low glass transition temperature, low modulus even at low temperature, say, below −40°C, high refractive index, and low viscosity. © 1992 John Wiley & Sons, Inc.
Synthesis and properties of uniform beads based on macroporous copolymer glycidyl methacrylate–ethylene dimethacrylate: A way to improve separation media for HPLC
Authors: Šmigol Vladimír , Švec František
Published: April 2003

Monodisperse beads based on hydrolyzed macroporous poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) for use as size‐exclusion HPLC packings were synthesized by the method of “activated” swelling of polystyrene seeds followed by a suspension polymerization of both methacrylates. Effects of the type and fraction of the swelling agent, inert porogenic solvent, and cross‐linking monomer on the uniformity of the particles, extent of the specific surface area, pore volume, pore size, and pore‐size distribution and chromatographic properties (size‐exclusion limit and column effciency) have been investigated. Trends leading to the synthesis of macroporous particles with predesigned properties for use in size‐exclusion high‐performance liquid chromatography in both aqueous and organic mobile phase were studied. © 1992 John Wiley & Sons, Inc.
Dynamics of the phase inversion process
Authors: Mchugh A. J. , Tsay C. S.
Published: April 2003

An analysis of the dynamics of phase inversion based on mathematical modeling and in situ experimental observations is presented. Calculations based on ternary diffusion models illustrate the effects of casting film composition, evaporation time, and film thickness on the precipitation time and resulting polymer film profiles, which correlate with observed final morphologies. An experimental method based on the use of dark ground optics, interface visualization, and reflected light illumination is used for in situ monitoring of the mass transfer and phase separation dynamics during the quench step. Observations on the systems water—dimethylsulfoxide cellulose acetate and water—dioxane—cellulose acetate show regions in the films corresponding to gel formation and growth, instabilities associated with finger formation, and homogeneous ternary diffusion. Data for the kinetics of the diffusion and gel front motions show that both propagate as the square root of time with rates dependent on the bath—film compositions. Examples of interface structures characteristic of deep quenching and nucleated droplet growth are also shown. Semiquantitative analyses in terms of the ternary models developed earlier and a phenomenological model for diffusion in the growing gel are used to explain the trends seen. © 1992 John Wiley & Sons, Inc.
Melt rheology and morphology of PP/SEBS/PC ternary blend
Authors: Gupta A. K. , Srinivasan K. R.
Published: April 2003

Melt rheological properties of the ternary blend of isotactic polypropylene (PP), styreneethylene–butylene–styrene terpolymer (SEBS), and polycarbonate (PC), PP/SEBS/PC, are studied in a wide range of composition, such that PP is the matrix and SEBS and PC are the minor components, with the proportion of one varying from 0 to 30% at various fixed compositions of the other. The respective binary blends, PP/SEBS and PP/PC, studied as the reference systems for interpretation of results on the ternary blends yielded interesting new information about the morphology development and its correlation with melt rheological properties of these binary blends. The studies include the measurement of melt rheological properties on a capillary rheometer in the shear rate range 101–104 s−1 at a fixed temperature of 240°C. The data presented as conventional flow curves are analyzed for the effect of blend composition and shear rate on pseudoplasticity, melt viscosity, and melt elasticity, and role of each individual component is identified. Morphology of dispersed phases of these blends is studied through scanning electron microscopy of the cryogenically fractured and suitably etched surfaces. Variations of morphology with blend composition and shear rate showed interesting correlation with melt rheological properties, which are discussed in detail. An important finding of the morphological studies is that in the PP/SEBS/PC ternary blend the SEBS phase forms two types of morphologies depending on the blend composition and shear rate: (i) simple droplets and (ii) boundary layer at the surface of the PC droplets. © 1993 John Wiley & Sons, Inc.
Rate of swelling of sodium polyacrylate
Authors: Ogawa Ikuko , Yamano Hideki , Miyagawa Kinjiro
Published: April 2003

The kinetics of the swelling of sodium polyacrylate (NaPA), a hydrophilic polymer, was studied gravimetrically, by microscopic observation, and calorimetrically. The swelling process followed first‐order kinetics and the rate constant was of the order of 10−2 s−1. The gravimetric method, however, was not useful for kinetic studies. The rate constant was depressed by the addition of sodium chloride. The activation energy of the swelling was 46.0 ± 6.2 (kJ mol−1) and decreased with the increase in sodium chloride concentration. In acid solution, the activation energy was almost the same as that in water. The heat of the swelling was 196 ± 17 J g−1 and did not vary with the addition of sodium chloride. © 1993 John Wiley & Sons, Inc.
Novel catalysts for the ring‐opening metathesis polymerization of norbornene‐type monomers
Authors: Goodall Brian L. , Kroenke William J. , Minchak Robert J. , Rhodes Larry F.
Published: April 2003

A novel family of metallate compounds has been developed for use in catalyst systems for the ring‐opening polymerization of dicyclopentadiene (DCPD) and other norbornene‐type monomers. Examples of these novel catalyst compounds are the organoammonium isopoly‐and heteropolymetallates. Applications of these metallates in combination with alkylaluminum‐type reducing cocatalysts are found in the production of both solution polymers, and cross‐linked resins from reaction injection molding (RIM). These catalyst systems have significant advantages over prior art catalysts. They are highly soluble in DCPD and other norbornene‐type monomers, thus eliminating the need for a reaction solvent. They also are insensitive to air and moisture, have unlimited shelf‐life in solution in norbornene‐type monomers, and do not function as Lewis acids. The chemistry of these catalyst systems is discussed, along with the benefits they provide to the properties of the final polymer products. © 1993 John Wiley & Sons, Inc.
Fourier transform infrared and 13C‐NMR spectroscopic characterization of model epoxy networks
Authors: Gallouedec F. , Costa‐Torro F. , Laupretre F. , Jasse B.
Published: April 2003

Model epoxy networks based on a diglycidylether of bisphenol A (DGEBA) or of butanediol (DGEBU) and cured with different mixtures of monoamines and diamines were prepared to allow changes in cross‐link density. The choice of aliphatic or aromatic amines permitted assessment of the influence of network chain flexibility. Solid state 13C‐NMR spectra showed that no secondary reactions leading to the creation of ether linkage occur during the condensation reaction. Glass transition temperatures (Tg) and the temperatures of the maximum of the exothermic cross‐linking reaction (Texo) were determined. A rectilinear increase of Tg as a function of the density of cross‐links was observed for all the systems under study. Similarly, an increase in the stiffness of the backbone units resulted in an increase in Tg. Time‐temperature‐transformation (TTT) isothermal cure diagrams were constructed and infrared kinetics were performed at 90°C. Gelation and vitrification times were shown to be dependent on the nature of the amines used to create the network structure. © 1993 John Wiley & Sons, Inc.
Viscometric studies of starch‐g‐polyacrylamide composites
Authors: Kaur Inderjeet , Misra B. N. , Barsola Raghuvir , Singla Kiran
Published: April 2003

Composites of starch‐g‐polyacrylamide, starch, and polyacrylamide have been prepared by gamma radiation‐initiated polymerization of acrylamide in the presence of starch in aqueous medium. The polymerization was studied as a function of the (i) amount of water (ii) monomer concentration, and (iii) total dose. The optimum conditions for maximum conversion of the monomer to homopolymer and graft copolymer have been evaluated. Percentage of grafting of polyacrylamide could not be determined precisely as both the homopolymer and the graft are soluble in common solvents and all attempts to separate the graft from the homopolymer were unsuccessful. However, the formation of the starch‐g‐polyacrylamide copolymer was confirmed by the turbidimetric studies using acetone as a nonsolvent. The products of polymerization of acrylamide in the presence of starch consisted of unreacted starch, starch‐g‐polyacrylamide, and polyacrylamide and is referred to as the composite. Acrylamide was also polymerized in the absence of starch using γ‐rays as means of initiation and the optimum conditions for maximum conversion of acrylamide to polyacrylamide have been evaluated. Viscosity behavior of the composite and polyacrylamide was studied in aqueous medium at 30±0.04°C. The reduced specific viscosity of the aqueous solution of acrylamide and the composite as well was found to increase with increasing dilution, the effect being more pronounced in the composite. This tends to indicate that both the homopolymer and the composite behave as polyelectrolytes. An attempt has been made to explain the polyelectrolytic behavior of the homopolymer and the composite. © 1993 John Wiley & Sons, Inc.
Adhesion of polyimide to silicon and polyimide
Authors: Jou Jwo‐Huei , Liu Chiung‐Hong , Liu Jong‐Min , King Jing‐Shin
Published: April 2003

The characteristics of the adhesions of polyimide to silicon and to polyimide and the autohesion of a polyimide blend have been investigated. As found, the peel strength of pyromellitic dianhydride–4,4′‐oxydianiline (PMDA–ODA) on silicon can be greatly improved by blending with 20 or 40% benzophenone tetracarboxylic dianhydride–p‐phenylene diamine (BPDA–PDA). Exposing in air for a 2 day period resulted in a serious deterioration in adhesion for the pure PMDA–ODA system, while in no deterioration for the blend systems. Regardless of adhesion or autohesion, the resulting peel strength decreased markedly with the increase of the curing temperature. It was also found that based on the same curing temperature the diffusion of NMP is much faster in the film of PMDA–ODA than in the blend containing 20% BPDA–PDA. Beside curing temperature, imide‐to‐imide compatibility seems to play an important role in affecting the adhesion characteristics. © 1993 John Wiley & Sons, Inc.
Silicone acrylates through the hydrosilation of polyacryloyloxy functional monomers with copolymers of dimethyl and hydrogen methylsiloxanes
Authors: Kokko Bruce J.
Published: April 2003

Silicone acrylates, as possible electron beam (EB) curable release coatings for paper, were prepared by the platinum‐catalyzed hydrosilation of polyacryloyloxy functional monomers with copolymers of dimethylsiloxane and hydrogen methylsiloxane (PDMHMS). The hydrosilation of either 1,6‐hexanediol diacrylate (HDDA) or trimethylolpropane triacrylate (TMPTA) with PDMHMS occurs to only one of the 2 or 3 available olefinic groups, respectively, as long as excess monomer is present. The amount of excess monomer needed to prevent gelation during hydrosilation or subsequent storage in excess of 1 month appears to be dependent on the hydrogen methylsiloxane content of the PDMHMS. A release coating having excellent cohesive and adhesive strength on paper was obtained by the EB curing of the product of hydrosilation of TMPTA with a PDMHMS containing 4 mol % hydrogen methylsiloxane at a dose‐to‐cure of 2 Mrad, but the aged release force was excessively high. The poor aged‐release performance was likely due to dilution of the dimethylsiloxane content of the coating with excess monomer required to stabilize the silicone acrylate. © 1993 John Wiley & Sons, Inc.
Preparation of polycarbonate/metal salt gas separation membranes
Authors: Lai Juin‐Yih , Chen Shih‐Hsiung , Lee Mei‐Hsiu , Shyu S. S.
Published: April 2003

Polycarbonate (PC) membranes possess high O2/N2 selectivity and mechanical strength, but have low gas permeability. In order to improve the pure PC membrane's gas permeability and selectivity of O2/N2, in this study we attempt to combine transition metal salts into the membrane to form a complex membrane. Tensile strength and elongation at break of the membrane are not significantly changed. The effect of casting solution composition and solvent evaporation time on morphology, gas permeability, and selectivity of O2/N2 of PC membranes are studied. The gas permeabilities of PC/DMF/Metals membranes are significantly improved, as compared to those of pure PC membrane. For example, an oxygen permeability of 137 cm3 (STP)‐cm/cm2‐sec‐cmHg and separation ratio of oxygen to nitrogen of 4.0 for PC/DMF/CuCl2 membrane with [PC/CH2Cl2]/[CuCl2/DMF] = 17/3 mL/mL, and CuCl2/DMF = 0.1 g/mL, can be obtained. The FT–IR spectra and elementary analysis suggest that there is interaction among metal, DMF, and PC. © 1993 John Wiley & Sons, Inc.
Effect of diethylene glycol (DEG) on the crystallization behavior of poly(ethylene terephthalate) (PET)
Authors: Patkar Mahesh , Jabarin S. A.
Published: April 2003

The effect of diethylene glycol (DEG) on the crystallization of poly(ethylene terephthalate) (PET) was studied under isothermal and dynamic conditions. The strain‐induced crystallization of PET and its relationship to DEG content was also studied. The samples were isothermally and dynamically crystallized in the differential scanning calorimeter (DSC). The thermograms were then analyzed to determine the kinetic parameters. Strain‐induced crystallization was studied by stretching samples at different strain rates. These samples were then annealed for various periods of time and quenched to room temperature. Birefringence and density were measured on the annealed samples. Results indicate that the DEG content reduces the rate of crystallization of PET when crystallizing from the melt, isothermally and dynamically. When crystallizing from the glassy state, the effects of DEG are not prominent. The mechanism of crystallization is not affected by the amount of DEG, within the range of DEG contents evaluated. In the case of strain‐induced crystallization, increased DEG content reduces the crystallinity of PET at intermediate strain rates, but at higher strain rates, the crystallinity is not affected by the DEG content. © 1993 John Wiley & Sons, Inc.
High‐temperature thermoplastic elastomers via the grafting reaction of polyarylate onto EPDM rubber
Authors: Dean Barry D.
Published: April 2003

Polyarylate monofunctionally terminated with a 1,2‐dihydrobenzocyclobutene group undergoes thermally initiated grafting reactions onto ethylene/propylene/nonconjugated diene rubber via the Diels—Alder reaction between the diene (benzocyclobutene) and the dienophile (pendant unsaturation on the EPDM). Characterization of the graft copolymer(s) is presented as is the resultant thermoplastic elastomeric mechanical performance exhibited by the graft copolymers. © 1993 John Wiley & Sons, Inc.
The disintegration rate of traditional and chemically modified plastic films in simulated fresh‐ and sea‐water environments
Authors: Leonas Karen K.
Published: April 2003

Six plastic films with varying chemical compositions in three different accelerated weathering environments were evaluated for disintegration. The films included two traditional films (LDPE and polystyrene), three with enhanced photodegradability (2% ECO and 10% ECO and LDPE with a vinyl ketone graft), and one with enhanced biodegradability (LDPE with 6% corn starch). The films were exposed to UVA‐340 bulbs to simulate sunlight while in fresh water, salt water, or no water conditions. Disintegration of the films was determined by monitoring the change in physical properties of tensile strength at break, elongation at break, and toughness at break at selected intervals throughout the exposure period. Both the chemical composition of the film and the exposure environment produced significant differences in disintegration rates. Two of the films with enhanced photodegradability (2% and 10% ECO copolymers) disintegrated more rapidly than did the other films in this study. The environment where no water was present resulted in the fastest disintegration rate for the films when compared with the fresh‐water environment. However, two films, LDPE and LDPE with 6% corn starch, degraded more rapidly in the salt‐water environment than in the other two environments due to the presence of oxidation catalysts in the water system. © 1993 John Wiley & Sons, Inc.
Composite membranes formed by plasma‐polymerized acrylic acid for ultrafiltration of bleach effluent
Authors: Cho D. L. , Ekengren Ö.
Published: April 2003

Composite membranes were formed by deposition of plasma‐polymerized acrylic acid (PPAA) films onto porous commercial membranes to improve the rejection, especially of chlorinated compounds, in ultrafiltration of E‐stage bleach effluent. Although increased rejections were accompanied by reduced flux, in most cases, the reductions were not significant considering the extent of increased rejections. A good composite membrane showed the AOX removal of 94% (76% before the modification) and the chemical oxygen demand (COD) removal of 84% (67% before the modification) with 33% reduction of the flux. The permeate was optically clean. The improved rejection is attributed to the tightly crosslinked network of a plasma polymer film and its negatively charged surface. Ultrathin film thickness and the hydrophilic property of a plasma polymer film minimize the reduction of flux. © 1993 John Wiley & Sons, Inc.
Relative solubility of tetrachlorohexafluorobisphenol‐A polycarbonate in various compounds
Authors: Beck H. N. , Mah R. W. , Sanders E. S.
Published: April 2003

The relative solubility of tetrachlorohexafluorobisphenol‐A polycarbonate was observed in 127 organic compounds comprising 14 different chemical classes at room temperature and up to about 225°C. The polymer is soluble in numerous esters, ketones, halocarbons, heterocyclics, and amides. It is poorly soluble in alcohols and fluorocarbons. Correlation of observed solubility with Hildebrand total solubility parameters was poor; a much better correlation was observed with Hansen three‐dimensional parameters. The solubility parameter of the polymer was estimated to be 9.1 (cal/cm3)1/2 (18.7 MPa1/2) from the averages of the Hansen parameters for 26 experimentally identified solvents. © 1993 John Wiley & Sons, Inc.
Selection of elastomeric membranes for the removal of volatile organics from water
Authors: Nijhuis H. H. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

A wide range of homogeneous elastomeric membranes has been prepared using dicumylperoxide as a general cross‐linking agent. The membranes have been used for both equilibrium sorption measurements and steady‐state pervaporation experiments to study solution–diffusion phenomena in the removal of volatile organic components from aqueous solutions. Pervaporation experiments have been performed under identical hydrodynamic conditions in order to fix the boundary layer mass transfer coefficient at a constant and known value. For comparison of the permeabilities of different pervaporation membrane materials, this is of utmost importance. A wide range of selectivity factors up to a value of 100,000 are obtained, whereas usually the permeabilities for the organic component are in the range of 10−10−10−9m2/s and 10−14−10−12m2/s for water. The permeation and sorption data obtained for the various elastomers have been related to the chemical and physical nature of the elastomers through the solubility parameter and the glass transition temperature, respectively. Both diffusional and sorption effects seem to be important, determining the water‐transport behavior in the elastomeric membranes. The solubility of the organic component appears to be independent of this combined solubility parameter. Differences in the permeabilities of the organic component can primarily be ascribed to structural parameters in the membrane material, like degree of unsaturation and presence of steric side groups. © 1993 John Wiley & Sons, Inc.
Preparation of ethylene copolymers containing pendant unsaturation for radiation crosslinking
Authors: Ekman Kenneth B. , Näsman Jan H. , Sjöström Håkan
Published: April 2003

The work presented here suggests that the radiation crosslinking of particular ethylene copolymers can markedly be enhanced by introduction of pendant radiation‐sensitive functional groups and that reactive melt processing offers an attractive alternative to introduce the pendant groups. m‐Isopropenly‐α,α‐dimethylbenzyl isocyanate was found to react in high yields(>80%) during a few minutes of reactive mixing with an ethylene hydroxyethyl methacrylate copolymer, and no residual monomers were found in the polymer after 10 min of mixing. Copolymers that contained from 0.1 to 1.2 mol % of pendant unsaturation were prepared. The functionalized copolymer, which contained 1.2 mol% of pendant unsaturation were prepared. The functionalized copolymer, which contained 1.2 mol % of pendant unsaturation, formed 90% gel after having received a radiation dose of 100 kGy. The corresponding value for the unfunctionalized copolymer was 25% gel. Furthermore, ethylene copolymers containing 0.3–1.4 mol % of acrylate or 0.1–0.4 mol % of methacrylate side groups were prepared by mixing an ethylene vinyl alcohol copolymer with acrylic acid or by mixing an ethylene acrylic acid copolymer with glycidyl methacrylate. Although the conversion of these esterification reactions was low, the amount of incorporated pendant unsaturation was sufficient to crosslink the polymers to high gel contents (>80%) already at a radiation dose of 10 kGy. © 1993 John Wiley & Sons, Inc.
A comparison between miniemulsion and conventional emulsion terpolymerization of styrene, 2‐ethylhexyl acrylate and methacrylic acid
Authors: Masa Juan A. , De Arbina Lourdes López , Asua José M.
Published: April 2003

The kinetics of the high solids content miniemulsion terpolymerization of styrene, 2‐ethyl hexyl acrylate and the methacrylic acid and the final properties of the latexes produced by this method were compared with those resulting from the corresponding conventional emulsion polymerization process. The final latex properties considered were: latex viscosity both prior and after neutralization, mechanical stability, chemical stability, and freeze‐thaw stability. © 1993 John Wiley & Sons, Inc.
Thermally and anionically initiated cure of bismaleimide monomers
Authors: Seris A. , Feve M. , Mechin F. , Pascault J. P.
Published: April 2003

A kinetic and thermodynamic study of the thermally or anionically induced cure of aromatic bismaleimide monomers (namely 2,4‐bismaleimidotoluene, 4,4′‐bismaleimidodiphenylmethane and their eutectic mixture) is presented. Calorimetric investigations allowed the determination of heats of polymerization and activation energies for both types of initiations, and the values found are compared with data in the literature. Isothermal cures were also carried out with and without anionic initiator (typically imidazole). SEC measurements were used to monitor the conversion of the monomers as a function of time. The thermally induced polymerization seems to proceed in a rather heterogeneous way, owing to an initiation that is too slow: gelation appears at first only as the formation of microgels, with no immediate increase in the viscosity; macrogelation occurs some time after. On the contrary, the anionically induced polymerization is more homogeneous. A complete study of a particular reacting system revealed no interference between radical and anionic polymerization over a wide range of temperatures, and in this case gelation results in an immediate increase in viscosity. However, the conversion at the gel point is unexpectedly high, which can be interpreted as the result of a very fast initiation as well as of transfer reactions. Glass transition temperatures were also measured as a function of time and curing temperature in order to study the influence of vitrification on the kinetics and to check for the existence of a unique relation between Tg and conversion. This actually proved to be correct as long as diffusion does not slow down the reaction; in this case Gillham's treatment of Tg versus in t was successfully applied and led to the correct value of the activation energy. All the measurements allowed us to establish the time‐temperature‐transformation cure diagram for a specific reacting system. © 1993 John Wiley & Sons, Inc.
Effects of the addition of a liquid crystalline copolyester to polystyrenes on blending torque and mechanical properties of blends
Authors: Ogata N. , Tanaka T. , Ogihara T. , Yoshida K. , Kondou Y. , Hayashi K. , Yoshida N.
Published: April 2003

Blending of polystyrenes (PS) with a thermotropic liquid crystalline polymer (LCP) was performed by using a continuous corotating twin screw extruder. The influence of LCP content on the blending process was studied by changing the barrel heater temperature and the screw speed. The torque of screw shafts, generated during the blending process, was influenced by LCP content and its influence was not simple. The torque generated during the blending process was not directly related to the apparent melt viscosity of blends. Further, the effects of the matrix viscosity on the morphology and mechanical properties of the PS/LCP blends were studied using three grades of PS as matrix resins. It was found that the size of the LCP dispersed phase decreased with increasing matrix viscosity. Consequently, the mechanical properties of the PS/LCP blend were improved. © 1993 John Wiley & Sons, Inc.
Microdeformation mechanisms in propylene–ethylene block copolymer
Authors: Hayashi Kosei , Morioka Tetsuya , Toki Shigeyuki
Published: April 2003

Blends of propylene–ethylene block copolymer (PEB) and propylene homopolymer (PP) were prepared to give various rubber contents (4–20 wt %). By diluting the PEB with PP with molecular weight equal to that of the PEB matrix, molecular characteristics of all the blends were kept constant. The rubber particle size and size distribution of all the blends were almost constant, so that the interparticle distance decreased with increased rubber content. According to the observation of the fracture behavior at −20°C, a brittle to ductile transition was found at the rubber content of 16 wt %. Microdeformation behavior of the blends was investigated in the region of brittle to ductile transition by using transmission electron microscopy. In the case of the brittle sample with low rubber content, crazing and voiding were observed. Whereas even in the ductile sample with high rubber content, crazing certainly took place before shear yielding. The origin of ductile fracture could possibly be attributed to the relaxation of strain constraint by the microvoids contained in the craze. © 1993 John Wiley & Sons, Inc.
Characterization of cellulose acetate in acetone solution. Studies on prehump II in GPC pattern
Authors: Funaki Yoshinori , Ueda Kazuyoshi , Saka Shiro , Soejima Shigeru
Published: April 2003

Cellulose acetate in acetone solution is known to show some peaks in its chromatogram as measured by gel‐permeation chromatography. These peaks are named from the shorter elution time as prehump I, prehump II, and main hump. In our previous paper, we characterized prehump I. In this study, the second peak, prehump II, was fractionated by using the large‐scale GPC column and its molecular properties were investigated. The results have shown that the molecules of prehump II are not aggregated but molecularly dispersed with some anionic residues. These anionic groups may be sulfuric acid groups introduced during the acetylation process as a catalyst that interact repulsively with the anionic groups of the GPC column gel. This resulted in the phenomenon that the prehump II elutes earlier than the main hump in the GPC chromatogram. © 1993 John Wiley & Sons, Inc.
Miscibility and phase behavior in blends of poly(hydroxyether of bisphenol A) with poly(ethylene oxide‐co‐propylene oxide)
Authors: Qipeng Guo , Keshi Sun , Tianru Fang , Yuchen Qi , Zhiliu Feng
Published: April 2003

The miscibility of poly(hydroxyether of bisphenol A) (phenoxy) with a series of poly(ethylene oxide‐co‐propylene oxide) (EPO) has been studied. It was found that the critical copolymer composition for achieving miscibility with phenoxy around 60°C is about 22 mol % ethylene oxide (EO). Some blends undergo phase separation at elevated temperatures, but there is no maximum in the miscibility window. The mean‐field approach has been used to describe this homopolymer/copolymer system. From the miscibility maps and the melting‐point depression of the crystallizable component in the blends, the binary interaction energy densities, Bij, have been calculated for all three pairs. The miscibility of phenoxy with EPO is considered to be caused mainly by the intermolecular hydrogen‐bonding interactions between the hydroxyl groups of phenoxy and the ether oxygens of the EO units in the copolymers, while the intramolecular repulsion between EO and propylene oxide units in the copolymers contributes relatively little to the miscibility. © 1993 John Wiley & Sons, Inc.
Graft copolymerization of 4‐vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method
Authors: Kaur Inderjeet , Misra B. N. , Barsola Raghuvir
Published: April 2003

An attempt has been made to graft copolymerize 4‐vinyl pyridine onto isotactic polypropylene hydroperoxide by mutual irradiation method in an aqueous medium. Polypropylene hydroperoxide has been prepared by irradiating recrystallized polypropylene beads from a Co60 source in the presence of air. The resulting polypropylene hydroperoxide beads have been used as the backbone polymer and grafting of 4‐vinyl pyridine has been studied as a function of various reaction parameters. Optimum conditions for maximum percentage of grafting have been evaluated. Rate of grafting (Rg) has been determined as a function of preirradiation dose and initial monomer concentration. Water has been found to affect percentage of grafting. The graft copolymers have been characterized by spectroscopic method and isolation of the grafted poly(4‐VP) from the graft copolymer. A plausible mechanism is proposed to explain the mutual grafting of 4‐vinyl pyridine onto polypropylene hydroperoxide. © 1993 John Wiley & Sons, Inc.
Effects of crosslinking on physical properties of phenol–formaldehyde novolac cured epoxy resins
Authors: Ogata Masatsugu , Kinjo Noriyuki , Kawata Tatsuo
Published: April 2003

To clarify the relationship between crosslinking density and physical properties of phenol–formaldehyde novolac cured epxy resin and factors governing their physical properties, we studied various properties of cured resins having different crosslinking densities. The resins were prepared with various curing accelerators and raw epoxy resins having different molecular weights. We found that as the crosslinking density of a cured resin increases, glass transition temperature (Tg) rises and the relaxation time becomes longer. Furthermore, in the rubbery region, the coefficient of linear thermal expansion drops and the elastic modulus become larger, while, in the glassy region, the coefficient of linear thermal expansion, specific volume, water absorption, diffusion coefficient, and permeability all increase but the elastic modulus becomes smaller. The WLF analysis on the relaxation behaviors of typical cured resin showed that cured resin with a higher crosslinking density decreases in the fractional free volume. This behavior is completely opposite from the relationship predicted from the temperature dependency of specific volume. While the coefficient of thermal expansion of free volume decreases as the crosslinking density increases for the cured resin, it coincides well with the tendency predicted from the difference in coefficient of cubic thermal expansion in the rubbery and glassy regions of each cured resin. That the free volume obtained from WLF analysis shows a relationship opposite to the predicted free volume as based on the temperature dependency of specific volume is explained as follows: Namely, the free volume obtained from the WLF analysis is a hole free volumeVhwhich contributes to fluidity andVhdecreases with the crosslinking density. On the other hand, the free volume predicted from the specific volume is a sum of the interstitial free volumeViandVh.Viincreases with the crosslinking density and thisViincrease exceeds the decrease ofVh. Therefore, the free volume predicted from the specific volume increases with the crosslinking density. Consequently, the influence of free volume on the relationship between the crosslinking density and physical properties of cured resin can be interpreted as follows. As the crosslinking density increases on cured resins,Tgrises, the relaxation time is lengthened, and the coefficient of linear thermal expansion becomes smaller in the rubbery region because, as the crosslinking density increases,Vhdecreases. Since crosslinking density increases on cured resins, the coefficient of linear thermal expansion, water absorption, diffusion coefficient, and permeability become larger, and the elastic modulus becomes smaller in the glassy region because, as the crosslinking density increases,Viincreases and, accordingly, molecular chain packing becomes looser; i.e., the specific volume increases. © 1993 John Wiley & Sons, Inc.
The structure of filled and unfilled thermotropic liquid crystalline polymer injection moldings
Authors: Plummer C. J. G. , Zülle B. , Demarmels A. , Kausch H.‐H.
Published: April 2003

Studies of the microstructure and orientation in thermotropic liquid crystalline polymer injection moldings have been carried out using a variety of techniques to reveal the complex hierarchical structure. The effect of particle filler on the level of molecular orientation in the flow direction appears relatively weak, but at high filler contents, there is a marked disruption of coarse structure in the matrix. © 1993 John Wiley & Sons, Inc.
A new mechanism for increasing tear strength and cut‐growth resistance of elastomers
Authors: Stewart Charles W.
Published: April 2003

A new mechanism is presented for increasing the tear strength of noncrystallizing elastomers over a broad temperature range. It is shown that the incorporation, into elastomers, of a plastic filler with the proper yield strength can substantially increase tear strength by decreasing the excess stress that develops at the tip of a sharp cut in an elastomer strip under tension. To be effective at low aspect (length/diameter) ratio, the yield strength of the plastic must be of the same order of magnitude as the tensile strength of the elastomer to which it is added. The analysis is strictly valid only for very small deformations, where crack‐tip blunting can be ignored, and for an applied stress sufficiently low that the plasticyielding zone is very small relative to the crack length. It provides a useful model, at least, for the development of a new mechanism for increasing the tear strength of fluoroelastomers at sufficiently high temperatures, which is of significant practical importance. Examples of the use of a new fluoroplastic micropowder to provide over a fourfold increase in tear strength of several fluoroelastomers at high temperatures are given. © 1993 John Wiley & Sons, Inc.
Concentration dependence of diffusivities of penetrants in glassy polymer membranes
Authors: Sada E. , Kumazawa H. , Wang J.‐S.
Published: April 2003

Steady‐state permeation rates for pure CO2, CH4, and O2 through two kinds of homogeneous dense membranes, copolymer of methyl methacrylate and n‐butyl acrylate and poly(methyl methacrylate), were measured at three temperatures between 20 and 40°C and upstream pressures up to 3 MPa. The logarithms of the mean permeability coefficients for CO2 in both membranes increased linearly or quadratically with increasing upstream pressure, whereas the mean permeabilities for CH4 and CO2 were independent of pressure. The pressure dependence of the mean permeability coefficient for CO2 was interpreted in terms of a modified free‐volume model of diffusion for a Henry's law population in glassy polymers. © 1993 John Wiley & Sons, Inc.