bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow method for study of gas transport in polymers. Application to the study of oxygen, nitrogen, and carbon dioxide permeation through cellulose acetate membranes
Authors: Nguyen X. Q. , Šipek M. , Hynek V. , Nguyen Q. T.
Published: April 2003

Transient permeation of oxygen, nitrogen, and carbon dioxide through certain cellulose acetate (CA) dense membrances made from solutions in dioxane and dioxane‐added ethanol were studied by the flow method. In order to explain the overshoots for transient permeation rates in the latter case, a new model is proposed. It postulates a time‐dependence solubility coefficient, in the form of a series of exponential terms, which is combined in Fick's second law and solved. The model fits well the obtained permeation kinetics, leading to values of the diffusion, and permeation coefficients, and the structure change‐related time. The overshoots are explained by the formation of unstable structure from dioxane‐ethanol solvent mixtures, a memory effect of aggregated chains, which undergoes consolidation upon gas penetration. The stable state which results from the consolidation process is the same as that of membrances obtained from pure dioxane solutions. © 1994 John Wiley & Sons, Inc.
Nonlinear viscoelasticity of a vulcanized elastomer
Authors: Kontou E.
Published: April 2003

The material nonlinearities in the viscoelastic behavior of rubbers at modest‐to‐large deformations have been studied. A vulcanized network based on the styrene–butadiene elastomer has been tested in stress‐relaxation experiments at room temperature for a wide range of deformations. After time–strain separabality was confirmed, the damping function could be calculated and introduced into the Boltzmann superposition integral. The equilibrium stress–strain behavior of the system could then be described, while comparison with other theoretical equations has also been made. © 1994 John Wiley & Sons, Inc.
Thermally stimulated depolarization current studies on PC/PTBF blends
Authors: Kalkar A. K. , Kundagol Shankar , Chand Suresh , Chandra Subhas
Published: April 2003

Thermally stimulated depolarization current (TSDC) studies have been carried out on blends of polycarbonate (PC) and poly(p‐t‐butyl phenolformaldehyde) (PTBF) using electric poling at temperatures ranging from 348°K to 383°K. The PC/PTBF blends poled at identical electric field (Ep) and temperature (Tp) exhibit a continuous distribution of polarizability (in general, in the range 300°K to 450°K) with a blend composition dependent single peak (TM). With increasing Ep and Tp, the TSDC peak of a blend shifts toward higher temperature with increasing peak current (IM) and charge (Q) associated with the peak. The effects of polarization field and temperature indicate that the polarization in the blend system is due to induced dipole formation. The activation energy decreases with increasing PTBF content in the blend, indicating shallow traps in PC/PTBF electret. The present blend electrets, however, comparative to its two components PC and PTBF, store more charge but decay faster. © 1994 John Wiley & Sons, Inc.
Structure/permeability relationships of polyamide‐imides
Authors: Gao Xuesong , Lu Fengcai
Published: April 2003

Structure/permeability correlations for a family of aromatic polyamide‐imides are presented. The variations in chemical structure lead to significant changes in permeability. The crystallization of PAP results in a very low permeability. The introduction of bulky group tends to increase permeability without a corresponding decrease in permselectivity. This result contributes to the inhibition of chain packing and segmental mobility. Wide‐angle X‐ray diffraction measurements of average segmental spacing of the materials and fractional free volume calculations characterize the packing of the different polymers. © 1994 John Wiley & Sons, Inc.
Gas‐sweeping pervaporation: A method for studying the transport of solvent mixtures in polymers: Application to the methanol–propan‐1‐ol‐cellulose triacetate system
Authors: Nguyen X. Q. , Nguyen Q. T. , Clement R. , Uchytil P.
Published: April 2003

A new method using a batch gas‐sweeping pervaporation was proposed for the measurement of different transport parameters of a polymer film to a solvent mixture. In addition to the total permeation flux and the selectivity of the film to the mixture, the diffusion coefficients and the permeation coefficients of the components can be determined. The method, which is based on new solutions of the second Fick law in which the upstream concentration is time‐dependent, was applied to the transport of methanol‐propan‐1‐ol mixtures through a cellulose triacetate membrane and their results were compared with those obtained in vacuum pervaporation. Both the methods give equivalent selectivity and permeation fluxes at all methanol contents. The diffusion coefficient of methanol, which was ca. 10−7 cm2/s in cellulose triacetate when pure methanol was used, was found to be much smaller when methanol was mixed with propan‐1‐ol (ca. 10−9cm2/s). From the practical viewpoint, the cellulose triacetate membrane shows a high permeation flux with a rather good selectivity to methanol. © 1994 John Wiley & Sons, Inc.
Comparison of thermal techniques for glass transition measurements of polystyrene and cross‐linked acrylic polyurethane films
Authors: Achorn Peter J. , Ferrillo Rosalie G.
Published: April 2003

There are few quantitative comparisons in the literature between glass transitions (Tg) measured by differential scanning calorimetry (DSC) and by dynamic mechanical analysis (DMA). Also, in the case of DMA, two different operational definitions have been used to obtain the glass transition, namely, the loss modulus (E″) and damping (tan δ) peak temperatures. We propose a new DMA definition of Tg and demonstrate that it agrees with DSC Tg measurements within ±2°C for both thermoplastic polystyrene and thermoset cross‐linked acrylic polyurethane films with measurable tan δ peaks. The glass transitions for a single polystyrene standard and several cross‐linked acrylic polyurethane films were measured by DSC. Additionally, E″ and tan δ peak temperatures were measured by DMA as a function of frequency and temperature. Empirically, it was determined that the average of the E″ and tan δ peak temperatures measured at 1 rad/s oscillation frequency corresponds to the glass transition measured by the ASTM E1356 DSC test method. © 1994 John Wiley & Sons, Inc.
Preparation, characterization, and thermal behavior of MMA–N‐aryl maleimide copolymers
Authors: Bharel Renu , Choudhary Veena , Varma I. K.
Published: April 2003

The work describes the synthesis and characterization of copolymers of methyl methacrylate (MMA) and N‐o‐tolyl maleimide (MO)/N‐p‐tolyl maleimide (MP)/4‐maleimido benzoic acid (MB). The copolymers were synthesized by varying the mol fraction of N‐aryl maleimides from 0.1 to 0.5 in the initial feed using azobisisobutyronitrile (AIBN) as an initiator and tetrahydrofuran as the solvent. The copolymer composition was determined from the 1H‐NMR spectra by taking the ratio of proton resonance signals due to OCH3 of MMA (δ=3.59 ppm) and the aromatic protons (δ=7.0–7.3 ppm) of N‐aryl maleimides. The monomer reactivity ratios of MMA–MP were r1=0.926±0.001 and r2=0.47±0.03 and MMA–;MO were r1=1.37±0.005 and r2=0.31±0.01. The initial decomposition temperature of copolymers and glass transition temperatures increased with increasing N‐aryl maleimide content in the backbone. © 1994 John Wiley & Sons, Inc.
Some mechanical properties of solvent‐treated polypropylene films
Authors: Ugbolue S. C. O. , Uzomah T. C.
Published: April 2003

The amount of polypropylene (PP) extracted by hot solvent extraction increased with increasing naphtha in a naphtha/reformate solvent blend. The stress–strain curves formed the basis for the calculation of several mechanical properties of the residual film. The yield stress, the natural draw ratio, secant modulus, breaking factor, and work expended in drawing were maximum at a 10/90 naphtha/reformate composition. These were explained in terms of extraction of low molecular weight and atactic materials leaving a more stereoregular block, giving maximum properties with the least removal of polymer materials. Further increases in the naphtha component, however, decreased these properties, possibly due to the greater solubilizing effect of naphtha for the PP chains. © 1995 John Wiley & Sons, Inc.
Elastomer–carbon black interaction: Influence of elastomer chemical structure and carbon black surface chemistry on bound rubber formation
Authors: Roychoudhury A. , De P. P.
Published: April 2003

The contribution of elastomer polarity and reactivity to bound rubber formation has been investigated. In this study, a number of elastomers of different chemical nature have been tested. The surface of the carbon black (N110) has also been modified by nitric acid oxidation in order to increase the concentration of surface functional groups. The experimental results have shown that the bound rubber formation is barely related to the polarity of the polymers. It is the reactive sites in both the elastomer and carbon black which are mainly responsible for bound rubber formation. It therefore appears that the elastomer/carbon black interaction leading to the formation of bound rubber is essentially a chemical process involving primary bond formation between elastomer and carbon black. The oxidized carbon black exhibits a higher surface activity which may be due to an increased concentration of oxygen‐containing reactive surface sites, namely, phenolic hydroxyl, carboxyl, lactone, and quinone groups. © 1995 John Wiley & Sons, Inc.
Cross‐linking of poly(methyl methacrylate) by aminolysis of ester functions with diamines
Authors: Pavlinec J. , Lazar M.
Published: April 2003

The cross‐linking of poly(methyl methacrylate) (PMMA) macromolecules by primary aliphatic diamines was carried out at 413–473 K, above the polymer glass transition temperature. The spherical grains of the suspension‐prepared polymer (0.25–0.8 mm) and the molar ratio to amine above 20 were used. The reaction is characterized by an induction period before the macroscopic gel was observed and by fast network formation. Both phenomena are temperature‐dependent (87± 2 kJ mol−1). The rate of gelation is dependent also on the type of diamine; the shorter induction period of gelation and the higher rate of cross‐linking were observed when amino groups were separated with longer alkyl chains. From the kinetics of amine uptake with PMMA, however, it can be concluded that gel formation is influenced also by the reactivity of amine in the transamination reaction and by the amount of bounded diamine. Aminolysis of PMMA ester groups proceeds from the very beginning of heating of the reaction charge. The polymer cross‐linking prevails when there is more than 60% of diamine attached to PMMA in dependence on the amine type used. © 1995 John Wiley & Sons, Inc.
Crosslinked hydroxypropyl cellulose films retaining cholesteric liquid crystalline order. I. Effects of cast conditions and heat treatment on the textures and order of films
Authors: Suto Shinichi , Suzuki Kuniaki
Published: April 2003

To eliminate the shear‐induced band texture and wrinkled texture observed on the free surface of cellulosic solid cast films retaining cholesteric liquid crystalline order, we proposed a storing process of the cast solutions: the solution is stored in the same solvent vapor atmosphere as the solution. The effect of cast conditions (the storing time) on those textures and the cholesteric liquid crystalline order was determined using the lyotropic liquid crystalline solution of hydroxypropyl cellulose in methanol with crosslinker. Furthermore, the effect of heat treatment on the liquid crystalline order in the cast films was determined. The resultant crosslinked films were observed with a polarized microscope and a scanning electron microscope, and were investigated with circular dichroism. Our findings showed that the proposed storing process is needed before starting the cast process. During the process the textures vanished, due to the relaxation of the residual stress in the solution, the cholesteric liquid crystalline order became stable, and the cholesteric pitch decreased with increasing storing time. The heat treatment also affected the liquid crystalline order of the films; the peak in the circular dichroism spectrum sharpened and shifted with heat treatment, and the shift in peak seemed to depend on the crosslinker concentration. Furthermore, the crosslinking proceeded with heat treatment. © 1995 John Wiley & Sons, Inc.
Hydrolytic aging of polycarbonate. I. Physical aspects
Authors: Ghorbel I. , Thominette F. , Spiteri P. , Verdu J.
Published: April 2003

The hydrolytic aging of an unstabilized industrial sample of polycarbonate was studied at 40, 70, 80, and 90°C, 100% RH. The water absorption characteristics show that, at equilibrium, the polymer absorbs about 0.04 mol water per ester group and that the equilibrium is reached after about 10–40 h exposure, i.e., far before irreversible changes of physical properties are observed. Differential scanning calorimetry reveals the combined effects of hydrolytic chain scission and physical aging on glass transition temperature. Investigations on tensile yield properties showed that hydrolytic chain scission leads to a significant decrease of the apparent Eyring's activation volume. These observations strongly support the hypothesis that there are preexisting or hydrolysis‐induced defects responsible for an heterogeneous distribution of chain scissions that would be concentrated into localized microdomains. © 1995 John Wiley & Sons, Inc.
Effects of poly(vinyl acetate) and poly(methyl methacrylate) low‐profile additives on the curing of unsaturated polyester resins. I. Curing kinetics by DSC and FTIR
Authors: Huang Yan‐Jyi , Su Chin‐Cheng
Published: April 2003

The effects of two low‐profile additives (LPA), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) on the curing kinetics during the cure of unsaturated polyester (UP) resins at 110°C were investigated by using a differential scanning calorimeter (DSC) and a Fourier transform infrared spectrometer (FTIR). The effects of temperature, molar ratio of styrene to polyester CC bonds, and LPA content on phase characteristics of the static ternary systems of styrene–UP–PVAc and styrene–UP–PMMA prior to reaction were presented. Depending on the molar ratio of styrene to polyester CC bonds, a small shoulder or a kinetic‐controlled plateau in the initial portion of the DSC rate profile was observed for the LPA‐containing sample. This was due to the facilitation of intramicrogel crosslinking reactions since LPA could enhance phase separation and thus favor the formation of clearly identified microgel particles. FTIR results showed that adding LPA could enhance the relative conversion of polyester CC bonds to styrene throughout the reaction. Finally, by use of a microgel‐based kinetic model and static phase characteristics of styrene–UP–LPA systems at 25°C, the effects of LPA on reaction kinetics regarding intramicrogel and intermicrogel crosslinking reactions, relative conversion of styrene to polyester CC bonds, and the final conversio have been explained. © 1995 John Wiley & Sons, Inc.
UV‐curable acrylic resins for production of glass laminates
Authors: Decker C. , Moussa K.
Published: April 2003

Glass laminates have been readily obtained by photocuring at ambient temperature of an acrylic adhesive consisting either of a liquid resin or a solid thermoplastic polymer. The light‐induced polymerization process was followed by real‐time infrared spectroscopy. Close to 100% conversion was reached within a few seconds of exposure, by taking as the photoinitiator an α‐hydroxy alkylphenone or an aryl phosphine oxide. A liquid formulation containing an aliphatic polyurethane–acrylate oligomer, acrylic acid, and butyl acrylate gives the best performance in terms of reactivity, adhesion, impact resistance, and transparency. The impact resistance was further increased by introducing a polycarbonate core between the two glass plates. The solid thermoplastic polymer was obtained either by casting from a solution containing an aliphatic polyurethane, an acrylate oligomer, and the photoinitiator or by mixing these compounds in the molten state and further extrusion. The glass assembly was heated above the softening temperature (80°C) under a 1 MPa pressure and cured by a 1 min exposure to UV radiation to give a strongly adhesive laminate showing good transparency and long term weatherability. © 1995 John Wiley & Sons, Inc.
Studies on the preparation and properties of conductive polymers. VIII. Use of heat treatment to prepare metallized films from silver chelate of PVA and PAN
Authors: Chang Liang‐Tau , Yen Chih‐Chao
Published: April 2003

Metallized polymer films were prepared from polyacrylonitrile or poly(vinyl alcohol) silver chelate solution by heat treatment. These metallized film exhibited low surface resistivity around 100Ω/cm2. The surface of these conductive films was proved to be metallized using X‐ray analysis. The metal adhered on the film was believed to be responsible for the improvement of electrical conductivity. The effects of types and concentrations of silver salt, types and volume of solvent, and drying time on the conductivity of metallized films were investigated. © 1995 John Wiley & Sons, Inc.
Microstructure and mechanical properties studies of poly(vinyl alcohol)–lead salts complexes
Authors: Bakr N. A. , Abdel‐Hamid M. I. , El‐Hanafy O.
Published: April 2003

Poly(vinyl alcohol) (PVA) was found to form complexes with PbCl2, Pb(NO3)2, and Pb(CH3COO)2. Different complex compositions were prepared by casting technique. Microdomains were observed in the case of the PbCl2‐PVA system. Complexes of PbCl2‐PVA system are somicrystalline over the entire composition range. PbCl2‐PVA complexes are stable to temperatures greater than 350°C in comparison to 225°C of pure PVA. The general features of the microdomains depends upon the temperature and the salt concentration. The hardness properties of the binary mixture were found to change in a nonlinear mode exhibiting a maximum value with the increase of the PbCl2 content and in a linear mode for the other salts. © 1995 John Wiley & Sons, Inc.
Short coir fiber‐reinforced natural rubber composites: Effects of fiber length, orientation, and alkali treatment
Authors: Geethamma V. G. , Joseph Reethamma , Thomas Sabu
Published: April 2003

Natural rubber is reinforced with untreated coir fiber chopped to different lengths, viz., 6, 10, and 14 mm. Mixes were also prepared using 10 mm‐long coir fibers treated with 5% sodium hydroxide solution for different time intervals, viz., 4, 24, 48, and 72 h. These composites were vulcanized at 150°C. The vulcanization parameters, processability characteristics, and stress–strain properties of these composites were analyzed. The rubbercoir interface bonding was improved by the addition of a resorcinol–hexamethylenetetramine dry‐bonding system. The reinforcing property of the alkali‐treated fiber was compared with that of the untreated one. The extent of fiber orientation in the composite was determined from green strength measurements. From anisotropic swelling studies, the extent of fiber alignment and the strength of fiber–rubber interface adhesion were analyzed. Scanning electron microscopic studies were carried out to investigate the fiber surface morphology, fiber pullout, and fiber–rubber interface. © 1995 John Wiley & Sons, Inc.
Thermal and mechanical properties of phenolphthalein polyethersulfone/poly(phenylene sulfide) blends
Authors: Yang Yuming , Li Binyao , Zhang Yingjun , Zhang Yan , Zhuang Guoqing
Published: April 2003

The thermal and mechanical properties of phenolphthalein polyethersulfone/poly(phenylene sulfide) (PES‐C/PPS) blends were studied using a differential scanning calorimeter, a dynamic mechanical analyzer, and mechanical characterization. The morphologies of fracture surfaces were observed by scanning electron microscopy. The blends are multiphase systems with strong interaction between the two phases. It is of interest that, although the strength and ductility of PPS are lower than those of PES‐C, the addition of PPS can improve markedly the impact strength of PES‐C without changing its higher strength. The PPS can also act as a flow aid for PES‐C. © 1995 John Wiley & Sons, Inc.
Applications of computer difference spectroscopy in ion‐exchange resins analysis
Authors: Rodriguez A. S. , Flores R. Ma. E.
Published: April 2003

Infrared spectra demonstrate the use of computer difference spectroscopy and other dataprocessing routines to derive and enhance the difference spectra that relates the concentration of a resin to the concentration of other resins in the mixture. Therefore, a simple quantitative treatment accounting for the resin concentration has been determined. © 1995 John Wiley & Sons, Inc.
The stability of poly(ether urethane)/polydimethylsiloxane interpenetrating polymer networks
Authors: Ali S. A. M. , Hourston D. J. , Manzoor K. , Williams D. F.
Published: April 2003

Interpenetrating polymer networks (IPNs) are a special type of polymer blend consisting of two polymer networks synthesized and/or cross‐linked independently within each other. One potential approach for the preparation of composite materials from polymers having desirable physical characteristics obtained by modifying their surfaces with physiologically acceptable polymers involves IPN technology. An IPN based on a poly(ether urethane) and polydimethylsiloxane has been synthesized and charaterized using optical microscopy, dynamic mechanical analysis, and scanning electron microscopy. The stability of poly(ether urethane)/polydimethylsiloxane composites were studied in hydroxyl radical aqueous solutions over 30 weeks. The data suggest that these composites have good potential for biomedical applications. © 1995 John Wiley & Sons, Inc.
Direct use of mixing data for modeling high‐viscosity, melt‐phase, condensation polymer reactors
Authors: Neogi Swati , Sampson Kendree J.
Published: April 2003

Mathematical models for simultaneous reaction and mass transfer occurring in the manufacture of high‐viscosity condensation polymers are considered. Particle tracking experiments are used to estimate convective flow rates and mixing volumes in a disc‐ring reactor configuration. These results are incorporated directly into a mixing‐cell model without resorting to the use of restrictive assumptions regarding the convective mixing. Both a penetration theory model and a flash evaporation model are used to simulate the transport at the liquid–vapor interface. Although widely used in previous studies, the penetration theory model is ultimately rejected because it underpredicts the overall reactivity. Model results predict interactions between agitation rate, residence time, and the overall reaction rate for commercial‐scale systems producing poly(ethylene terephthalate). The model is partially verified by comparison with degassing data. © 1995 John Wiley & Sons, Inc.
Large transient shearing of molten polymers: Predictions of rate‐dependent and nonaffine network models
Authors: Xu Y. Z. , De Kee D. , Fong C. F. Chan Man
Published: April 2003

Analytical expressions of shear stress evolution for arbitrary transient flows are obtained, based on a rate‐dependent network (RDN) model as well as on a nonaffine network (NAN) model. Predictions of both models are evaluated for various step histories against experimental results on linear and branched polyethylene melts (LDPE and HDPE). Agreement with experiments justifies the usefulness of the computed stress functions regarding the predictions of shear responses in melt processing. A slow transient process is more adequately simulated by an NAN model than by an RDN model. The very slow reentanglement process following cessation of flow is poorly described by either model. This fact implies that additional relaxation mechanisms are involved. In the linear viscoelasticity of small deformation, elastic relaxation occurs. In processes involving large shear rates, additional parameters are needed to account for the structural changes accompanying the relaxation process. © 1995 John Wiley & Sons, Inc.
Role of PbO in covulcanization of carboxylated nitrile–polyacrylic rubber blend in the presence of ethylene thiourea or mercaptobenzothiazole
Authors: Chowdhury P. , Chakravorti M. C. , Das C. K.
Published: April 2003

The effects of metal oxide (PbO) on covulcanization of the blend [carboxylated nitrile rubber (XNBR)–Polyacrylic rubber (ACM) = 50 : 50] in the presence of 2‐mercaptobenzothiazole (MBT) or ethylene thiourea (ETU) have been evaluated to elucidate the curing mechanism. The optimum mole ratio of ETU–PbO and MBT–PbO with respect to cure characteristics and physical properties have been found to be 1 : 1.5 and 1 : 0.5, respectively. The examination of infrared (IR) spectra reveals that crosslinking occurs at the CCl cure site of the ACM and COOH cure site of the XNBR. Based on the optimum mole ratios and Spectral analysis a scheme of reactions has been proposed. © 1995 John Wiley & Sons, Inc.
Radiopaque epoxy resins
Authors: Chatterjee Gautam , Cabasso Israel , Smid Johannes
Published: April 2003

Transparent, X‐ray contrast (radiopaque) epoxy resins were obtained by dissolving up to 25 wt % triphenylbismuth in the commercial epoxy resin prepolymers EPON‐815, DER‐330, DER‐383, and DEN‐431 which were then hardened with diethylenetriamine. The radiopacities of the mixtures were found to be proportional to the molar concentration of the radiopaque additive. The systems follow the relationship, R = Ro + (Ra − Ro) Va Ma where R, Ro, and Ra are the radiopacities of the mixture, the pure epoxy resin, and triphenylbismuth, respectively (expressed in mm aluminum/mm resin); Ma and Va denote the molar concentration and molar volume of the bismuth compound. Ra for triphenylbismuth was found to be 7.4 ± 0.2 mm Al/mm resin; the average value of Ro for the four epoxies equals 0.16 ± 0.1 mm Al/mm resin. The amount of amine required to harden the radiopaque resins was far less for the epoxy novolac resin DEN‐431 than for the three bisphenol‐A based epoxies. The concentration of triphenylbismuth required to impart a radiopacity equivalent to that of aluminum measures 14.6 wt % in EPON‐815, 14.8 wt % in DER‐330, 14.9 wt % in DER‐383, and 15.9 wt % in DEN‐431. The radiopaque resins remain transparent indefinitely, even when exposed to water. © 1995 John Wiley & Sons, Inc.
Modification of wettability of a stainless‐steel plate by cathodic plasma polymerization of trimethylsilane–oxygen mixtures
Authors: Wang Tinghao F. , Yasuda Hirotsugu K.
Published: April 2003

Wettability (by water) of a stainless‐steel plate was modified by depositing an ultrathin layer of a plasma polymer of trimethylsilane (TMS) and an oxygen mixture. Plasma polymerization was carried out by cathodic glow discharge polymerization, in which a substrate stainless‐steel plate was used as the cathode of the de glow discharge. The plasma polymer of TMS (oxygen mol fraction = 0) is very hydrophobic, but the addition of oxygen in the monomer mixture increased the hydrophilicity of the plasma polymer. The value of cos θ (θ: advancing contact angle of water) linearly increased with the mol fraction of oxygen in the monomer mixture. Oxygen in the monomer mixture acts as (1) an ablating agent of a carbon‐based plasma polymer and (2) a comonomer for a silicon‐based plasma polymer. The atomic composition of a plasma polymer, which can be expressed as SiCxOy, changes (x decreases and y increases) as the mol fraction of oxygen increases. © 1995 John Wiley & Sons, Inc.
Synthesis of poly(benzylmethacrylate)‐co‐perfluorooctylethylmethacrylate) and electrooptical properties of the resultant polymer/liquid crystal composite films
Authors: Kawatasuki Nobuhiro , Ono Hiroshi
Published: April 2003

Methacrylate copolymers of benzylmethacylate (BMA) and perfluorooctylethylmethacrylate (FMA) were synthesized and applied to the polymer/liquid crystal (LC) composite films. The copolymers were prepared by a radical solution polymerization. The high composition of FMA resulted in a precipitation during the polymerization. The contact angle of the LC on the copolymer films decreased with increasing FMA composition. Due to a small interaction between the LC and the copolymers, the copolymer/LC composite films showed low driving voltage in the range of 18–25 Vrms, corresponding to about 1/3 the value of the poly(methyl methacrylate) (PMMA)/LC composite film. © 1995 John Wiley & Sons, Inc.
Tensile properties of chemically modified ring‐ and rotor‐spun cotton yarns
Authors: Subramaniam V. , Thambidurai S.
Published: April 2003

The effects of chemical treatments and modifications on the tensile properties of ring‐and rotor‐spun cotton yarns is discussed. The rotor‐spun yarns treated with zinc chloride show a higher tenacity at low stretch levels compared to sodium hydroxide, whereas with sodium hydroxide, the rotor‐spun yarns show higher tenacity at higher stretch levels compared with zinc chloride. The aqueous‐treated rotor‐spun yarns show a higher change in tenacity compared to ring‐spun yarns. Sodium hydroxide‐treated yarns before resin treatment show a higher retained tenacity compared to zinc chloride‐treated yarns. The substitution treatment after swelling and stretching to 100% shows a higher tenacity than that of the slack substituted yarns. © 1995 John Wiley & Sons, Inc.
Preparation and characterization of perlite‐filled high‐density polyethylenes. III. Impact properties
Authors: Akin‐Öktem G. , Tinçer T.
Published: April 2003

Impact properties of perlite‐filled high‐density polyethylene (HDPE) composites were studied with the Charpy method by using both notched and unnotched samples. γ‐Aminopropyltriethoxy silane (γ‐APS, A‐1100) was used as a silane coupling agent to improve the interfacial adhesion. The influences of the molecular parameters of HDPEs, molecular weight, degree of branching, degree of crystallinity, and also the effect of γ‐APS on the impact properties are represented in this work. © 1995 John Wiley & Sons, Inc.
Parameter estimation in emulsion copolymerization using reaction calorimeter data
Authors: Barandiaran María J. , De Arbina Lourdes López , De La Cal José C. , Gugliotta Luis M. , Asua José M.
Published: April 2003

The feasibility of estimating the kinetic parameters of emulsion copolymerization using only calorimetric measurements was investigated by simulation. It was found that for the case in which the average number of radicals per particle exceeds 0.5 only two of the three estimable parameters (kI, ka, and kt) could be estimated together provided that an accurate value for the third parameter is available from independent measurements. For systems with n̄<0.5, the three unknown parameters kI, kd, and ka were accurately estimated. © 1995 John Wiley & Sons, Inc.
Effect of processing conditions on the structure development in the welding region of injection‐molded poly(arylene ether ketone). III
Authors: Ulcer Y. , Cakmak M. , Hsiung C. M.
Published: April 2003

Effect of injection‐molding process conditions including mold temperature and injection speed on the structure developed at the weld region of poly(arylene ether ketone) was investigated using MMBX (matrixing micro beam X‐ray diffraction) and image analysis techniques. The polymer exhibited multilayer structural formations at and near the weld region, and these were found to be alternating highly crystalline and low crystalline regions. With the exception of the converging section of the cavity, no significant orientations were observed through the X‐ray diffraction method. However, polarized light microscopy studies revealed that the bands of higher crystallinity possess higher birefringence as compared to the intervening regions. This suggested that these bands are formed under an orientational flow field. The geometrical pattern of these multilayer formations changes depending on the injection‐molding condition particularly with injection speed and mold temperature. Tensile test results indicate that the samples with no weld regions generally possess higher tensile strength. This difference between the tensile properties of the samples possessing weld and no weld decreases at high injection speeds. Izod impact strength exhibited an unusual behavior: The welded parts actually possess higher impact strength. This was attributed to the formation of multilayer structures at the weld zone. © 1995 John Wiley & Sons, Inc.
In‐line dielectric monitoring of monomer conversion in a batch polymerization reactor
Authors: Crowley Timothy J. , Choi Kyu Yong
Published: April 2003

In‐line monitoring of monomer conversion is studied using a low‐frequency dielectric sensor during solution polymerization of methyl methacrylate in a laboratory‐scale batch reactor. It has been found that the induction period due to the presence of an inhibitor can be determined by the dielectric sensor to detect the starting point of polymerization. The dielectric loss factor that changes with the progress of polymerization is empirically correlated with monomer conversion measured by the off‐line gravimetric method at different temperatures and initiator concentrations. It is demonstrated that dielectrometry can be used as an in‐line monitoring method in free‐radical polymerization. © 1995 John Wiley & Sons, Inc.
Thermal aging of bisphenol‐A polycarbonate/acrylonitrile–butadiene–styrene blends
Authors: Guest M. J. , van Daele R.
Published: April 2003

Thermal aging of immiscible bisphenol‐A polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) blends containing 25, 60, and 75% PC and the PC and ABS blend components have been studied. Changes in Izod impact properties and dynamic mechanical spectra are reported following aging at 90, 110, and 130°C for times up to 1500 h. PC/ABS blends containing 60 and 75% PC were found to retain high impact performance following aging at elevated temperatures, compared to the PC blend component. Dynamic mechanical spectroscopy is an effective probe for investigating the structure–property changes occurring and the mechanisms of aging. For PC and ABS, the changes were mainly due to physical aging of the amorphous polymers when aged below the glass‐transition temperature. For the PC/ABS blends, oxidative degradation additionally contributes to loss of toughness. Although structure–property changes are related to the behavior of the blend components, additional factors of potential importance for multiphase polymer–polymer systems have been identified, including a redistribution of stabilizers during the blend manufacture. © 1995 John Wiley & Sons, Inc.
FT‐IR spectroscopic investigations of photochemical grafting of amphiphiles onto polyacrylonitrile surfaces
Authors: Böhme Peter , Hicke Hans‐Georg , Ulbricht Mathias , Fuhrhop Jürgen‐Hinrich
Published: April 2003

The photoreactive amphiphile p‐(stearyl amido) benzoyl azide (SABAz) was synthesized and grafted onto surface of thin polyacrylonitrile (PAN) films by irradiation with UV light. Two different techniques were applied, namely, Langmuir–Blodgett (LB) deposition and casting from solution. A high degree of order and a hydrophobic surface were established by reflection‐absorption FT‐IR spectroscopy (RA‐IR) and contact angle measurements. The stability against treatment with water, tetrahydrofuran, and chloroform was tested. A considerable amount of amphiphilic molecules remains on the surface also after treatment with chloroform. RA‐IR spectra taken from photomodified PAN films prepared by both techniques are almost identical after chloroform treatment, indicating a similar coupling mechanism. © 1995 John Wiley & Sons, Inc.
Structural changes of PVC plastisols in progress of gelation and fusion as investigated with temperature‐dependent viscoelasticity, morphology, and light scattering
Authors: Kwak Seung‐Yeop
Published: April 2003

The structural changes of poly(vinyl chloride) (PVC) plastisols during mixing of PVC with a plasticizer was investigated; as the temperature was increased, the system was found to transform from a suspension of solid particles in a liquid medium to a swollen gel and ultimately to a fused homogeneous matrix. The dynamic viscoelastic measurements were utilized to continuously monitor the changes of moduli under a controlled heating rate, employing a mechanical spectrometer. Characteristic changes in the viscoelastic behavior were associated with changes in particulate morphology as observed with a scanning electron microscope (SEM). Both viscoelastic and morphological observations were shown to provide details of structural changes in conjunction with the behavior of the PVC–plasticizer interaction, enabling a qualitative discrimination of the gelation and fusion processes. An in situ small‐angle light‐scattering (SALS) method was performed to make a quantitative estimate for the swollen particles of PVC while they were in the progress of gelation and fusion. From the manner of increase in correlation distances, along with the changes in viscoelastic moduli and morphology, the swelling behavior of the particulate structures were examined on the quantitative basis and brief insight into the complex behavior of the PVC–plasticizer interaction began to be unfolded. © 1995 John Wiley & Sons, Inc.
Studies on miscibility of blends of poly(ethylene‐co‐methyl acrylate) and poly(dimethyl siloxane) rubber by melt rheology
Authors: Bhattacharya A. K. , Santra R. N. , Tikku V. K. , Nando G. B.
Published: April 2003

Rheological studies of the blends of poly(ethylene‐co‐methyl acrylate) (EMA) and poly(dimethyl siloxane) (PDMS) rubber have been carried out at various temperatures and different shear rates by a Monsanto processability tester. The melt viscosities of the blends are found to be higher than that calculated as per the additivity rule, showing a positive deviation, an indication of synergism present in the blends during melt processing. This confirms our earlier finding that the blends are miscible throughout the composition range. The activation energy of flow of the blends are always higher than that calculated as per the additivity rule. The comparatively higher activation energy for the 30 : 70 EMA–PDMS rubber blend among the systems studied confirms our earlier finding that extent of reaction between EMA and PDMS rubber is significantly higher at this proportion of the blends studied. This substantiates the miscibility between blends of EMA and PDMS rubber throughout the composition range. © 1995 John Wiley & Sons, Inc.
Prediction of mechanical properties of weather‐induced degraded plastics in saudi arabia
Authors: Amin M. B. , Hamid S. H. , Rahman F.
Published: April 2003

Empirical equations have been developed to predict the mechanical properties of greenhouse films when exposed to natural weather conditions for long durations. Tensile strength and percent elongation data obtained for the Dhahran site was used to develop empirical equations. Prediction models were developed with exposure time as independent parameter for both tensile strength and percent elongation, which were taken as dependent parameter. The mean deviations for tensile strength and percent elongation were found to be 2.5 and 1.2%, respectively. Weather data of Dhahran for the period of natural exposure is also presented. © 1995 John Wiley & Sons, Inc.
Aspects on interaction between multistage stabilization of polyacrylonitrile precursor and mechanical properties of carbon fibers
Authors: Wang P. H. , Yue Z. R. , Li R. Y. , Liu J.
Published: April 2003

The progression of polyacrylonitrile (PAN) fibers on multistage stabilization stage has been monitored by following the variations in density, elemental composition, morphological aspect, and mechanical properties. The effects of various processing conditions during the multistage stabilization on the mechanical properties of final carbon fibers were evaluated in detail. To achieve an optimal extent of stabilization of PAN fibers is critical as the final mechanical properties of carbon fibers are concerned. This aim can be realized by adjusting and matching the temperatures in each step and the processing rates during multistage stabilization. Imposing stretching on multistage stabilization is beneficial to mechanical properties of carbon fibers. © 1995 John Wiley & Sons, Inc.
Preparation and characteristics of ultrafine metal particles immobilized on fine polymer particles
Authors: Tamai Hisashi , Sakurai Hiroyuki , Hirota Yoshifumi , Nishiyama Fumitaka , Yasuda Hajime
Published: April 2003

Ultrafine metal particles immobilized on fine copolymer particles were produced by reduction of copolymer particles–metal ion complexes. Submicrometer‐size copolymer particles containing nitrogen, prepared by emulsifier‐free emulsion polymerization, were applied. Transmission electron microscopy (TEM) observation and X‐ray diffraction analysis indicated that ultrafine noble metal particles with diameter below 10 nm were formed and uniformly immobilized on the surface of copolymer particles. © 1995 John Wiley & Sons, Inc.
Improving adhesion in interleaf composites using plasma processing
Authors: Nay John C. , Pitt William G. , Armstrong‐Carroll Eileen
Published: April 2003

A novel radio frequency (RF) plasma processing technique, known as plasma induced polymerization (PIP), was used in a multistep plasma process to deposit a thin, uniform layer of viscoelastic material on Upilex‐S high‐temperature polyimide film in order to enhance adhesion between the film and the resin in carbon fiber interleaf composites using epoxy (Hercules 8551‐7A) resin systems. In a three‐phase study, the processing parameters of residence time, plasma power, plasma pressure, and monomer gas were varied to investigate adhesion improvement. Depositions were characterized using scanning electron microscopy and X‐ray photoelectron spectroscopy (XPS) analysis. Compressive mode II strain energy release rate (GIIc) was characterized by end‐notched flexure testing to rank and predict the best RF process for a thermoplastic film interleaf composite structure using polymide film. Adhesion was improved by as much as 140% over the adhesive performance of untreated Upilex‐S using the epoxy resin system. However, adhesive performance was improved in the relatively low temperatures (177°C) processing system, and this plasma deposition may not be stable at the higher processing temperatures needed for processing polymide matrix systems such as PMR‐15. © 1995 John Wiley & Sons, Inc.
Plasma polymerization of hexafluoropropylene: Film deposition and structure
Authors: Chen R. , Gorelik V. , Silverstein M. S.
Published: April 2003

Thin, pinhole‐free, highly adhering films for advanced technology applications can be deposited through plasma polymerization, a low temperature, solvent‐free process. This research studies the influence of plasma environment (power, pressure, and monomer mass flow rate (Fm)) on the plasma polymerization of hexafluoropropylene (HFP) using a common industrial parallel‐plate plasma reactor. The deposition and structure of the transparent, yellow, and highly adhering plasma polymerized HFP (PPHFP) film are investigated. The rate of polymerization (Rp) increases with power (W) and reaches a plateau when the plasma changes from energy starved to monomer starved while the rate of etching (Re) continues to increase. The rate of deposition (Rd), the difference between Rp and Re, increases with W, reaches a maximum, and then decreases. In a monomer starved plasma Rd increases with Fm or pressure through a more efficient utilization of the energy supplied at a given W or even at a given W/Fm. The abstraction of F and the preferential scission of the CCF3 bond can explain the F/C ratio of 1.5, the significant amount of double bonds, and the relative lack of CF3 in a PPHFP that consists of CF3, CF2, and CF groups. A gas phase dominated polymerization produces submicrometer particles some of which agglomerate into spheres. Both the particles and the spheres deposit on the surface and are incorporated into the film with further polymerization. © 1995 John Wiley & Sons, Inc.
Surface modification of aromatic polyamide film by aminoethanethiol solution for silicon rubber composites
Authors: Inagaki N. , Tasaka S. , Kawai H.
Published: April 2003

The surface modification of poly(p‐phenylene terephthalamide) (PPTA) film with 2‐aminoethanethiol (AET) to adhere to silicon rubber was investigated. The combination of the AET treatment and the silane coupling treatment is an effective surface modification of the PPTA film for this adhesion. The x‐ray photoelectron spectroscopy (XPS) analyses show that the AET treatment does not generate sulfur functionalities at the surface of the PPTA film but does generate oxygen functionalities. In the AET treatment process, a part of the amide groups near the surface of the PPTA film is hydrolyzed to form carboxylic acid groups and amino groups. The oxygen functionalities are condensed at the film surface, and nitrogen functionality is diluted at the film surface. The C(O)O moiety at the PPTA film surface may be a key factor for the adhesion with silicon rubber. The C(O)O moiety is mobile from the bulk of the PPTA film to the film surface. Hot water treatment of the original PPTA film makes the impossible adhesion with the silicon rubber possible. The hot water treatment, however, is not as powerful a surface modification as the AET treatment. © 1995 John Wiley & Sons, Inc.
Rheological characteristics of proanthocyanidin polymers from Pinus radiata. I. Rheological behavior of water‐soluble extract fractions and phlobaphenes
Authors: Kim Seungrok , Mainwaring David E.
Published: April 2003

The rheological characteristics of the solutions of the whole extracts and their fractions from the Pinus radiata bark were investigated. The viscosity changes upon addition of aqueous NaOH solution into the solutions of the hot water extracts are due mainly to the dissolution of the phlobaphene fraction. The polyelectrolyte character was established from the solutions of the hot‐water extracts. The kinetics of the size growth of naturally forming phlobaphenes could be observed by photon correlation spectroscopy (PCS) from the solutions of hot‐water extracts. Mild sonication could degrade phlobaphenes partly and this indicates that the formation of phlobaphenes is partly associated with colloidal interaction. © 1995 John Wiley & Sons, Inc.
Isothermal cure kinetics of a diglycidyl ether of bisphenol A/1,3‐bisaminomethylcyclohexane (DGEBA/1,3‐BAC) epoxy resin system
Authors: Barral L. , Cano J. , López A. J. , López J. , Nogueira P. , Ramírez C.
Published: April 2003

By employing differential scaning calorimetry, DSC, we have studied, under isothermal conditions, the kinetics of the cure reaction for a system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3‐bisaminomethylcyclohexane (1,3‐BAC) as a curing agent, over the temperature range of 60–110°C. We have determined the conversions reached at several cure temperatures and the reaction rates. The experimental data, showing an autocatalytic behavior, were compared with the model proposed by Kamal, which includes two rate constants, k1 and k2, and two reaction orders, m and n. This model gives a good description of cure kinetics up to the onset of vitrification. The activation energies for these rate constants were 44–57 kJ/mol. The reaction orders present a moderate change but their sum is in the range 2.5–3. Diffusion control is incorporated to describe the cure in the latter stages (postivitrification region). By combining the autocatalytic model and a diffusion factor, it was possible to predict the cure kinetics over the whole range of conversion. © 1995 John Wiley & Sons, Inc.