bluuebunny/crossref_metadata_2025 huggingface dataset:
One‐stage method of preparing core–shell particles
Authors: He W. , Tong J. , Wang M. , Pan C. , Zhu Q.
Published: April 2003

A one‐stage method of preparing code–shell particles was developed for the system containing silicone oils and glycidle methacrylate (GMA). Although the formation of core–shell particles for the systems containing silicone oils and methyl methacrylate (MMA) or styrene (ST) is possible in view of thermodynamics, the core–shell particles were not obtained. Factors such as better compatibility of silicone oils with vinyl monomers, higher swelling degree of silicone rubber in the vinyl monomers, and larger addition rate of thevinyl monomers with Si—H during the crosslinking of silicone oil containing vinyl group and Si—H (SVB and SHB) do not favor the formation of core–shell particles. X‐ray photoelectron spectrometer (ESCA) was used in determining the formation of core–shell particles. The mechanism of the formation of core–shell particles is discussed. © 1995 John Wiley & Sons, Inc.
Effect of the Sb2O3 catalyst on the solid‐state postpolycondensation of poly(ethylene terephthalate)
Authors: Kokkalas Demetris E. , Bikiaris Demetris N. , Karayannidis George P.
Published: April 2003

The effect of Sb2O3, which is used as the main catalyst in the production of poly(ethylene terephthalate) (PET) by melt polymerization, was studied on solid‐state postpolycondensation. It was observed that the catalyst works efficiently even in the solid state. The number‐average molecular weight of a PET prepolymer with an Sb2O3 content of 2000 ppm was increased from 18,350 to 40,800 after heating at 210°C for 8 h under vacuum (2–3 Pa), whereas when the catalyst was absent, the molecular weight of the same prepolymer under the same conditions was just increased to 22,500. The activation energies and the frequency factors of the esterification and ester interchange reactions, which take place simultaneously during solid‐state postpolycondensation, were determined. © 1995 John Wiley & Sons, Inc.
Immobilization of β‐galactosidase onto polymeric supports
Authors: Rejikumar S. , Devi Surekha
Published: April 2003

Poly(vinyl alcohol) cross‐linked with para‐formaldehyde (PVA–F) and natural polysaccharide–chitosan in bead form and salicylic acid–resorcinol–formaldehyde polymeric resin (SRF) in powder form were used for immobilization of β‐galactosidase through covalent linkages. Various activation processes and conditions were optimized. Immobilized enzyme showed very good storage stability at room temperature. Durability of the enzyme was also improved on immobilization. On repeated use of enzyme immobilized on chitosan beads, no loss was observed in enzyme activity even after 10 batches. Michaelis constant Km and maximum reaction velocity Vm were calculated for free and immobilized enzyme systems. Effect of pH and temperature on enzyme activity was estimated and energy of activation (Ea) and inactivation constant (Ki) for free and immobilized enzyme were calculated. © 1995 John Wiley & Sons, Inc.
Use of carbon fibril additives to reduce the dc resistivity of elastomer‐based composites
Authors: Farriss C. W. , Kelley F. N. , Von Meerwall E.
Published: April 2003

We have prepared insert model solid rocket propellants of two kinds, polycaprolactone (PCP) networks highly (60%) plasticized with triacetin and hydroxyl‐terminated polybutadiene (HTPB) cross‐linked with isophorone diisocyanate, both filled with over 65% NaSO4 and Al powders as well as traces of fine carbon fibrils 100 Å thick and several micrometers long. Sheets of these dieletric composites were used for dc surface and volume electrical resistivities near room temperature. Addition of less than 1% fibrils in the PCP composites reduces volume resistivity by a factor of 10. The amount required for HTPB is only 0.1% leaving processability unaffected; resistivity reduction rises from one to nearly four orders of magnitude as potential differnce in increased from 10 to 500 V. Addition of fibrils to HTPB composites is a promising candidate for minimizing the incidence of dangerous electric discharge events. © 1995 John Wiley & Sons, Inc.
Determination of interfacial tension between PA/PP and LCP/PP by IFR method and effect of compatibilization on interfacial tension
Authors: Kirjava J. , Rundqvist T. , Holsti‐Miettinen R. , Heino M. , Vainio T.
Published: April 2003

The dynamic imbedded fiber retraction (IFR) method was used to measure the interfacial tension between two molten polymers. The aim was to evaluate the applicability of this method for polypropylene (PP) used as matrix, and two polyamide (PA6, PA66) and thermotropic main‐chain liquid crystalline polymer fibers. The effect on the interfacial properties of modifying the PP matrix with compatibilizers was studied as well. The IFR method was found to be suitable for evaluating the interfacial properties of these polymer blends. The measured interfacial tensions correlated well with the morphology and mechanical properties of the blends and values calculated from the harmonic mean equation. Although the measured interfacial tensions were generally lower than the theoretical ones, the order of the values for the different polymer pairs was similar. © 1995 John Wiley & Sons, Inc.
Characterization of coatings of poly(hexamethylene adipamide) deposited on carbon fibers by interfacial polymerization techniques
Authors: Varelidis P. C. , Skourlis T. P. , Bletsos J. V. , McCullough R. L. , Papaspyrides C. D.
Published: April 2003

Polyamide coatings deposited on carbon fibers by means of an interfacial in situ polymerization technique have been examined. Two different coating processes were used, depending on the length of the carbon fibers (short or long). The effect of the concentration of the monomer reactants on the quantity of coating deposited on the fibers has been determined using thermogravimetric analysis (TGA). Characterization techniques used to identify the nature of the coating process product included Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). Using the above techniques, IR spectra were collected and identified, and important polymer properties, such as morphology, melting point, and the molecular weight of the polymer coating were determined. © 1995 John Wiley & Sons, Inc.
Graft copolymerization of N‐vinylpyrrolidone onto gelatin
Authors: Gao Jian‐Ping , Li Zhi‐Chong , Huang Ming‐Zhi
Published: April 2003

The graft copolymerization of N‐vinylpyrrolidone (VP) onto gelatin in aqueous medium, with α,α′‐azobisisobutylonitrile as initiator, has been studied. The effects of various reaction parameters such as temperature, reaction time, as well as the concentrations of initiator, monomer, and gelatin on the percentage of grafting and grafting efficiency were also studied. The chain‐transfer constant of isopropanol in this system was calculated. Finally, the grafted samples were analyzed with IR, DSC, TEM, and SEM measurements. © 1995 John Wiley & Sons, Inc.
Improvement of hot water resistance of poly(vinyl alcohol) hydrogel by acetalization and irradiation techniques
Authors: Darwis Darmawan , Yoshii Fumio , Makuuchi Keizo , Razzak Mirzan T.
Published: April 2003

In order to improve the heat stability of poly(vinyl alcohol) (PVA) hydrogel, acetalized PVA was irradiated with electron beam irradiation. The acetalization was strongly affected by PVA water content. There is an optimum water content of 20–30% for acetalization of PVA. The PVA gave maximum tensile strength at a dose of 100 kGy before or after acetalization. The PVA hydrogel maintained tensile strength of 10 MPa, even after 90 min boiling (98°C) in water or autoclave sterilization (121°C). It was confirmed that irradiation after, or before, acetalization is effective for enhancing heat resistance of a PVA hydrogel. The hydrogel is transparent, soft, has high tensile strength, and high hot water resistance. © 1995 John Wiley & Sons, Inc.
Bending behavior of gelatin/poly(hydroxyethyl methacrylate) IPN hydrogel under electric stimulus
Authors: Ma Ji Tao , Liu Ling Rong , Yang Xian Jin , De Yao Kang
Published: April 2003

This article deals with an interpenetrating polymer network composed of crosslinked gelatin (Gel) with glutaraldehyde (GA) and poly(hydroxyethyl methacrylate) (PHEMA) crosslinked with N,N′‐methylene bisacrylamide (BisAm). The hydrogel network is able to bend under an electric field stimulus. The composition of the interpenetrating polymer network (PN), pH, ionic strength, and voltage can influence the degree of bending. The mechanism of the electromechanichemical (EMC) effect is discussed as well. © 1995 John Wiley & Sons, Inc.
Hydrolytic thermal degradation of poly(naphthoyleneimide benzimidazole) in concentrated sulfuric acid
Authors: Lavrenko P. N. , Okatova O. V.
Published: April 2003

Translational diffusion in 96% H2SO4 and intrinsic viscosity of poly(naphthoyleneimide benzimidazole) (PNIB) have been investigated in different stages of its degradation in solution in the temperature range from 65 to 120°C. The degradation rate constant k has been determined from the change in molecular weight M of degraded products with time at the fixed temperature of solution. The activation energy of the process E was calculated from the temperature dependence of k. The difference in E values at low and high temperatures was found. At degradation temperatures above 90°C, the activation energy of hydrolysis was obtained as E = 133 kJ/mol, which coincides with that of aromatic polyamides in sulfuric acid. The data obtained are compared with the results of the investigations of optical properties of products of PNIB degradation in solution and PNIB stability in the solid state. An explanation of anomalies observed during PNIB degradation at low temperatures is suggested. © 1995 John Wiley & Sons, Inc.
Biodegradable polyester blends for biomedical application
Authors: Zhang Lianlai , Xiong Chengdong , Deng Xianmo
Published: April 2003

A new family of bioabsorbable materials suitable for biomedical applications was designed and prepared by means of blending of some available polyesters to develop new biodegradable materials tailored for different requirements. Multiphase polymer blends containing poly(d, l‐lactide) (PLA), poly(ε‐caprolactone) (PCL), poly(d, l)‐lactide‐co‐poly(ethylene glycol) (PELA), poly(ε‐caprolactone) ‐co‐poly(ethylene glycol) (PECL), and poly(ß‐hydroxybutyrate) (PHB), PLA/PCL, PELA/PECL, PHB/PLA, PHB/PELA, PHB/PCL, and PHB/PECL blends were respectively investigated. It was found that PLA/PCL, PHB, and PHB/PLA and PHB/PCL blends were seemingly immiscible, with their morphology and hydrolytic behavior were determined by the composition of the blends. On the other hand, the miscibility of PELA/PECL, PHB/PELA, and PHB/PECL blends was improved by using PELA and/or PECL block copolymers that contained poly(ethylene glycol) (PEG) as compatibilizer. The blends showed to a certain extent miscibility, fine phase morphology, and fast hydrolysis. © 1995 John Wiley & Sons, Inc.
Miscibility and peel strength of acrylic pressure‐sensitive adhesives: Acrylic copolymer–tackifier resin systems
Authors: Kim Hyun‐Joong , Mizumachi Hiroshi
Published: April 2003

Influence of miscibility between the components in acrylic pressure‐sensitive adhesives upon their peel strength P as a function of temperature has been studied. In case of miscible blend systems, incorporation of tackifier resins into the pressure‐sensitive adhesive systems results in the modification of the bulk properties, including Tg, and a plot of P against ΔT gives a smooth master curve, where ΔT is defined as the difference between the temperature of peel test and Tg of the blend. However, in case of immiscible blends where two phases exist in the system, no master curve can be obtained, and P of an acrylic copolymer decreases as the tackifier content increases. In this case, physical properties and adhesive performance will be governed by a matrix phase, and a dispersed phase will act as a filler. © 1995 John Wiley & Sons, Inc.
Microporous polypropylene hollow fibers with double layers
Authors: Nagō Satoshi , Mizutani Yukio
Published: April 2003

Microporous polypropylene hollow fibers with double layers were prepared by stretching double layered polypropylene microtubes containing polymethylsilsesquioxane fillers: the relatively smaller filler in the inner layer and relatively larger filler in the outer layer. The resultant hollow fibers have a finely interconnected fibrous structure parallel to fiber axis. Their N2 gas permeabilities were measured to estimate the fibrous structure: tortuosity factor, effective porosity, and pore size. © 1995 John Wiley & Sons, Inc.
Graft polymerization of acrylic acid onto starch using potassium permanganate acid (redox system)
Authors: Mostafa Kh. M.
Published: April 2003

Graft polymerization of acrylic acid (AA) onto rice starch using postassium permanganate/acid redox system as initiator was investigated. When starch was reacted with KMnO4 solution, MnO2 was deposited onto starch. The dependence of MnO2 amount deposited was directly related to KMnO4 concentration. Subjecting the MnO2‐containing starch to a solution consisting of monomer (AA) and acid (citric, tartaric, oxalic and hydrochloric acid) formed poly(AA)–starch graft copolymers. The graft yield, expressed as meq COOH/100 g starch, was measured by the amount of MnO2 deposited, AA concentration, material‐to‐liquor ratio, kind and concentration of acid, as well as temperature and duration. Finally, the newly prepared poly(AA)–starch graft copolymers were applied to cotton textiles to determine their suitability as sizing agents. The highest graft yield was obtained with citric acid and the least with hydrochloric acid, with tartaric and oxalic acid in between. The graft yield increased by increasing the concentration of acid to a certain concentration beyond which grafting leveled off. A similar trend was observed when the magnitude of grafting was related to the amount of MnO2 deposited. The graft yield increased by increasing the polymerization temperature from 30° to 50°C. Increasing the temperature to 60°C is accompanied by decreased grafting. On the other hand, fabric samples sized with poly(AA)–starch graft copolymers acquire higher tensile strength, elongation at break, and abrasion resistance than that sized with native rice starch, i.e., poly(AA)–starch graft copolymers serve as good sizing agents for cotton textiles. A tentative mechanism for grafting rice starch with AA using the KMnO4/acid redox system was elucidated. © 1995 John Wiley & Sons, Inc.
Protonation of polyaniline by surface‐functionalized polymer substrates
Authors: Pun M. Y. , Neoh K. G. , Kang E. T. , Loh F. C. , Tan K. L.
Published: April 2003

The protonation of solution‐coated emeraldine (EM) base by sulfonic and carboxylic acid groups on surface‐functionalized low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) films were characterized by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and conductivity measurements. Surface functionalizations were achieved by sulfonation (for LDPE, HDPE, PP, and PET), by hydrolysis (for PET), and by near‐UV‐light‐induced surface graft copolymerization with the Na salt of styrene sulfonic acid and acrylic acid (for all substrates). The efficiency of surface functionalization by graft copolymerization is substantially enhanced for substrates pretreated with O3 or Ar plasma. Protonation levels of 50% can be readily achieved for EM coated on sulfonic acid, but not carboxylic acid, functionalized surfaces. The extent of protonation, however, is also dependent on the microstructures of the modified substrate surfaces. In all cases, charge transfer interactions between the EM layer and the functionalized substrates readily result in good adhesion of the electroactive polymer on the polymer substrates to give rise to conductive surface structures. © 1995 John Wiley & Sons, Inc.
Characterization of a glycidyl azide polymer composite propellant: Strain rate effects and relaxation response
Authors: Duncan E. J. S.
Published: April 2003

Uniaxial tension tests were completed on a developmental GAP/PSAN solid rocket propellant at constant strain rates ranging over three decades and at five different temperatures. An analysis of the maximum stress (strength) and the strain at maximum stress showed that there is a relatively narrow range of temperatures and strain rates that give rise to strains at maximum stress that exceed 18%. The long‐term equilibrium strain capability (strain endurance) appears to be between 10% and 12%. The trend of the strength and initial deformation moduli were log‐linear with the reciprocal of the strain rate across three decades. However, the shifted master curves were log‐curvilinear in form. The relationship between the strength and the initial modulus can be approximated by a power law. A series of stress relaxation tests was completed at a level of 4% strain and at five different temperatures. The initial portion of the shifted master relaxation curve is concave‐up with correspondingly high stresses and moduli. It decays with time approaching a log‐constant slope. Tensile moduli derived from constant strain rate tests were found to be consistently higher in value than the moduli as a function of time determined from relaxation tests, for an equivalent shifted time. Preliminary evidence suggests that the tensile modulus as a function of the reciprocal of shifted strain rate can be equated to the relaxation modulus as a function of shifted time through an adjustment factor. This relationship extends the relaxation modulus results back a further three and one‐half decades of shifted time. © 1995 John Wiley & Sons, Inc.
Surface and interfacial FTIR spectroscopic studies of latexes. IX. The effect of homopolymer and copolymer structures on surfactant mobility in Sty/BA latices
Authors: Niu B.‐J. , Urban Marek W.
Published: April 2003

The effects of homopolymer and copolymer compositions and structures in styrene/n‐butyl acrylate (Sty/BA) latices on sodium dioctyl sulfosuccinate (SDOSS) surfactant mobility and its preferential concentration at the film–air (F–A) and film–substrate (F–S) interfaces were examined using attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy. It appears that the SDOSS concentration at the F–S interface is highest when the Sty/BA feed ratio is 50/50, and the excess of Sty results in migration of SDOSS surfactant to the F–A interface. This behavior is attributed to the increased glass transition temperature and diminished compatibility between surfactant molecules and copolymer latex. This study also shows that the primary factors that influence exudation to either F–A or F–S interfaces are surface tension of the substrate, glass transition temperature, water flux during coalescence, and compatibility between latex components. © 1995 John Wiley & Sons, Inc.
Preparation and characterizations of thermotropic copolyesters of p‐hydroxybenzoic acid, sebacic acid, and hydroquinone
Authors: Hsiue Lin‐Tee , Ma Chen‐Chi M. , Tsai Hong‐Bing
Published: April 2003

A series of copolyesters of p‐hydroxybenzoic acid (HBA), sebacic acid and hydroquinone were prepared by melt polycondensation of p‐acetoxybenzoic acid, sebacic acid and p‐phenylene diacetate. The copolyesters were characterized by IR, NMR, DSC, polarized microscopy, and X‐ray diffraction. It was found that the copolyesters exhibited liquid crystallinity when the HBA content was 25–67 mol %. The copolyesters with an HBA content of 25–43 mol % showed a nematic phase and a biphasic range, and the isotropization temperature increased as the HBA content increased. The copolyesters with an HBA content of 54–67 mol % showed a nematic phase up to above 400°C. The liquid crystalline order increased as the HBA content increased due to the increased of the average length of the rigid moieties. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of fluorinated poly(imide–amide–sulfone)s
Authors: Bruma M. , Mercer F. , Fitch J. , Cassidy P.
Published: April 2003

A series of new, fluorinated poly(imide–amide–sulfone)s has been synthesized by solution polycondensation of aromatic diamines containing sulfone groups with diacid chlorides incorporating both imide and hexafluoroisopropylidene units. These polymers are soluble in polar amidic solvents, and their solutions can be cast into colorless, thin, flexible films having good electrical insulating properties and high thermal stability. The dielectric constant value is 3.49–3.68. The decomposition temperature in air is 464–479°C, and the glass transition temperature is in the range 279–359°C. All these characteristics have been discussed and compared with those of related fluorinated poly(imide–amide)s which do not contain sulfone groups and with other imide polymers without hexafluoroisopropylidene units. © 1995 John Wiley & Sons, Inc.
Coexistence of ductile, semiductile, and brittle fractures of elastomer‐modified polycarbonates
Authors: Liu Wen‐Bing , Chang Feng‐Chih
Published: April 2003

Phenomenologically, coexistence of ductile, semiductile, and brittle fractures in an apparently identical impact testing condition for the elastomer‐modified polycarbonates containing a sharper notch and at high test temperatures has been found. At the ductile–brittle transition temperature, approximately 10% of specimens fractured in the semiductile mode with impact strength about the average of the ductile and brittle modes. The fracture surface of this semiductile mode shows ductile tearing flow in the plane‐stress regions near the edges and brittle crack in the plane‐strain central region. This unusual semiductile fracture occurs only on the thicker specimens with a sharper notch where clear plane‐stress and plane‐strain are present. © 1995 John Wiley & Sons, Inc.
Study on copolymer emulsion containing an epoxy group
Authors: Xu Zushun , Lu Guohong , Cheng Shiyuan , Li Jianzong
Published: April 2003

Methyl methacrylate, butyl acrylate, acrylic acid, and various amounts of glycidyl methacrylate (GMA) were copolymerized by a semicontinuous seeded emulsion copolymerization to be a four‐component copolymer emulsion; the copolymers were characterized using swelling capacity, transmission electron microscopy (TEM), etc. The effect of glycidyl methacrylate and its content on the properties of emulsion and copolymer films was studied. The self‐crosslinking reaction of the copolymer was investigated by FTIR and DSC. It was found that the swelling capacity of the crosslinked copolymer films decreased with increase of the glycidyl methacrylate content, the morphology showed a core–shell structure, and the copolymer emulsion possessed a self‐crosslinking property. © 1995 John Wiley & Sons, Inc.
Creep behavior of biaxial cold‐rolled polypropylene
Authors: Li J. X. , Cheung W. L.
Published: April 2003

Polypropylene was biaxially rolled up to 60% at ambient temperature, and the tensile creep behavior over the temperature range 27 to 60°C was investigated using a dead‐load apparatus. The degrees of crystallinity of the as‐molded and rolled PP were determined using a differential scanning calorimeter (DSC) and density bottle. The DSC showed a slight change in the crystallinity during the early stage of the rolling process, while the density bottle indicated a continuous drop of the density with increasing rolling reduction. The elongation due to rolling was found almost fully recoverable when the samples were thrown into hot silicon oil at 180°C. The effects of cold rolling on creep strain, secondary creep strain rate, and creep activation energy were investigated. Cold rolling led to an increase in the creep strain and secondary creep strain rate. The creep activation energy was found to increase with increasing rolling reduction. Within the secondary creep stage, the creep process in polypropylene is mainly due to the α‐relaxation process and most of the creep strain was recoverable. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of new aromatic poly(ether ketone)s
Authors: Mercer Frank W. , McKenzie Martin T. , Merlino Gloria , Fone Matilda M.
Published: April 2003

A general method for the preparation of aromatic poly(ether ketone)s containing amide, amide‐imide, cyano, oxadiazole, and pyridazine moieties has been developed. Polymerization is based on a ketone‐activated halide displacement from amide‐, amide‐, imide‐, cyano‐, oxadiazole‐, or pyridazine‐containing bis(4‐fluorobenzoyl) moieties by bisphenoxides in a polar aprotic solvent. The bis(4‐fluorobenzoyl) moieties were prepared by reaction of 4‐fluorobenzoyl chloride with diphenoxy monomers containing amide, amide‐imide, cyano, oxadiazole, or pyridazine groups under modified Friedel–Crafts conditions in methylene chloride. All of the polyether ketones prepared were amorphous and exhibited Tgs ranging from 134 to 218°C. In addition, films of the aromatic polyether ketones displayed good thermal stability and flexibility. The dielectric constants of the films were characterized as a function of relative humidity (RH). © 1995 John Wiley & Sons, Inc.
Effects of physical aging and carbon dioxide absorption in bisphenol‐A polycarbonate
Authors: Risch Brian G. , Wilkes Garth L.
Published: April 2003

Thermal and mechanical behavior of bisphenol‐A polycarbonate was studied as a function of thermal history and absorbed mass fraction of CO2. Physical aging at 120°C for one week produced dramatic changes in both the thermal and mechanical behavior. Gas absorption studies indicated that although initial diffusion was somewhat retarded in the aged samples, both aged and unaged polycarbonate samples showed identical equilibrium absorbed gas values at 6500 K Pa and identical gas desorption behavior. Absorbed CO2 was shown to dramatically reduce the glass transition of polycarbonate indicating that CO2 plasticizes polycarbonate. Additionally, samples which had been aged and absorbed a mass fraction of 0.07–0.10 of CO2 showed thermal and mechanical behavior identical to that of a glass quenched from above Tg with identical absorbed mass fraction. Once the absorbed gas was desorbed, the thermal and mechanical properties were similar to those of a glass freshly quenched from above Tg. This study demonstrates that sufficient CO2 gas absorption followed by desorption reverses physical aging in polycarbonate. © 1995 John Wiley & Sons, Inc.
Graft copolymerization of polyacrylonitrile (PAN) onto nylon 6/nylon 66 and simultaneous homopolymerization: A comparative study. II
Authors: Gopalan A. , Vasudevan T. , Manisankar P. , Paruthimalkalaignan G. , Ramasubramanian A. , Hariharan S. S.
Published: April 2003

The kinetics of graft copolymerization of polyacrylonitrile (PAN) onto nylon 6/nylon 66 and the simultaneous homopolymerization initiated by potassium peroxomonosulfate (PMS)–ascorbic acid (H2A) redox systems were studied separately. Various kinetics parameters were evaluated and analyzed to have a comparison among the systems. The occurrence of simultaneous homopolymerization was evident through rate parameters. When the backbone was changed, the following order was observed for grafting efficiency: polyester (PET) > nylon 6 ≳ nylon 66. © 1995 John Wiley & Sons, Inc.
Influence of molecular structure on the degradation mechanism of degradable polymers: In vitro degradation of poly(trimethylene carbonate), poly(trimethylene carbonate‐co‐caprolactone), and poly(adipic anhydride)
Authors: Albertsson Ann‐Christine , Eklund Maria
Published: April 2003

Relationships between molecular structure and the degradation mechanism of degradable polymers are of special interest for temporary medical applications. The in vitro degradation study of three aliphatic polymers—poly(trimethylene carbonate) (PTMC), poly(trimethylene carbonate‐co‐caprolactone) (PTMC‐PCL), and poly(adipic anhydride) (PAA)—revealed that these polymers exhibit degradation times from several years (PTMC) to 1 day (PAA). PTMC degraded unexpectedly slow, accompanied by very small changes in weight loss, molecular weight (SEC), and in morphology (DSC, SEM). The degradation was independent of initial molecular weight, ionic strength of the water solution, temperature, and shaking motions. The copolymer PTMC‐PCL showed a higher degradation rate compared to PTMC, with preferential degradation of amorphous parts leading to an increase in % crystallinity. The surprisingly rapid degradation of PAA showed characteristics typical for a surface‐like eroding system in contrast to PTMC and PTMC‐PCL. The degradation products corresponded to the repeating unit of the polymers. The hydrolysis rate increases in the order carbonate, ester, anhydride, and by combining different molecular structures we achieve specific degradation behavior. A change in hydrolysis rate of the labile bond is predicted by altering the electronegativity of groups near the carbonyl‐oxygen region. © 1995 John Wiley & Sons, Inc.
Generalization of kinetics in the reaction of isocyanates and polyols for modeling a process‐yielding linear polyurethane, 1
Authors: Król Piotr
Published: April 2003

A general kinetic reaction network has been suggested for the gradual chian growth polyaddition process for the synthesis of linear chain polyurethane. Based on the results from the kinetic investigation of the reactions of model aromatic/aliphatic isocyanates and alcohols and hydroxyethers, some methods were set forth to provide rate‐constant values for the reactions included in this network. Model equations were derived from the collision theory, giving dependencies of reaction rate constant values on the molecular weights of the reacting substances. It was found that it was the structure of the reactants that had the most significant effect on the rate of carbamate‐yielding reactions; the effects derived from temperature, catalyst, and size of reacting molecules follow. © 1995 John Wiley & Sons, Inc.
Rheological characterization of 4,4′‐bis (diethylamino)benzophenone‐functionalized polybutadienes with low and medium vinyl content
Authors: Alcántar Norma A. , Salinas María Del R. , Herrera Rafael , Manero Octavio
Published: April 2003

In this article a mechnical spectroscopic study of a series of low (≃8%) and medium (≃ 70%) vinyl‐content polybutadiences, some of them functionalized with 4,4′‐bis(diethylamino)‐benzophenone, is presented. Characterization of polymers with well‐known structure by small‐amplitude oscillatory shear flow enabled investigation of the effect of the vinyl content and functional groups on the rheological behavior of the samples in the linear viscoelastic region. The Doi–Edwards viscolastic model, without any adjustable parameter, proved to be adequate to describe the relationship between the macro/micro structure of the polymers and their viscoelastic properties. Results indicate that the vinyl content and functional groups modify the rheological behavior extensively. © 1995 John Wiley & Sons, Inc.
Effects of catalyst on sequence distribution and transparency of poly(tetramethylene terephthalate)–poly(tetramethylene ether) segmented copolymers
Authors: Shi Youheng , Wu Meiyan
Published: April 2003

Polyether‐polyester segmented copolymer based on hard segments of tetramethylene terephthalate (PBT) and soft segments of poly(tetramethylene ether glycol) (PTMG) was synthesized by four kinds of catalyst: tetrabutyl titanate and magnesium acetate (Ti‐Mg); tetrabutyl titanate and triethanolamine; tetra(isopropyl) titanate; and isopropoxy(triethanolaminato) titanate, respectively. Their segment sequence distributions were analyzed by 13C‐NMR, based on different chemical shifts of aromatic quaternary carbons in the three different triad sequences. The effects of catalyst on sequence distribution and transparency were investigated. It was found that the copolymer has lower probability of B‐T‐B when Ti‐Mg was used as catalysts, and results in higher transparency. © 1995 John Wiley & Sons, Inc.
On‐line conversion monitoring through ultrasound propagation velocity measurements in emulsion polymerization
Authors: Canegallo S. , Apostolo M. , Storti G. , Morbidelli M.
Published: April 2003

An on‐line sensor for estimating conversion from measurements of ultrasound propagation velocity in emulsion polymerizations has been developed. The sensor does not require a sampling circuit, because it can be directly plugged in the reacting mixture. The performance of the sensor has been tested by comparison with off‐line gravimetric measurements of conversion under various operating conditions. These include the homopolymerization of methyl methacrylate and vinyl acetate, with different values of the monomer to water ratio and the initial concentrations of emulsifier and initiator. The results obtained using either an empirical calibration curve or a suitable a priori model indicate excellent reliability of the sensor with somewhat lower accuracy at low conversion values, i.e., when monomer droplets are present. © 1995 John Wiley & Sons, Inc.
NEW‐TPI thermoplastic polyimide: Structure and relaxation using SAXS and TSDC
Authors: Lu Sharon Xin , Cebe Peggy , Capel Malcolm
Published: April 2003

The thermoplastic polyimide RegulusTM NEW‐TPI has been studied using small‐angle X‐ray scattering (SAXS) and thermally stimulated depolarization current (TSDC). SAXS was used to study the development of lamellar structure during isothermal or nonisothermal crystallization. The one‐dimensional electron‐density correlation function was used to determine structural parameters. The long period, lamellar thickness, and amorphous layer thickness increase as crystallization temperature increases from 300 to 360°C. By combining melting‐point data with SAXS results, we report the side and fold surface free energies of NEW‐TPI crystals, which are 29 ± 3 and 41 ± 3 erg/cm2, respectively. Real‐time SAXS was carried during nonisothermal cold‐crystallization at 5°C/min. The long period decreases, while lamellar thickness, linear crystallinity, and interphase thickness increase, with increasing temperature. These changes are explained by a crystal‐insertion model. TSDC was used as a more sensitive probe of the amorphous phase structure below 300°C. Both semicrystalline and amorphous NEW‐TPI exhibit complex TSDC behavior. Above the glass transition, amorphous NEW‐TPI has a strong TSDC peak attributed to short‐range‐ordered structures, which may serve as nucleation sites for subsequent crystallization. This peak was not seen in semicrystalline material. At the glass transition, both amorphous and semicrystalline NEW‐TPI have a strong TSDC peak. In the semicrystalline polymer, relaxation of the amorphous dipoles is slightly restricted by the crystals, which results in a smaller relaxation peak and a shift to higher temperature. Below Tg, another TSDC peak occurs which is not due to dipolar relaxation. This peak is attributed to the combined effects of space charge, electrode type, ionizable species, and interfacial charges. © 1995 John Wiley & Sons, Inc.
Sorption, desorption, resorption, redesorption, and diffusion of haloalkanes into polymeric blend of ethylene–propylene random copolymer and isotactic polypropylene
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S.
Published: April 2003

Molecular transport of haloalkanes into sheets of a polymeric blend of an ethylene–propylene random copolymer and isotactic polypropylene has been studied by a sorption gravimetric technique in the temperature interval of 25–70°C. For all liquids, equilibrium sorption, desorption, resorption, redesorption, and degree of penetrant overshoot have been influenced by the nature of the liquid and the temperature. Diffusion coefficients were calculated from the sorption–desorption kinetic curves using Fick's mathematical relations. The values of diffusion coefficients followed the Arrhenius‐type behavior. The temperature‐dependent sorption data were analyzed using the van't Hoff relation. The activation parameters for diffusion and heat of sorption data were discussed in terms of the molecular interactions between liquids and the polymer chain segments. The experimental and calculated results are discussed on the basis of the chemical nature of liquids. © 1995 John Wiley & Sons, Inc.
Studies on natural rubber bound para‐phenylenediamine antioxidants in NBR
Authors: Avirah Shanti A. , Joseph Rani
Published: April 2003

Para‐phenylenediamine (PD) was chemically attached to depolymerized natural rubber by a photochemical reaction. The rubber bound PD was characterized by TLC, 1H‐NMR, IR, and TGA. The efficiency and permanence of the bound PD were compared with conventional antioxidants in NBR vulcanizates. The rubber bound PD was found to be less volatile and more resistant to water and oil extraction. The vulcanizates showed improved aging resistance in comparison to vulcanizates containing conventional antioxidants. The liquid rubber bound antioxidant reduces the amount of plasticizer required for compounding. © 1995 John Wiley & Sons, Inc.
Structure development in processing of polypropylene films with additives
Authors: Radhakrishnan S. , Kane K. , Kadu A. , Natu H. P.
Published: April 2003

The crystallization behavior, modification of crystalline form, and orientation in polypropylene processed by blow film extrusion was studied as a function of processing parameters as well as different types of additives. The isothermal crystallization rate was greatly enhanced in the presence of certain additives, especially CaCO3. The crystalline form was predominantly α type in both compression molded or blow extruded films. However, there was an unusually large intensity of the α040 peak in the X‐ray diffraction of the latter case films. The variation of the peak intensities and the increase of birefringence with increase of take‐up speed has been explained on the basis of orientation induced by uniaxial stress in the machine direction. This orientation contained two components, namely the orientation of the b axis of the crystallites and the orientation of loosely bound polymer chains in the amorphous regions. © 1995 John Wiley & Sons, Inc.
Solvent crazing as a stress‐induced surface adsorption and bulk plasticization effect
Authors: Kefalas V. A.
Published: April 2003

In solids with low bulk modulus, like polymer glasses, concentration of stress due to surface defects and other kinds of inhomogeneities can induce substantial surface tension reduction and bulk plasticization in extremely localized regions. This effect becomes important in the presence of organic liquids. As a liquid comes into contact with the polymer surface and as stress is applied, a point is reached when the work to draw new surface area becomes minimal. In addition, at least up to a diffusion limited extent, bulk solvation can also take place locally. At this point, solvent crazing initiates in the presence of a triaxial stress field, and craze fibrils are easily drawn with additional deformation. For van der Waals (WL) interactions between polymer and solvent, two different expressions for solvent craze initiation have been derived. The first is derived assuming interfacial tension reduction (ITR) is the dominant mechanism for solvent craze initiation. The second is derived assuming that flaw tip bulk plasticization (BP) is the main mechanism for solvent craze initiation. Existing experimental data on six different glassy polymers was also examined with respect to the above two expressions. A relatively good functional relation (straight line passing near the origin) was found for a wide spectrum of glassy polymers and apolar (WL) liquids, for both the (ITR) and (BP) cases. Additional assumptions made in this analysis, especially about the stress concentration factor and the bulk modulus of the materials, indicate a better correlation with interfacial tension reduction data, in the case of (WL) liquids. However, better controlled experiments would be necessary to properly identify the mechanisms of environmental crazing, even in the case of (WL) liquids. © 1995 John Wiley & Sons, Inc.
Morphology and properties of blends of polyethylene with a semiflexible liquid crystalline polymer
Authors: Mantia F. P. La , Geraci C. , Vinci M. , Pedretti U. , Roggero A. , Minkova L. I. , Magagnini P. L.
Published: April 2003

Blends of three polyethylene (PE) samples (two HDPE grades and LLDPE) with an experimental sample of a semiflexible liquid crystalline polymer (SBH 1:1:2 by Eniricerche) have been prepared in a Brabender compounder. The processing‐aid effect of the LCP has been demonstrated by the decreased energy required for extruding the blends, as compared to that needed for neat PE. The thermal properties, as studied by differential scanning calorimetry (DSC), have shown that the two components of the blends are immiscible. However, the dispersed SBH phase has been found to act as a nucleating agent for the crystallization of LLDPE, whereas no such effect was observed for HDPE. This has been taken as an indication that the phase interactions of SBH with LLDPE are more pronounced than with HDPE. The morphological study of the blends, done by scanning electron microscopy (SEM), has confirmed this conclusion. In fact, the SBH particles show a much better dispersion and a narrower size distribution in the LLDPE/SBH blends. The mechanical properties of the blends have been studied on compression‐molded specimens. The results indicate that the reinforcing effect of SBH is practically none for both HDPE grades. In fact, the elongation at break decreases to very low values, and the tensile strength is also reduced, when the LCP concentration increases beyond 5–10%, whereas the tensile modulus does not vary appreciably, over the whole (0–20%) LCP range investigated. On the contrary, the tensile modulus of the LLDPE/SBH blends increases up to ca. 50%, and the elongation at break decreases more smoothly, on increasing the SBH content up to 20%. © 1995 John Wiley & Sons, Inc.
Characterization of KEVLAR fibers using selected probes
Authors: Rebouillat S. , Escoubes M. , Gauthier R. , Vigier A.
Published: April 2003

The characterization of KEVLAR‐29 fibers has been performed by studying their interactions with three model compounds in gaseous form. Water, aniline, and epoxystyrene were used for this purpose. The effects on the nature of these interactions of two types of surface engineering, namely the coating with an epoxy resin and a reactive plasma treatment, were also studied. The results obtained from the three analytical techniques used in this work provide a more fundamental understanding of the fiber bulk properties vs. their surface characteristics. The diffusion, condensation, plasticization, and adsorption mechanisms involved during the interactions between the probes and the KEVLAR fibers are evidenced and discussed. © 1995 John Wiley & Sons, Inc.
Partial specific volume and thermal expansion coefficient of poly(N‐vinylimidazole)
Authors: Morales E. , Gómez‐antón M. R. , Piérola I. F.
Published: April 2003

The density of poly(N‐vinylimidazole) dilute solutions in methanol, triethylene glycol, dimethyl sulfoxide, and N,N‐dimethylformamide as well as in an aqueous neutral (with and without ionic strength) and acid solution have been measured at several temperatures. The specific volume of the polymer in bulk has been determined experimentally and theoretically, following the group aditivity method, and both values were coincident. Partial specific volume and thermal expansion coefficient were found to be solvent‐dependent. These results were interpreted in terms of the different types of solvation or the interaction of polymer‐solvent. © 1995 John Wiley & Sons, Inc.
Hydropolysilanes as precursors to silicon carbide
Authors: Shieh Yeong‐Tarng , Sawan Samuel P.
Published: April 2003

A systematic study of the roles of three different types of monomers and their compositions in hydropolysilane homo‐, co‐, and terpolymers on their pyrolytic yields to silicon carbides was performed. The diorganodichlorosilane monomer, serving to increase molecular weights of the polymers, is not a significant factor in pyrolytic yields. The organotrichlorosilane monomer, leading to branched structures of the polymers, is helpful in obtaining high pyrolytic yields. The monoorganodichlorosilane monomer, providing crosslinking sites for the polymers, is useful in retarding decomposition during pyrolysis. The precursor‐to‐ceramic conversion chemistry was studied using thermogravimetry, infrared spectroscopy, X‐ray powder diffraction, and Rutherford backscattering spectrometry. The pyrolytic yields were not pyrolysis‐time‐dependent but decreased as the pyrolysis temperature increased. The apparent crystalline size increased as both the pyrolysis time and temperature increased. For a 30 min pyrolysis, the pyrolysis temperature must be over 1000–1200°C to provide a crystalline pyrolytic residue. © 1995 John Wiley & Sons, Inc.
Polymer encapsulation of arsenic‐containing waste
Authors: Carter M. , Baker N. , Burford R. P.
Published: April 2003

The potential for encapsulation of arsenic waste by combination with two commodity polymers was evaluated. Initial studies employed nontoxic substitutes, these being gypsum and calcium carbonate, with host polymers being predominately a recycled grade of polyethylene (PE) and a synthetic elastomer. The latter was used at low processing temperatures with rather volatile arsenic compounds. The gypsum caused processing difficulties due to evolved water, but the CaCO3 was able to be readily combined at high volumes. Arsenic trioxide was able to be incorporated at modest levels in PE and was less successfully combined with the rubber. However, the higher processing temperatures needed for PE caused the As2O3 to sublime. Less volatile calcium arsenite, readily prepared from As2O3, was able to be mixed at high volume ratios with the rubber, although processing with PE was less successful. These results may be used in conjunction with other methods for stabilization and would be applicable to other forms of medium‐ to high‐level waste. © 1995 John Wiley & Sons, Inc.
Liquid chlorine as chlorinating agent for preparation of chlorinated natural and synthetic rubbers
Authors: Cataldo Franco
Published: April 2003

In order to overcome the use of solvents like carbon tetrachloride (during the industrial preparation of chlorinated natural rubber or chlorowaxes) which are suspected of damaging the layer of atmospheric ozone, I proposed the use of liquid Cl2 as both chlorinating agent and solvent. It is shown that natural rubber or synthetic cis‐1,4‐polyisoprene can be swelled by liquid chlorine at −40°C. By equilibrating to room temperature, the rubber is chlorinated by the expansion of the chlorine trapped in the rubber granules in a process resembling popcorn formation. Chlorine uptake was found to be 56.5% and the chlorinated rubber obtained was studied by FT‐IR spectroscopy. Cis‐1,4‐polybutadiene, when chlorinated with liquid chlorine, gives a hard insoluble product with chlorine content of 36%. © 1995 John Wiley & Sons, Inc.
Diffusion‐controlled sorption of dye by cylindrical fibers: Matching empirical and theoretical models
Authors: Etters J. Nolan
Published: April 2003

Under quite specific, limiting assumptions, sorption of molecular probes by cylindrical fibers can be described by use of the conventional diffusion equation solutions of Hill, Newman, Wilson, Crank, Carman–Haul, or Urbanik. In addition, sorption also may be described by use of relatively simple empirical equations. Statistical analysis reveals which one of three empirical, exponential equations best fits theoretical data generated by use of formal solutions to the diffusion equation, and the selected equation is then applied to real data. © 1995 John Wiley & Sons, Inc.