bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of certain processing variables on the form ii to form i phase transformation in polybutene‐1
Authors: Hong Kwang‐Bum , Spruiell Joseph E.
Published: April 2003

Density and wide angle x‐ray scattering techniques were used to study the form II to form I phase transformation in polybutene‐1. The influence of deformation by cold rolling, orientation produced by melt processing (film blowing), and certain additives blended with the homopolymer on the phase transformation behavior were examined. A new technique based on a combination of wide angle X‐ray diffraction and density measurements was devised to determine the relative fractions of form I, form II, and amorphous phases present. Small reductions in thickness by cold rolling cause a rapid partial transformation to form I followed by further transformation at enhanced rates. The enhancement of crystal transformation by cold rolling is primarily the result of the stresses or strains applied rather than the orientation produced. The introduction of molecular orientation by melt processing also enhances the rate of the form II to form I phase transformation, but it is rather less effective than small amounts of cold rolling which themselves produce comparatively little change in molecular orientation. The mechanical blending of polypropylene with polybutene‐1 was found to accelerate the form II to form I phase transformation, while another additive (1‐naphtylacetamide) known to be a good nucleating agent for crystallization of polybutene‐1 did not increase the rate of phase transformation when added at concentration levels needed to nucleate crystallization from the melt.
Effect of solvent balance on the surface properties of poly(vinyl chloride)
Authors: Wildman Gary C. , Hsu S.‐J. Raymond
Published: April 2003

Films of poly(vinyl chloride) have been cast from solutions of varying thermodynamic quality and the film properties studied by inverse phase gas chromatography. The solvents included tetrahydrofuran, cyclohexanone, and mixtures of toluene with both tetrahydrofuran and cyclohexanone. The solvent composition was followed during evaporation and film formation for the mixed solvents, and it was shown that the slower evaporating solvent component has the greatest effect on the surface properties of the films. The porosity of the polymer film surfaces is interpreted in terms of the mobility of the polymer chains during film formation. At high concentrations, polymer chain–polymer chain interactions become stronger when thermodynamically less powerful solvents are used or are last to leave during film formation; therefore, the solvent balance has a critical influence on the film surface properties. Annealing the poly(vinyl chloride) above the glass transition temperature reduces the surface porosity of the cast polymer.
Influence of processing conditions on structure development and mechanical properties of poly(butylene terephthalate) filament
Authors: Lu Fu‐Min , Spruiell J. E.
Published: April 2003

A study of the relationship between the drawing and annealing conditions of melt‐spun poly(butylene terephthalate) filaments and the resulting structure and mechanical properties is described. The relative amount of β‐form crystal content was found to increase with increase in draw ratio and to be directly proportional to the drawing stress for a given draw ratio. As drawing stress decreases with increase of draw temperature, the β content decreases rapidly with increased draw temperature. Annealing reduces the amount of β‐phase but increases the α‐phase content and crystallinity. The effect of these structural variations on the mechanical properties is examined. The mechanical properties are shown to be very sensitive to the structure of the filaments and, hence, to the processing conditions.
Diffusion and solubility of hydroxy compounds in polyolefines
Authors: Koszinowski Johannes
Published: April 2003

The diffusion and relative solubility coefficients of some alcohols, phenols, and antioxidants have been measured by a permeation method for LDPE at room temperature. The diffusion coefficients of the hydroxy compounds are compared with those of the alkanes. The diffusion coefficients of the alkanes mark out upper limiting values which are not exceeded by the hydroxy compounds of comparable molecular weight.
The role of surfactant structure and monoethanolamine in the environmental stress cracking of polycarbonate
Authors: Faulkner Douglas L.
Published: April 2003

The critical strains required to initiate cracking of polycarbonate exposed to a number of poly(oxyethylene)ethoxylate surfactants were determined. Solubility parameters of the surfactants were calculated from knowledge of the molecular structure. A model proposed by Jacques and Wyzgoski that uses the square of the solubility parameter difference of the surfactant and polycarbonate and the surfactant molar volume was determined to be useful for predicting critical strains for polycarbonate. A major assumption in this model is that stress cracking is related to swelling or plasticization of the polymer by the cracking agent, which ultimately leads to the polymer's failure. However, the model does not predict the observed strong stress cracking of polycarbonate by monoethanolamine. In this investigation it was determined that polycarbonate is chemically degraded by monoethanolamine. This degradation is sufficient to initiate stress cracking at lower strains than would otherwise be predicted by solubility parameter and molar volume concepts. With the knowledge obtained from this investigation, it is possible to predict which poly(oxyethylene)ethoxylate surfactants are stress cracking agents for polycarbonate.
Melting of ultrahigh molecular weight polyethylene
Authors: Wang Xi‐You , Salovey R.
Published: April 2003

On heating in DSC, samples of UHMWPE show a single, fairly sharp, melting endotherm which may be increased to a peak temperature of 147°C and 77% crystallinity by annealing at elevated temperatures. An irreversible conversion of nascent to folded crystals, between 134 and 142°C, was observed by heating nascent UHMWPE powder in the calorimeter. In the presence of n‐hexatriacontane, the melting endotherm of UHMWPE was depressed and broadened and the conversion of nascent to melt‐crystallized polyethylene facilitated on heating. A melt‐crystallized mixture of ordinary linear polyethylene (HDPE) and UHMWPE was not resolved on remelting. After annealing this mixture for 12 h at 130°C, HDPE was fractionated and the melting of UHMWPE was sharpened. Crystals of UHMWPE, prepared from dilute solution in xylene, show a single sharp melting endotherm and high crystallinity, but the melting peak is reduced in temperature compared to nascent crystallized powder.
Polyacrylate‐graft silica gel as a support of lipase intersterifying triacylglycerol in organic solvent
Authors: Nakatsuka Takuo
Published: April 2003

Butyl acrylate was graft polymerized onto silica gel, which had been doubly modified with γ‐aminopropyltriethoxysilane and 4,4′‐azobis(4‐cyanovaleric acid). 2‐(Methoxycarbonnyl)ethyltrichlorosilane was treated on another silica gel. The ester groups on both silica gel surfaces were transformed to azide to immobilize lipase. The activities of the immobilized lipase for interesterfication of triacylglycerol in isopropyl ether were examined and compare with that of adsorbed lipase on silica gel, and the polyacrylate‐graft silica gel was found to be an effectual support for the enzymatic interesterification. An apparent shift of the reaction equilibrium by removing water as an azeotrope of isopropyl ether is also described.
Effect of graft copolymerization of 2‐hydroxyethyl methacrylate on the properties of polyester fibers and fabric
Authors: Abdel‐Bary E. M. , Sarhan A. A. , Abdel‐Razik H. H.
Published: April 2003

Graft copolymerization of hydroxyethyl methacrylate (HEMA) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (BP) as initiator was carried out in water and in water/organic solvent as a reaction medium. The effect of initiator concentration, reaction time, temperature, and reaction medium as well as addition of FeSO4 to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing BP concentration up to 0.016 mol/L and then decreased upon further increase in initiator concentration. Increasing the monomer (HEMA) concentration up to 0.48 mol/L improves significantly the graft yield. Raising the polymerization temperature up to 85°C causes a significant increase in grafting yield; further increase in temperature leads to decrease in graft yield. Incorporation of Fe+2 ions in the polymerization system decrease the graft yield. The same situation is encountered when water/solvent mixture is used as reaction medium. Solvent employed were methanol, toluene, and benzene.
Copolymerization of acrylamide with cationic monomers in solution and inverse‐microsuspension
Authors: Baade W. , Hunkeler D. , Hamielec A. E.
Published: April 2003

The free radical copolymerization of acrylamide with three of the most commonly used cationic comonomers diallyldimethylammonium chloride, dimethylaminoethylmethacrylate, and dimethylaminoethylacrylate, the latter two quaternized with methyl chloride, was investigated. The polymerizations were carried out with azocyanovaleric acid and potassium persulfate over the temperature range 45–60°C. The copolymer reactivity ratios were determined with the error‐in‐variables method using residual monomer concentrations, measured by a Nalco HPLC method. This combination of estimation procedure and analytical technique has been found to be superior to any methods used previously for the estimation of reactivity ratios for cationic‐acrylamide copolymers.
High density polyethylene‐g‐maleic anhydride preparation in presence of electron donors
Authors: Gaylord Norman G. , Mehta Rajendra , Kumar Vijay , Tazi Mohammed
Published: April 2003

The reaction of molten HDPE with MAH at 215 and 250°C using di‐t‐amyl peroxide and t‐butyl cumyl peroxide as catalysts yielded HDPE‐g‐MAH accompanied by crosslinked polymer. The formation of the latter, increased by the presence of MAH and insoluble in refluxing xylene, was prevented by the presence of electron donor additives, i.e., dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and tri(nonylphenyl) phosphite (TNPP). A charge containing 0.0625–0.125% catalyst, 5% MAH and 0.5% additive, all based on HDPE and added to the molten HDPE in four portions, resulted in gel‐free polymer with an MAH content of 0.7–1.7%. HDPE‐g‐MAH with the least color was obtained with TNPP, followed by DMAC and DMSO. Notwithstanding the absence of gel in the HDPE‐g‐MAH prepared from HDPE with a melt flow of 17 g/10 min, the carboxylated HDPE had a melt flow of 0.0–1 g/10 min, indicative of an increase in the molecular weight of the product. This is attributed to a coupling reaction between MAH radicals appended to the HDPE backbone (HDPE–MAH·) and HDPE radicals formed as a result of hydrogen abstraction from HDPE by radicals from the catalyst and/or excited MAH.
Preparation of glucose oxidase membrane for the application of glucose sensor by plasma activation
Authors: Hsiue G. H. , Liu C. H. , Wang C. C.
Published: April 2003

Plasma activation is a method that takes the advantage of low temperature plasma to immobilize the bioactive materials. An active immobilized glucose oxidase membrane was obtained via plasma‐initiated polymerization of acrylic acid. The obtained immobilized enzyme is very active and stable. After 100 tests, the response error of the glucose sensor is less than 5% and its linear detecting range is 0–300 ppm. A hydrophilic PP film treated by Ar or NH3 plasma was used for the preparation of the immobilized glucose oxidase membrane. The obtained immobilized enzyme is also very active and stable. After 180 tests, the response error of the glucose sensor is less than 4% and its linear detecting range is 0–300 ppm. Furthermore, SEM was used to study the mophology of the glucose oxidase membranes obtained via both methods. And ESCA was used to analyze the plasm‐initiated polymerization products and the plasma‐treated PP films so as to obtain the optimum conditions for the immobilization of bioactive materials.
Permeability of silicone polymers to ammonia and hydrogen sulfide
Authors: Stern S. A. , Bhide B. D.
Published: April 2003

Permeability coefficients, P̄, for NH3 AND H2S in 11 different types of silicone membranes were measured in the temperature range from 10.0 to 55.0°C and at pressures up to 115 psig (∼ 7.8 atm). The values of P̄ for NH3 and H2S in different silicone polymers decrease considerably as the bulkiness of the functional groups in the side and backbone chains of these polymers increases. the substitution of SiO bonds with stifer SiC bonds in the backbone chains also results in a considerable decrease in gas permeability. the values of P̄ for NH3 and H2S increse exponentially with incresing δp, the pressure difference across the membrancs. The temperature dependence of NH3 and H2S varies greatly: P̄ can increase, decrease, or pass through a minimum with increasing temperature, depending on the nature of the silicone polymer. The temperature dependence of P̄ is also affected in some cases by Δp. The permeability behavior of silicone polymers to NH3 and H2S is compared with that to other penetrant gases, and the factors which might affect this behavior are discussed.
A new approach for the estimation of kinetic parameters in emulsion polymerization systems. I. Homopolymerization under zero–one conditions
Authors: Asua J. M. , Adams M. E. , Sudol E. D.
Published: April 2003

A new method for the estimation of kinetic parameters in emulsion polymerization systems is presented. This method is based on studies of the evolution of monomer conversion in chemically initiated seeded emulsion polymerization systems. In this paper, homopolymerization under zero—one conditions is considered. The method is based on a fundamental model that includes the free radical balance in the aqueous phase and fundamental parameters such as the entry and exit rate coefficients, the termination rate constant in the aqueous phase, and the rate coefficient for initiator decomposition. These parameters, as well as the propagation rate constant, are the estimable parameters. This method, which uses all available data simultaneously in order to estimate the parameters, is checked by using simulated experimental data generated with exact values of the parameters. The criteria for deciding the usefulness of the present approach are the closeness of the fit to the original data and the match of the estimated kinetic parameters to the exact values of the parameters. It was found that accurate values of the parameters are obtained with the present approach provided that a sufficient number of experiments with a minimum range of variation are available. A study of both the minimum number of experiments and the minimum range of variation of the experimental conditions needed to estimate reliable parameters is presented. Also, the effect of both random and systematic errors is included in this study. Finally, a comparison between the present approach and those previously published in the literature is presented.
Synthesis and characterization of imide end‐capped oligoesters of terephthalic acid and 2‐methyl‐2‐propyl‐1,3‐propanediol
Authors: Acevedo M. , De La Campa J. G. , Abajo J. De
Published: April 2003

Hydroxytelequelic oligoesters of molecular weight (Mn) between 500 and 3000 were prepared from dimethylterephthalate (DMT) and 2‐methyl‐2‐propyl‐1,3‐propanediol (MPPD) by ester interchange polycondensation. They were modified by reaction of their end hydroxyl groups with N‐(4‐chlorocarbonylphenyl) maleimide and N‐(4‐chlorocarbonylphenyl) nadimide. Spectroscopic (NMR), chromatographic (GPC), and calorimetric (DSC) analyses demonstrated that MPPD oligoterephthalates are less reactive than previously used glycols (diethylene glycol, DEG) and only nadimide‐modified oligomers could be readily synthesized. Attempts to introduce maleimide groups at the chain ends led to crosslinked materials. Furthermore, some relationships between molecular weight and properties (Tg, thermal stability, etc.) could be outlined. The oligomers, unmodified and modified, proved to be essentially amorphous.
Polyurethane elastomers based on molecular weight advanced poly(ethylene ether carbonate) diols. II. Effects of variations in hard segment concentration
Authors: Harris Robert F. , Joseph Michael D. , Davidson Carla , Deporter Craig D. , Dais Virginia A.
Published: April 2003

A series of polyurethane elastomers were studied in which the soft segment composition was a molecular weight advanced poly(ethylene ether carbonate)diol (2025 mol wt) and the hard segment composition was based on MDI/1,4‐butanediol. These polyurethane elastomers had a constant soft segment composition and block length, a constant hard segment composition, but a variable hard segment block length and concentration (31.9–65.2 wt % hard segment). Properties such as rubbery plateau modulus, solvent resistance, melting point, hardness, tensile strength, and hard segment run length all improve with increasing hard segment concentration. DMA and DSC data indicate a partially phase mixed morphology. However, phase mixing must occur at domain boundaries since the soft segment Tg is nearly invariant with hard segment concentration. Annealing studies indicate that the optimum post‐cure temperature, for 1 h, is about 175°C.
Water self‐diffusion coefficient determination in an ion exchange membrane by optical measurement
Authors: Zelsmann H. R. , Pineri M. , Thomas M. , Escoubes M.
Published: April 2003

The self‐diffusion coefficient of water in a perfluorinated ionic membrane has been measured for different water contents corresponding to water vapor pressures less than the saturated one. The isotope method usually employed in the liquid state was extended to vapors, which led us to an observation of three different isotopic species by quantitative far IR spectroscopy. Two measurement methods are presented permitting a determination of the time lag and hence of the diffusion coefficient. The slow variation of the diffusion coefficient with the water concentration, as well as the good agreement of the numerical results given by different methods (permeation‐sorption) are explained by the fact that no plasticization occurs. This result has been independently verified by other experiments.
Interfacial phenomena controlling particle morphology of composite latexes
Authors: Chen Yi‐Cherng , Dimonie Victoria , El‐Aasser Mohamed S.
Published: April 2003

A thermodynamic analysis and a mathematical model were derived to describe the free energy changes corresponding to various possible morphologies in composite latex particles. Seeded batch emulsion polymerization was carried out at 70°C using as seed monodisperse polystyrene latex particles having different surface polarity. The surface polarity was estimated by contact angle measurement at the latex “film”/water interface for octane as the probe liquid. Methyl methacrylate and ethyl methacrylate were polymerized in a second stage seeded emulsion polymerization using polystyrene particles as seed in the presence of a nonionic stabilizer, nonyphenol polyethylene oxide (Igepal Co‐990). Two types of initiators, potassium persulfate (K2S2O8) and azobisiobutyronitrile (AIBN), were used to change the interfacial tension between the second stage polymer (in monomer) and water interface. The values of the interfacial tension of polymer solutions in the second stage monomer vs. the aqueous phase, measured by drop‐weight–volume method under conditions similar to those prevailing during the polymerization, correlated well with the determined particle surface polarity and the observed TEM particle morphology. The results showed that, rather than the polymer bulk hydrophilicity, the surface particle polarity is the controlling parameter in deciding which phase is inside or outside in the composite particle. The variation of the polymer phase interfacial tension with polymer concentration was also estimated. Based on experimentally measured interfacial tensions, composite particle configurations were predicted. The predicted morphologies showed good agreement with the observed particle morphologies of the composite latexes.
Ultraviolet‐curable, abrasion‐resistant, and weatherable coatings with improved adhesion
Authors: Lewis Larry N. , Katsamberis Dimitris
Published: April 2003

A UV‐curable coating for plastics that is abrasion resistant and weatherable is described. The coating consists of colloidal silica functionalized with methacryloxypropyltrimethoxy‐silane (MAPTMS) in a matrix of acrylic monomers. The formulation employs diethoxyacetophenone (DEAP) as a photoinitiator and a sulfonated benzotriazole as a UV absorber. It has been found that the adhesion of the coating depends greatly on the type of acrylic monomers used and the application parameters. Transmission electron microscopy (TEM) analysis shows that improved adhesion is due to the formation of an interpenetrating layer between coating and substrate.
Morphological studies on roll extruded, plasticized composites
Authors: Alexandru L. , Zamin J. , Sundararajan P. R.
Published: April 2003

A study of the morphologies of polymer/carbon black composites, plasticized with small molecule organics, is presented. Four different plasticizers and three different polymers were used. In all cases, the plasticizers depress the Tg of the polymers. Whereas in some cases the organic small molecule was found to be molecularly dispersed in the polymer matrix, phase separation occurred in other cases beyond a certain composition. In the latter instances, the excess plasticizer formed crystalline aggregates and a depression of the melting point of the plasticizer was observed. The samples were prepared by a process similar to roll extrusion, which causes biaxial orientation of the crystalline aggregates.
Permeability of vitamin B‐12 in chitosan membranes. Effect of crosslinking and blending with poly(vinyl alcohol) on permeability
Authors: Nakatsuka Shuji , Andrady Anthony L.
Published: April 2003

The permeability and diffusion of vitamin B‐12 in chitosan, crosslinked chitosans, and chitosan/poly(vinyl alcohol) (PVA) blends were studied using “lag time” technique. Apparently the diffusion coefficient, D, for both crosslinked and blended chitosan membranes depends solely upon the equilibrium swelling ratio, Q, of the material in water. The functional dependence of D on Q was obtained from the data. The partition coefficients calculated for vitamin B‐12 in all membranes studied were nearly constant (K ≈ 0.4). The results are shown to be consistent with the “pore type” transport mechanism for vitamin B‐12 in these chitosan membranes.
Fracture and impact properties of polycarbonates and MBS elastomer‐modified polycarbonates
Authors: Chang Feng‐Chin , Wu Jiann‐Shing , Chu Line‐Hwa
Published: April 2003

Mechanical properties of polycarbonates (PCs) and elastomer‐modified polycarbonates with various molecular weights (MW) are investigated. Higher MW PCs show slightly lower density, yield stress, and modulus. The ductile–brittle transition temperature (DBTT) of the notched impact strength decreases with the increase of PC MW and with the increase of elastomer content. The elastomer‐modified PC has higher impact strength than does the unmodified counterpart if the failure is in the brittle mode, but has lower impact strength if the failure is in the ductile mode. The critical strain energy release rate (Gc) measured at −30°C decreases with the decrease of PC MW. The extrapolated zero fracture energy was found at Mn = 6800 or MFR = 135. The Gc of the elastomer‐modified PC (MFR = 15, 5% elastomer) is about twice that of thee unmodified one. The presence of elastomer in the PC matrix promotes the plane–strain localized shear yielding to greater extents and thus increases the impact strength and Gc in a typically brittle fracture. Two separate modes, localized and mass shear yielding, work simultaneously in the elastomer‐toughening mechanism. The plane–strain localized shear yielding dominates the toughening mechanism at lower temperatures and brittle failure, while the plane–stress mass shear yielding dominates at higher temperatures and ductile failure. For the elastomer‐modified PC (10% elastomer), the estimated extension ratio of the yielding zone of the fractured surface is 2 for the ductile failure and 5 for the brittle crack. A criterion for shifting from brittle to ductile failure based on precrack critical plastic‐zone volume is proposed.
Starch–poly(ethylene‐co‐acrylic acid) composite films. Effect of processing conditions on morphology and properties
Authors: Fanta G. F. , Swanson C. L. , Shogren R. L.
Published: April 2003

Formulations containing 4 parts cornstrach, 5 parts poly(ethylene‐co‐acrylic) (EAA), 1 part urea, and 1.6 parts of either water or aqueous ammonia were extruded at either 110–120°C or 150–160°C; and the resulting extrudates were then extrusion‐blown into films. Complex formation between EAA and starch was measured by either X‐ray diffraction or by solvent extraction of uncomplexed EAA. Although the processing temperature had only a minor effect on the amount of EAA complexed by starch, use of aqueous ammonia rather than water in these formulations increased the amount of complexed EAA by about a factor of 2. In films prepared with aqueous ammonia, the polysaccharide phase was present as submicron‐sized domains. When ammonia was omitted from these formulations, the polysaccharide phase was less uniform in size and contained particles that were over an order of magnitude larger than those observed with ammonia.
Molecular weight distribution of the methyl methacrylate (MMA) polymer separated from the MMA‐grafted silk fiber
Authors: Tsukada Masuhiro , Goto Yoko , Freddi Giuliano , Yamamoto Takashi , Nakabayashi Nobuo
Published: April 2003

The molecular weight distribution of poly‐methyl methacrylate (poly‐MMA) chains separated from MMA‐grafted silk fibers obtained by using potassium persulfate (KPS) and tri‐n‐butylborane (TBB) as initiator of the graft‐copolymerization reaction have been examined by gel permeation chromatography (GPC). GPC elution pattern of poly‐MMA chains shows a bimodal molecular weight distribution. The two peaks have been identified as heavy and light component. The average molecular weight of the heavy component ranges from 48.5 to 200 kD for poly‐MMA copolymerized by the KPS reaction system and from 336 to 816 kD for the poly‐MMA copolymerized by the TBB reaction system. The light component has an average molecular weight lower than 1,000 D and its value is almost similar in all the samples examined. Scanning electron microscopy (SEM) analysis revealed the presence of MMA oligomers formed on the fiber surface during grafting. The molar ratio between poly‐MMA chains and silk fibroin attains a constant value that seems to be specific for a certain reaction system. A linear correlation has been observed between the weight gain and the average molecular weight of the poly‐MMA chains. These findings suggest the effect of grafting parameters on the molecular weight and molecular weight distribution of the grafted polymer, as well as its influence on the physical properties and textile performances of MMA‐grafted silk fibers.
Residual stress in particulate epoxy resin by X‐ray diffraction
Authors: Nishino Takashi , Airu Xu , Matsumoto Takeshi , Matsumoto Kanki , Nakamae Katsuhiko
Published: April 2003

Residual stress in particulate epoxy resin was investigated by X‐ray diffraction. Microdeformation of incorporated Al and α‐SiO2 crystal, which was induced by the residual stress, could be detected as a shift of X‐ray diffraction peak. The residual stress at the interface between the adherend and the particulate epoxy resin was found to decrease with the increase of volume fraction of filler. It was shown that the difference in the thermal expansion coefficients between the adherend and the particulate epoxy resin is much more effective on residual stress than the increment of Young's modulus owing to the incorporation of filler. When epoxy resin was cured on the Al plate, incorporated particles were subjected to a tensile stress; while cured on polytetrafluoroethylene sheet, particles were subjected to a compressive stress. The incorporation of some inorganic particles is considered effective to reduce the residual stress.
On the graft polymerization of styrene and acrylonitrile onto polybutadiene in the presence of vinyl acetate. I. Preparation of graft polymers
Authors: Schellenberg J. , Hamann B.
Published: April 2003

In order to modify the graft polymers of styrene and acrylonitrile onto polybutadiene (ABS polymers), the preparation of the graft products of styrene, acrylonitrile, and vinyl acetate onto polybutadiene rubber by emulsion polymerization was described and theoretically studied up to a high degree of conversion. Depending on the residual monomer content of the products, the polymer composition obtained in the experiment was compared with the theoretical one for the substitution of certain quantities of styrene, acrylonitrile, or styrene and acrylonitrile by vinyl acetate in the mass ratio of 3 : 1. Deviations were discussed. The specific viscosity of the polymers of styrene, acrylonitrile, and vinyl acetate separated from the elastomer phase, considerably decreases during the substitution of acrylonitrile by increased vinyl acetate quantities.
Preparation and characterization of hydrogels obtained by grafting of acrylonitrile onto cassava starch by ceric ion initiation
Authors: Vera‐Pacheco M. , Vázquez‐Torres H. , Canché‐Escamilla G.
Published: April 2003

Graft starch‐polyacrylonitrile copolymers have been obtained from cassava starch (yucca starch or tapioca), which was pre‐heated at 65 and 95°C for different lengths of time. The copolymerization was carried out by using ceric ion as initiator at different concentrations (2.0 to 8.0 mmol/L) and also varying both the length of time of copolymerization and the ratio of monomer to starch. The composition, or grafting parameters, of all the obtained copolymers was determined by weight difference after they were extracted with dimethylformamide and hydrolyzed with an acidic solution. Samples of these copolymers were also hydrolyzed with an aqueous solution of potasium bydroxide to produce the corresponding hydrogels, and its absorbency in water was determined. © 1993 John Wiley & Sons, Inc.
Chemical composition and physical properties of Gonometa rufobrunnae silk
Authors: Freddi G. , Bianchi Svilokos A. , Ishikawa H. , Tsukada M.
Published: April 2003

Chemical composition and physical properties of silk fibers from Gonometa rufobrunnae, a silkworm belonging to the family Lasiocampidae (order Lepidoptera, class Insecta) have been studied. G. rufobrunnae silk fibroin contains a large amount of glycine and alanine, as well as hydroxyl, acidic, and basic amino acids. The gly/ala ratio is 1.5, similar to that of Bombyx mori silk fibroin. The ratio between polar and nonpolar amino acids is higher than that of either domestic (family Bombycidae) or wild (family Saturniidae) silk fibroins. The sericin is characterized by a large amount of hydroxyl amino acids, mainly serine. The infrared spectrum of G. rufobrunnae silk fibroin showed characteristic absorptions at 1630, 1530, and 700 cm−1 attributed to the β structure and at 1650 and 1540 cm−1 due to the random‐coil conformation. The birefringence and isotropic refractive index values were 0.027 and 1.559, respectively. The differential scanning calorimetry (DSC) curve showed two minor endothermic peaks at 222 and 288°C, together with a major endothermic peak at 344°C, attributed to the decomposition of the fibroin with β conformation. The fibers exhibited a maximum contraction peak (4.3%) at about 230°C. The dynamic storage modulus (E′) exhibited an abrupt drop at 190°C, while the loss modulus (E″) curve increased above 185°C with a sharp slope. The surface of degummed G. rufobrunnae silk fibers was very smooth. The shape of the cross section was triangular, round, or roundish shaped. Some fibers were very flat, showing a ribbonlike shape. © 1993 John Wiley & Sons, Inc.
Polyethylene toughened by CaCO3 particle: Brittle‐ductile transition of CaCO3‐toughened HDPE
Authors: Fu Qiang , Wang Guiheng , Shen Jiusi
Published: April 2003

The dependencies of the notched Izod impact toughness of HDPE / CaCO3 blends on CaCO3 particle concentration and particle size are analyzed. It was found that the notched Izod impact strength (S) of HDPE / CaCO3 blends depends discontinuously on CaCO3 particle concentration. A brittle‐ductile transition occurs when the CaCO3 volume fraction (Vf) increases to a critical value (Vηf). Furthermore, a brittle‐ductile transition master curve can be constructed by taking the matrix ligament thickness (L) into account as a parameter instead of Vf. The results show that the critical matrix ligament thickness (Lc) is a single parameter for the transition and Lc = 5.2μm for HDPE / CaCO3 blends. The impact strength, however, varies considerably with CaCO3 particle size, which shows that CaCO3 particle size is another dominating parametor for the toughness of HDPE / CaCO3 blends. © 1993 John Wiley & Sons, Inc.
Activation of wood surface by corona treatment to improve adhesive bonding
Authors: Sakata Isao , Morita Mitsuhiro , Tsuruta Natsuhi , Morita Kenzo
Published: April 2003

Oxidative activation of resinous wood surfaces by a corona treatment to improve adhesive bonding was studied. It was found that the wettability of the veneers, including hardwoods, softwoods, and tropical woods increased with an increase in the degree of treatment, and the gluability increased rapidly after the initial mild treatment. To elucidate the nature of any chemical change occurring on the wood surface, the dyeing examination of the wood and its components with Schiff's reagent was made, and the results showed a higher dyeing ability for corona‐treated samples compared to untreated ones, indicating that aldehyde groups increased by the corona treatment. The treatment affected the alcohol‐benzene extractives, and oxidized them to produce aldehyde groups. Especially, the neutral fraction in the extractives was significantly affected. On the other hand, negligible chemical effects of the treatment on the surface modification of the wood's main components were seen. Both the untreated and corona‐treated samples adsorbed basic dye to the same extent of coloration. Thus, no measurable carboxyl groups increased on the surface of the samples. It seems that an increase in the wettability of corona‐treated wood veneers resulted mainly from the oxidation of the high hydrophobic surface layer of neutral fraction substances in the extractives, and from the reduction in their hydrophobicity. © 1993 John Wiley & Sons, Inc.
Permeability and diffusion of gases in segmented polyurethanes: Structure–properties relations
Authors: Galland G. , Lam T. M.
Published: April 2003

To determine the structure‐transport properties relations, we synthetized segmented polyether polyurethane with increasing rigidity. The formulation is based on poly(tetramethylene oxide diol) (PTMO) of different molecular weights, diphenylmethane aiisocyanate (MDI), and butanediol (BD). The synthesis is effectuated in bulk. The phaseseparation degree of the soft segments is determined by ΔCp measurements. The volume fractions and compositions of soft and hard phases are calculated with the help of Tg values. The polyurethanes studied correspond to three types of morphology: soft‐phase matrix, phase‐inversion, and hard‐phase matrix. The best phase segregation is observed in the phase‐inversion region. The time‐lag method is used for determining the permeability, diffusion, and solubility coefficients of gases (He, O2, N2, CO2, Freon 11) in polyurethane at different temperatures. Activation energies of permeation and diffusion and dissolution energy are calculated. The most important factor in diffusion is the chain mobility in the soft phase, which is represented with a good approximation by M̄n, the molecular weight of soft segments. The phase‐inversion region where the ratio surface/volume is minimum gave the lowest solubility coefficient. Freon 11 presents a particular interaction with polyurethane; polyurethane membranes are broken when immerged in Freon 11, except the one which has the morphology of the inversion region. © 1993 John Wiley & Sons, Inc.
Infrared identification of carboxylic acids formed in polymer photooxidation
Authors: Wilhelm Catherine , Gardette Jean‐Luc
Published: April 2003

Several low molecular weight carboxylic acids with different substitutions were introduced into various polymer matrices: polypropylene, polystyrene, poly(butylene terephthalate), MDI‐based polyurethane, and poly(vinyl chloride). These acids were then submitted to chemical treatments by sulfur tetrafluoride and ammonia. Derivatization reactions by SF4 and NH3 gave, respectively, acyl fluorides and carboxylate ions. The wavenumbers corresponding to the v̄co maxima of the carboxylic acids, acyl fluorides, and carboxylate ions were determined. For each one of these species, noticeable shifts were recorded that depended on the nature of the substitutents as well as on the nature of the polymer matrix. In addition, samples of the chosen polymers were exposed to photoaging. Photooxidized samples were reacted with SF4 and NH3. Their IR characteristics were determined before and after the treatments. Comparison with the results obtained with the molecular acids permitted us to specify the chemical structure of the acids formed by photooxidation and then to determine the oxidation sites on the macromolecular chains of the different polymers. © 1994 John Wiley & Sons, Inc.
Experimental investigation on high conversion free‐radical polymerization of behenyl acrylate
Authors: Baruah Shashi D. , Laskar Narayan C. , Subrahmanyam Bulusu
Published: April 2003

An experimental investigation on the kinetics of free‐radical polymerization of behenyl (a mixture of 14.8% n‐octadecyl, 15.1% n‐docosyl) acrylate initiated with benzoyl peroxide was conducted at 70°C using a HAAKE rotational viscometer. Molecular weight measurements and differential scanning calorimetric studies of the samples are also described and the results are compared with those obtained by batch reactions conducted under a nitrogen atmosphere. A high monomer order of 1.61±0.11 and a low initiator order of 0.35±0.04 was obtained. The role played by the long methylene chain in behenyl acrylate is also discussed. © 1994 John Wiley & Sons, Inc.
Sorption/desorption properties of ethanol, toluene, and xylene in poly(dimethylsiloxane) membranes
Authors: Sun Yi‐Ming , Chen Jack
Published: April 2003

Sorption/desorption kinetics and sorption equilibria have been determined for ethanol, toluene, and xylene vapors in a poly(dimethylsiloxane) membrane containing about 32 wt % silica resin at 25°C. Dependence of diffusion coefficient on vapor activity and sorption isotherms have been compared to identify the transport mechanisms of those penetrants in the PDMS membrane. The analysis of Zimm–Lundberg clustering functions showed that all three penetrants had a tendency to form clusters and ethanol molecules might be immobilized by the residual silanol groups within the silica resin in the membrane. The diffusion coefficient of toluene was roughly constant and that of xylene slightly decreased as increasing the vapor activity due to the competing effects of penetrant clustering and solvent swelling of polymer. The diffusion coefficient of ethanol versus activity exhibited a maximum due to the effects of ethanol immobilization and cluster formation. The freevolume effect by solvent swelling to diffusion was obscured by either penetrant clustering or immobilization for the three penetrant–polymer systems. © 1994 John Wiley & Sons, Inc.
Stress relaxation in short sisal‐fiber‐reinforced natural rubber composites
Authors: Varghese Siby , Kuriakose Baby , Thomas Sabu
Published: April 2003

Stress relaxation behavior of chemically treated short sisal fiber‐reinforced natural rubber composite was studied. The effect of bonding agent, strain level, fiber loading, fiber orientation, and temperature has been studied in detail. The existence of a single relaxation pattern in the unfilled stock and a two‐stage relaxation mechanism for the fiber‐filled composite is reported. The relaxation process is influenced by the bonding agent, which indicated that the process involved fiber‐rubber interface. The rate of stress relaxation increased with fiber loading, whereas it decreased with aging. © 1994 John Wiley & Sons, Inc.
Crystalline structure of polyacrylonitrile–iodine complex
Authors: Kim Hong Sung , Cho Hyun Hok
Published: April 2003

The existence of structural order is found in the polyacrylonitrile (PAN)‐iodine complex obtained by immersing PAN film in an aqueous solution of I2/KI. We provide an interpretation for the key features of this structural order and for the structural change of PAN by iodine sorbing. The observed diffractions suggest that iodine penetrates into the crystalline phase of PAN at relatively low iodine concentrations and are intercalated between PAN molecular cylinders in the form of polyiodine columns that are composed mainly of I (most likely the I2/I complex). Pseudohexagonal crystals of PAN are expanded uniaxially by replacement of PAN molecular cylinders by the polyiodine columns. The intercalated polyiodine column layers are arrayed parallel with PAN chain layers in the crystalline phase. The results led to a proposal of an intercalation model for the crystalline structure of the PAN–iodine complex. The crystalline structures are expected to exist with two different types of the polyiodine layers. The crystalline transition between these structures occurs by thermal mobility of PAN chains. © 1994 John Wiley & Sons, Inc.
Hydrolysis of polycaprolactone fibers by lipase: Effects of draw ratio on enzymatic degradation
Authors: Mochizuki Masatsugu , Hirano Madoka , Kanmuri Yoshihiro , Kudo Kazushige , Tokiwa Yutaka
Published: April 2003

Using polycaprolactone (PCL) fibers drawn with various draw ratios, the effects of draw ratio on enzymatic degradation were studied in order to understand the influence of fine structure on biodegradation. Degradability of PCL fibers as monitored by total organic carbon (TOC) formation or weight loss decreased with increase in draw ratio due to higher crystalline content. There were some distinct features of degradation behavior among the fibers, because the fibers underwent significant change in molecular organization of the polymer, such as crystallinity and orientation, during drawing processes. From scanning electron microscopy (SEM) photographs showing that the enzyme preferentially attacked amorphous or less ordered regions rather than crystalline or more ordered regions of the fiber, spherulites were observed in the undrawn fiber, and on the other hand, fibrillar stripes along the fiber axis were observed in the drawn fibers, which suggest that the spherulites in the undrawn fiber were extended to be broken, and fibril structures were formed during the drawing processes. These SEM photographs suggest that there are differences of crystal structures in addition to crystallinity among the fibers with different draw ratio, which significantly affects the enzymatic degradation behavior of the fibers. The diameter of the fibers became gradually slim, macroscopically uniform, as enzymatic degradation proceeded although it was dependent on draw ratio. It is evident that the degradation proceeded in the crystalline regions as well as the amorphous regions. © 1995 John Wiley & Sons, Inc.
The fracture behavior of phenolphthalein polyether–ether ketone at elevated temperature for long terms
Authors: Yang Yuming , He Tianbai , Yu Fusheng
Published: April 2003

The fracture behavior of phenolphthalein polyether–ether ketone (PEK‐C) affected by physical aging at 200°C was studied by tensile experiments, scanning electron microscopy, and differential scanning calorimetry observations. The ductile–brittle fracture transition (DBT) caused by physical aging can be considered as a competition between fracture mechanisms of crazing and shear yielding. The aging time required for the DBT is found to be around 400 h, based on the morphological studies and tensile experiments. The shear yielding component of the mechanical deformation could erase the aging effect, thus a deaging phenomenon occurs. We found that the deaging phenomenon has an intrinsic relationship with the extent of aging in the specimen and as a result of the fracture behavior. © 1995 John Wiley & Sons, Inc.
Structure of some styrene–divinylbenzene copolymers
Authors: Wojaczyñska M. , Kolarz B. N.
Published: April 2003

Structures of copolymers of styrene and divinylbenzene (50% crosslinking degree) prepared in suspension polymerization in the presence of mixtures of nonsol (heptane or decane) and sol (toluene or tetralin) diluents were investigated. The studies showed that the diluents enriched with nonsol solvents resulted in an increase of pore volumes and posities for the prepared copolymers. The sol diluents affected mainly the gel regions of the polymer matrices. Isotropic swelling of the matrices prepared in the presence of toluene is the opposite of the effect observed for tetralin family copolymers. The virtual difference of both kind of matrices was demonstrated in the sorption of phenol. The tetralin family copolymers were characterized by a prolonged time for column breakthrough. © 1995 John Wiley & Sons, Inc.
Diffusion hindrance vs. wood‐induced catalytic activation of MUF adhesive polycondensation
Authors: Pizzi A. , Panamgama L. A.
Published: April 2003

The reaction of hardening of melamine–urea–formaldehyde (MUF) adhesive resins in the presence of wood and cellulose was confirmed to have a lower energy of activation than the MUF adhesive alone, both in the presence or absence of ammonium chloride hardener, thus both in mildly acid and mildly alkaline environments. DSC exotherms showed that during hardening of melamine to melamine, melamine to urea, and urea to urea crosslinks through methylene bridges occur. Only the earliest reaction, mainly melamine to melamine crosslinking, presents a decrease in energy of activation which can be assigned to catalytic activation by the cellulosic substrate. The other types of crosslinking reactions (i) appear not to occur due to the more favorable and rapid melamine to melamine reaction which precedes them at lower temperature or (ii) do not present catalytic activation by the substrate but rather hindrance by it or (iii) variation of their energy of activation appears to be due to increased diffusion hindrance by the substrate caused by the increasing molecular weight of the resin while hardening. This because the Kissinger equation plots of the resin alone are in the main linear, for all the exotherms, indicating that in hardening of the resin alone diffusion problems appear to be limited. © 1995 John Wiley & Sons, Inc.
A new approach to chemical characterization of polymer surfaces
Authors: Lloyd Thomas B. , Ferretti Kathleen E. , Lagow Joyce
Published: April 2003

The “three‐liquid” contact angle procedure of Good et al. was applied to polymer films of varying Lewis acidic and basic nature to test the procedure. Surface energy parameters with the units of mJ/m2 are determined for the surfaces. These are γLWs (Lifshitz‐van der Waals or apolar), γ+s (acidic), and γ−s (basic). Very little has yet been published on this new method, and this study found it to be promising. More research on the procedure is warranted. The study included films of basic polymethylmethacrylate (PMMA), and predominately acidic chlorinated polyvinylchloride (CPVC) and polyvinylfluoride (PVF) as well as the series: polyethylene (PE) and PE copolymerized with 1.8% and 7.0% acrylic acid. In some of the experiments receding contact angles were measured, and the surface energy parameters determined in order to cast more light on the mechanism of contact angle hysteresis. © 1995 John Wiley & Sons, Inc.