bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical structure and dynamic mechanical behavior of silk fibers modified with different kinds of epoxides
Authors: Shiozaki Hideki , Tsukada Masuhiro , Gotoh Yoko , Kasai Nobutami , Freddi Giuliano 
Published: April 2003

AbstractThe chemical reactivity of epoxide molecules toward silk fibroin was investigated by determining the rate of conversion of reactive amino acid residues. Significant differences were found between two different bifunctional epoxides, diglycidyl ethers of ethylene glycol (E) and resorcinol (R), the former reacting at a higher extent with arginine and tyrosine. The moisture regain decreased by reaction with epoxides, at a variable rate and extent, according to the hydrophobic/hydrophilic properties of epoxides. A two‐step behavior was observed when moisture regain values relating to the silk content in modified silk, fibers were plotted as a function of the weight gain. Dynamic mechanical data showed that the major loss peak became broader and its temperature shifted to lower values following the increase of weight gain. The loss peak temperatures showed a linear relationship with the amount of weight gain. The fine structural changes induced by reaction with eposides will be discussed in terms of chemical and steric factors of the epoxides, as well as of epoxide location within the different structural domains of silk fibers. © 1994 John Wiley & Sons, Inc.
Aqueous solution properties of poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)]
Authors: Lee Wen‐Fu , Tsai Chan‐Chang 
Published: April 2003

AbstractThe aqueous solution properties of a cationic poly(trimethyl acrylamido propyl ammonium iodide) [poly(TMAAI)] were studied by measurements of reduced viscosity, intrinsic viscosity, and flocculation test. The reduced viscosity and intrinsic viscosity of this cationic polyelectrolyte were related to the types and concentration of added salt. “Soft” salt anions were more easily bound on the quaternary ammonium (R4N+) of poly(TMAAI) than those of “hard” salt anions. Halide anions are hard anions; consequently, hard cations were more easily attracted to halide anions for reducing the binding degree of halide anion on the quaternary ammonium group (R4N+). Some salt ions were observed to strongly attract the quaternary ammonium of the cationic polymeric side chain for coagulation of the polymers. This effect would make the polymeric aqueous solution become turbid. The intrinsic viscosity behavior for cationic polyelectrolyte resulting from the electrostatic repulsive force of the polymer chain is contrasted with polyampholyte. A comparison of various flocculants as to the effect of flocculation was also studied. © 1994 John Wiley & Sons, Inc.
Micellar effect on the kinetics of ceric ion‐initiated polymerization of acrylonitrile in the presence of organic substrate
Authors: Patra C. M. , Singh B. C. 
Published: April 2003

AbstractThe micellar effect on the kinetics of ceric ion‐initiated polymerization of acrylonitrile (AN) in the presence of N‐acetylglycine has been studied in the temperature range 30–50°C. The neutral emulsifier (Triton X‐100) has no effect on the Rp, whereas both anionic (NaLS) and cationic (NCTAB) emulsifiers accelerate the rate of polymerization appreciably. Comparison of the effect of different organic substrates on the rate of polymerization has been made. Various effects such as the concentration of metal ion, surfactant, monomer, sulfuric acid, organic solvents, and inorganic salts on Rp have also been investigated. The most remarkable feature of the investigation involves the enhancement of Rp in the presence of micelles. A suitable mechanism for the derivation of the rate expression for the above system is proposed along with the calculation of activation energy and prediction of optimum conditions. © 1994 John Wiley & Sons, Inc.
Effects of reactive functional groups in the compatibilizer on mechanical properties of compatibilized blends
Authors: Wu Chung‐Jen , Kuo Jen‐Feng , Chen Chuh‐Yung , Woo Eamor 
Published: April 2003

AbstractThe compatibility of blends of polyamide‐6/[styrene‐(ethylene‐butylene)‐styrene] triblock copolymer (SEBS) was enhanced with a compatibilizer, maleated SEBS, whose compositions were varied from 0 to 4 wt % of the blends. The maleated SEBS (MA‐g‐SEBS) was synthesized by reacting (grafting) maleic anhydride (MA) with SEBS in the laboratory at various maleic anhydride concentrations ranging from 8 to 13 wt % of the maleated compatibilizer. The effects of graft levels of the reactive MA functional group in the compatibilizer on the effectiveness in compatibilizing the blends were investigated. The morphology and the impact strengths of the compatibilized blends were determined. It was found that, depending on the maleated extents, the compatibilizer influenced significantly the properties of the blends. Although the maleated extents (graft ratios) of the compatibilizer is influential, the concentrations of the compatibilizer in the blends more sensitively affected the mechanical properties of the compatibilized blends. In summary, this study has shown that by increasing the MA contents (within the reported window) in the compatibilizer, the impact toughness could be more dramatically improved. © 1994 John Wiley & Sons, Inc.
Kinetics study of slurry‐phase propylene polymerization with highly active Mg(OEt)2/benzoyl chloride/TiCl4 catalyst
Authors: Kim Il , Choi Hong Ki , Kim Jae Ha , Woo Seong Ihl 
Published: April 2003

AbstractPropylene was polymerized in a slurry phase over superactive and stereospecific catalyst prepared by the reaction of Mg(OEt)2 with benzoyl chloride and TiCl4 in the presence of AlEt3 with or without an external donor. A kinetic analysis of propylene polymerization was carried out. The polymerization rate was first order with respect to monomer concentration and the dependence of overall polymerization rate on the concentration of AlEt3 can be explained by the Langmuir adsorption mechanism. Maximum activity was observed around an Al/Ti mole ratio of 20. The average rate over 90 min of polymerization as a function of temperature showed a maximum around 42°C and the overall activation energy was 8.5 kcal/mol at T < 42°C and −4.0 kcal/mol at T > 42°C. The analysis of the phenomenon of an optimum temperature gave 2.2 kcal/mol for the activation energy of the rate‐determining step, and 6.3 kcal/mol, for the adsorption energy of AlEt3. The addition of small amount of p‐ethoxyethyl benzoate (PEEB) as an external donor increased the percentage of isotactic polymer to 98% and slightly increased activity in spite of the decrease in the concentration of active centers due to the stabilizing effect of the active centers by the external donor. The temperature showing maximum yield was shifted to the higher temperature when AlEt3 and PEEB ([AlEt3]/[PEEB] = 5) was used as a cocatalyst. © 1994 John Wiley & Sons, Inc.
A comparison of methods for the estimation of polymer/monomer interaction parameters: The polystyrene/n‐butyl methacrylate system methacrylate system
Authors: Durant Yvon G. , Sundberg Donald C. , Guillot J. 
Published: April 2003

AbstractTo measure the polymer/monomer interaction parameter as a function of composition, a set of partially cross‐linked synthetic latices has been produced by batch and semicontinuous emulsion polymerization. The degrees of cross‐linking have been measured by DMA and also predicted by computer simulation based on kinetic data. With equilibrium monomer swelling experiments achieved on films made from these polymers, two curves of the interaction parameter vs. the polymer fraction have been computed. These curves compare favorably with a theoretical model based on a Unifac procedure for the estimation of monomer activity. Two different data bases, liquid‐liquid and liquid‐vapor equilibria, have been used in the Unifac model. For the polystyrene/n‐butyl methacrylate system, a linear relationship found between the interaction parameter and composition is both predicted and measured experimentally. In all cases, this interaction parameter is found to increase with polymer concentration. © 1994 John Wiley & Sons, Inc.
Suspended emulsion, a new process for vinyl chloride polymerization: Morphology control through surface active additives
Authors: Vindevoghel Ph. , Nogues P. , Guyot A. 
Published: April 2003

AbstractSuspended emulsion is a new polymerization process in which a water phase containing the initiator is suspended in an organic phase containing the monomer; the polymer formed is insoluble in both the organic and water phase. The final morphology of the polymer is a powder of grains (around 100–300 microns) formed with agglomerates of primary particles (around 1 micron). This article describes the effects of small amounts of either suspending agents (water‐soluble polymers) or surfactants. These effects concern mainly the morphology (grain and particle size), but also the polymerization kinetics. A rather homogeneous distribution of grains and particles inside the grain may be obtained by using a cellulosic polymer as the suspending agent and an anionic surfactant such as sodium dodecyl sulfate. © 1994 John Wiley & Sons, Inc.
Particle sizing of flocculated latex particles by physisorption of nitrogen
Authors: Janssen E. A. W. G. , Zirkzee H. F. , German A. L. , Maxwell I. A. 
Published: April 2003

AbstractPhysisorption of nitrogen at one specific pressure is used to determine the specific surface area of a flocculated polystyrene latex by applying BET theory. Assuming that a flocculated sample of Polymer latex is composed of distinct spherical latex particles (i.e., there is no coagulation of particles), the volume–surface‐average diameter can be calculated. The resulting diameters are compared to sizes obtained using a disc centrifuge sedimentometer, which fractionizes the particles by sedimentation. The diameters from both techniques were in good agreement, showing that physisorption of nitrogen, which is a simple technique, can be used to determine sizes of flocculated latex particles. This agreement also shows that the flocculation of the polystyrene latex produced separate nonporous spherical particles. When flocculation of a latex is done above its glass transition temperature, coagulation will occur. While other particle sizing techniques can produce particle size distributions, the physisorption of nitrogen only gives the volume–surface‐average diameter. However, one advantage of the physisorption of nitrogen is that it covers a broad range of particle sizes compared to most other techniques. © 1994 John Wiley & Sons, Inc.
Cyano‐substituted polyester, polyurethanes, and epoxy resin derived from 2,6‐bis(4‐hydroxybenzylidene)‐1‐dicyanomethylene–cyclohexane
Authors: Diakoumakos Constantions D. , Mikroyannidis John A. 
Published: April 2003

AbstractThe condensation of cyclohexanone with 4‐hydroxybenzaldehyde utilizing dry HCI as the catalyst afforded 2,6‐bis(4‐hydroxybenzylidene)cyclohexanone. The latter was condensed with malononitrile to yield 2,6‐bis(4‐hydroxybenzylidene)‐1‐dicyanomethylene–cyclohexane, which was used as the starting material for the preparation of a novel class of polyesters, polyurethanes, and epoxy resins. In addition, a model diester and diurethane were synthesized and their spectroscopic data were correlated with those of the corresponding polymers. It was shown that the introduction of the dicyanomethylene groups in the polymer backbone remarkably improved the polymer solubility as well as its thermal stability. The crosslinked polymers obtained upon curing the polyester and polyurethanes at 300°C for 40 h were stable up to 365–407°C in N2 or air and afforded anaerobic char yields of 64–70% at 800°C. © 1994 John Wiley & Sons, Inc.
Microgelation in the curing reaction of unsaturated polyester resins
Authors: Liu S. B. , Liu J. L. , Yu T. L. 
Published: April 2003

AbstractA series of unsaturated polyesters were synthesized with various chemical structures and molecular weights. These unsaturated polyesters were used to study the curing reaction with styrene by using gel permeation chromatography and differential scanning calorimetry. The variation of the size of microgel particles during the curing reaction in unsaturated polyester–styrene resins was studied by using gel permeation chromatography. The size and structure of the microgels depend strongly on the polymer chain length and the number of vinyl groups on each unsaturated polyester chain. Using the differential scanning calorimetric method, the conversion of styrene and polyester vinyl groups during the reaction was measured. The experimental results of this study revealed that microgel formation has a great effect on the curing reaction of unsaturated polyester resins. © 1994 John Wiley & Sons, Inc.
Cyclotrimerization of isocyanate groups. II. Catalyzed reactions of phenyl isocyanate in the presence of 1‐butanol or butyl‐N‐phenylurethane
Authors: S̆pírková Milena , Kubín Miroslav , S̆pac̆ek Pavel , Krakovský Ivan , Dus̆ek Karel 
Published: April 2003

AbstractCyclotrimerization of phenyl isocyanate at 30–50°C in the presence of 1‐butanol or butyl‐N‐phenylurethane and catalysts of tertiary amine, quaternary ammonium salt, or carboxylate types in 1,4‐dioxane was studied by reverse‐phase liquid chromatography. Urethane, allophanate, urea, biuret, isocyanurate, and isocyanate model compounds were found in the system. Stability of all reaction products was also examined. The time dependence of evolution of various products depends on the catalyst type and temperature. The overall reaction scheme was proposed. © 1994 John Wiley & Sons, Inc.
Grafting mechanism in SBR–St–MMA core–shell emulsion copolymerization
Authors: Zhao Jianqing , Yuan Huigen , Pan Zuren 
Published: April 2003

AbstractThe graft copolymerization of styrene and methyl methacrylate on SBR latex particles in the core–shell emulsion process was conducted in a 600 mL glass stirred vessel with the BPOFe2+ redox initiator. The effects of the principal factors such as the polymerization temperature, monomer‐to‐polymer ratio, the frequency of monomer addition and conversion on the grafting degree, and the grafting efficiency were studied. The surface‐controlled process model was proposed to describe the grafting mechanism. © 1994 John Wiley & Sons, Inc.
Effect of extruder type on the properties and morphology of reactive blends based on polyamides
Authors: Majumdar B. , Keskkula H. , Paul D. R. 
Published: April 2003

AbstractThe morphology and mechanical properties of polyamide‐based blends prepared in single and corotating twin‐screw extruders were compared using transmission electron microscopy (TEM) techniques. Reactive polyamide blends with SEBS‐g‐MA (a maleated styrenic triblock copolymer with ethylene–butvlene midblocks), EPR‐g‐MA (a maleated ethylene/propylene rubber), and ABS were selected for the purpose of this investigation. For blends of SEBS‐g‐MA with difunctional (nylon x,y) polyamides (e.g., nylon 6,6; nylon 12,12), the twin‐screw extruder was more effective in producing a finer dispersion of the rubber phase, which resulted in a significant lowering of the ductile–brittle transition temperature in case of the nylon 6,6 blend. On the other hand, blends of SEBS‐g‐MA with the mono‐functional nylon 6 material led to rubber particles that were too small for toughening for both extruder types employed in this work. For nylon 6/EPR‐g‐MA blends, the single‐screw extruder led to blends with excellent low‐temperature impact properties for both single‐step and masterbatch mixing techniques, whereas nylon 6/EPR‐g‐MA blends prepared in a single‐step operation in the twin‐screw extruder were brittle under ambient conditions. For difunctional polyamide blends with ABS (compatibilized with an imidized acrylic polymer), the morphology and mechanical properties were found to be independent of the extruder type employed for processing. © 1994 John Wiley & Sons, Inc.
Physical, mechanical, and morphological behavior of sequential polybutadiene–poly(methyl methacrylate) interpenetrating polymer networks
Authors: Das Bibekananda , Gangopadhyay Tanmoy , Sinha Sudipta 
Published: April 2003

AbstractBoth full and semi‐interpenetrating polymer networks (IPNs) of polybutadiene and poly(methyl methacrylate) were synthesized by sequential polymerization. The effect of compositional variation and the cross‐linking agent of both elastomer and plastomer on the physical, mechanical, and morphological properties were investigated. Full‐IPNs exhibited improved tensile strength, modulus, tear strength, gel content, and density, whereas the corresponding semi‐IPNs exhibited better toughness and elongation at break. Phase morphology of full‐IPNs were characterized by compact, tight network structures compared to those of semi‐IPNs. © 1994 John Wiley & Sons, Inc.
J‐integral studies of crack initiation and crack tip‐blunting of phenolphthalein polyether ketone
Authors: Han Yanchun , Yang Yuming , Li Binyao , Feng Zhiliu 
Published: April 2003

AbstractThe J‐integral is applied to characterize the fracture initiation of phenolphthalein polyether ketone (PEK‐C) for which the concepts of linear elastic fracture mechanics (LEFM) are inapplicable at high temperatures for reasonably‐sized specimens due to extensive plasticity. The multiple‐specimen resistance curve technique recommended by the ASTM is the basic method employed. The values of JIC increase with increasing temperature. The crack tipblunting of PEK‐C is observed. The parameters, such as crack opening displacement (COD), δ0, and the stretching increment Δab1 are introduced to describe the blunting phenomenon. The δ0 increases with increasing temperature, as does Δab1. This indicates that the blunting occurs easily as the temperature increases; i.e., as the material's yield stress, σy steadily falls. The relationships between δ0, Δab1, and σy are also discussed. © 1994 John Wiley & Sons, Inc.
Synthesis and thermal characterization of chemically modified phenolic resins
Authors: Antony Rosy , Pillai C. K. S. 
Published: April 2003

AbstractPhenolic resins with improved/altered thermal stability and flame retardancy were prepared by introducing flame retardant elements such as phosphorus and bromine at the monomer stage, followed by condensation with formaldehyde or hexamethylene tetramine (HMTA). Thus, monophenyl phosphoric acid (MPPA), monophenyl phosphoric acid–formaldehyde resin (MPPAF), brominated phenol–formaldehyde resin (BrPF) and 2,4,6‐tribromophenyl‐phosphoric acid–formaldehyde resin (BrMPPAF) were prepared and characterised. Thermal stability and flammability of these polymers were evaluated by TGA and LOI respectively and compared with those of phenol–formaldehyde resin (PF) and phosphorylated phenol–formaldehyde resin (PPF). The TGA (in air) of MPPAF showed enhanced thermal stability (char yield 66%) over that of PF (char yield 52%) and PPF (char yield 58%) indicating the role of phosphorus in imparting thermo‐oxidative resistance to PF. The enhancement is better when phosphorus is introduced at the monomer stage. The incorporation of bromine, however, brought about an unexpected reduction in the thermal stability of PF (char yield: BrPF, 2% and BrMPPAF, 26%). Both phosphorus and bromine are found to enhance the LOI values of PF (cured) from 35 to 50, 48, and 56, respectively, for MPPAF, BrPF, and BrMPAFF. A comparison of LOI values of these resins with their char yield suggests a condensed phase mechanism for phosphorus and vapor phase mechanism for bromine operating during thermal decomposition. © 1994 John Wiley & Sons, Inc.
Effect of solvent or hydrophilic polymer on the hydration melting behavior of polyacrylonitrile
Authors: Min Byung Ghyl , Son Tae Won , Kim Byoung Chul , Lee Chul Joo , Jo Won Ho 
Published: April 2003

AbstractThe effect of solvent, DMF, and hydrophilic polymer on the hydration melting behavior of Tae Kwang polyacrylonitrile‐based copolymer (T‐PAN) was investigated by DSC measurement. The melting temperature (Tm) of T‐PAN was sharply lowered by incorporating water under autogenous pressure, but leveled off above a critical water content: 23 wt %. However, an additional incorporation of DMF into the hydrated T‐PAN further lowered the Tm, even above the critical water content. On the other hand, addition of water‐soluble poly(acrylic acid), poly(vinyl alcohol), and poly(ethylene glycol) or water‐swellable starch to the hydrated PAN slightly raised the Tm. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of different mixtures of acrylic monomers on amylopectin. Swelling behavior
Authors: Castellano I. , Pascual B. , Vazquez B. , Goñi I. , Gurruchaga M. 
Published: April 2003

AbstractHydroxylic and nonhydroxylic acrylates—methyl acrylate (MA), ethyl acrylate (EA), butylacrylate (BA), hydroxypropyl methacrylate (HPMA), ethylenglycol dimethacrylate (EGDMA), and mixtures of HPMA–MA, HPMA–EA, HPMA–BA in a 50/50 feed composition—were grafted onto amylopectin with different amounts of crosslinking agent, EGDMA. Percent of total conversion, percent crude grafting, and influence of pH in water content were studied. In this sense it was only at pH 10 when a real variation in the water content could be seen. It was also proved that the highest values were obtained when one of the comonomers was EGDMA with a 34 mol% of the initial feed composition. © 1994 John Wiley & Sons, Inc.
Grafting cellulose acetate with styrene maleic anhydride random copolymers for improved dimensional stability of cellulose acetate
Authors: Nie Li , Narayan Ramani 
Published: April 2003

AbstractGraft copolymers of cellulose acetate (CA, d.s.:2.45) with styrene maleic anhydride random copolymers (SMAs) were synthesized by reacting the hydroxyls on CA backbone with the anhydride on SMA. The formation of graft copolymers leads to compatibilized blends with microscopic phase domains under appropriate conditions. The grafting reaction was studied in detail. The uniform dispersion of SMA in the CA matrix brings new properties to the grafting reaction products. Tests from acetone‐cast films showed improved dimensional stability in comparison to cellulose acetate; i.e., in the presence of 50% SMA in the formulation, there is more than 50% reduction on the dimensional change as compared to CA. The dimensional stability of the grafting products is better or comparable to cellulose triacetate. There are, for the alloys, reduced moisture adsorption, improved tensile strength, tensile modulus, reduced elongation, as compared to cellulose acetate. © 1994 John Wiley & Sons, Inc.
Surface properties of a segmented polyurethane containing amphiphilic polymers as additives
Authors: Kober Maria , Wesslén Bengt 
Published: April 2003

AbstractTwo different types of amphiphilic polymers were used as surface‐modifying additives to a polyetherurethane, Pellethane 2363–75D, which has Tg close to room temperature. The additives used were a segmented polyetherurethane designated Pol C, and Pluronics PE6800 and PE9400, i.e., triblock copolymers of propylene oxide and ethylene oxide. Pol C was prepared from poly(ethylene glycol), methylene diphenylene diisocyanate, and a fatty acid monoglyceride. The properties of the blends were investigated in their unhydrated state and after water immersion at 23°C and 80°C. Surface composition, water absorption, and leakage of additives to the aqueous phase have been studied. From ESCA and contact angle measurements it was concluded that Pol C was enriched in the surface layer of the matrix material after water immersion at 80°C. The Pluronics showed less effects on the surface properties of the matrix material, probably because of their high water solubility. © 1994 John Wiley & Sons, Inc.