bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermally induced crosslinking between polyacrylic acid and epoxidized natural rubber. III. Effect of carbon black filler and mixer rotor speed
Authors: Mallick A. , Tripathy D. K. , De S. K. 
Published: April 2003

AbstractHigh‐temperature molding of Brabender‐mixed blend of polyacrylic acid (PAA) and epoxidized natural rubber (ENR) causes thermally induced crosslinking between PAA and ENR. Studies on Monsanto rheometry of the blend and physical properties, solvent swelling, and dynamic mechanical properties of the molded blend show that both mixer rotor speed and carbon black filler influence the crosslinking between the component polymers. For example, the extent of crosslinking for the 50–50 PAA–ENR blend was found maximum when the component polymers were mixed at 40 rpm, but the same blend filled with 30 phr HAF carbon black filler showed maximum crosslinking when mixing was carried out at 120 rpm. The results have been explained on the basis of formation of network on the filler surface, which in turn depends on two competing factors: increase in bound rubber formation with increase in filler loading at a fixed rotor speed and enhanced degradation of ENR at higher mixer rotor speed at a fixed filler loading. © 1994 John Wiley & Sons, Inc.
Decomposition behavior of polyurethanes via mathematical simulation
Authors: Chang Wally L. 
Published: April 2003

AbstractA series of polyurethane elastomers with different hard‐segment contents of 24% (M24), 34% (M34), 50% (M50), and 100% (M100) have been investigated through thermogravimetric analysis (TGA) measurement and mathematical simulation. The fourth‐order Runge–Kutta method was used to solve the differential equations, and the solutions were obtained by running a written computer program. The activation energy and the frequency factor of polyurethane decomposition can be obtained by only one nonisothermal measurement of TGA. The same values of the activation energy and the frequency factor were obtained using the different constant heating rates under air for the elastomer with a hard‐segment content of 34%. The activation energy decreases as the hard‐segment content of polyurethanes increases. The polyurethane materials can be used at room temperature for several millennia failure through lifetime calculation. Comparison of the values of t1/2, the heat stability of polyurethanes decreases in the following order: M24 > M34 > M50 > M100; this phenomenon can be explained due to the heat instability of the urethane group. The highest concentration of the urethane group in the M100 structure results in the worst heat stability. © 1994 John Wiley & Sons, Inc.
Synthesis and evaluation of dialkyl furan‐2,5‐dicarboxylates as plasticizers for PVC
Authors: Sanderson R. D. , Schneider D. F. , Schreuder I. 
Published: April 2003

AbstractDi(2‐ethylhexyl), di(2‐octyl), dihexyl, and dibutyl furan‐2,5‐dicarboxylate were synthesized from furfural and characterized for their plasticizing abilities toward PVC by dynamic mechanical thermal analysis (DMTA) with di(2‐ethylhexyl) phthalate (DOP) as the standard of reference. DMTA gave values for the depression of the glass transition temperature (Tg) per mass fraction of plasticizer, and it also yielded a set of parameters, relative to those for DOP, which describe the compatibility of the furan diesters with PVC. The efficiency in lowering Tg as exhibited by di(2‐ethylhexyl) furan‐2,5‐dicarboxylate is similar to that of its benzenoid analog, DOP, and was determined at 2.41 and 2.45°C per mass % plasticizer, respectively. All four furan diesters were found to be more compatible toward PVC than toward DOP, with dibutyl furan‐2,5‐dicarboxylate the most highly compatible. © 1994 John Wiley & Sons, Inc.
Effect of solvent precipitation on the crystallization behavior and morphology of nylon 6,6
Authors: Muellerleile Joan T. , Freeman John J. 
Published: April 2003

AbstractThis work describes the effect of solvent precipitation on the crystallization behavior and morphology of nylon 6,6. We found that solvent precipitation of nylon 6,6 induces elevated crystallization temperatures upon cooling from the melt (Tmc) and highly nucleated morphologies that rival those induced by rapid, thermal reprocessing such as melt reextrusion or heterogeneous nucleating agents such as CaF2. The primary techniques used to characterize these changes in crystallization behavior and morphology were differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide‐angle X‐ray scattering (WAXS). Several other supplementary techniques were employed for identifying the origin of the crystallization behavior and morphological changes after solvent precipitation. Our results are consistent with the hypothesis in which dissolved nylon reorients to form ordered H‐bonded regions that later serve as nucleation sites during melt processing. Finally, (Tmc) decreased with nylon 6,6 solution concentration prior to precipitation. These results suggest that polymer entaglements in solution also affect the crystallization behavior and morphology of the solvent‐precipitated nylon 6,6. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of main‐chain liquid crystalline polyurethane elastomers
Authors: He Xiangdong , Jia Xudong , Yu Xuehai 
Published: April 2003

AbstractLiquid crystalline polyurethane elastomers (LCPUE) have been synthesized by a two‐step block copolymerization reaction. The main‐chain LCPUEs are based on two biphenyl‐type mesogenic diol chain extenders (HB2 and HB6), a poly(tetramethylene oxide) (PTMO) soft segment, and different diisocyanates, icluding 4,4′‐diphencylmethane diisocyanate (HDI), and 1,4‐(3,5,5‐trimethyl)cyclohexane diisocyanate (IPDI). The polyurethanes were characterized by FTIR dichrosim, DSC, DMA, WAXD, and polarized optical microscopy. Most of the polyurethane samples exhibited nematic thermortopic liquid crystal behavior and had physical properties typical of thermoplastic elastomers. The liquid crystal properties are strongly related to the interaction between the hard and soft segments of the polyurethane. As the compatibility of the soft and hard segments increased, the thermal stability of the liquid crystal phase and the transition temperatures decreased and the range of the transition became narrower, Uniaxial extenstion analysis shows that two orientation mechanisms exist in the LCPUE systems. These samples had fairly high strength and modulus and good membrane‐forming ability. © 1994 John Wiley & Sons, Inc.
A novel TLCP blended with PET and PC matrices
Authors: Joslin Scott , Jackson Woodward , Farris Richard 
Published: April 2003

AbstractThis investigation focused on the potential of improving the performance of poly(ethylene terephthalate) (PET) and polycarbonate (PC) fibers by incorporating a novel thermotropic liquid crystalline copolymer (TLCP). The degree of mechanical enhancement obtained in the fibers incorporating 20 wt % TLCP depended upon the chosen matrix material and the processing conditions. The PET matrix systems did not exhibit any modulus improvements until after posttreatment of the fibers. Following posttreatment, the blends exhibited a modulus of 24 GPa, an increase of 40% compared to the PET control fiber. The PC systems exhibited a 1 GPa modulus increase in the as‐spun fiber blends, but improvement was negligible after fiber posttreatment. The morphologies of the as‐spun and posttreated fibers suggest that different mechanisms of reinforcement are occurring depending upon the matrix material selected. © 1994 John Wiley & Sons, Inc.
Preparation of zeolite filled glassy polymer membranes
Authors: Duval J.‐M. , Kemperman A. J. B. , Folkers B. , Mulder M. H. V. , Desgrandchamps G. , Smolders C. A. 
Published: April 2003

AbstractThe incorporation of zeolite particles in the micrometer range into polymeric matrices was investigated as a way to improve the gas separation properties of the polymer materials used in the form of membranes. The adhesion between the polymer phase and the external surface of the particles appeared to be a major problem in the preparation of such membranes when the polymer is in the glassy state at room temperature. Various methods were investigated to improve the internal membrane structure, that is, surface modification of the zeolite external surface, preparation above the glass‐transition temperature, and heat treatment. Improved structures were obtained as observed by scanning electron microscopy, but the influence on the gas separation properties was not in agreement with the observed structural improvements. © 1994 John Wiley & Sons, Inc.
Proton exchange membranes by radiation grafting of styrene onto fep films. III. Structural investigation
Authors: Gupta Bhuvanesh , Haas Otto , Scherer Günther G. 
Published: April 2003

AbstractStructural investigation on proton‐exchange membranes, obtained by the radiation grafting of styrene onto FEP films and subsequent sulfonation, was carried out by differential scanning calorimetry. The membrane crystallinity was found to show a decreasing trend with increasing degree of grafting. The melting temperature of all the membranes also showed a slight decrease as compared to the ungrafted FEP. The results have been explained in terms of the cumulative effect of the decrease in the crystalline/amorphous ratio by the incorporation of amorphous polystyrene grafts and of disruption of spherulitic crystallites of the FEP component in the membranes. The glass transition temperature of the membranes with different water contents was also evaluated. A correlation of the glass transition temperature with the residual water in dried membranes was established. © 1994 John Wiley & Sons, Inc.
Rubber toughened styrene/methyl methacrylate/butyl methacrylate composites by the concentrated emulsion pathway
Authors: Ruckenstein Eli , Li Hangquan 
Published: April 2003

AbstractSolutions of rubber in mixtures of styrene, methacrylate, and/or butyl methacrylate containing proper amounts of initiator have been polymerized to produce novel polymer composites—MBBS. In these composites, it is expected that tri‐component and bi‐component copolymers as well as homopolymers coexist. The tensile behavior of composites of various compositions was investigated. At certain weight ratio of monomers, excellent combinations of tensile strength, elongation, and toughness were obtained, which are better than those of most commercial engineering plastics. There is an optimum amount of butyl methacrylate, which is dependent upon the contents of the other monomers, for which the toughness acquires a maximum value. The concentrated emulsion polymerization was employed to prepare the MBBS composite latexes and the products were compared with those prepared via bulk polymerization. While the two polymerization methods provide high, comparable tensile properties and toughness, the concentrated emulsion method generates latexes which can be more easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc.
Non‐markovian diffusion processes in polymers and a stretched exponential relaxation constitutive equation
Authors: Stastna J. , De Kee D. , Harrison B. 
Published: April 2003

AbstractNon‐Markovian diffusion transport in polymers was studied. Applying the results of various researchers, a stretched exponential relaxation function was obtained and a linear viscoelastic constitutive equation formulated. Frequency dependent material functions, obtained from this constitutive equation were studied and the results successfully compared with experimental data for polyethylene oxide solutions. Sorption kinetics in a polymeric film were also studied. © 1994 John Wiley & Sons, Inc.
Through‐thickness distribution of LCP in PPS/LCP blends
Authors: Shonaike G. O. , Hamada H. , Yamaguchi S. , Nakamichi M. , Maekawa Z. 
Published: April 2003

AbstractThrough‐thickness distribution of liquid crystalline polymer (LCP) of blends containing polyphenylene sulfide (PPS) and LCP was investigated using differential scanning calorimetry and scanning electron microscopy. The effect of the LCP distribution on the mechanical test was checked through bending testing of the various compositions of the injection molded samples. These studies showed a nonuniform distribution of LCP in the PPS‐rich region where the LCP content in the skin layer was higher than in the core layer or boundary between the two layers. The LCP component was uniformly distributed in the LCP‐rich region. The increase of bending modulus with increasing LCP content was attributed to the reinforcing nature of the LCP fibrils in the skin layer. © 1994 John Wiley & Sons, Inc.
Effect of poly(vinylidene fluoride) on the ionic conductivity and morphology of PEO–salt polymer electrolytes
Authors: Whang Wha‐Tzong , Yang Li‐Huy , Fan Yu‐Wen 
Published: April 2003

AbstractThe high dielectric constant polymer poly(vinylidene fluoride) (PVDF) was blended with PEO–Salt polymer electrolytes to improve their ionic conductivity. PVDF did improve the room‐temperature ionic conductivity of the polymer electrolytes PEO–LiCF3CO2 and PEO–LiBF4, and the ionic conductivity at room temperature went up one order of magnitude with 10−5S/cm for LIB4M–PF4 being the most prominent. PVDF exhibited strong effects on the ionic conductivity and morphology of the polymer electrolytes, such as weakening the association of poly(ethylene oxide) (PEO) with the salt, hindering the formation of the PEO–salt complex, enlarging the crystalline PEO phase in LIAnM–PFm polymer electrolytes, and reducing the crystalline PEO phase in LIBnM–PFm polymer electrolytes. Both LIA4M–PF4 and LIB4M–PF4 polymer electrolytes formed a new PEO–PVDF–salt complex. The new complex in the former was crystalline, but that in the latter was amorphous. © 1994 John Wiley & Sons, Inc.
Ultraviolet curing acrylated chlorinated low‐molecular‐weight guayule rubber wood filler and finish
Authors: Thames Shelby F. , He Z. Alex 
Published: April 2003

AbstractAcrylated chlorinated low‐molecular‐weight guayule rubber (ACLMWGER) has been systhesized and characterized with Fourier Tranform infrared spectroscopy, solid‐state nuclear magnetic responance spectroscopy, and differential scanning calorimetry, We have found that ACLMWGER is useful as a prepolymer in 100% solids ultraviolet (UV) curing wood coatings. The properties of the coatings are equal or superior to coatings prepared from acrylated chlorinted rubber synthesized from commerical masticated natural rubber. However, when low‐molecular‐weight guayule rubber (LMWGR) serves as the feedstock, the cost of producing ACLMMWGR is significantly reduced since no mastication is needed. © 1994 John Wiley & Sons, Inc.
Photochemically modified thin‐film composite membranes. II. Bromoethyl ester, dioxolan, and hydroxyethyl ester membranes
Authors: Trushinski B. J. , Dickson J. M. , Childs R. F. , McCarry B. E. , Gagnon D. R. 
Published: April 2003

AbstractA photochemically active thin‐film composite membrane was made by the interfacial copolymerization of a mixture of 3‐diazo‐4‐oxo‐3,4‐dihydro‐1,6‐naphthalene disulfonylchloride and naphthalene‐1,3,6‐trisulfonylchloride in CCl4 with aqueous 1,6‐hexanediamine on the surface of a polysulfone ultrafiltration membrane. The chemical functionality of the resulting polysulfonamide membrane surface was modified via a photochemical reaction in the presence of various nucleophiles to form membranes containing bromoethyl ester, dioxolan, and hydroxyethyl ester functionality. Surface analysis techniques of attenuated total reflectance–FTIR, scanning electron microscopy (SEM), energy disperse spectral analyzer (SEM/EDS), and electron spectroscopy (ESCA) were used to confirm the changes in the chemistry of the thin‐film composite membranes. Changes in chemistry, on irradiation, were also examined with model compounds. The reverse osmosis flux and separation of various solutes with these membranes are reported and discussed in terms of the photochemical modifications of the membrane surface. © 1994 John Wiley & Sons, Inc.
Modulus evaluation of particulate composites using generalized viscosity model for solutions with suspended particles
Authors: Sudduth Richard D. 
Published: April 2003

AbstractThe theoretical relationship between the shear modulus of a particulate reinforced composite and the viscosity of a solution with suspended particles was first proposed by Goodier. Since that time several partially successful attempts have been made in the literature to derive equations to describe the available relative shear modulus–particulate concentration data. Recently a new generalized suspension viscosity equation appeared in the literature which for the first time addresses the detailed effects of particle size, particle size distribution, and packing fraction. This new viscosity equation was applied to available modulus literature on particulate composites in this study. Four significant particulate composite modulus derivations in the literature were all shown in this study to yield the same theoretical “intrinsic modulus” of a particulate composite. The generalized viscosity–modulus equation yielded an excellent fit of the shear modulus–particulate concentration data of both Smallwood and Nielsen using a variable intrinsic modulus. Some fillers predicted the Einstein limiting value of the intrinsic modulus while other fillers yielded intrinsic modulus values that were either larger or smaller than this value. The intrinsic modulus for carbon black in rubber was much larger than Einstein's predicted value. However, intrinsic modulus values smaller than Einstein's prediction were obtained at temperatures below the glass transition temperature of the matrix. Unfortunately, the previously obtained direct relationship between the particle interaction coefficient and particulate size for suspension viscosities with a constant intrinsic viscosity was not obtaind for shear modulus—particulate concentration data using a variable intrinsic modulus. © 1994 John Wiley & Sons, Inc.
Epoxy resin based on 4,4′‐dihydroxydiphenysulfone. I. Synthesis and reaction kinetics with 4,4′‐diaminodiphenylmethane and 4,4′‐diaminodiphenylsulfone
Authors: Sýkora V. , Špaček V. , Dobáš I. 
Published: April 2003

AbstractEpoxy resins based on 4,4′‐dihydroxydiphenylsulfone (DGEBS) and diglycidyl ether of bisphenol A (DGEBA) were prepared by alkaline condensation of 4,4′‐dihydroxydiphenylsulfone (bisphenol S) with epichlorohydrin and by recrystallization of liquid, commercial bisphenol A‐type epoxy resin, respectively. Curing kinetics of the two epoxy compounds with 4,4′‐diaminodiphenylmethane (DDM) and with 4,4′‐diaminodiphenylsulfone (DDS) as well as Tg values of the cured materials were determined by the DSC method. It was found that the SO2 group both in the epoxy resin and in the harener increases Tg values of the cured materials. DGEBS reacts with the used hardeners faster than does DGEBA and the curing reaction of DGEBS begins at lower temperature than does the curing reaction of DGEBA when the same amine is used. © 1994 John Wiley & Sons, Inc.
Studies upon the fine structure and selected physical and physicochemical properties of butrylchitin membranes
Authors: Urbańczyk G. , Lipp‐Symonowicz B. , Jeziorny A. , Urbaniak‐Domagala W. , Wrzosek H. 
Published: April 2003

AbstractThe effect of varying the molecular weight of butyrylchitin membranes cast from methylene chloride on their properties has been investigated. Characterization analyses include X‐ray, scanning calorimetry and tensile stress‐strain. The crystal structure of the butyrylchitin was shown to consist of fringed micelles, irrespective of the molecular weights examined, and of lower crystal volume fraction than usually found for chitin membranes, 0.3 versus 0.5, respectively. The membranes exhibit greater ductility and less swelling in physiological salt solution with increasing molecular weight. © 1994 John Wiley & Sons, Inc.
Polylactide. I. Continuous dry spinning–hot drawing preparation of fibers
Authors: Horáček I. , Kalíšek V. 
Published: April 2003

AbstractThe mechanical properties and in vitro degradability of gamma‐rays sterilized and non‐sterlized PLLA fibers prepared by a continuous dry spinning–hot drawing process were studied in relation to the spinning solution composition. Chloroform/cyclohexane mixtures of different volume ratios were used for dissolution either purified or as polymerized (with a residual monomer) PLLA. The fibers obtained had average or poor mechanical properties and a porous structure with a pointed outer skin. No increase of the degradation rate was observed except for the fibers formed from pure chloroform with a residual monomer at a drawing temperature of 110°C. At chloroform/cyclohexane volume ratio of 6:4 the process resulted in nearly hollow fiber formation. © 1994 John Wiley & Sons, Inc.
Induced accelerated autocondensation of polyflavonoid tannins for phenolic polycondensates. I. 13C‐NMR, 29Si‐NMR, X‐ray, and polarimetry studies and mechanism
Authors: Meikleham N. , Pizzi A. , Stephanou A. 
Published: April 2003

AbstractPolyflavonoid tannins have been found to autocondense and harden when in presence of small amounts of SiO2 at high pH. Small amounts of boric acid and AICI3 were found to have the same effect. The mechanism of tannin autocondensation to hardening was found to depend on the Lewis acid behaviour of the additives used. Such mechanism involves Lewis acid acceptance of electrons from the ether oxygen of the flavonoid unit pyran ring with subsequent facilitation of base‐induced heterocycle opening. The reactive C2 site created by heterocycle opening proceeds to autocondense with the reactive A‐ring of a flavonoid unit on another chain denying to the flavonoid the possibility of intramolecular rearrangements to catechinic acid and phlobatannin which occur in model compounds. Si has been shown to pass through a coordination state of 5, by CP‐MAS 29Si‐NMR. The portion of Si, which has not been able to complete the reaction due to premature hardening, remains attached to the flavonoids, in this coordination state, in the hardened network. The Si portion, which has completed the reaction and caused the hardening, reverts instead to SiO2 and is detached from the flavonoid. The SiO2, H3BO3, and AICI3 mechanism shows that their presence also reverses the relative facility of cleavage between interflavonoid bond and heterocycle opening in mainly procyanidin and profisetinidin tannins. © 1994 John Wiley & Sons, Inc.
Effect of the low‐temperature relaxation on toughness of cured epoxy resins
Authors: Ochi Mitsukazu , Ikegawa Kayo , Ueda Shigehisa , Kotera Kazuhiro 
Published: April 2003

AbstractThe relation between the magnitude of low‐temperature relaxation and toughness was investigated for epoxy resins cured with some position isomers of naphthalenediols. A well‐defined relaxation was observed near room temperature for a system cured with 2,6‐dihydroxynaphthalene. The relaxation was denoted here as the β′‐relaxation. The values of the stress intensity factor, Kc, in this system was considerably higher than those of the other cured systems in the temperature region over the β′‐relaxation temperature. This is explained by the increase in the plastic deformation region at the crack front with an increase in the temperature near the crack tip caused by the presence of the β′‐relaxation. © 1994 John Wiley & Sons, Inc.