bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flocculation of carbon black in filled rubber compounds. I. Flocculation occurring in unvulcanized compounds during annealing at elevated temperatures
Authors: Böhm Georg G. A. , Nguyen My N. 
Published: April 2003

AbstractIt has been found that appreciable carbon black flocculation can occur in filled rubber stocks during storage or vulcanization in the absence of shear. The kinetics of this flocculation process were studied by means of low strain dynamic mechanical property and electrical conducitvity measurements. The results showed the rate of flocculation to be governed by the type and concentration of carbon black, polymer macrostructure, mixing history, and annealing temperature. A mechanism responsible for the formation of this carbon black network structre was proposed and the resulting changes in the physical properties of vulcanizates prepared from these rubber compounds were elucidated. © 1995 John Wiley & Sons, Inc.
Effect of macroglycol structure and its molecular weight on physicomechanical properties of polyurethanes
Authors: Hundiwale D. G. , Kapadi U. R. , Pandya M. V. 
Published: April 2003

AbstractThe molecular weight of polyester polyol plays an important role in controlling mechanical and dynamic mechanical properties of polyurethanes. Two systems are studied for evaluation of these properties. Since the properties of polyurethanes are derived from the properties of various constituents involved in their synthesis, the magnitude of properties of polyurethanes are also studied. Dynamic mechanical properties are analyzed using a dynamic mechanical analyzer that employs the principle of compound resonance. © 1995 John Wiley & Sons, Inc.
Solution studies of cellulose tricarbanilates obtained in homogeneous phase
Authors: Terbojevich M. , Cosani A. , Camilot M. , Focher B. 
Published: April 2003

AbstractA number of cellulose samples was submitted to homogeneous phase carbanilation in dimethylacetamide/LiCl. The process is quantitative and leads to a completely substituted product, as verified by elemental analysis and UV spectroscopy. Tricarbanilated samples were characterized by viscometric and light‐scattering measurements in tetrahydrofuran. Our results are in good agreement with those reported in the literature, concerning products obtained in the heterogeneous phase. Gel permeation chromatography was performed for evaluating the molecular weight distribution of the parent cellulose, using both universal and linear calibration. The chromatographic technique is not adequate for samples exhibiting a high degree of polymerization. © 1995 John Wiley & Sons, Inc.
Gas‐phase photoinduced graft polymerization of acrylic acid onto polyacrylonitrile ultrafiltration membranes
Authors: Ulbricht Mathias , Oechel Annett , Lehmann Claudia , Tomaschewski Georg , Hicke Hans‐Georg 
Published: April 2003

AbstractHeterogeneous surface modification of polyacrylonitrile (PAN) ultrafiltration (UF) membranes is realized with UV irradiation‐initiated graft polymerization of acrylic acid (AA) from the gas phase onto photoinitiator (benzophenone, BP)‐coated samples. In the absence of monomer, PAN functionalization by ketyl radicals dominates after UV excitation of sorbed BP. With AA, graft and total polymer yield increase with BP loading and UV irradiation time. Average molecular weight and distribution of PAA homopolymer—formed in parallel during graft polymerization—are analyzed with gel permeation chromatography. Morphology of PAN‐gr‐AA UF membranes is checked with scanning electron micrographs (SEMs) and atomic force microscopy. Chemical changes are characterized with FTIR‐ATR spectroscopy and SEM/EDX analyses, indicating a pronounced surface selctivity of the graft polymer modification (localized in the upper 5‐μm membrane thickness). The amount of grafted PAA systematically reduces membrane permeability and increases dextrane retention, as verified in UF experiments. Photo graft polymer modificationof UF membranes will be applied to adjust membrane performance by controlling surface hydrophilicity and permeability using other monomers and/or further graft polymer functionalization. © 1995 John Wiley & Sons, Inc.
Biodegradability of poly(vinyl acetate) containing a pyridinium group
Authors: Kawabata Nariyoshi , Kurooka Teruya 
Published: April 2003

AbstractAn attempt has been made to give biodegradability to poly(vinyl acetate) by partial modification of the chemical structure. Poly(vinyl acetate) containing a small amount of N‐benzyl‐4‐vinylpyridinium chloride (PVAc‐co‐VPC) and that containing 16 mol % of methyl acrylate and a small amount of the pyridinium group (PVAc‐co‐MA‐co‐VPC) showed significant degradation when placed in an aeration tank of sewage works. Control polymers possessed of no pyridinium group did not show significant degradation under these conditions, and the extent of weight reduction during the treatment increased with the content of the pyridinium group. The weight reduction exhibited an uppermost limit after 7 days of the treatment, and the pyridinium group disappeared from the polymer during the early period. Incorporation of the pyridinium group into poly(vinyl acetate) appeared to have improved the biodegradability. Gel permeation chromatographic analysis showed that the low molecular weight fraction was more easily degraded than was the high molecular weight fraction. In the degradation of PVAc‐co‐MA‐co‐VPC, the unit of methyl acrylate was more easily removed than that of vinyl acetate. © 1995 John Wiley & Sons, Inc.
A study on rheologic behavior of polyphenylene sulfide
Authors: Hou Canshu , Zhao Baocheng , Yang Jie , Yu Zili , Wu Qixian 
Published: April 2003

AbstractRheologic behavior of the common Ryton‐type poly(phenylene sulfide) (PPS) and Fortron PPS has been studied using a capillary rheometer. The effects of shearing rate, shearing stress, and temperature on the apparent viscosities of PPS are discussed. The non‐Newtonian index and the activation energy of the viscous flow were obtained. The results show that the apparent viscosity of the Ryton PPS decreased obviously with increase of shearing rate or shearing stress, and with increase of the temperature, the apparent viscosity is not considerably decreased. On the contrary, the apparent viscosity of the Fortron PPS is more sensitive to temperature than to shearing rate and shearing stress. © 1995 John Wiley & Sons, Inc.
Polyaniline/polypropylene film composites with high electric conductivity and good mechanical properties
Authors: Yang Jiping , Zhao Chuntian , Cui Di , Hou Jianan , Wan Meixiang , Xu Mao 
Published: April 2003

AbstractPolyaniline/polypropylene composites were prepared by oxidative polymerization of aniline in biaxially stretched polypropylene microporous films with ammonium persulfate as the oxidant. A continuous permeation/diffusion polymerization process was used in order to incorporate more polyaniline in the composite. The influence of reaction time and temperature and the concentration of monomer and oxidant aqueous solutions on the electric conductivity of the composites was investigated. The composites may exhibit a loose particulate surface morphology and a compact surface with a ring‐shaped structure. The content and distribution of polyaniline in the composite and, hence, its electric conductivity and surface properties can be controlled over a wide range. Composites with the combination of high electric conductivity and good mechanical properties can be obtained under proper conditions. The composite films were flexible and strong enough and have electric conductivity as high as 5–6 S/cm. © 1995 John Wiley & Sons, Inc.
Segmented block copolyetheramides based on nylon 6 and polyoxypropylene. II. Structure and properties
Authors: Yu Yeong Chool , Jo Won Ho 
Published: April 2003

AbstractStructure–property relationships of segmented block copolyetheramides based on nylon 6 and polyoxypropylene (POP) were investigated as a function of the compositions and block lengths of the hard and soft segments by using differential scanning calorimetry, dynamic mechanical analysis, FT‐IR spectroscopy, wide angle x‐ray diffractometry (WAXD), and tensile testing. The nylon 6–D4 copolymers with the shortest soft segment exhibited the two‐phase structure of a crystalline nylon 6 phase and an amorphous phase composed of the hard and soft segments. Also they showed the tensile properties characteristic of a plasticized thermoplastic. On the other hand, the nylon 6–D20 and nylon 6–D40 copolymers exhibited the three‐phase structure of a crystalline nylon 6 phase, an amorphous nylon 6‐rich phase, and an amorphous POP‐rich phase. The nylon 6–D20 copolymers had better elastic properties with the increase of soft segment content; however, the nylon 6–D40 copolymers with the longest soft segment showed a substantial reduction of the elongation at break due to lack of the crosslinking density. © 1995 John Wiley & Sons, Inc.
Properties of blends of starch and synthetic polymers containing anhydride groups. II. Effect of amylopectin to amylose ratio in starch
Authors: Bhattacharya Mrinal , Vaidya Utpal R. , Zhang Dongmei , Narayan Ramani 
Published: April 2003

AbstractCorn starch with different amylopectin to amylose ratios was blended with styrene maleic anhydride copolymer (SMA) and ethylene–propylene‐g‐maleic anhydride copolymer (EPMA). The starch had an amylose content of approximately 0, 50, and 70%. The concentration of starch in the blend was kept constant at 60% by weight. The samples were melt blended in a corotating twin screw extruder. Scanning electron micrographs showed that the amount of starch granules remaining in the samples varied with the torque. Optical micrograph showed that starch/EPMA blends formed a cocontinuous phase in all blends irrespective of starch variety. For starch/SMA blends, the starch granules remained dispersed in the SMA phase. The torque during blending, tensile strength, water absorption, storage and loss modulus, and data on biodegradability of the blends are presented. Tensile strength and water absorption correlated well with the torque generated during blending: the higher the torque, the lower the tensile strength and the higher the water absorption. The tensile strength of blends containing SMA decreased when the humidity increased. Fractured surfaces of starch/SMA blends exhibited brittle failure; for the ductile starch/EPMA blends, shear tearing appeared to be the major failure mechanism. For blends containing EPMA, the percentage elongation increased with increased humidity. Dynamic mechanical analysis of the blends showed two sharp peaks for tan δ vs. temperature plot for starch/EPMA plots, but showed a single peak for starch/SMA blends. Starch/EPMA blends had a higher percentage of water aborption that became constant after 20 days. Using the ASTM test method D5902, the starch content in the samples was found to degrade. © 1995 John Wiley & Sons, Inc.
Studies on solvent evaporation and polymer precipitation pertinent to the formation of asymmetric polyetherimide membranes
Authors: Huang Robert Y. M. , Feng Xianshe 
Published: April 2003

AbstractThe characteristics of solvent evaporation and polymer precipitation during the formation of asymmetric aromatic polyetherimide (PEI) membranes via the dry/wet phase inversion method are studied and the results are discussed with reference to membrane preparation. It is shown that the solvent evaporation from the surface of freshly cast films in early evaporation stages can be quantified by an empirical equation with two parameters. Analysis of the evaporation parameters partially explains the interaction effect of membrane preparation variables on membrane performance. The phase separation data for systems PEI/DMAc/H2O and PEI/NMP/H2O with and without LiNO3 additive are determined using the turbidimetric titration method. The kinetic data on solvent–nonsolvent exchange and additive leaching during polymer precipitation in nonsolvent water are measured. The results presented here offer a qualitative basis for the development of asymmetric PEI membranes. © 1995 John Wiley & Sons, Inc.
Short pineapple‐leaf‐fiber‐reinforced low‐density polyethylene composites
Authors: George Jayamol , Bhagawan S. S. , Prabhakaran N. , Thomas Sabu 
Published: April 2003

AbstractShort pineapple‐leaf‐fiber‐(PALF)‐reinforced low‐density polyethylene (LDPE) composites were prepared by melt‐mixing and solution‐mixing methods. In the melt‐mixing technique, a mixing time of 6 min, rotor speed of 60 rpm, and mixing temperature of 130°C were found to be the optimum conditions. Tensile properties of melt‐mixed and solution‐mixed composites were compared. Solution‐mixed composites showed better properties than melt‐mixed composites. The influence of fiber length, fiber loading, and orientation on the mechanical properties has also been evaluated. Fiber breakage and damage during processing were analyzed from fiber distribution curve and optical and scanning electron micrographs. Considering the overall mechanical properties and processability characteristics, fiber lenght of 6 mm was found to be the optimum length of pineapple leaf fiber for the reinforcement in LDPE. The mechanical properties were found to be enhanced and elongation at break reduced with increasing fiber loading. Longitudinally oriented composites showed better properties than randomly and transversely oriented composites. Recyclability of the composite was found to be very good. A comparison of the properties of the PALF‐reinforced LDPE composites with those of other cellulose‐fiber‐reinforced LDPE systems indicated superior performance of the PALF–LDPE composites.© 1995 John Wiley & Sons. Inc.
Role of crack tip shielding mechanisms in fatigue of hybrid epoxy composites containing rubber and solid glass spheres
Authors: Azimi H. R. , Pearson R. A. , Hertzberg R. W. 
Published: April 2003

AbstractThe fatigue crack propagation (FCP) resistance of epoxy‐based composites containing various concentrations of solid glass spheres (SGS) and/or reactive liquid rubber (CTBN) was examined. The FCP results show that the simultaneous use of rubber and solid glass spheres (hybrid composites) results in synergistic improvement in FCP resistance of composites through the entire crack growth regime. The nature of synergistic interactions was elucidated by careful examination of the fatigue fracture surfaces and the subfatigue fracture surfaces of fatigue samples. It was shown that when rubber particles cavitate in the vicinity of the glass spheres, regardless of the nature of the interface, glass particle debonding from the matrix is suppressed due to a change in the crack tip localized stress state. This, in turn, results in improved pinning/bridging efficiency of the glass spheres. Furthermore, it was shown that crack tip plastic zone‐rubber particle interactions induce a transition in FCP behavior of rubber‐modified epoxies. Consequently, crack tip shielding mechanisms become active when the size of the plastic zone at the crack tip becomes large compared to the size of the rubber particles. © 1995 John Wiley & Sons, Inc.
Short sisal fiber reinforced styrene‐butadiene rubber composites
Authors: Kumar R. Prasantha , Amma M. L. Geethakumari , Thomas Sabu 
Published: April 2003

AbstractStyrene‐butadiene rubber (SBR) composites were prepared by incorporating short sisal fibers of different lengths and concentrations into the SBR matrix in a mixing mill according to a base formulation. The curing characteristics of the mixes were studied and the samples were vulcanized at 150°C. The properties of the vulcanizates such as stress‐strain behavior, tensile strength, modulus, shore‐A hardness, and resilience were studied. Both the cured and uncured properties showed a remarkable anisotropy. It has been found that aspect ratio in the range of 20–60 is effective for sufficient reinforcement. The mechanical properties were found to increase along and across the grain direction with the addition of fibers. The effects of fiber length, orientation, loading, type of bonding agent, and fiber‐matrix interaction on the properties of the composites were evaluated. The extent of fiber orientation was estimated from green strength measurements. The adhesion between the fiber and the rubber was enhanced by the addition of a dry bonding system consisting of resorcinol and hexamethylene tetramine. The bonding agent provided shorter curing time and enhanced mechanical properties. The tensile fracture surfaces of the samples have been examined by scanning electron microscopy (SEM) to analyze the fiber surface morphology, orientation, fiber pull‐out, and fiber‐matrix interfacial adhesion. Finally, anisotropic swelling studies were carried out to analyze the fiber‐matrix interaction and fiber orientation. © 1995 John Wiley & Sons, Inc.
Computer simulation of melt spinning of polypropylene fibers using a steady‐state model
Authors: Bhuvanesh Y. C. , Gupta V. B. 
Published: April 2003

AbstractA mathematical model that includes crystallization in the spinline and the effect of crystallization on the extensional viscosity and the various physical properties of polypropylene has been developed and used to help in identifying the various factors that can affect the spun yarn characteristics. The model is used to simulate effects of spinning parameters on fiber physical properties, temperature, and stresses. The experimental observation of a minimum in density of the spun yarn at high throughput rates, when density is plotted as a function of take up velocity, has been investigated in some detail. It has been found that all conditions which can substantially affect the rate of cooling and the orientation of the polymer in the spinline, viz, throughput rate, spinning temperature, and spinning speed have an important bearing on the temperature range in which crystallization can take place in the spinline and thus affect the density. It is suggested that in addition to these factors, the formation of different crystal modifications at different spinning speeds could also contribute to the reduction in density of these samples. The model cannot reflect the observation of density changes occurring due to the formation of different crystal modifications. Nevertheless, it can be of use in understanding the effects of various process conditions on the cooling rate and the orientation of the polymer in the spinline. © 1995 John Wiley & Sons, Inc.
Dehydration of lesquerella oil
Authors: Thames Shelby F. , Yu Haibin , Wang Min D. , Schuman Thomas P. 
Published: April 2003

AbstractThe dehydration of lesquerella oil has been accomplished for the first time. Dehydration was performed using sulfuric acid, sulfates and phosphates, acidic clay, and aluminum oxide as dehydration catalysts. Dehydration products were characterized by infrared (FTIR), ultraviolet (UV), and proton nuclear magnetic resonance (1H‐NMR) spectroscopies. Color grades, acid values, hydroxyl values, and iodine values were obtained by established ASTM methods. Dehydration of either lesquerolic or ricinoleic acids creates slightly more conjugated diene than nonconjugated diene. Product mole ratios of conjugated to nonconjugated diene versus catalyst type varied from 1.1 to 1.6. Dehydrated lesquerella oil containing about 28 mol % conjugated (77.8 mol % total) diene has an iodine value of 147. Drying properties were also examined. Dehydration converts nondrying lesquerella oil into a drying oil with a drying velocity equivalent to a commercially dehydrated castor oil. © 1995 John Wiley & Sons, Inc.
Simulation of intensity of segregation distributions using three‐dimensional fem analysis: Application to corotating twin screw extrusion processing
Authors: Lawal Adeniyi , Kalyon Dilhan M. 
Published: April 2003

AbstractThe corotating twin screw extrusion flow is simulated to generate the distributions of intensity of segregation and integral measures of mixing and forwarding. The simulation focused on the lenticular kneading disk elements that necessitated the application of a three‐dimensional finite element method to solve the conservation equations. The intensity of segregation distributions were determined by introducing a tracer blob numerically and tracking the concentration of the tracer particles as a function of location and time. In spite of the chaotic nature of the dynamics of this flow, the analyses provided the broad features of twin extrusion flow and its ability to mix. The processing characteristics of kneading disks were found to depend on the stagger angle and complemented earlier numerical and experimental results on residence time distributions and color incorporated tracer analyses. © 1995 John Wiley & Sons, Inc.
Mechanism of crosslinking of papers with polyfunctional carboxylic acids
Authors: Zhou Y. J. , Luner P. , Caluwe P. 
Published: April 2003

AbstractBrief thermal curing of papers treated with an aqueous solution of polyfunctional carboxylic acids and NaH2PO4 imparts substantial wet strength to the papers. The effectiveness of such carboxylic acids increases with their functionality in the order 1,2,3,4‐butanetetracarboxylic acid (BTCA) > tricarballylic acid (TCA) ≫ succinic acid. The two main stages of the curing reaction of papers, i.e., pendant attachment of the polyfunctional carboxylic acids via esterification with cellulosic hydroxyl groups, and its further reaction with another cellulose hydroxyl group producing crosslinks of the cellulose fibers were analyzed separately using a combination of acid‐base and conductometric titrations. The extent of reaction of the polyfunctional carboxylic acids with paper was followed by pH titration, which shows the total decrease in acid functions as the curing progresses and is directly related to the total consumption of carboxylic acids groups by ester attachment and ester crosslinking steps. The conductometric titration, on the other hand, measures the increase in carboxylic acids bound to cellulose units of the paper as a direct result of previous esterification steps. Our studies reveal that the reaction of BTCA with papers is essentially quantitative after 15 min of curing. The amount of once‐reacted BTCA increases in the initial phases of the curing reaction and then decreases as more and more carboxylic acid units are converted into crosslinking sites, while the amount of crosslinked BTCA increases throughout the curing reaction. The reaction profile of papers with TCA differs from that of BTCA in that the curing reaction is initially dominated by the formation of ester appendages; crosslinking becomes the main reaction only after extended curing times. We attribute this difference to the ability of BTCA to form an highly reactive difunctional crosslinking reagent at the outset of the curing reaction, while TCA is initially monofunctional in its reaction with cellulosic hydroxyl groups (formation of a monoanhydride). The relationship between the wet tensile strength of the treated papers and their degree of crosslinking is also discussed. © 1995 John Wiley & Sons, Inc.
Synthesis and properties of polybenzimidazobenzophenanthrolines
Authors: Zhou Wenle , Lu Fengcai 
Published: April 2003

AbstractPolycondensation of 1,4,5,8‐naphthalenetetracarboxylic dianhydride (NTDA) with 3,3′‐diaminobenzidine (DAB) and 3,3′4,4′‐tetraaminodiphenyl ether (TADPE), respectively, in N,N′‐dimethylacetamide (DMAc) at room temperature was found to produce high‐viscosity polybenzimidazobenzophenanthroline (PBIPA) precursors. The PBIPA films, exhibiting excellent thermal and mechanical properties, were conveniently prepared by the heat cure of precursors. UV‐vis spectra and IR spectra of PBIPA were measured. The permeability to H2, O2, and N2 of these two polymer membranes was determined at 30°C and 1 atm. © 1995 John Wiley & Sons, Inc.