bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrally skinned polysulfone hollow fiber membranes for pervaporation
Authors: Koops G. H. , Nolten J. A. M. , Mulder M. H. V. , Smolders C. A.
Published: April 2003

From polysulfone as polymer, integrally skinned hollow fiber membranes with a defect‐free top layer have been spun. The spinning process described here differs from the traditional dry‐wet spinning process where the fiber enters the coagulation bath after passing a certain air gap. In the present process, a specially designed tripple orifice spinneret has been used that allows spinning without contact with the air. This spinneret makes it possible to use two different nonsolvents subsequently. During the contact time with the first nonsolvent, the polymer concentration in the top layer is enhanced, after which the second coagulation bath causes further phase separation and solidification of the ultimate hollow fiber membrane. Top layers of ± 1 μm have been obtained, supported by a porous sublayer. The effect of spinning parameters that might influence the membrane structure and, therefore, the membrane properties, are studied by scanning electron microscopy and pervaporation experiments, using a mixture of 80 wt % acetic acid and 20 wt % water at a temperature of 70°C. Higher fluxes as a result of a lower resistance in the substructure could be obtained by adding glycerol to the spinning dope, by decreasing the polymer concentration, and by adding a certain amount of solvent to the bore liquid. Other parameters studied are the type of the solvent in the spinning dope and the type of the first nonsolvent. © 1994 John Wiley & Sons, Inc.
Selective crosslinking in polymer blends. I. Novel selective crosslink systems for polypropylene/unsaturated elastomer blends
Authors: Inoue Toshio
Published: April 2003

Two novel systems were developed to selectively crosslink dispersed unsaturated elastomer particles in saturated polyolefin matrices under dynamic crosslinking conditions. One system comprises N,N′‐m‐phenylene‐bis‐maleimide (PM) as a crosslinker and 6‐ethoxy‐2,2,4‐tri‐methyl‐1,2‐dihydroquinoline or polymerized‐ (2,2,4‐trimethyl‐1,2‐dihydroquinoline) as an activator. They are believed to form charge‐transfer‐complexes to produce PM radicals, which accelerate the crosslinking reaction of the elastomer. The other comprises PM as a crosslinker and 9,10‐dihydrophenanthrene as an activator. These are believed to act as a hydrogen acceptor and a hydrogen donor, respectively, involving transference of a hydrogen radical between them to produce a PM radical. These crosslink systems convert the unsaturated elastomer particles in the polyolefin matrices to crosslinked particles selectively without causing degradation or crosslinking of the matrices, because the radicals produced from the systems are carbon radicals and abstract only hydrogen radicals at the allylic positions of the unsaturated elastomers and not a hydrogen radical at the secondary or tertiary carbons of the polyolefin. The reactions and their confirmed selectivity were conducted on PP/EPDM blend, PP/SBS blend, PP/SIS blend, PP/1,2‐PB(1,2‐polybutadiene) blend, and PP/PE/EPDM blend, respectively. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of acrylonitrile and methacrylonitrile onto gelatin by mutual irradiation method
Authors: Kaur Inderjeet , Barsola Raghuvir , Gupta Anita , Misra B. N.
Published: April 2003

In order to improve upon certain properties of gelatin graft copolymerization of acrylonitrile (AN) and methacrylonitrile (MAN) onto gelatin has been studied in aqueous medium using γ rays as a source of initiation. Optimum conditions for affording maximum percentage of grafting have been evaluated as a function of various reaction parameters. The grafted polyacrylonitrile (PAN) was isolated from the graft copolymer by acid hydrolysis, and the average molecular weight (Mv) of the isolated polymer has been determined viscometrically. The graft copolymers were characterized by IR spectroscopic methods and thermogravimetric analysis (TGA). Acrylonitrile was found to be more reactive than methacrylonitrile toward graft copolymerization. © 1994 John Wiley & Sons, Inc.
Vibrational spectra of some diisocyanates in the liquid state or on EPDM‐40 rubber surface
Authors: Kondyurin Alexey , Klyachkin Yuri
Published: April 2003

IR transmission and Raman spectra of toluylene diisocyanate and hexamethylene diisocyanate and IR spectra of diphenylmethane diisocyanate, partially polymerized diphenylmethane diisocyanate, and polyisocyanurate were obtained. Toluylene diisocyanate and partially polymerized diphenylmethane diisocyanate form associates in the liquid state, which leads to anomalous intensity changes and a frequency shift to the νas (NCO) band in the spectrum of the treated rubber surface with time. The associate formation influences positively the properties of diisocyanates as rubber‐surface modifiers for adhesion. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of unsaturated polyester diol–polyurethane hybrid polymer network
Authors: Xu Mei Xuan , Xiao Jing Song , Zhang Wen Hua , Yao Kang De
Published: April 2003

This article deals with the synthesis and properties of poly[(propylene glycol maleate)‐co‐(propylene glycol phthalate)] diol (PGMPD)/polyester–urethane or polyether–urethane hybrid polymer networks (HPNs). The polyurethane type and the molar ratio of NCO/OH have an effect on their properties. The structure–property relationship is discussed as well. © 1994 John Wiley & Sons, Inc.
Mechanical properties of LDPE/granular starch composites
Authors: Willett J. L.
Published: April 2003

The mechanical properties of composites of granular starch and low density polyethylene (PE) have been studied as functions of starch volume fraction ϕ, granule size, and presence of compatibilizer. Property–volume fraction relationships were interpreted using various theories of composite properties. The dependence of elongation (ϵ ∼ ϕ1/3) and tensile strength (σ ∼ ϕ2/3) agree with theoretical predictions, although the proportionality constants are less negative than theoretical values. The addition of compatibilzer (ethylene‐co‐acrylic acid copolymer, EAA) did not significantly affect the elongation or tensile strength, but significantly increased the composite tensile modulus. The cornstarch/PE moduli could be described by the Kerner or Halpin‐Tsai equations. Analysis of the composite moduli data using the Halpin‐Tsai equation allowed the estimation of the modulus of granular starch. The value obtained, 15 GPa, is considerably greater than most unfilled synthetic polymers of commercial importance, but significantly lower than the modulus of cellulose. It is also greater than a previously reported value of 2.7 GPa. © 1994 John Wiley & Sons, Inc.
Interaction of nylon 6‐clay surface and mechanical properties of nylon 6‐clay hybrid
Authors: Usuki Arimitsu , Koiwai Akihiko , Kojima Yoshitsugu , Kawasumi Masaya , Okada Akane , Kurauchi Toshio , Kamigaito Osami
Published: April 2003

We synthesized nylon 6‐clay hybrid materials using four types of clay minerals, montmorillonite, saponite, hectrite, and synthetic mica. The mechanical properties of their injection molded specimens were measured according to ASTM. Nylon 6‐clay hybrid using montmorillonite was superior to the other hybrids in mechanical properties. This might result from the difference in the interaction between nylon molecules and silicates in the hybrids. To clarify this hypothesis, we synthesized intercalated compounds of the clay minerals with glycine as the model of the hybrids, and analyzed the interaction using 15N cross polarization magic angle spinning (CP/MAS) NMR spectroscopy. The 15N‐NMR result reveals that the positive charge density on the nitrogen of the intercalated compound based on montmorillonite was largest in all the intercalated compounds. It was suggested that montmorillonite interacted strongly with nylon 6 by ionic interaction. This ionic interaction was one of the reasons why these hybrid materials had superior mechanical properties. © 1995 John Wiley & Sons, Inc.
Microstructural evolution of a silicon oxide phase in a perfluorosulfonic acid ionomer by an in situ sol–gel reaction
Authors: Mauritz K. A. , Stefanithis I. D. , Davis S. V. , Scheetz R. W. , Pope R. K. , Wilkes Garth L. , Huang Hao‐Hsin
Published: April 2003

Nanocomposites were produced via sol–gel reactions for tetraethylorthosilicate within the cluster morphology of perfluorosulfonic acid films. Small‐angle x‐ray scattering revealed that the polar/nonpolar nanophase‐separated morphological template persists despite invasion by the silicon oxide phase. Scanning electron microscopy (ESEM–EDAX) studies have indicated that the greatest silicon oxide concentration occurs near the surface and decreases to a minimum in the middle. Optical and ESEM micrographs revealed a brittle, surface‐attached silica layer at high silicon oxide contents. © 1995 John Wiley & Sons, Inc.
A study of the rate of formation of polysulfides of tetramethylthiuram disulfide
Authors: Geyser M. , McGill W. J.
Published: April 2003

The rate of formation of tetramethylthiuram polysulfides (TMTP), that play an important role in vulcanization, was studied. After a short induction period (<30 s), tetramethylthiuram disulfide (TMTD) and TMTD‐sulfur mixes, heated to 130–150°C in the absence of rubber, rapidly form a series of TMTPs. The concentrations of TMTPs of lower sulfur rank increase most rapidly, indicating that sulfur atoms are added to the accelerator sequentially. The incorporation of sulfur molecules to give TMTPs, which subsequently desulfurate, does not occur. Equilibrium concentrations of the various TMTPs are achieved in about 2 min. Little tetramethylthiourea is formed below 200°C. Tetramethylthiuram monosulfide (TMTM) is stable, but TMTM‐sulfur mixes form TMTPs. A mechanism is proposed to account for the large amount of TMTM formed on heating TMTD in the absence of sulfur and the correspondingly higher TMTP concentrations in the presence of sulfur. © 1995 John Wiley Sons, Inc.
Physical properties and dyeability of NaOH‐treated silk fibers
Authors: Freddi Giuliano , Kato Hiroshi , Tsukada Masuhiro , Allara Giulia , Shiozaki Hideki
Published: April 2003

Domestic (Bombyx mori) and wild (tussah, Antheraea pernyi) silk fabrics were treated with diluted NaOH solutions by the pad/batch method. The equillbrium moisture regain of tussah silk fibers increased steadily with alkaline treatment, while that of B. mori did not change. B. mori tensile strenght and elongation at break were slightly impaired. The average molecular orientation and crystallinity of both kinds of silk remained unchanged. Differential scanning calorimetry (DSC) and thermomechanical analysis(TMA) showed that the thermal behavior of B. mori silk was almost unaffected, while that of tussah exhibited slight changes in the temperature range 250–300°C. By dynamic mechanical measurements (DMA) it was elucidated that both storage and loss moduli of B. mori silk fibers decreased following NaOH treatment. On the other hand, tussah silk exhibited a noticeable upward shift of the major loss peak. Alkali‐treated tussah silk fibers, dyed with an acid dyestuff, attained a lower degree of dye‐bath exhaustion. © 1995 John Wiley & Sons, Inc.
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

It 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

The 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

A 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

Heterogeneous 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

An 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

Rheologic 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

Polyaniline/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

Structure–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

Corn 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

The 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

Short 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

The 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

Styrene‐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

A 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

The 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

The 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

Brief 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

Polycondensation 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.
Spectral study of modified polyvinylic alcohol submitted to chemical and heat treatments
Authors: Hubca G. , Tomescu M. , Hillebrand M. , Iovu H.
Published: April 2003

The IR and UV spectra of modified polyvinyl alcohol with the following structure were investigated: (x = 1–3; R = alkyl radical, preferably methyl). The specific absorptions were identified and correlated with the structural changes produced by the chemical and heat treatment of the polymer precursor. © 1995 John Wiley & Sons, Inc.
Light‐scattering and size‐exclusion chromatographic characterization of hydroxyethyl cellulose acetate
Authors: Wu Chi , Siddiq Mohammad , Jiang Suhong , Huang Yong
Published: April 2003

A recently developed analytical method of combining off‐line laser light scattering (LLS) and size exclusion chromatography (SEC) was used to investigate a set of moderately distributed hydroxyethyl cellulose acetate (HECA) samples in tetrahydrofuran (THF) at room temperature. Our results have shown that this new LLS + SEC method is suitable for the characterization of molecular weight distribution of HECA. By using this method, we have simultaneously determined two calibrations of V (cm3) = 45.3 − 1.89 log (M) and D (cm2/s) = 2.45 × 10−4 M−0.60, where M is the molecular weight of HECA; V, the elution volume in SEC; and D, the translational diffusion coefficient in dynamic LLS. In addition, our results have also indicated that the chain conformation of HECA in THF at room temperature is a slightly extended linear coil. © 1995 John Wiley & Sons, Inc.
Modeling of poly(phenylene oxide) reactors
Authors: Misra M. , Gupta Santosh K.
Published: April 2003

A simple model is presented for the polymerization of poly(phenylene oxide) (PPO) in the presence of mass‐transfer limitations. The mass balance and moment equations for this system compose a hierarchy of infinite ordinary differential equations. Closure conditions similar to those used for nylon 6 are used to truncate the set of moment equations. The rate constants are adjusted to achieve a reasonable fit between model predictions and one set of available experimental data on the variation of the number‐average chain length (μn) with time. The monomer conversion and the polydispersity index (PDI) are predicted. The PDI of the entire macromolecular species is found to very with time in an interesting manner (a decrease is predicted with time during certain periods). This is due to the effect of mixing of two sets of macromolecular species present in the reaction mass having different concentrations, as well as different individual values of μn and PDI. Sensitivity results are reported to identify the important parameters and operating conditions. It is found that the values of μn are very sensitive to even small changes in the operating conditions which decrease the mass‐transfer rates. © 1995 John Wiley & Sons, Inc.
Modification of polyamide fibers (PA6) by grafting polyacrylamide (PAM)
Authors: Bucheñska Jadwiga
Published: April 2003

The grafting of polyacrylamide (PAM) onto PA6 knitted fabric in aqueous systems under the atmosphere of nitrogen or air was examined. The grafting process was initiated by oxidation with air oxygen, forming hydroperoxide groups. Effects of time and temperature of oxidation and of the grafting conditions, such as concentration of monomer, temperature, and time, on the rate and degree of grafting were determined. The optimum grafting conditions, ensuring the minimum amount of homopolymer, were found (oxidation temperature 413 K, oxidation time 10 min, grafting temperature under nitrogen 353–373 K, grafting time 1 h, monomer concentration 0.7 mol/dm3). The activation energy of the grafting under nitrogen and air at 313–373 K was found to be 25.74 and 42.25 kJ/mol, respectively. The hydroscopicity, capillarity, disperse dye absorption, and electrical resistance of the modified PA‐6 fabrics were determined. Some improvement of these properties was observed, depending on the degree of PAM grafting and the type of posttreatment with hydrazine and 3‐bromopropionic acid. © 1995 John Wiley & Sons, Inc.
Synthesis and processing of PMR‐15/LaRC‐TPI semi‐IPN systems
Authors: Tai H. J. , Jang B. Z. , Wang J. B.
Published: April 2003

To improve the fracture toughness of PMR‐15 polyimide and to alleviate its high susceptibility to microcracking induced by thermal cycling, a thermoplastic polyimide, LARC‐TPI, was incorporated to form a sequential semi‐interpenetrating polymer network (semi‐2 IPN). The imidization kinetics of LARC‐TPI in the semi‐IPNs were studied using a thermal gravimetric analyzer. Both the solvent and the glass transition temperature of the semi‐IPN were found to have significant effects on the imidization kinetics. The kinetics could be modeled by a two‐step reaction: the first step being a second‐order reaction followed by a second step, which is a first‐order diffusion‐controlled reaction. Differential scanning calorimetry was chosen to investigate the curing of PMR‐15 and PMR‐15/LARC‐TPI semi‐IPNs. The curing process was well correlated by a first‐order reaction kinetics, which suggested that the reverse Diels‐Alder reaction of the Norbornene end group was the rate controlling step. The glass transition temperatures of these semi‐IPNs were again found to play important an important role in dictating the curing kinetics. A higher proportion of LARC‐TPI or a higher glass transition temperature of the semi‐IPN prepolymer tended to result in a slower curing reaction. The optimum molding cycle of PMR‐15 and PMR‐15/LARC‐TPI semi‐IPNs were then determined from the obtained kinetics. © 1995 John Wiley & Sons, Inc.
High‐pressure viscosity and density of polyethylene solutions in n‐pentane
Authors: Kiran Erdogan , Gokmenoglu Zeliha
Published: April 2003

Viscosity and density of homogeneous one‐phase solutions (1 wt %) of polyethylenes with narrow molecular weight distributions (Mw = 2150, 15,520, 108,000, and 420,000) in n‐pentane were determined at 398, 413, and 428 K over a pressure range from 20 to 60 MPa. Measurements were done with a special falling cylinder type viscometer that permits simultaneous determination of viscosity, density, and phase state of the solutions. It is shown that the viscosities of these solutions can be correlated with density (p) using the exponential relationships μ − A exp {B/(1 − Voρ)} or μ = C1 exp (C2ρ), which are based on free‐volume considerations. Analysis of the temperature dependence of viscosity at fixed pressures, and its pressure dependence at fixed temperatures show that the flow‐activation energies for these solutions are in the range 8–12 kJ/mol, and the apparent activation volumes are in the range 30–45 cm3/mol. Evaluation of the specific viscosity and analysis of the molecular weight dependence of intrinsic viscosity in accordance with Mark–Houwink type relationship μ = KMa suggest a value of 0.5 for the exponent a, which is typical of poor or theta solvents. © 1995 John Wiley & Sons, Inc.
EGF‐dependent and independent activation of MAP kinase during Drosophila oogenesis
Authors: Dammai Vincent , Hsu Tien
Published: April 2003

Receptor tyrosine kinase (RTK) signaling is involved in multiple cell fate determination during Drosophila oogenesis. To address the problem of signaling specificity, we sought to systematically document the expression pattern of activated MAP kinase, the downstream effector of RTK signaling. We show that MAP kinase is activated in some of the cell types in which Drosophila EGF receptor signaling is known to function. MAP kinase activation is also associated with many cell migration events. Finally, MAP kinase is activated by heat stress without altering follicle cell fates. The implications of these findings are discussed. Anat Rec Part A 272A:377–382, 2003. © 2003 Wiley‐Liss, Inc.
Effect of lifetime lactation on breast cancer risk: A Korean Women's Cohort Study
Authors: Lee Soon Young , Kim Miyong T. , Kim Seon Woo , Song Mi Sook , Yoon Soo Jin
Published: April 2003

The objective of our study was to examine the effect of lifetime lactation on breast cancer risk among premenopausal women. The data were from a prospective cohort study with a follow‐up period of 6 years in Korea (1995–2000). The cohort was composed of 110,604 premenopausal parous Korean women, aged 20 years and older, who received health insurance from the Korea Medical Insurance Corporation and who had medical evaluations in 1992 and 1994. Multivariate Cox proportional hazard models were tested, controlling for age, age at menarche, number of children, age at first pregnancy, oral contraceptive use, smoking, exercise and obesity. At baseline, 57,440 (51.9%) reported breastfeeding and 4,584 (4.1%) reported breastfeeding more than 24 months. From 1995–2000, 360 incident cases of breast cancer (61.8/100,000 person‐years) occurred. Compared to parous women who had no history of lactation, a period of lactation of 13–24 months decreased the risk of breast cancer (RR, 0.7; 95% CI, 0.5–1.1), and this risk was decreased even further for those who breastfed for more than 24 months (RR, 0.6; 95% CI, 0.3–1.0). There was a clear trend of decreasing breast cancer risk with the duration of lactation (p for trend <0.001). In conclusion, our study of a large Korean cohort provides additional empirical evidence to current theoretical conjecture that lactation decreases the risk of breast cancer among premenopausal women. © 2003 Wiley‐Liss, Inc.
RhoA and lysophosphatidic acid are involved in the actin cytoskeleton reorganization of astrocytes exposed to ethanol
Authors: Guasch R.M. , Tomas M. , Miñambres R. , Valles S. , Renau‐Piqueras J. , Guerri C.
Published: April 2003

Astroglial cells play an important role in maintaining neuronal function in the adult and in the developing nervous system. Ethanol exposure induces profound alterations in the astrogliogenesis process, affecting important cell functions, including intracellular protein trafficking. Because the actin cytoskeleton plays a crucial role in intracellular protein transport, the aim of the present study was to analyze the effects of ethanol on actin cytoskeleton organization and the involvement of the RhoA signaling pathway in these effects. We show that RhoA and lysophosphatidic acid (LPA), an upstream activator of RhoA, stimulate the formation of stress fibers and focal adhesion in cortical astrocytes in primary culture. Exposure of cultured astrocytes to different concentrations of ethanol profoundly disorganizes the actin cytoskeleton, leading to the formation of actin rings at the cell periphery and decreasing the content of focal adhesion proteins. Furthermore, LPA treatment or RhoA transfection revert the ethanol‐induced actin alterations in astrocytes, whereas transfection with an inactive mutant of RhoA is unable to revert the actin ring organization. In addition, inhibition of endogenous RhoA by C3 exoenzyme effectively blocks ethanol‐induced actin ring formation. These results suggest that the effects of alcohol on actin cytoskeleton organization are mediated by the RhoA signaling pathway. Disruptions in actin organization may impair important astrocyte functions, participating in ethanol‐induced astroglial and brain damage during development. © 2003 Wiley‐Liss, Inc.
Kinetics of the reaction of O3with selected benzenediols
Authors: Tomas Alexandre , Olariu Romeo I. , Barnes Ian , Becker Karl H.
Published: April 2003

The kinetics of the reaction of O3with the aromatic vicinal diols 1,2‐benzenediol, 3‐methyl‐1,2‐benzenediol, and 4‐methyl‐1,2‐benzenediol have been investigated using a relative rate technique. The rate coefficients were determined in a 1080‐L smog chamber at 298 K and 1 atm total pressure of synthetic air using propene and 1,3‐butadiene as reference compounds. The following O3reaction rate coefficients (in units of cm3molecule−1s−1) have been obtained:k(1,2‐benzenediol) = (9.60 ± 1.12) × 10−18,k(3‐methyl‐1,2‐benzenediol) = (2.81 ± 0.23) × 10−17,k(4‐methyl‐1,2‐benzenediol) = (2.63 ± 0.34) × 10−17. Absolute measurements of the O3rate coefficient have also been carried out by measuring the decay of the dihydroxy compound in an excess of O3. The results from these experiments are in good agreement with the relative determinations. Atmospheric implications are discussed. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 223–230, 2003
Über die einwirkung von hexamethylendiisocyanat auf benzolincludierte zellwolle
Authors: Krässig von H.
Published: April 2003

Cellulose eines Zellwollgewebes kann nach Verdrängung des Wassers durch Inclusion mit Benzol mit Hexamethylendiisocyanat umgesetzt werden. Die Zellwolle hatte nach der Behandlung einen Stickstoffgehalt von bis zu 3,5%, was einem Verhältnis von 4 Molen C6H10O5 zu 1 Mol Diisocyanat entspricht. Der Quellwert dieser Zellwolle ist auf ca. 50% erniedrigt und die Cellulose in Kupferhydroxyd‐Ammoniak unlöslich. Die Diisocyanat‐vernetzung ist waschfest. Durch Behandlung der mit Diisocyanat vernetzten Gewebe mit 85%iger Ameisensäure und der mit Kaliumbisulfat abgebauten Proben mit 10%iger Natronlauge wird gezeigt, daß das Diisocyanat unter Bildung von Diurethanbrücken mit der Cellulose reagiert.