bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rheological properties of highly swollen hydrogel suspensions
Authors: Budtova T. V. , Budtov V. P. , Navard P. , Frenkel S. Ya. 
Published: April 2003

AbstractThe shear rheology of diluted to concentrated suspensions of weakly cross‐linked sodium polyacrylate hydrogels were investigated by concentric cylinder rheometry. The size of the swollen gel particles is dependent on the initial size of the dry particle and on the nature of the added salt. Polyvalent salts are more efficient for contracting the swollen particles than monovalent ones. When suspended in water or in monovalent salt solutions, the viscosity at low concentrations shows a behaviour very similar to the one of flexible polymer solutions. Below the critical overlap concentration, the viscosity is independent of shear rate. The intrinsic viscosity is very large, on the order of 10–15 dL/g. This is in agreement with the large size of these swollen particles. Suspensions of such swollen gel particles are thus a good model for extremely high molecular weight polymer solutions. In polyvalent salt solutions different behaviour of the viscosity curves versus concentration was observed. This effect is caused by chemical cross‐linking of the hydrogel by polyvalent ions. © 1994 John Wiley & Sons, Inc.
Kinetics and reaction mechanism of fenton's‐reagent‐initiated graft copolymerization of acrylonitrile onto sodium alginate
Authors: Shah S. B. , Patel C. P. , Trivedi H. C. 
Published: April 2003

AbstractThe kinetics and mechanism of grafting of acrylonitrile (AN) onto sodium alginate (SA) using Fenton's reagent (Fe2+–H2O2) has been studied. The experimental results are found to be in good agreement with the proposed kinetic scheme. © 1994 John Wiley & Sons, Inc.
Simultaneous measurement of water diffusion, swelling, and calcium carbonate removal in a latex paint using FTIR–ATR
Authors: Balik C. M. , Xu J. R. 
Published: April 2003

AbstractAn in‐situ FTIR–ATR method has been used to monitor the sorption processes of water and pH 1.3‐sulfurous acid in two latex paints and the base polymer common to both. The sorption kinetics could not be described by a simple Fickian model. The spectra also showed evidence of polymer swelling, which was confirmed in separate swelling measurements. Anomalous behavior was noted for the latex paint containing CaCO3 when exposed to sulfurous acid. The amount of water sorbed by this sample went through a maximum, then decreased to a constant level. This was accompanied by similar variations in the degree of swelling of the sample. These changes are explained by the rapid loss of CaCO3 from this particular paint upon exposure to acidic solutions, followed by structural rearrangement to fill in the voids left by the CaCO3 particles. © 1994 John Wiley & Sons, Inc.
A generalized model to predict the viscosity of solutions with suspended particles. IV. Determination of optimum particle‐by‐particle volume fractions
Authors: Sudduth Richard D. 
Published: April 2003

AbstractA new approach has been introduced to establish the optimum composition for all particles within a mixture or suspension to achieve the optimum packing fraction, φn, and/or the minimum viscosity, η. The derivation to obtain the optimum particle volume fraction assumed that a previously developed optimum composition for binary particles applied to any two particle volumes Vi and Vj in the mixture. The composition of the maximum packing fraction for a mixture of more than two particles was then assumed to be calculable from the optimized relationship of each separate binary pair of particle volumes Vi and Vi in the mixture. This derived equation was successfully shown to predict the optimum particle‐to‐particle composition of McGeary's experimentally measured binary, tertiary, and quaternary mixtures. The difference between the calculated and measured volume fractions was no greater than 3.85% and, in most instances, was significantly less than 3.85%. The maximum packing fractions, φn, determined experimentally by McGeary, were also successfully predicted to better than 3.26%. Theoretical particle‐to‐particle volume fractions evaluated for an example pressure‐agglomerated latex appeared to predict the particle‐size distribution only within a narrow range of particle sizes. However, when the theoretical and experimental results were evaluated as a function of the number of particles for each particle diameter, it was apparent that the agglomerated distribution closely approximated the theoretical optimum distribution above 600 Å. Agreement with theory below 600 Å was unsatisfactory. The decrease in viscosity of the example agglomerated latex appeared to have been enhanced as the optimum theoretical particle‐size distribution was approached. © 1994 John Wiley & Sons, Inc.
Fracture toughness and morphology of phenolphthalein poly(ether sulfone)–thermotropic liquid crystalline polymer blends
Authors: Yang Yuming , Yin Jinghua , Li Binyao , Zhuang Guoqing , Li Gang 
Published: April 2003

AbstractBlends of a new phenolphthalein poly(ether sulfone) (PES‐C) and a thermotropic liquid crystalline polymer (LCP) were prepared by melt‐blending in a twin‐screw extruder. Rheological properties, fracture toughness, KIC, and morphology of the blends were studied. It was found that the addition of LCP could reduce the melting viscosity and improve the fracture toughness of the PES‐C matrix. The morphology of the LCP phase for the fractured section changed with increasing LCP content in the blend from dropletlike to fibrillar and layered structure. Strong interfacial adhesion could be observed at a lower content of LCP. The toughening mechanisms by blending LCP were also discussed. © 1994 John Wiley & Sons, Inc.
Compostability of cellulose acetate films
Authors: Gardner Robert M. , Buchanan Charles M. , Komarek Ron , Dorschel Debbie , Boggs Christy , White Alan W. 
Published: April 2003

AbstractComposting is an accelerated biological decay process viewed by many to be a potential solution to the solid‐waste management crisis existing in many parts of the world. As part of a program to develop environmentally nonpersistent polymers that are compatible with a composting environment, we have developed a bench‐scale compost methodology that emulates a high efficiency municipal windrow composting operation. A series of cellulose acetate films, differing in degree of substitution, were evaluated in this bench‐scale system. In addition, commercially available biodegradable polymers such as poly(hydroxybutyrate‐co‐valerate) (PHBV) and polycaprolactone (PCL) were included as points of reference. Based on film disintegration and on film weight loss, cellulose acetates, having degrees of substitution less than approximately 2.20, compost at rates comparable to that of PHBV. NMR and GPC analyses of composted films indicate that low molecular weight fractions are removed preferentially from the more highly substituted and slower degrading cellulose acetates. © 1994 John Wiley & Sons, Inc.
Miscibility in blends of sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(p‐bromostyrene‐co‐o‐bromostyrene)
Authors: Vuković Radivoje , Bogdanić Grozdana , Kurešević Vjera , Srića Vlasta , Karasz Frank E. , MacKnight William J. 
Published: April 2003

AbstractMiscibility in blends of random copolymers of p‐bromostyrene (pBrSt) and o‐bromostyrene (oBrSt) [P(pBrSt‐co‐oBrSt)] with partially sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SPPO) have been studied by differential scanning calorimetry (DSC). For an SPPO of given degree of sulfonylation, a miscibility window in terms of the isomeric composition of the brominated copolymer was seen; the location and width of the window was a function of sulfonylation. In general, copolymers with a higher content of pBrSt exhibit miscibility with SPPOs with higher degrees of sulfonylation. Upon annealing to temperatures of 280° and 320°C, only small changes in the miscibility regime were observed. The miscibility behavior was analyzed on the basis of the mean‐field theory in terms of the individual segmental interaction parameters. © 1994 John Wiley & Sons, Inc.
Effects of processing parameters and molecular weight distribution on the tensile properties of polypropylene fibers
Authors: Andreassen Erik , Myhre Ole Jan , Hinrichsen Einar L. , Grøstad Kristin 
Published: April 2003

AbstractThe tensile properties of polypropylene fibers, produced in a short‐spin line, are correlated with the parameters of the three processing stages (spinning, drawing, and annealing), and with the molecular weight distribution. In general, tensile stiffness and strength increase with increasing molecular orientation, while the elongation at break decreases. The degree of orientation is determined by the deformation ratios and temperatures of the first two stages. Tensil modulus and strength also increase with increasing annealing stage shrinkage ratio. All the tensile properties, including the elongation at break, increase with increasing average molecular weight. The mechanisms of crystallization and deformation are related to the molecular weight distribution in different ways. Hence, the tensile modulus is highest for broad distributions when the draw ratio is low, and for narrow distributions when the draw ratio is high. The tensile strength increases and the elongation at break decreases as the width of the molecular weight distribution decreases, for all combinations of processing parameters. The distribution of tensile strength, for fibers with high draw ratios, broadens as the molecular weight distribution narrows. The total draw ratio of fibers, as experienced during processing and testing, and the true stress at break, are discussed in terms of deformation rates and relaxation times. © 1994 John Wiley & Sons, Inc.
ESR studies of molecular motions at the interphase region of a blendlike polymeric material
Authors: Pekcan Önder , Demir Yusuf , Güven Olgun 
Published: April 2003

AbstractThe molecular motions of spin probes at the interphase region of poly(methyl methacrylate) particles sterically stabilized by polyisobutylene (PIB) were studied by ESR spectroscopy. The correlation times (τ) were measured by using the methods of Freed and Kivelson. Activation energies for different modes of motion were calculated at wide temperature range between −140 and 140°C. Viscosities were estimated in methanol saturated PIB channels in the polymer particles. © 1994 John Wiley & Sons, Inc.
Direct electrodeposition of thin‐layer (phenylene–carbazolylene) copolymers
Authors: Aboulkassim A. , Faid̈ K. , Chevrot C. 
Published: April 2003

AbstractThin (phenylene–carbazolylene) copolymer films of controlled composition can be directly deposited onto solid cathodes such as indium tin oxide (ITO) glass or glassy carbon through a dehalogenative polycondensation of 4,4′‐dibromobiphenyl and 3,6‐dibromo‐N‐alkylcarbazole mixtures in the presence of an electrogenerated zero‐valent nickel catalyst. The electrochemical and optical properties of the resulting thin films have been studied. The electrochemical behavior reveals two distinct electronic states that depend on the copolymer composition and structure. The first electronic state is characterized by either only one redox process, attributed to the presence of phenylene‐disubstituted carbazolic units in the case of copolymers with the highest proportion of phenylene, or two successive redox processes, attributed to the occurrence of a radical cation and dication of carbazolic diades, in the case of copolymers with the lowest proportion of phenylene. The second electronic state shows in all cases a single redox system occurring at a higher potential than the first state and due to phenylene moieties in the copolymer. All the electrodeposited copolymer films were found to be reducible in the same manner as pure poly(p‐phenylene). © 1994 John Wiley & Sons, Inc.
Structure and dielectric properties of poly(vinyl chloride) thermoplastic elastomer blends
Authors: Radhakrishnan S. , Saini D. R. 
Published: April 2003

AbstractThe structure, development, morphology, and dielectric relaxation have been investigated in poly(vinyl chloride)–thermoplastic elastomer (copolyester–ether) blends having different compositions. The changes in the intensities of dielectric relaxation peaks for the β and γ processes with respect to blend composition have been found to be associated with corresponding changes in crystalline structure and morphology of the elastomeric component. The critical composition for observing such modification of properties is about 50% of poly(vinyl chloride) above which the blend becomes almost amorphous. © 1994 John Wiley & Sons, Inc.
Rheological behavior and thermal stability of poly(phenylene sulfide)/vectra‐B950 blends
Authors: Valenza A. , La Mantia F. P. , Minkova L. I. , De Petris S. , Paci M. , Magagnini P. L. 
Published: April 2003

AbstractBlends of polyphenylene sulfide (PPS) with a commercial, wholly aromatic, liquid crystalline polymer (LCP), Vectra‐B950, have been prepared by melt‐blending. Their rheological behavior has been studied in order to determine if the LCP displays a processing aid ability, and under what conditions it gives rise to potentially reinforcing fibrils dispersed in the PPS matrix. The problem of the thermal stability of PPS/LCP blends, which has been considered by some authors as the main obstacle to the production of usable materials due to the evolution of gaseous substances during processing, has been discussed. © 1994 John Wiley & Sons, Inc.
Physical modification of polyacrylonitrile precursor fiber: Its effect on mechanical properties
Authors: Wang P. H. , Liu J. , Li R. Y. 
Published: April 2003

AbstractPolyacrylonitrile precursor fiber of a special grade for making carbon fibers was modified by stretching in the prestabilization stage to various extents. The effect of such stretching on tensile properties of the original precursor fiber, intermediate (oxidized) fiber, and resultant carbon fiber prepared through a continuous process was monitored. Improvements in tensile modulus of fibers at various stages were observed with increasing stretch ratios. However, no obvious enhancement of tensile strength of final carbon fibers was found. © 1994 John Wiley & Sons, Inc.
Estimation of sphere‐size distributions in two‐phase polymeric materials from transmission electron microscopy data
Authors: Gleinser W. , Maier D. , Schneider M. , Weese J. , Friedrich Chr. , Honerkamp J. 
Published: April 2003

AbstractThe blending of two immiscible polymer samples can lead to spherical inclusions of one component in a matrix of the other component. The mechanical solid‐state properties as well as the flow behavior of the m+lt depend on the size of the spheres in the blend. For that reason, the sphere‐size distribution is of major interest. Information about this distribution is often obtained by analyzing thin slices of the blend with transmission electron microscopy. In that way, however, the sphere‐size distribution itself is not obtained. The reconstruction of the sphere‐size distribution is introduced as a stereological problem, well known in fields as metallurgy, biology, geology, and medicine. It is shown that the sphere‐size distribution can be reconstructed using a regularization method as implemented in the program FTIKREG. © 1994 John Wiley & Sons, Inc.
Electron‐beam‐initiated grafting of triallyl cyanurate onto polyethylene: Structure and properties
Authors: Chaki Tapan K. , Roy Sanjoy , Despande R. S. , Majali A. B. , Tikku V. K. , Bhowmick Anil K. 
Published: April 2003

AbstractElectron‐beam (EB)‐initiated grafting of triallyl cyanurate (TAC) onto polyethylene (PE) has been carried out over a range of radiation dose (2–20 Mrad) and concentrations of TAC (0.5–3 parts by weight). The grafting level, as determined from IR spectroscopy, is maximum at a 10 Mrad radiation does using 1 part TAC. With increasing TAC level at a 15 Mrad dose, the grafting level is higher only after 1.5 parts TAC. The gel content increases with radiation dose in the initial stages. X‐ray studies indicate two peaks at 10.6–10.8° and 11.7–11.9° and the corresponding interplaner distances of 4.15 and 3.80 Å. With increase in radiation dose or TAC level, the crystallinity decreases in the initial stage and then increases. It shows a decreasing trend again at higher radiation dose. The interplanar distance or the interchain distance of the modified polymer does not change. However, the crystallite size increases initially and then decreases. The tensile properties are relatively insensitive to the variation of radiation dose because of the interplay of various factors. The dielectric loss, tan δ, shows a maximum at a 10 Mrad dose and minimum at 5 and 15 Mrad due to changes of polarity and the carrier mobility. © 1994 John Wiley & Sons, Inc.
Linear polythioesters. XXII. Products of interfacial polycondensation of bis(4‐mercaptomethylphenyl)sulfide with some aliphatic and isomeric phthaloyl dichlorides
Authors: Podkościelny Wawrzyniec , Rudż Wiesław 
Published: April 2003

AbstractNew polythioesters were obtained by interfacial polycondensation of bis(4‐mercaptomethylphenyl) sulfide with some aliphatic and isomeric phthaloyl dichlorides. To determine optimal conditions for polycondensation, the polythioester from bis(4‐mercaptomethylphenyl) sulfide and sebacoyl dichloride was chosen as a model system. The influence of some factors on the reduced viscosity and the yield were studied. Polythioesters from aliphatic and isomeric phthaloyl dichlorides were prepared under the same optimal conditions as those established for the reaction of the dithiol with sebacoyl dichloride. The structure of all polythioesters was determined by elementary, infrared spectra, and X‐ray analysis. Initial decomposition temperature and maximum rate of decomposition temperature were defined from the curves of thermogravimetric analysis. Some physicochemical, mechanical, and electrical properties have been determined. © 1994 John Wiley & Sons, Inc.
Photodegradation of polyethylene films formulated with a titanium‐based photosensitizer and titanium dioxide pigment
Authors: Angulo‐Sanchez J. L. , Ortega‐Ortiz H. , Sanchez‐Valdes S. 
Published: April 2003

AbstractThis work reports on the photodegradation of low‐density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow‐extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
Graft copolymers of methy methacrylate onto canna starch using manganic pyrophosphate as an initiator
Authors: Gao Jian‐Ping , Tian Ru‐Chuan , Yu Jiu‐Gao , Duan Meng‐Lin 
Published: April 2003

AbstractIn this article, the graft copolymerization of methy methacrylate with canna‐starch under the initiating of manganic pyrophosphate was investigated systemly. It was found that the percentage of grafting, grafting efficiency, and rate of grafting were all dependent, to some extent, on the concentration of the initiator, monomer and starch, as well as reaction time and temperature. The rate equation of graft copolymerization established from the experimental results was similar to the equation derived from the reaction mechanism. The graft copolymer was investigated with an infered spectroscope, scanning electron microscope, and x‐diffraction methods. © 1994 John Wiley & Sons, Inc.
Graft copolymerization of 2‐hydroxyethylmethacrylate onto chitosan films and their blood compatibility
Authors: Singh D. K. , Ray Alok R. 
Published: April 2003

AbstractThis article examines the blood compatibility of chitosan grafted with 2‐hydroxyethyl‐methacrylate (HEMA) using 60Co gamma radiation. The effect of various syntheses conditions on the grafting was determined. The solvent composition has a marked effect on the degree of grafting. Maximum yield was obtained in an equivolume mixture of a water–methanol system. The percent grafting increased with the increase in the monomer concentration up to 20 vol % in a total dose of 0.216 Mrad. The percent grafting was found to be higher at a lower dose rate for a constant total dose of 0.216 Mrad. The swelling of grafted chitosan films decreased on increasing graft level. The grafted copolymers showed improved blood compatibility as compared to original chitosan sample. © 1994 John Wiley & Sons, Inc.
Kinetics of crazing in polybutadiene/polystyrene blends
Authors: Spiegelberg Stephen H. , Argon Ali S. , Cohen Robert E. 
Published: April 2003

AbstractThe crazing behavior of blends of polystyrene (PS) and a low molecular weight polybutadiene (PB) was examined as part of a continuing study of toughening mechanisms in thermoplastic polymers. These PS/PB blends attain high levels of toughness from the stress‐activated plasticizing action of the polybutadiene (PB), a mechanism that is active only in the region of a growing craze. The plasticization is therefore localized and leads to enhanced toughness without loss in stiffness. The net result of this plasticization is a reduction in craze flow stress accompanied by an increase in craze velocity, which, in turn, allows the specimen to reach substantial strains‐to‐fracture in uniaxial deformation under an imposed strain rate. The ability of the PB to plasticize a growing craze is expected to be a function of the mobility of the PB. To investigate the role of diluent mobility, tensile tests and craze velocity measurements were conducted at −20°C and compared with previously published results collected at 23°C. Although the blends displayed high levels of toughness at 23°C, the blends tested at −20°C showed brittle behavior. Craze velocities measured at −20°C were 2 orders of magnitude lower than the results at 23°C. Addition of 3 wt % PB at −20°C led to craze velocities only as large as those found in pure PS at 23°C. Comparison of the craze velocities with an asymptotic theoretical model describing the dependence of the craze velocity on the PB content showed good agreement with the results at −20°C and only fair agreement with the room‐temperature results. © 1994 John Wiley & Sons, Inc.
Polymerization of acrylonitrile using magnetron deposition technique
Authors: Shirodkar V. S. , Jathar R. T. , Bapat A. M. , Kulkarni S. D. , Bhat N. V. 
Published: April 2003

AbstractPolymerization of acrylonitrile (PAN) in a capacitively coupled glow discharge under magnetic enhancement was studied. The design aspects of a magnetron electrode and its characteristics are described. The study suggests that an improved magnetron design helps in achieving a higher monomer conversion ratio that improves the quality of films and allows the use of lower system pressure. Thin, uniform, pinhole free films of PAN having very high molecular weight were formed. © 1994 John Wiley & Sons, Inc.