bluuebunny/crossref_metadata_2025_split huggingface dataset:
Manufacture and physical properties of alginate fiber papers as an analysis model of cellulosic fiber papers
Authors: Kobayashi Yoshinari , Matsuo Ryûkichi , Kawakatsú Hironobu 
Published: April 2003

AbstractThe staple fibers of Ca alginate or alginic acid were found to have interfiber self‐bonding, which allowed us to make papers composed of fibers with homogeneous fiber diameter and fiber length without binders. The analysis of the effect of the molecular weight (MW) and fiber diameter on physical properties of the sheets showed that strength factors, except zero span breaking length and tear index, increased with increase of MW of alginic acid up to 6 × 105 dalton. The folding endurance was the most sensitive to MW, requiring a MW of 5 × 105 dalton or higher to reach the level of 10 folds. The breaking length of alginate fiber papers ranged from 2.0 to 3.5 km and was higher than that of the corresponding free acid fiber sheets. Investigation of the effect of fiber length indicated that the folding endurance increased almost linearly with increase in fiber length but that the breaking length and tear index were maximum at a fiber length of 3.0 mm, suggesting that these factors were mainly influenced by sheet formation. The paper formability of the metallic salts of alginate fiber was as follows: Ca2+ > Ba2+ > Al3+ > > Fe3+. The admixture of acidic polysaccharides, such as pectin and κ ‐carrageenan with Na alginate, also made it possible to spin continuous yarn. Papers obtained from the admixed fibers had higher bulk density and Young's modulus by 1.5–1.8 times and were very transparent, just like glassine paper. X‐ray microanalysis showed that the Ca alginate fiber had no skin‐core structure, homogeneously distributing Ca2+ in whole fiber.
Heterogeneous styrene–divinylbenzene copolymers in collapsed and reexpanded states
Authors: Okay O. , Balkaş T. I. 
Published: April 2003

AbstractThe pore structure of styrene–divinylbenzene (DVB) copolymers formed by phase separation before or after gelation was compared using apparent densities and mercury porosimetry. The copolymers were prepared with di‐2‐ethylhexyl phthalate (DOP) as diluent. The pore structure of copolymers formed in homogeneous gelation can collapse upon drying in the rubbery state. The collapsed pores have a mean diameter of about 100–200 Å corresponding to the interstices between the microspheres. The collapsed microspheres reexpand again during the sulfonation or chloromethylation reactions, or during the solvent exchange. The pore structure of styrene–DVB networks formed in heterogeneous gelation do not collapse on drying in the swollen state, this being a stable and permanent porosity. The critical crosslink density for transition from homogeneous to the heterogeneous gelation represents a borderline between stable and unstable porosity. The drastical change of swelling and porosity values at the critical crosslink density is due to the collapse of unstable pores.
Polybutadiene hydroperoxide by singlet oxygen: Its grafting and morphology in polystyrene matrix
Authors: Peng F. M. 
Published: April 2003

AbstractSinglet oxygen was used to synthesize hydroperoxide functional groups onto a polybutadiene. These hydroperoxides served as grafting sites for the preparation of polybutadiene‐modified polystyrene by a bulk polymerization process. As anticipated, the dispersed polybutadiene droplet size decreased as the level of hydroperoxidation increased. Various types of morphology, similar to those of butadiene–styrene diblock and styrene–butadiene–styrene triblock copolymer systems, were obtained. Furthermore, at an extremely high level of hydroperoxidation, a unique reticular structure of polybutadiene was developed.
Effect of radiation chemical treatment on sisal fibers I. Radiation induced grafting of ethyl acrylate
Authors: Zahran A. H. , Zohdy M. H. 
Published: April 2003

AbstractRadiation induced graft copolymerization of ethyl acrylate onto sisal fibers was investigated. It was fond that the percent added‐on of ethyl acrylate to sisal fibers was prohibitively low when using the direct grafting method due to excessive hompolymerization. The preirradiation method was found to be invalid for improving the grafting content. In the presence of small amounts of styrene (St) the copolymerization can be achieved with little homopolymer formation by the direct grafting technique. The presence of sulfuric acid in the grafting solution enhances the grafting of styrene–ethyl acrylate comonomer to sisal fibers. the effect of different solvents, monomer concentration, and irradiation doses were followed. Sisal fibers were treated with sodium hydroxide, sulfuric acid, and combined treatment of both of them. The effect of these treatments on the grafting content was investigated. The grafting yield decreased when sisal fibers were subjected to alkali treatment under tension. However, sisal fibers pretreated with 0.4N sulfuric acid showed a slight increase in the grafting yield over the untreated samples.
Invariant kinetic parameters of polymer thermolysis. I. Oxidative degradation of flame‐retardant polyesters
Authors: Lesnikovich A. I. , Levchik S. V. , Levchik G. F. 
Published: April 2003

AbstractThe paper gives an analysis of the data reported by J. D. Cooney and others. [J. Appl. Polym. Sci., 29, 911 (1984)] on the kinetics of oxidative degradation of flame‐retardant polyesters [poly(ethylene terephthalate)]. A linear correlation is shown to exist between the parameters of the kinetic compensation effect. A formal interpretation of the correlation is given as well as its interpretation within two alternative polyester degradation schemes. The above correlation allowed the invariant kinetic parameters of the process log Â = 15.7±1.3;Ê = 183±16 (min−1; kJ/mol) to be estimated, which seem to characterize the destruction of the polyester bond in the presence of oxygen. It is shown that Â and Ê may be used to characterize the kinetics of polyester oxidative degradation during combustion, while the compensation parameter T̂; may characterize the flame‐retardant effect.
Effects of mechanical drawing on gas transport in an emulsion acrylic multipolymer
Authors: El‐Hibri M. J. , Paul D. R. 
Published: April 2003

AbstractA study was conducted on the gas sorption and transport properties of a multiphase commercial acrylic polymer trade‐named Korad ACV before and after subjecting the polymer to mechanical drawing operations. The Korad system is an emulsion‐polymerized amorphous composite comprised of a glassy, predominantly PMMA matrix phase and a ply(butyl acrylate)‐dispersed phase surrounded by a PMMA/PBA copolymer shell. Large increases (up to eightfold) in permeabilityPto several gases were observed upon drawing Korad. The observed changes in the permeability to He, Ar, N2, and CH4on drawing were correlated with the draw ratio, drawing temperature, and molecular diameter of the gas penetrant. Most of the increase in permeability occurred at low draw ratios (1–2). The increases inPwere most dramatic for drawing temperatures below or near theTgof the matrix phase (about 90°C) and were quite small for drawing temperatures 30°C or more above the matrixTg. The extent of the permeability increase also depended on the gas, being greatest for CH4and essentially imperceptible for He. The changes in permeability behavior were interpreted in terms of a morphological transformation in the phase of the drawn Korad, which causes the originally dispersed rubber particles to assume a more continuous character. The behavior of the composite was modeled by the Takayanagi and Nielson treatments of two‐phase composite systems. Volumetric, thermal, mechanical, and viscoelastic properties were measured for the as‐received and processed Korad films to elucidate physical changes in the drawn polymer.
The concept of solid solvent as a processing aid
Authors: Chung Chan I. 
Published: April 2003

AbstractThe concept of solid solvent entails the use of low‐molecular weight crystalline materials (LMC) as a processing aid. A LMC as an ideal solid solvent mixed into a polymer is expected to become a solvent for the polymer at high processing temperatures, reducing the melt viscosity and thus enhancing the processability, but to become a nonsolvent for the polymer at low use temperatures precipitating out of the polymer without adversely affecting the properties of the polymer. The feasibility of such a concept was examined using acetanilide as a potential solid solvent for polystyrene (PS) and two ABA‐type block copolymers containing PS end blocks. Acetanilide demonstrated the essential features required of a solid solvent supporting the concept of solid solvent. It had a high solubility in PS at high temperatures very effectively reducing the melt viscosity of PS and the block copolymers, and it precipitated out of PS at low temperatures although it had an undesirably high residual solubility. The concept of solid solvent appears to be a viable one.
The effect of some catalysts on the curing of oxiranes with p‐phenylenediamine
Authors: Kishore K. , Joseph Mary , Dharumaraj Verghese , Vijayshree M. N. 
Published: April 2003

AbstractThe effect of some alcohols, acetylacetonates of transition metals, and manganese stearate and naphthenate on the curing reaction of a diglycidyl ether of ether of bisphenol‐A with p‐phenylenediamine is studied. Maximum catalytic activity is shown by the manganese compounds and triethanolamine.
Polymerization of olefins through heterogeneous catalysis. III. Polymer particle modelling with an analysis of intraparticle heat and mass transfer effects
Authors: Floyd S. , Choi K. Y. , Taylor T. W. , Ray W. H. 
Published: April 2003

AbstractPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. Intraparticle heat and mass transfer effects are investigated for a range of catalyst activities. For slurry polymerization, intraparticle mass transfer effects may be significant at both the macroparticle and microparticle level; however, for normal gas phase polymerization, microparticle mass transfer effects appear more likely to be important. Intraparticle temperature gradients would appear to be negligible under most normal operating conditions.
A kinetic scheme for an amine‐epoxy reaction with simultaneous etherification
Authors: Riccardi Carmen C. , Williams Roberto J. J. 
Published: April 2003

AbstractThe curing reaction of an epoxy resin with a diamine is analyzed, taking into account the possibility of simultaneous etherification. A kinetic scheme is derived and fitted to experimental results for the reaction of commercial bisphenol A diglycidyl ether (BADGE) with diaminodiphenyl sulfone (DDS). Total reaction heat, vitrification curve, and reactivity ratio of secondary to primary amine hydrogens are experimentally characterized. It is shown that the etherification reaction is significant at T > 150°C, at intermediate and high reaction extents when the primary amine has been sufficiently depleted.
Elastomer solvent interactions III‐effects of methanol mixtures on fluorocarbon elastomers
Authors: Myers Mark E. , Abu‐Isa Ismat A. 
Published: April 2003

AbstractFluorocarbon elastomers exhibit high volume swell in methanol, but not in ethanol or other alcohols. Proton nuclear magnetic resonance (NMR) data indicate that neat methanol exists as a hydrogen‐bonded tetramer with a solubility parameter close to that of the fluorocarbon elastomer, thus causing the high swell. The NMR and volume swell data show further correlations: Increased temperature or dilution of methanol with nonpolar solvents or water breaks down the hydrogen‐bonded structure and reduces the volume swell. Mixtures of methanol and ethanol form mixed tetramer species. In this case the volume swell can be predicted by statistical theory which indicates that an all‐methanol tetramer and a tetramer containing one ethanol molecule are the only swelling species. Similarly, a tetramer singly substituted with butanol is too bulky to swell the elastomer. Thus the molecular structure of methanol and its mixtures as determined by NMR provides an explanation for the swelling of fluorocarbon elastomers in these environments.
The effect of precipitation on the molecular weight distribution of cellulose tricarbanilate
Authors: Wood Barry F. , Conner Anthony H. , Hill Charles G. 
Published: April 2003

AbstractThe effect of precipitation on the molecular weight distributions of cellulose tricarbanilate (CTC) samples prepared from α‐pulp, hydrolyzed α‐pulp, and Avicel was determined using size exclusion chromatography (SEC). Precipitation of the CTC samples in methanol resulted in the loss of a low molecular weight fraction accounting for 26% of the weight of the hydrolyzed α‐pulp, 20% of the Avicel, and 5% of the α‐pulp. Precipitation in a methanol/water mixture resulted in less fractionation; in this case, however, the reaction byproducts were also precipitated. These results indicate that the molecular weight distribution of precipitated CTC may not accurately reflect the molecular weight distribution of the original cellulose. SEC analysis of the nonvolatile products from the carbanilation reaction offers a simple method for determining the complete molecular weight distribution of this cellulose derivative.
Effect of sequence distribution of poly(vinyl alcohol‐vinyl acetate) on the coloring reaction with iodine
Authors: Hirai Toshihiro , Okazaki Akira , Hayashi Sadao 
Published: April 2003

AbstractRed complex formation between poly(vinyl alcohol‐vinyl acetate) with iodine was investigated from the standpoint of its application as a measure of sequence distribution in the copolymer. Defining a parameter Y which means a ratio of the bound triiodide ion to the VAc unit in a copolymer, we could relate the Y value to the sequence probabilities. Sequence probabilities have also been evaluated by differential thermal analysis. Comparing the probabilities obtained from both methods, the iodine complexation method is concluded to be a complementary method with thermal analysis, that is, the iodine complexation method is applicable to the VAc unit‐rich copolymers, in which the melting point cannot be measured by the thermal analysis.
Molecular weight distribution of polyphenylene sulfide by high temperature gel permeation chromatography
Authors: Stacy Carl J. 
Published: April 2003

AbstractPoly(phenylene sulfide) (PPS) has been characterized using a novel high temperature gel permeation chromatograph (GPC). Samples were injected in slurry form at ambient temperature, and redissolved by an in‐line precolumn heater at 250°C. A viscometer consisting of a capillary tube with inlet and outlet taps connected to a sensitive differential pressure transducer was used as sole detector, with deflections converted to concentration using the column calibration. Columns and viscometer were operated at 210°C. Universal calibration was carried out using intrinsic viscosity/molecular weight relations for polystyrene and PPS, determined by light scattering. Satisfactory operation was confirmed by agreement between intrinsic viscosity calculated from GPC with independently measured values, and comparisons with melt flow data. Samples of PPS tested were found to be of relatively narrow distribution, with Mw/Mn typically less than two.
Melaminium molybdate smoke and fire retarders for poly(vinyl chloride)
Authors: Kroenke William J. 
Published: April 2003

AbstractMelaminium molybdates are shown to be very effective smoke and fire retarder additives for PVC. In a simple tin stabilized rigid PVC compound the preferred melaminium β‐octa‐molybdate outperformed MoO3 and other common molybdenum smoke retarders. Combinations of melaminium molybdates with compounds of copper formed very efficient smoke‐reducing and char‐forming synergistic additive systems for PVC. For example, combining the octamolybdate with a series of different copper compounds consistently gave smoke reductions of about 85% in the flaming mode of the NBS Smoke Chamber at a total additive level of 5 parts per hundred parts of PVC. These large reductions in smoke were accompanied by large increases in the amount of char formed and retained as combustion residues.
Effect of the molecular weight of poly(ethylene glycol), used for the surface treatment of calcium carbonate, on the tensile modulus of filled oriented polypropylene
Authors: Mitsuishi Kazuta , Kodama Soji , Kawasaki Hitoshi 
Published: April 2003

AbstractA relation between tensile modulus of oriented polypropylene filled with calcium carbonate, and modified with poly(ethylene glycol) (PEG) or alkyl phenyl ether derivatives (APED) of different molecular weights was investigated. Upon stressing, voids appear in the composites material. For systems prepared with unmodified CaCO3, the void volume increases with an increase of filler content. For systems containing modified CaCO3, the void volume is smaller than the one of the reference material and decreases with an increase of PEG or APED molecular weights (which range from 400 to 4000 for PEG). Moreover, the relative modulus of oriented composites, Edc/Edr, are reasonably accounted by the void volume irrespective of filler content and modifier molecular weight, wherein Edc, Edr are respectively the modulus of oriented composites and the modulus of oriented polymer matrix.
Some water‐soluble copolymers from lignin
Authors: Chen R. L. , Kokta B. V. , Daneault C. , Valade J. L. 
Published: April 2003

AbstractThe utilization of lignin materials would be enhanced if lignin properties could be altered through chemical modification. Towards this end, lignosulfonate, recovered from spent pulping liquors, was grafted with acrylamide or acrylic acid, using redox initiation. Study was made of the effects of some reaction variables (such as reaction medium, lignin/monomer ratio, and initiator concentration) on the copolymerization efficiency and on the copolymer characteristics. Lignosulfonate having bivalent counterions yielded better copolymerization results than that having univalent cations. Aqueous solutions of graft copolymers displayed high viscosities, and exhibited promising stability during storage and against shearing, suggesting the potential use of copolymers as water‐thickening agents.
Stress–strain properties of linear aromatic polyesters in the nonlinear viscoelastic range
Authors: Ng Tie Hwee , Williams H. Leverne 
Published: April 2003

AbstractThe stress–strain curves for a series of linear aromatic polyesters were curve‐fitted to yield constant parameters for the one‐dimensional and three‐dimensional constitutive equations for nonlinear viscoelastic properties. Using these constants, the stress–strain curves could be reconstituted somewhat better by the one‐dimensional equations, but the agreement with the three‐dimensional curves was good. The same constants can be used to predict creep and stress–relaxation, the data for which are in a companion paper.
The reversible plasticization of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p‐acetoxybenzoic acid with 1,1,1,3,3,3‐hexafluoro‐2‐propanol
Authors: Shih H. H. , Hornberger L. E. , Siemens R. L. , Zachariades A. E. 
Published: April 2003

AbstractIn recent mechanooptical studies with solution cast films of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p‐acetoxybenzoic acid from 1,1,1,3,3,3‐hexafluoro‐2‐propanol, a volatile solvent with bp 59°C, we observed that the solvent plasticizes and affects considerably the stress–strain behavior of the copolyester at ambient temperature. Whereas a dry copolyester film is typically brittle failing at ≤ 10% strain, a film containing 12% w/w 1,1,1,3,3,3‐hexafluoro‐2‐propanol can be stretched readily to ≥ 300% strain. When the solvent is removed by evaporation or by heating at an elevated temperature (≥ 120°C), the films lose their ductility, indicating that the plasticization is reversible.
Optimization of polymer‐solvent interaction in a multisolvent system by the UNIFAC group‐contribution method
Authors: Tseng Chi‐Ming , El‐Aasser Mohamed S. , Vanderhoff John W. 
Published: April 2003

AbstractThe solubility parameter scheme is an exceptionally useful tool for predicting the solubility behavior of simple polymer systems. However, this scheme is unable to handle well enough complicated systems, such as those involving donor‐acceptor interactions and those containing more than two solvents. More advanced thermodynamic treatments and computer techniques, such as UNIFAC, can be a key to solving these kinds of problems.The UNIFAC group‐contribution method utilizes a volume parameter and a surface‐area parameter for each structural group and a pair of interaction‐energy parameters for each pair of groups, which can be deduced from experimental activity data. The method was originally derived for mixtures of ordinary liquids and has been extended to polymer solutions by adding a free‐volume correction. The modified UNIFAC method can be used to estimate the activities of solvents in a polymer solution, even when no experimental data are available for the mixture.In the present study, the UNIFAC method was applied to optimize polymer‐solvent interactions in three‐solvent systems. A three‐dimensional plot, displaying polymer activity as a function of the solvent composition, was constructed for each polymer system. The minimum in polymer activity was used as the criterion for maximum polymer‐solvent interaction. Dissolution rate and solution clarity were used to test the polymer‐solvent interaction experimentally. Comparison of theoretical predictions with experimental results indicated that a better agreement could be obtained by using the UNIFAC method rather than the solubility parameter method.
Short fiber‐reinforced thermoplastic elastomers from blends of natural rubber and polyethylene
Authors: Akhtar S. , De P. P. , De S. K. 
Published: April 2003

AbstractThermoplastic elastomer blends of natural rubber (NR) with high density polyethylene (HDPE) and with low density polyethylene (LDPE) were reinforced with short silk fiber. Processing characteristics such as torque and temperature developed during mixing and the effect of processing parameters such as nip gap and number of passes in the mill necessary to secure maximum orientation of the fibers in the blends were studied. A small nip gap and a single pass in the mill were found to give best results. Of the different mixing sequences studied, the sequence where short fibers followed by rubber were added to the molten thermoplastic was found to give a uniform dispersion of fibers. Fiber breakage and the change in aspect ratio of the fibers after mixing were also examined. It was observed that, as a direct consequence of the mixing sequence, each fiber was coated with a layer of thermoplastic. Although the properties improved on the addition of the dry bonding system of silica–resorcinol–hexamethylenetetramine, the comparatively long curing time required for full development of adhesion between the fibers and the matrix proved to be a major disadvantage associated with the incorporation of the bonding system. The tensile and tear properties were substantially enhanced, but the ultimate elongation decreased sharply with increasing loading of short fibers in the blends. The effect of fiber orientation and the development of anisotropy in the properties was also noted. Scanning electron microscopy (SEM) studies of the benzene‐extracted surfaces of the NR/HDPE (high density polyethylene) blends substantiated the theory of fibers behaving like “mechanical anchors” between the rubber and thermoplastic phase. The effect of fiber loading on the tear and tensile properties of the blends of NR/LDPE with varying blend ratios was studied. Most pronounced improvement in the properties on the addition of short fibers was observed in the high rubber blends. As the plastic content in the blends increased, the short fibers were found to have a lesser influence on the properties. SEM photomicrographs of the tensile and tear fracture surfaces indicated the fiber orientations and the effect of orientation, fiber loading, and blend ratios on the nature of fracture.