bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vanadium‐cyclohexanone–initiated graft copolymerization of methyl methacrylate onto jute fibers
Authors: Mohanty A. K. , Singh B. C. , Mishra M. 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate (MMA) was carried out on jute fibers using a V5+ ‐cyclohexanone redox initiator system. The effect of the concentration of acid, monomer, and V5+ on graft yield have been studied. In order to obtain optimum conditions of grafting, the effects of temperature, acid, reaction medium, solvent, and some inorganic salts on graft yield have been investigated. The most remarkable features of the investigation include the proposition of a mechanism and derivation of rate expression for the grafting process. More than 100% grafting could be achieved with the present system.
Control of solute permeability based on pH‐induced reversible conformational change in block copolypeptide membrane
Authors: Minoura Norihiko , Aiba Sei‐Ichi , Fujiwara Yukihiko 
Published: April 2003

AbstractAn ABBA‐type block copolypeptide membrane composed of L‐glutamic acid (A) and L‐leucine (B) was prepared, and a solute permeability of the membrane was studied. According to the observation of electron microscope, the membrane had the phase‐separated morphology that the domains consisting of poly(L‐glutamic acid) blocks are emebedded in a continuous matrix of the poly(L‐leucine) phase. The reversible conformational change of the poly(L‐glutamic acid) from α‐helix to random coil induced by changing the pH of the external medium was presumed to occur in the domains on the basis of the results of infrared absorption spectra. In the pH dependence of the diffusion coefficients of KCl, NaCl, and LiCl in the membrane, a considerable decrease was found at about pH 4, and thought to result from the conformational transition. In an acidic medium, the permeability of KCl, NaCl, and NiCl was higher then that of glucose, but this order was reversed in higher pHs. These results indicate that the poly(L‐glutamic acid) domains in the membrane function as channels for solute transport.
Plasma polymerized membranes and gas permeability. II
Authors: Sakata Jiro , Yamamoto Minoru , Hirai Masana 
Published: April 2003

AbstractThin films were deposited onto porous substrates by plasma polymerization using three kinds of organosilicic compounds, tetramethylsilane (TMS), hexamethyldisiloxane (M2), and octamethylcyclotetrasiloxane (D4). Those composite membranes showed different characteristics of gas permeability. When D4 was plasma‐deposited onto a porous substrate, the composites membrane showed the highest oxygen permeability and the lowest oxygen‐to‐nitrogen permeability ratio. The composite membrane prepared from TMS showed the permeability characteristics opposite to the membrane obtained from D4. Infrared spectrum of the polymer from D4 resembles that of dimethylpolysiloxane. The plasma polymers from TMS and M2 showed different profiles in SiO absorption bands in the range 1100–1000 cm‐1 or in absorption bands of SiCH3 groups in the range 850–750 cm‐1 from respective monomers. X‐ray photoelectron spectroscopic observation indicated that all the plasma polymers contained more than two species of Si atom with different oxidation states. The greater part of Si atoms in plasma polymers took the same oxidation states in corresponding monomer. The gas permeability characteristics were closely related to the oxidation states of Si atom in the plasma polymers.
Effect of molecular weight on high‐speed melt spinning of nylon 6
Authors: Koyama Kiyohito , Suryadevara Jogendra , Spuriell Joseph E. 
Published: April 2003

AbstractAn extensive experimental study of the structure and properties developed in as‐spun nylon 6 filaments is reported. Five polymers representing different molecular weights in the range 25,000–73,000 g/mol (viscosity average) were studied. These polymers were melt spun over a range of spinning speeds using an air drag type of drawdown device. Maximum take‐up velocities achieved were in the neighborhood of 4000 m/min. The structure and properties of the as‐spun filaments were characterized using density, DSC, WAXS, SAXS, birefringence, and tensile tests. The structural characteristics and properties of the filaments are strongly dependent on molecular weight. Generally, higher molecular weight leads to higher modulus and filament tenacity and lower elongation to break in the as‐spun filaments. The structural changes with molecular weight are rather complicated; the complications are explained in terms of changes of crystallization rate and attainable crystallinity.
Effect of time‐temperature path of cure on the water absorption of high Tg epoxy resins
Authors: Aronhime M. T. , Peng X. , Gillham J. K. , Small R. D. 
Published: April 2003

AbstractThe effect of different time—temperature paths of cure on the water absorption of high Tg epoxy resins has been investigated. The resins were cured isothermally for different times, with the following results: as extent of cure increased, the glass transition temperature (Tg) increased, the room temperature (RT) modulus decreased, the RT density decreased, the RT diffusion coefficient appeared to decrease, and the RT water absorption increased. The decrease in RT density is related to an increase in free volume, which controls the amount of water absorbed. A qualitative model accounts for the increase in RT free volume with increasing cure. The model is based on a restricted decrease of free volume on cure due to the rigid molecular segments in the cured resin systems. The sorption isotherms can be characterized by the dual mode theory at low activities but at high activities the sorption is complicated by penetrant clustering. A thermodynamic approach, independent of the absorption model, can correlate sorption data at different temperatures. The diglycidyl resin was also cured for extended times at three temperatures, in an effort to achieve full cure at each temperature. For these, the higher the cure temperature, the lower the RT density, which could result from the lower initial density of materials cured at higher temperatures. The equilibrium water absorption increased with increasing cure temperature, consistent with the decrease in RT density. The systems studied were a diglycidyl ether of bisphenol A cured with an aromatic tetrafunctional diamine, trimethylene glycol di‐p‐aminobenzoate (Tg∞ = 156°C), and a triglycidyl ether of tris(hydroxyphenyl)methane cured with the same amine (Tg∞ = 268°C).
Preparation and reactions of polymers having 1‐aroyl‐2‐(3‐pyridyl)ethylenes as photosensitive groups
Authors: Watanabe Shoji , Ichimura Kunihiro , Suda Yoshio 
Published: April 2003

AbstractThe reactions of 1‐aroyl‐2‐(3‐pyridyl)ethylenes (APE) with polychloromethylstyrene (PCMS) yield polymeric systems which undergo rapid crosslinking upon short exposure to ultraviolet (UV) light. The photochemical reaction of polymers as well as model compounds was followed by the measurement of UV absorption of APE and the analysis of extinction coefficient difference (ED) diagrams.1
Determination of cellulose accessibility by differential scanning calorimetry
Authors: Bertran Maria Silvia , Dale Bruce E. 
Published: April 2003

AbstractThe thermal behavior of various cellulose samples with different degrees of crystallinity as measured by X‐ray diffraction techniques was studied with a differential scanning calorimeter (DSC). The broad endothermic peak which appears between 110 and 160°C is due to loss of absorbed (bound) water. Since a direct relationship was observed between the area of this peak and the crystallinity of the sample, a new procedure for estimating cellulose accessibility (which is related to crystallinity) was proposed and developed. DSC curves obtained on cellulose samples preconditioned at certain constant relative humidities were used to determine sample accessibilities by the proposed method. The accessibility values obtained by DSC showed excellent agreement with crystallinity values determined by more traditional techniques. Completely amorphous cellulose was obtained by anhydrous deacetylation of cellulose triacetate and was used as the standard amorphous cellulose material.
Dynamic mechanical properties of thermoplastic elastomers from polypropylene–natural rubber blend
Authors: Kuriakose Baby , De S. K. , Bhagawan S. S. , Sivaramkrishnan R. , Athithan S. K. 
Published: April 2003

AbstractThe dynamic mechanical properties of thermoplastic elastomers from polypropylene natural rubber blends have been evaluated with special reference to the effect of blend ratio and extent of dynamic crosslinking of the elastomer phase. The effects of HAF black and silica fillers have also been studied. It has been found that increasing the proportion of elastomer phase reduced the storage modulus and increased the loss tangent values of the blends. The effect of dynamic crosslinking was found to be more prominent in blends containing higher proportion of elastomer phase. The improvement in storage modulus and decrease in loss tangent values were quite remarkable with increase in extent of crosslinking in these blends. The 70:30 NR:PP blend was found to exist as a two‐phase system, both the components forming continuous phases of the blend.
Qualitative and quantitative analysis of methyl acrylate or methyl methacrylate of acrylonitrile fibers by pyrolysis gas chromatography
Authors: Saǧlam Mehmet 
Published: April 2003

AbstractDegradation gases evolved from methyl acrylate or methyl methacrylate of acrylonitrile fibers were analyzed by pyrolysis gas chromatography. For determining polymer composition, optimum pyrolysis conditions were determined and calibration was accomplished by using acrylonitrile–methylacrylate and acrylonitrile–methyl methacrylate model copolymers. Out of the 23 samples examined, 10 were found to contain methyl acrylate and five methyl methacrylate comonomers, in the range of 3.5–8.0%. The reproducibility of the method was good, the coefficient of variations was ±2% for methyl acrylate and ±2.5% for methyl methacrylate. Compositions were in agreement with those determined by other methods.
Structure and properties of dynamically cured EPDM/PP blends
Authors: Ha Chang Sik , Ihm Dong Joon , Kim Sung Chul 
Published: April 2003

AbstractThe structure and properties of polyolefin blends of ethylene–propylene–diene terpolymer (EPDM) and polypropylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured with PP under shear with dicumyl peroxide (DCP) at different shear conditions (blend–cure). Blends were also prepared for comparison from EPDM which were dynamically cured in the absence of PP and blended later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastic composition were studied. In blend–cure, the melt viscosity increased with increasing DCP concentration in blends of 75% EPDM and 25% PP, but it decreased with increasing DCP concentration in blends of 75% PP and 25% EPDM. In cure–blend, however, the melt viscosity increased with increasing DCP concentration for all compositions. The melt viscosity decreased with increasing intensity of the shear mixing presumably due to the formation of the smaller segregated microdomain of the crosslinked EPDM gels in both blend–cure and cure–blend materials. The crystallization rate was higher in EPDM/PP blends than in PP homopolymer. The crystallization rates for various blending conditions were also compared.
Synthesis, characterization, and properties in aqueous solution of poly(starch‐g‐[1‐amido‐ethylene)‐co‐(sodium 1‐(2‐methylprop‐2N‐yl‐1‐sulfonate)amidoethylene)])
Authors: Meister John J. , Patil Damodar R. , Jewell Margaret C. , Krohn Kyle 
Published: April 2003

AbstractGraft terpolymers of starch, 2‐propenamide, and sodium 2‐methyl‐3‐imino‐4‐oxohex‐5‐ene‐1‐sulfonate can be made by cerium‐IV‐initiated, free‐radical polymerization of an aqueous monomer mixture on starch. Synthesis is conducted on aqueous, gelled, lintnerized potato starch at 30°C under a nitrogen atmosphere. Yields range from 50 to 100 wt % and products contain 9–52 wt % starch, 1–51 wt % 1‐acidoethylene, and 18–65 wt % sodium 1‐(2‐methylprop‐2N‐yl‐1‐sulfonate)amidoethylene. Repeat unit ratios in the reaction product approximate monomer ratios in the reaction mixture. Fraction of starch grafted in a reaction decreases as the mole fraction of sulfonated monomer in the reaction mixture increases. No proof has been found for grafting of synthetic side chains to starch in monomer mixtures containing only sulfonated monomer. Starch graft copolymers with side chains composed of 1‐amidoethylene units and a sulfonated 1‐amidoethylene unit derivative, 1‐(sodium[2‐methylprop‐2N‐yl‐1‐sulfonate])amidoethylene, are water‐soluble, thickening agents. The rheology of solutions of these copolymers is a function of the ratio of nonsulfonated to sulfonated repeat units in the synthetic chains of the molecule. Aqueous solutions of these products are shear thinning and have power law exponents which decrease 1) with increasing product concentration or 2) as the nonsulfonated to sulfonated repeat unit ratio moves toward 3/1. Limiting viscosity number of product in water decreases with increasing shear rate of measurement or with increasing salt concentration of the solvent. Formulas are derived from the theories of Kirkwood and Flory which show that for copolymers with constant molecular weight, expansion coefficient, and limiting viscosity number increase as the fraction of sulfonate‐containing repeat units in the chain increase. This theoretical requirement and the limiting viscosity data for groups of samples prepared under identical synthesis conditions are used to show that molecular weight of the graft copolymer decreases as the fraction of sulfonated repeat units in the copolymer increases. Screen factor measurements show product solutions to be viscoelastic.
Thermal effects in poly(hexamethylene adipamide) and polyoxymethylene at high hydrostatic pressures
Authors: Rodriguez E. L. , Filisko F. E. 
Published: April 2003

AbstractThe temperature changes as a result of rapid hydrostatic pressure applications are reported for poly(hexamethylene adipamide) (nylon 66) and poly(oxymethylene) (POM) in the reference temperature range from 298 to 423 K and in the pressure range from 13.8 to 200 MN/m2. The adiabatic temperature changes were found to be a function of pressure and temperature. A curve fitting analysis showed that the empirical curve (∂T/∂P) = ab(ΔP)b−1 described the experimental thermoelastic coefficients obtained from the experiments. The data were analyzed by determining the predicted thermoelastic coefficients derived from the Thomson equation (∂T/∂P) = αT0/ρCp. The experimental and predicted Grüneisen parameter γT were also determined. The relationship between the thermal effects and the chain molecular motion is discussed by including dynamic mechanical analysis and DSC measurements for the nylon 66 and POM samples.
In vitro chemical degradation of poly(glycolic acid) pellets and fibers
Authors: Ginde Rajiv M. , Gupta Rakesh K. 
Published: April 2003

AbstractThe influence of macroscopic dimensions, heat treatment, and polymer morphology on the chemical degradation of poly(glycolic acid) (PGA) fibers and pellets was examined in media of different pH values by monitoring the sample mass, dimensions, crystallinity, mechanical strength, and surface character. The degradation was found to be chemically controlled and independent of fiber size. The rate was an order of magnitude faster in alkaline vs. acidic media. In general, the pellets degraded faster than fibers, and while the latter showed little surface deterioration, scanning electron photomicrographs of the pellets revealed considerable surface degradation with circumferential microcracks progressing into longitudinal cracks with increasing immersion times and pH. Concomitantly, DSC measurements showed a steady increase in crystallinity for both fibers and pellets. The fiber tensile strength decline was independent of diameter and more drastic in alkaline media. Additionally, the heat‐treated fiber was always stronger than the non‐heat‐treated one. It is concluded that crystallinity and polymer chain orientation, in addition to immersion media, influence PGA degradation. Also, the loss in strength results from chain scission in the amorphous regions while mass loss occurs when polymer chains become small enough to be soluble. These different variables offer a means of modifying PGA fiber tensile properties.
Curing behavior of unsaturated polyester resin with mixed initiators
Authors: Han Chang Dae , Lee Dai‐Soo 
Published: April 2003

AbstractThe curing behavior of unsaturated polyester resin with mixed initiators was investigated both experimentally and theoretically. For the experimental investigation, we used various combinations of low and high‐temperature initiators to cure a general‐purpose unsaturated polyester resin and determined the rate of cure and the degree of cure, using differential scanning calorimetry and infrared spectroscopy. For the theoretical investigation, we used the mechanistic kinetic model described in our previous paper. It has been demonstrated that the mechanistic model is very useful for predicting the curing behaviour of unsaturated polyester resin with mixed initiators, using information on the rate constants of the individual initiators and the concentration of the initiator. Such an approach will help reduce, if not eliminating completely, the number of tedious and time‐consuming curing experiments that would otherwise have to be performed.
Binding of heavy metal ions by chemically modified woods
Authors: Morita Mitsuhiro , Higuchi Mitsuo , Sakata Isao 
Published: April 2003

AbstractThree chemically modified woods were prepared and used for the binding of heavy metal ions. Wood–polythylenimine composite (wood–PEI) was found to be effective for the adsorption of heavy metal ions such as Hg2+, Cu2+, and other metal ions which tend to form stable ammine complexes. Adsorption of metal ions on a wood–PEI derivative containing dithiocarbamate group (DTC–wood) was higher than that by wood–PEI. Especially, the reactivity of DTC–wood with Hg2+ was quite high and the binding capacity of about 5 mmol/g was easily attainable. The rate of adsorption on these wood‐based adsorbents was very high, and adsorption of about 70% of total binding capacity was accomplished in the first 1 h. This may be due to a highly porous structure and a hydrophilic nature of the wood which constitutes the skeleton of the adsorbents. Amidoximated wood (AO–wood) prepared by the reaction of cyanoethylated wood with hydroxylamine showed selective adsorptivity for uranium in sea water. More than 53% of uranium in the sea water used was adsorbed by the AO–wood.
Crystalline memory on polycarbonate
Authors: Filippo Giuseppe V. Di , González María E. , Gasiba María T. , Müller Alejandro V. 
Published: April 2003

AbstractA significant reduction on the time for thermal crystallization of Bisphenol‐A polycarbonate has been achieved by means of a previous crystallization step of the polymer in acetone, followed by a capillary extrusion processing at temperatures above its melting range (230–280°C). The crystallinity of PC was corroborated qualitatively by means of WAXS and quantitatively by means of DSC. The acetone‐crystallized polymer showed higher values of dynamic viscosity than its amorphous counterpart. Such difference decreased with the increase of the test temperature and disappeared at 280°C. The degree of crystallinity of thermally crystallized PC increased with the decrease of the capillary extrusion temperature of the acetone‐crystallized material. It is inferred that the time–temperature‐dependent long range molecular diffusion necessary for the total melting of the crystal fractions could not take place entirely for the short times employed (≈ 4 min), allowing the extruded polymer to behave as a self‐nucleated material.
Aging of EPDM rubber
Authors: Deuri A. Saha , Bhowmick Anil K. 
Published: April 2003

AbstractThe effect of oxidative and thermal aging of EPDM raw rubber and rubber vulcanizate on gelation, network structure, and techical properties has been studied over a wide range of temperatures and times of aging. Three grades of EPDM having different types of diene have been considered. The kinetics of aging of both raw rubber and vulcanizates has also been reported.Different network structures have been produced due to different reactivity of temonomers. Cross‐link density, cross‐link efficiency, polysulfidic linkage, zinc sulfide sulfur, combined sulfur, free sulfur, and sulfur inefficiency change with aging time and temperature. The number of polysulfidic cross‐links decreases continuously with increase in time or temperature of aging. There is no definite trend in other structural features. It is quite evident that postcuring reactions as well as destruction of cross‐links are taking place in the aging process. The predominance of the former or latter depends on the structure of the diene.Tensile and tear strength of the compounds decreases or increases with time or temperature of aging. At high temperature, it always decreases with time. Changes in these properties can be approximately correlated with changes in structure only at high temperature. At lower temperature, relations between network structure and technical properties are complicated owing to the competing reactions discussed above. In general, retention of properties of ENB‐EPDM vulcanizate is the best. The properties after aging do not exclusively depend on the network structure, nature of cross‐link, rank of sulfur, or pendant or cyclic sulfide. The backbone structure is important in all these cases. Changes are less drastic on aging in nitrogen, but a similar trend is found. Raw EPDM rubber forms a gel, which increases with temperature of aging. The activation energy for gelation has been found to be 98 kJ/mol, similar to the oxidation of diene‐containing rubbers.The activation energy for desulfurization of various grades of EPDM vulcanizates is 60–85 kJ/mol. The activation energy for fracture calculated from aging data is, however, 30–36 kJ/mol from tensile measurement and 32–46 kJ/mol from tear strength measurement.
Selective permeation of carbon dioxide through synthetic polymer membranes having pyridine moiety as a fixed carrier
Authors: Yoshikawa Masakazu , Ezaki Tomohiko , Sanui Kohei , Ogata Naoya 
Published: April 2003

AbstractSorption and permeation of CO2 were investigated by using synthetic polymer membranes having pyridine moiety or pyridine–Cu(II) complex group as a fixed carrier. The solubility data for CO2 were interpreted by the dual sorption model, Henry's law plus Langmuir‐type adsorption. The permeation results of CO2 through the present membranes containing pyridine moiety were analyzed in terms of the partial immobilization model, while the solubilities and permeablities of O2 and N2 obeyed Henry's law. Permselectivity of the present membrane for CO2 was achieved. These results were explained by the acid‐base interaction between CO2 molecules and fixed carrier in the present membrane.
Thermal stabilization of polyacrylonitrile fibers
Authors: Ko Tse‐Hao , Ting Hsing‐Yie , Lin Chung‐Hua 
Published: April 2003

AbstractPolyacrylonitrile (PAN) fibers pretreated with potassium permanganate have reduced the activation energy of cyclization and the oxidation time, and also improved the properties of the resultant carbon fibers. The activation energy of cyclization is reduced to 24 ± 1 kcal/mol from 30 ± 3 kcal/mol and the tensile strength of the carbon fibers increases by about 20−40%. The method of measuring the “aromatization index” (AI) value is modified and is recommended in checking the oxidation process. All fully stabilized PAN fibers have almost the same AI value. However, the oxidation time is decreases by 30 min when oxidation temperature is raised by 10°C.