bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman spectroscopy of urea–formaldehyde resins and model compounds
Authors: Hill Charles G. , Hedren Alicia M. , Myers George E. , Koutsky James A 
Published: April 2003

AbstractLaser Raman spectroscopy was used to analyze the structures of urea–formaldehyde resins. Band assignments were made on the basis of Raman studies of model compounds. Methylol and certain methylene functionalities could be differentiated in both the model compounds and the resins. Spectra of the resins at various stages of cure were also examined. Trends noted agreed with earlier studies on the kinetics and the proposed mechanism of the cure process. Laser Raman spectroscopy offers promise for elucidating the structures of urea–formaldehyde resins and for providing insight into the molecular phenomena of the cure and degradation of these resins.
Factors affecting the durability of Ca‐complexed methylmethacrylate copolymer films containing CaO–SiO2–H2O macromolecules
Authors: Sugama T. , Kukacka L. E. , Carciello N. , Warren J. B. 
Published: April 2003

AbstractA CaO–SiO2–H2O macromolecular–ionomer complex was found to be formed in the superficial layers of MMA–TMPTMA copolymer composite films made with filler containing hydraulic cement during exposure in an autoclave at temperatures up to 200°C. This complex acted to prevent the hydrothermal deterioration of the original composite films, which is important if the films are used as protective layers on metals. This complex also contributed significantly to hydrophobicity, a low energy surface, and less surface roughness, thereby lowering the intrinsic water permeability of the films. The glass transition temperature Tg and the tensile strength of the complexed films increased with increasing concentration of the cement additive used as a source of Ca2+ metallic ions, but they decreased when the cement concentration became excessive because of the chain enlargement caused by the growth of a large quantity of hydrated macromolecules. Ca2− ions were found to migrate from the cement grains in an aqueous medium and to have a crosslinking function connecting the oxidized metal surfaces and the functional carboxylate groups located in the pendent parts of the polymer molecules. The resultant shear bond strength of metal‐to‐metal lap joint specimens after exposure for 3 days to water at 150°C was twice as high as that for the samples made without cement.
Rejection of phenolic derivatives in aqueous solution by an interpolymer anionic composite reverse osmosis membrane
Authors: Koyama Kiyoshi , Kimura Eiichiro , Hashida Isao , Nishimura Masato 
Published: April 2003

AbstractReverse osmosis separation for 23 phenollic derivatives was examined by an anionic charged composite membrane. The solute permeation was carried out in single‐solute aqueous solution (200 mg/L) under applied pressure of 3.92–7.85 MPa at 25°C. The correlation between the solute rejection and polar parameters for phenolic derivatives has been investigated. For p‐alkylphenols, the solute rejection increased with molecular weight and/or molecular branching. In undissociated state, the rejection of phenolic derivatives was closely related with the Taft's number and the Hammett's number of substituents. Also rejections of phenolic derivatives depended upon the pH value of feed soultion and the polar effect of substituted groups. For example, rejections of aminophenols showed the minimum value at a certain pH value and on either side of the minimum point, the rejection of aminophenol increased. From these facts, the main factors in reverse osmosis serparation by an anionic composite membrane were discussed.
Polystyrene gel permeation chromatography packings grafted with polar monomers—synthesis and use in aqueous organic mobile phases
Authors: Heffernan J. G. , Sherrington D. C. 
Published: April 2003

AbstractA number of polystyrene resins of chromatographic quality (5–10 μm) have been prepared with significant residual double bond contents (∼ 2 mmol·g−1). These groups have been used as sites for the grafting of eight polar macromolecules in an attempt to produce a thin uniform coating of the resin surface. Three different grafting procedures have been examined and all products characterized in terms of their toluene and water imbibition. Materials showing promise as universal column packings for gel permeation chromatography have been synthesized on a larger scale and packed in tetrahydrofuran (THF) into standard columns. The plate count of each packed column has been evaluated, and the chromatographic performance of each assessed using polystyrene standards when the eluent was THF and polyethylene oxides when water and methanol were employed. The results are discussed in terms of some simple models describing the grafted resins.
Prediction and measurement of fatigue of lifetime distributions for elastomeric biomaterials
Authors: Gadkaree K. P. , Kardos J. L. 
Published: April 2003

AbstractSynthetic polymer biomaterials being considered for cardiovascular applications must perform under conditions of large cyclic deformations for long lifetimes. In designing with these materials and eventually qualifying them clinically, it would be extremely helpful to be able to predict the fatigue lifetimes accurately and reliably. In this article a calculational format is presented which predicts the lifetime distribution function for elastomeric sheets undergoing tension–tension fatigue. From a knowledge of the intrinsic tensile strength distribution and the effect of an “equivalent” edge flaw size on the tensile strength, the inherent flaw size distribution is determined. A tearing energy concept is utilized to determine the flaw growth law constants. Each of these three short‐term tests provides a pair of constants which, taken together, permit calculation of the fatigue lifetime distribution. When compared using Kolmogoroff statistics, experimental tensile–tensile fatigue results at 0.01 cps agreed well with the theoretically predicted lifetime distribution function.
Melt rheology of ion‐containing polymers. I. Effect of molecular weight and excess neutralizing agent in model elastomeric sulfonated polyisobutylene‐based ionomers
Authors: Bagrodia Shriram , Pisipati Ramesh , Wilkes Garth L. , Storey Robson F. , Kennedy Joseph P. 
Published: April 2003

AbstractMelt rheology of elastomeric triarm sulfonated polyisobutylene model ionomers has been studied. The molecular weights (Mn) of the polymers have been varied from 8300 to 34,000. The sulfonated materials were neutralized with potassium hydroxide either to the exact stoichiometric equivalence point or to twice this amount, i.e., 100% excess neutralizing agent was added. For comparison one nonsulfonated precursor of Mn = 8300 was also studied. It was observed that the introduction of one sulfonate group at each chain end of the triarm poly‐isobutylene molecule changes the state of matter at room temperature. Specifically, the unsulfonated materials are viscous liquids while the sulfonated ionomers are solid elastomers at room temperature. The zero‐shear melt viscosity of the unsulfonated precursor is 900 poise (90 Pa·s), at room temperature while for those materials neutralized with potassium hydroxide to the exact stoichiometric point it is above 9 × 103 poise (900 Pa·s) at 180°C. As expected, the zero shear viscosity increases with an increase in the molecular weight. Significant ionic interactions still persist at 180°C as evident by the high viscosity of the ionomers. However, at higher frequencies (∼600 rad/s), the melt viscosity decreases to about 5 × 103 poise for the different molecular weight materials. The melt viscosity of ionomers containing 100% excess neutralizing agent shows a dramatic increase. The excess KOH is speculated to be incorporated into the ionic domains rather than uniformly distributed throughout the matrix. This results in an increased strength of the ionic aggregates, thereby increasing the melt viscosities. Thus, due to the very pronounced effect on rheological properties it is important to know not only the extent of neutralization (up to full neutralization) but also the amount of excess neutralizing agent, if any, which is present in the sample.
Biodegradation of gelating‐g‐poly(ethyl acrylate) copolymers. II
Authors: Kumar G. Sudesh , Kalpagam V. , Nandi U. S. 
Published: April 2003

AbstractGelatin‐g‐poly(ethyl acrylate) copolymers were prepared in an aqueous medium using K2S2O8 initiator. Three copolymer samples with grafting efficiencies of 33.3%, 61.0%, and 84.0% were tested for their microbial susceptibility in a synthetic medium with pure cultures of Pseudomonas aeruginosa, Bacillus subtilis, and Serratia marcescens. The percent weight losses were recorded over 6 weeks of incubation period in nitrogen‐free and nitrogen‐rich media. The relationship between [log (rate)] during the first week of the test period and the composition of grafted samples showed a linear behavior. Pure cultures were more effective than the mixed inoculum, although there was no essential difference in the agressivity of different bacterial stains. Growth–time curves and pH measurement also complement these observations.
A model study for release of plasticizers from polymer films through vapor phase
Authors: Bellobono Ignazio Renato , Marcandalli Bruno , Selli Elena , Polissi Alessandra , Leidi Giorgio 
Published: April 2003

AbstractA model has been applied to release of plasticizers from polymer films through vapor phase, for which the overall rate of release may be generally determined by evaporation of the plasticizer from the surface of the film, and/or by migration to the surface at below saturation in the polymer. The experimental system employed made use of n‐butyl formate, diethyl‐phthalate, di‐n‐butylphthalate, and N,n‐butylbenzenesulfonamide as model molecules in polycaprolactam films, both with the aims of studying undesirable loss of plasticizers, and of simulating a model able to envisage releasing, at a constant rate, of any desired additive, with relatively high solubility and vapor pressure, to the content of packaging films. Experimental measurements were made (at 298–333 K) by investigating in a suitable cell the permeation of plasticizers both at concentrations below and above the saturation limit. Rate of evaporation of plasticizers from the membrane surface above the saturation limit, measured in this cell, were found to coincide satisfactorily with those calculated by application of the mass transfer theory to evaporation from a stationary liquid into a stirred gas, at a known velocity of gas flowing past the surface. From these latter rates and solubilities, the mass transfer coefficients H for evaporation could be obtained, as well as from experimental time lags the diffusivities Dp through the polymer membrane. In the light of the theoretical model a correlation was found between activation energies of H and evaporation enthalpies of the model molecules.
Emulsion polymerization of methyl methacrylate in the presence of burnt mazote boiler deposit
Authors: Moustafa A. B. , Badran A. S. , Shandy S. M. M. 
Published: April 2003

AbstractThe emulsion polymerization of methyl methacrylate (MMA) using different initiators was carried out in the absence and presence of burnt mazote boiler deposit (BMBD). When sodium persulfate or potassium persulfate was used, the initial rate of polymerization was found to decrease with increase of the burnt mazote boiler deposit concentration but to increase when sodium bisulfite was used as initiator. The initial rate of polymerization was found to be higher in nitrogen atmosphere than in air. The apparent activation energy (Ea) was found to be 12.4 × 104 J/mol and 16.3 × 104J/mol in the absence and presence of burnt mazote boiler deposit when potassium persulfate was used as initiator and 5.9 × 104 J/mol and 5.1 × 104 J/mol when sodium bisulfite was used as initiator, respectively. The mean average molecular weights for PMMA were found to increase with increase of the burnt mazote boiler deposit when sodium bisulfite was used as initiator.
Structure–property relationship in heat‐set poly(ethylene terephthalate) fibers. II. Thermal behavior and morphology
Authors: Gupta V. B. , Ramesh C. , Gupta A. K. 
Published: April 2003

AbstractThermal behavior of drawn poly(ethylene terephthalate) (PET) multifilament yarn which had earlier been heat‐set at various temperatures between 100°C and 250°C under “free to relax” and “taut at constant length” conditions is studied by differential scanning calorimetric (DSC) measurements. Structural studies are made by X‐ray diffraction and infrared absorption spectrophotometry. Two interesting observations are reported: (i) In the taut‐annealed samples, the noncrystallizable fraction increases and crystallizble fraction decreases with increasing heat‐setting temperature, the free‐annealed samples show the opposite effect; and (ii) a well crystallized free‐annealed sample melts at a higher temperature than the corresponding taut annealed sample. Both these observations are interpreted in terms of sample morphology; the free‐annealed samples have more perfect crystals and a more distrinct separation between the crystalline and amorphous phases which facilitates transport and diffusion resulting in an ease of reorganization.
Cation exchange resin from phosphorylated N‐vinylcarbazole formaldehyde copolymer
Authors: Biswas Mukul , Bagchi Subrata 
Published: April 2003

AbstractCrosslinked copolymers of N‐vinylcarbazole and poly N‐vinylcarbazole) and formaldehyde have been phosphorylated using PCl3 and anhydrous AlCl3 under different conditions. The cation exchange resins, thus obtained, have been characterized by elemental analyses, evaluation of total ion‐exchange capacities and salt‐splitting capacities, pH metric titration behavior, and IR analysis. The phosphorylated resin exhibites significantly better thermal stability than the corresponding sulfonated N‐vinylcarbazole–formaldehyde cation exchange resin or the unmodified N‐vinylcarbazole–formaldeyde copolymer, as well as the phosphorylated poly(N‐vinylcarbazole). The phosphorylated resins also behave as polymeric dyes with pH dependent color change. Possible explanations for color change and ion‐exchange capacity differences have been attempted on the basis of the structural characteristics of the resins.
Mechanical properties of paper sheets prepared from carbamoylethylated wood pulp
Authors: El‐Shinnawy Nabila A. , El‐Kalubi Samira F. 
Published: April 2003

AbstractCarbamoylethylation of wood pulp was carried out at different conditions including acrylamide concentration, time of impregnation, and medium of the reaction (aqueous and nonaqueous). Mechanical properties of paper sheets prepared from the carbamoyethylated cellulose were examined. Carbamoyethylated paper sheets showed improved double‐fold breaking length and burst factor irrespective of the reaction medium. Tear strength remained practically unaltered with aqueous carbamoylethylation but decreased in the case of non‐aqueous carbamoylethylation. Water retention value (WRV) decreased by carbamoylethylation especially when the latter was performed in nonaqueous medium.
Mechanical coagulation in emulsion polymerizations
Authors: Lowry Vern , El‐Aasser Mohamed S. , Vanderhoff John W. , Klein Andrew 
Published: April 2003

AbstractCoagulum formation for different emulsion polymerizations was correlated to various agitation parameters. For low Reynolds numbers, rotational speed was shown to be important, whereas, for high Reynolds numbers, power consumption was the important parameter. These results were theoretically tied to first‐order coagulation kinetics by incorporating shear rate relationships for flow in an agitated tank. For low Reynolds numbers, the average shear rate was assumed to be proportional to the rotational speed of the impeller. And for high Reynolds numbers, Kolmogorov's theory of locally isotropic flow was employed to relate the average shear rate to the power consumption.
Surface characterization of intact fibers by inverse gas chromatography
Authors: Gozdz Antoni S. , Weigmann Hans‐Dietrich 
Published: April 2003

AbstractInverse gas chromatography (IGC) was used to determine adsorption isotherms and isosteric heats of adsorption for several normal alkanes on a number of intact textile fibers and to determine the specific surface areas of these fibers. Surface areas obtained by IGC were in excellent agreement (except for cotton) with those calculated from the geometric dimensions of circular cross‐section fibers and with those obtained by the adsorption of krypton. Heats of adsorption were found to be only slightly higher than the corresponding heats of liquefaction of the probes. The effect of fiber surface purity on adsorption behavior as well as computerized data reduction are briefly discussed.
Properties of syndiotacticity‐rich poly(vinyl alcohol) thin film in water. I. Effect of the load on the extension of untreated thin film in water
Authors: Yamaura Kazuo , Matsuzawa Shuji 
Published: April 2003

AbstractThe effect of the load on the extension of untreated thin film of syndiotacticity‐rich poly(vinyl alcohol) (PVAVTFA) derived from vinyl trifluoroacetate was examined in water. The untreated thin film obeys Hooke's law under a certain constant load at 25°C. Young's modulus of untreated PVAVTFA film in water at 25°C was about 4.8 × 10−4 GPa. The maximum elongation of PVAVTFA film in water at 25°C is achieved for a short time under high load, whereas not under low load. The expansion of PVAVTFA thin film by the elevation of temperature of water occurs mildly in the range of temperature of 45–55°C under low load, whereas not under high load. The temperature at break Tb is in the range of 70–90°C and increasing load roughly tends to decreasing Tb. The elongation at break decreased with the increase in load.
Bulk resilience of fibers
Authors: Nachane R. P. , Iyer K. R. Krishna , Patil N. B. 
Published: April 2003

AbstractA theory has been developed for the average bending deformation of fibers in an assembly subjected to compression. It is shown that the maximum average bending deformation of the fibers does not exceed 17°, implying that the method of bulk resilience cannot be used as an indicator of elastic recovery of fibers for any precision measurements.
Rheological behavior of epoxy acrylate prepolymer during UV curing
Authors: Otsubo Yasufumi , Amari Takeshi , Watanabe Koichiro 
Published: April 2003

AbstractThe effects of sample thickness and curing temperature on the dynamic viscoelastic behavior were investigated during UV curing of an epoxy acrylate prepolymer by the use of an oscillating plate rheometer which was devised in our laboratory. Independent of light intensity, the values of dynamic viscosity plotted against exposure energy lie on a single curve which is approximated by two straight lines. The minimum exposure energy, which corresponds to that at the intersection of two lines, increases with increasing sample thickness and then starts to increase abruptly at a certain thickness. The critical sample thickness is comparable to the penetration depth of a light having a wavelength of 365 nm. The spectral sensitivity shows that the n–π* absorption at 365 nm by the photoinitiator is of primary importance in polymerization.
Chemical modification of chlorinated rubbers. II. Study of chlorinated natural rubber modified by amino–esters
Authors: Makani Siku , Brigodiot Maryvonne , MaréChal Ernest , Durand Jean‐Pierre , Dawans Francois 
Published: April 2003

AbstractThe synthesis of ethyl‐11‐aminoundecanoate and ethyl‐3‐aminobutyrate and the chemical modification of chlorinated natural rubber by these amino–esters were investigated in order to find useful materials for long‐life antifouling paints free from toxic moieties. Detailed reactions and fractionation schemes are described for isolating pure products; their structure was characterized by IR and NMR spectrometries.
Photodegradation kinetics of methyl salicylate in poly(methyl methacrylate)
Authors: Renschler Clifford L. 
Published: April 2003

AbstractIt has been found that methyl salicylate (MS) undergoes a photoinduced decarboxylation to form phenol with a quantum yield of ca. 8 × 10−5. The reaction is first order and the rate constant is proportional to the irradiance used. An activation energy of 1.2 kcal/mol was determined. Computer simulations were used to predict whether sufficient UV screening would be provided by MS‐containing PMMA lenses over the projected lifetime of solar photovoltaic devices. An effective screening lifetime of less than 2 years is predicted.
The ring‐opening polymerization of D,L‐lactide in the melt initiated with tetraphenyltin
Authors: Kohn F. E. , Van Den Berg J. W. A. , Van De Ridder G. , Feijen J. 
Published: April 2003

AbstractMelt polymerization conditions for D,L‐lactide initiated with tetraphenyltin were studied with regard to polymer molecular weight and weight distributions. “Single” polymerization, “multiple” polymerization (four or eight reactions at the same time), and time‐dependent studies are described. Single polymerizations using constant initiator concentrations resulted in a broad scattering of nonreproducible molecular weight values. Multiple polymerizations at constant initiator concentrations, however, resulted in nearly identical molecular weight profiles. Multiple polymerizations at different initiator concentrations did not show an inverse dependency of initiator concentration on polymer molecular weight. Both the single and multiple melt polymerizations resulted in rather broad molecular weight distributions. The presence of hydrolysis products of lactide during the melt polymerization most likely has a detrimental effect on molecular weight. After a short induction period the rather slow polymerization of D,L‐lactide resulted in a maximal molecular weight followed by a slight decrease in molecular weight to a constant value. It is concluded that the polymerization of D,L‐lactide in the melt initiated with tetraphenyltin does not proceed through a “living” mechanism.
Structural differences exhibited by networks prepared by chemical and photochemical reactions. III. Characterization by inverse GPC
Authors: Haidar B. , Vidal A. , Balard H. , Donnet J. B. 
Published: April 2003

AbstractThe use of a new method, inverse GPC, as a tool for the characterization of elastomeric networks, allowed the obtaining of the distribution curves of the network strands. In agreement with previous studies it was shown that photocrosslinked materials exhibit a more homogeneous distribution of the crosslink points than do peroxide cured samples. From the GPC distribution curves, it was possible to calculate Mc, the average molecular weight of a network strand.
PVC calendering: A simplified prediction technique
Authors: Ray A. , Shenoy A. V. 
Published: April 2003

AbstractA simplified technique for prediction of pressure distribution, velocity profiles, torque, and power requirements for the calendering of power‐law fluids is presented. The technique assumes isothermal conditions, is based on the lubrication approximation and Gaskell's analysis, and uses melt flow index as the only temperature‐dependent resin parameter for the prediction. The predictions are found to compare favorably with those made by Vlachopoulos and Hrymak for rigid PVC.