bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Reverse 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

A 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

Synthetic 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

Melt 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

Gelatin‐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

A 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

The 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

Thermal 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

Crosslinked 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

Carbamoylethylation 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

Coagulum 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

Inverse 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

The 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

A 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

The 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

The 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

It 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

Melt 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

The 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

A 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.
Studies on the radiolytic degradation of cellulose acetate membranes
Authors: Ramachandhran V. , Misra B. M.
Published: April 2003

The effect of γ‐irradiation on the performance of wet cellulose acetate membranes in the dose range of 2.5–10 Mrads was investigated using a 60Co source. Changes in transport properties and inherent viscosity of the membranes suggested continued degradation as a result of irradiation. Solubility and specific gravity changes accompanying irradiation indicated some sort of structural aggregation occuring at higher doses. Consumption of dissolved oxygen during irradiation and the extent of deacetylation of the membrane polymer were determined to study the kinetics of the degradative process. Analysis of the end products of irradiation was attempted by UV spectroscopy. ESR spectra of membrane polymer after irradiation were analyzed to identify the free radicals generated. A tentative mechanism of radiolytic degradation causing the observed performance failure is proposed.
Water‐soluble copolymers. XI. Selectivity in the graft copolymerization of acrylamide/N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide comonomers onto dextran by Ce(IV)‐induced initiation
Authors: McCormick C. L. , Park L. S.
Published: April 2003

Characteristic behavior in the graft copolymerization of acrylamide/N‐(1,1‐dimethyl‐3‐oxybutyl)acrylamide (AM/DAAM) comonomers onto dextran by Ce(IV)‐induced initiation was investigated. From a preliminary study, it was found that ceric ammonium nitrate polymerized AM/DAAM comonomer mixtures and diacetone acrylamide, but not acrylamide alone in the aqueous solution. The effect of grafting conditions on the graft copolymerization product was studied with the aid of aqueous size exclusion chromatography and the anthrone reagent. The selectivity of formation of the graft copolymer over random copolymer was found to increase as the reaction temperature and AM/DAAM ratio increased and as both the Ce(IV)/Dextran molar ratio and HNO3 concentration decreased. After establishing optimum grafting conditions, graft copolymer samples were prepared, and their aqueous solution behavior studied as functions of structure, temperature, and added salts.
Investigation of block copolymer micellization by high‐performance size‐exclusion chromatography
Authors: Špaček Pavel , Kubín Miroslav
Published: April 2003

The formation and decomposition of micelles of the three‐block copolymer polystyrene‐block‐poly(ethene‐stat‐butene)‐block‐polystyrene (Kraton G 1652, Shell) were investigated by high‐performance size‐exclusion chromatography in a mixed solvent dioxan–heptane. The association equilibrium may be shifted from the pure unimer to pure micelles by changing the composition of the mobile phase, and also (at constant composition) by a change in temperature. The shape of the chromatograms observed under conditions of comparable equilibrium concentrations of both species may be explained by the disturbance and reestablishment of the association equilibrium during separation in the chromatographic column. Experiments with changing flow rate show the dominating effect of degrading separation efficiency with increasing linear velocity of the mobile phase.
Radiation‐induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. VI. Permeability of sodium chloride and sodium sulfate
Authors: Bhattacharyya S. N. , Maldas D.
Published: April 2003

Acrylamide, styrene, and mixtures of acrylamide and styrene were grafted onto cellulose acetate film. The permeabilities of sodium chloride and sodium sulfate through the ungrafted and grafted cellulose acetate films were studied. Permeability increases with the increase in the extent of grafting of acrylamide; whereas it decreases with the increase in the extent of grafting of styrene onto cellulose acetate. The same trend in permeability was observed when cellulose acetate was grafted with the binary monomer mixture. Permeability is also found to depend on the nature of the solute dissolved in water. The results were discussed in terms of free volume concept of the water‐swollen films.
Infrared study of combined effect of γ‐radiation and elevated temperature on poly(vinyl chloride)
Authors: Rabie S. M. , Moharram M. A. , Daghistani A. Y.
Published: April 2003

Infrared absorption spectroscopy has been used to investigate the combined effect of γ‐radiation and heat on poly(vinyl chloride) (PVC). The recorded spectra showed that exposure of PVC samples to gamma doses from 0.5 to 15 Mrad results in remarkable changes in the absorbances of their absorption bands. Also, the exposure to doses from 3 to 15 Mrad results in an appearance of a CO band at 1720 cm−1 and OH band at 3450 cm−1. The nature of the formation of these bands was discussed in terms of peroxide‐mediated oxidative degradation mechanism. Moreover, it was found that heat treatment of PVC samples over the temperature range 25–180°C causes no noticeable changes in their spectra apart from slight changes in the absorbances of the bands. On other hand, it was found that heat treatment of the irradiated samples causes considerable increase in the intensity of the CO band. In addition to the well‐defined and sharp band appearing at 1720 cm−1, the spectra of the samples irradiated with 10 and 15 Mrad exhibited two bands at 1070 and 1120 cm−1. The obtained data led also to the conclusion that the CCl bands cannot be used as a measure of crystallinity of PVC.
Gas transport in poly(vinyl benzoate)
Authors: Hirose Takuji , Mizoguchi Keishin , Kamiya Yoshinori
Published: April 2003

The transport parameters of nine gases (O2, N2, CO2, He, Ne, Ar, Kr, Xe) through poly(vinyl benzoate) (PVB) have been measured by the time lag method above and below the glass transition temperature, Tg The results are compared with the related data of poly(vinyl acetate) (PVAc) by Meares and discussed as the effect of replacement of the methyl group by a phenyl group in the side chain of PVAc. Small molecules, such as H2, He, and Ne, diffuse more easily through PVAc than PVB, but the tendency is reversed for the larger gases. The activation energy for diffusion is proportional to the squares of the Lennard–Jones diameters of the gases below the Tg. On the other hand, above the Tg, linear relation is obtained to the cubes of the diameters. Solubility behavior is discussed by comparing the heats of solution for PVB and PVAc.
Bisulfite–persulfate‐initiated grafting of methyl methacrylate onto gelatin
Authors: KláSek A. , BačáKová M. , Kaszonyiová A. , Pavelka F.
Published: April 2003

Grafting of methyl methacrylate onto gelatin, initiated by the bisulfite–persulfate redox system, has been studied. Using the method of statistical planning of experiments, regression equations have been obtained describing the effects of the methyl methacrylate concentration and the composition of initiating system on the factors characterizing the grafting reaction. Possibilities of the reaction conditions optimalization are discussed.
Solution‐induced changes in the properties of polyethylenes
Authors: Ajji A. , Schreiber H. P. , Rudin A. , Teh J. W.
Published: April 2003

The chain entanglement states in high density, linear low density, and low density polyethylenes (HDPE, LLDPE, and LDPE) have been modified by recovering the polymers from solutions in trichlorobenzene (TCB) and p‐xylene. In the thermodynamically good solvent, TCB, the entanglement density is assumed to be sharply reduced, a condition which is carried over to the corresponding solids. These display transient, but large increments in tensile moduli, slight changes in stress at rupture, and decreases in dynamic mechanical parameters and in elongation at rupture. Scanning calorimetry also shows these solids to have reduced crystallinity. Much smaller property modifications are noted in corresponding samples recovered from p‐xylene. This liquid is a poorer solvent, particularly for HDPE and LLDPE. The results indicate that property modifications due to deliberate changes in the entanglement states of the polymers are a general phenomenon in the polyethylenes, and the magnitude of property changes depends on parameters of the molecular weight distribution. Chain branching does not seem to be a leading factor in the sensitivity of properties to modifications in the entanglement states. The property modifications produced by the present solution treatments are viewed as guides to the magnitude and duration of shear refining effects to be expected in HDPE, LLDPE, and LDPE polymers.
Dielectric behavior of wood–polystyrene composite
Authors: Poliszko Stefan , Hoffmann Grzegorz
Published: April 2003

The dielectric phenomena for alder wood natural and modified with polystyrene were studied. Temperature dependences of the complex permittivity components of these materials were obtained for the temperature interval from 100 to 450 K at the frequencies of measuring electric field of 420 Hz, 2 kHz, and 10 kHz. The changes in structure of wood cell walls were found, detected as an increase in number of polar functional groups taking part in the relaxation processes and as a partial freezing of conformational degrees of freedom of macromolecule fragments carrying these groups. The origin of the structural changes can be the efect of wood substance swelling caused by polystyrene, which penetrates the composite cell walls.
The viscoelastic properties of rubber–resin blends. III. The effect of resin concentration
Authors: Class J. B. , Chu S. G.
Published: April 2003

The viscoelastic properties of a rubber–resin blend, which influences performance of the blend as a pressure‐sensitive adhesive, depend upon the structure of the resin as well as its molecular weight. The effect of the concentration of a compatible resin in the blend was examined using a mechanical spectrometer. Four types of resins were used. These are the rosin esters, polyterpenes, pure monomer resins such as polystyrene and poly(vinyl cyclohexane), and petroleum stream resins. Each was examined in blends with both natural rubber and styrene–butadiene rubber over a range of concentrations. It is shown that the temperature of the tan δ peak for compatible systems can be predicted by the Fox equation, T = W1T + W2T, where W1 and W2 are the weight fractions of the resin and rubber, respectively, and the Tg's are the tan δ peak temperatures in K. The plateau modulus G for a blend can be identified as the G′ value in the rubbery plateau at the point where tan δ is at a minimum. The relationship between G and G, the plateau modulus for the undiluted elastomer, is shown to be proportional to the volume fraction of the elastomer raised to the 2.3–2.4 power for natural rubber with six different compatible resins. The exponent for styrene–butadiene rubber is 2.5–2.6 with four different resins. Using these relationships, both the tan δ peak temperature and plateau modulus can be predicted for a rubber–resin system from data on the unmodified elastomer and on one typical rubber–resin blend.
Simulation of Vortex growth in planar entry flow of a viscoelastic fluid
Authors: Mitsoulis E. , Vlachopoulos J. , Mirza F. A.
Published: April 2003

A numerical simulation of entry flow in a slit die has been undertaken for a fluid that is Newtonian in shear but exhibits normal stresses (Boger fluid). Experimentally measured normal stress and viscosity data are included in a simple rheological model. Flow patterns reveal the existence of vortices in the reservoir corners. Vortex size and intensity increase rapidly with elasticity level.
Evidence for the presence of cage reaction in the initiation step of thermal polymerization of styrenes by field desorption mass spectrometry
Authors: Hara J. , Teramae N. , Saito J. , Tanaka S.
Published: April 2003

Field desorption mass spectrometry (FDMS) was applied to the study of the initiation mechanism of thermal polymerization of styrenes. The FD mass spectrum was measured for a cooligomer of α,α,β‐trideuterostyrene and p‐methoxystyrene produced by thermal polymerization using ethylbenzene as a solvent, and this was compared with the spectrum of an oligomer of p‐methoxystyrene. The above two FD mass spectra showed characteristic differences, depending upon the number of hydrogen and deuterium atoms and upon the presence or absence of the methoxy group, in the oligomers. Molecular species observed in the spectra were identified based on these considerations. As a result, we could distinguish the “true trimer” produced from three monomers from the “cross trimer” produced from fragments of five monomers. It was found that the “true trimer” was the major constituent in the trimer region, and that the “true trimer” was produced mainly by the cage reaction between initiating radicals.
Characterization of reverse osmosis membranes prepared from the oxime of poly(4‐vinylpyridine‐co‐methyl vinyl ketone)
Authors: Oikawa Eizo , Igarashi Yusuke , Tsurumaki Shigeru
Published: April 2003

The copolymer (4VK) of 4‐vinylpyridine (4VP) and methyl vinyl ketone (MVK) was nearly quantitatively converted into an oxime (4VKX) which could be complexed with various metal salts. 4VKX was compared with 4VK in their membrane performance. When crosslinked with divinyl sulfone (DVS), the 4VKX membrane showed a higher strength than cellulose acetate (CA) membrane and a higher performance than 4VK membrane crosslinked with dihydrazine derivatives. The most adequate DVS content and copolymer composition were found to be 25 mol % based on MVK oxime and 1:1, respectively. A metal salt taken up by the membrane in a much larger amount tended to be highly rejected. The crosslinking quaternization of 4VKX with diisobutane (DIB) very effectively improved water permeability, as did 4VK, and gave a membrane performance superior to that of 4VK. The most appropriate charge ratio of DIB was 15–20 mol % based on 4VP. Some transport characteristics and compaction in a long‐term operation were investigated and discussed.
Equation of state for polymer liquids
Authors: Hartmann Bruce , Haque Mustafa A.
Published: April 2003

An empirical pressure–volume–temperature (PVT) equation of state is presented for polymers in the liquid state, i.e., above the melting point of a crystalline polymer or the glass transition of an amorphous polymer. In terms of reduced variables, the equation is given by \documentclass{article}\pagestyle{empty}\begin{document}$\overline {PV^5 } = \overline {T^{{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} } - \ln {\rm }\overline V $\end{document}. Values of the three reducing parameters are given for 23 polymers. Comparison of the predictions of this equation with experimental data are made for all of the polymers. The data are generally available up to a pressure of 2 kbar and a temperature 100°C above the melting or glass transition temperature. Measured and calculated volumes agree within about 0.001 cm3/g, which is the accuracy of the measurements. Detailed comparisons with the empirical Tait equation are made. Equations are also presented for isothermal bulk modulus, thermal expansion coefficient, and Gruneisen parameter.
Effects of water sorption at different temperatures on permanent changes in an epoxy
Authors: Netravali A. N. , Fornes R. E. , Gilbert R. D. , Memory J. D.
Published: April 2003

Crosslinked epoxy resins, tetraglycidyl 4,4′‐diamino diphenyl methane cured with 4,4′‐diamino diphenyl sulfone, were soaked in water at either 25°C or 70°C for varying lengths of time. The infrared spectra and DSC thermograms were obtained for samples that were soaked, or soaked and dried. There was a monotonic decrease in exothermic reaction energy with water content. The glass transition was also lowered, although samples soaked at 70°C showed a leveling in the Tg around 115°C. When the soaked samples were dried, the exothermic reaction energy showed near reversibility for samples soaked at 25°C while the 70°C samples were highly irreversible. IR of the latter samples showed that the 70°C water soaking resulted in reaction of some of the unreacted epoxide groups that remained after the initial cure.
Linear polythioesters. X. Products of interfacial polycondensation of bis(4‐mercaptophenyl)ether with izomeric phthaloyl chlorides
Authors: Podkoscielny Wawrzyniec , Wdowicka Danuta
Published: April 2003

New polythioesters were obtained by interfacial polycondensation of bis(4‐mercaptophenyl)ether with phthaloyl, isophthaloyl, and terephthaloyl chlorides. To determine the optimal conditions for interfacial polycondensation, the influence of the following factors on yield and value of reduced viscosity were studied: organic phase, 100% excess of sodium hydroxide, contribution of benzyltriethylammonium chloride as a catalyst, and the temperature of the reaction. A thorough examination of the process was carried out only for polycondensation of dithiol with phthaloyl chloride. Yield of all reaction products as well as reduced viscosity of only polythioesters from dithiol and phthaloyl chloride were found because these were the ones which were soluble in tetrachloroethane. The structure of all polythioesters was determined by elemental analysis and infrared spectra. Initial decomposition and initial intensive decomposition temperature were defined by the curves of thermogravimetric analysis. Some mechanical and electrical properties of polythioesters were determined.
The dynamic mechanical behavior of paper during drying
Authors: Htun Myat , De Ruvo Alf , Fellers Christer
Published: April 2003

The dynamic mechanical properties of paper during restrained drying are reported in this article. The apparatus used was a servohydraulic material testing system (MTS), connected to a computer unit. It has been found that the ratio of drying stress to elastic modulus at a given dry solids content corresponds to the instantaneous linear contraction of the sheet when the drying stress is relieved. It is therefore deduced that paper behaves as a linear viscoelastic body during restrained drying. The finding of a maximum loss coefficient and the drastic change in elastic modulus during drying of paper are interpreted in terms of a transitional change in the amorphous regions of wood polymers plasticized by water.
The effects of heat transfer in melt spinning
Authors: Maebius R. E.
Published: April 2003

Several heat transfer models are examined in order to assess the influence of convection and radiation upon the melt spinning of a Newtonian fluid. In the spinning of glass fibers, radiation is shown to be equally as important a mode of heat transfer as convection. Small changes in the spectral emissivity are shown to have a large effect on the shape of the jet and the drawing force required to attenuate the fiber.
Coupling of glass fiber with polypropylene by gamma radiation
Authors: Mukherjee A. K. , Sharma P. K.
Published: April 2003

The effect of 60CO gamma radiation on polypropylene and glass‐fiber‐reinforced polypropylene was investigated. The glass fiber content in the reinforced polypropylene was observed to influence the mechanical properties of the original polypropylene. The initial modulus and off‐set yield strength (at 0.25% strain) increased with the dose and glass fiber content. The tensile strength showed an initial decrease with the increase in glass fiber content followed by an increasing trend. A similar behavior was found with increasing dosage. The extent of fiber breakage during processing was higher at higher glass fiber content. However, the fiber length distribution became narrower beyond 2.45% glass fiber content in the polypropylene.
Enthalpy relaxation of filled copolymers
Authors: Kumar S. , Salovey R.
Published: April 2003

Excess enthalpy following annealing at various periods of time at Tg −10°C was measured by differential scanning calorimetry of electrophotographic toners, copolymers of styrene and butyl methacrylate containing carbon black. An approximate equilibrium enthalpy relaxation after annealing the pure copolymers for one month was 3.30 kJ/kg for a copolymer with 66.5% styrene and 2.72 kJ/kg for a copolymer containing 49.8% styrene. The rate of enthalpy relaxation was reduced by increasing the styrene content of the pure copolymer. The incorporation of a carbon black with high surface area reduces the rate of enthalpy relaxation, increasing in effectiveness with butyl methacrylate concentration.
Rubber‐toughening in polypropylene
Authors: Jang B. Z. , Uhlmann D. R. , Sande J. B. Vander
Published: April 2003

To deformation and fracture behavior of several polypropylene (PP) and rubber‐modified PP materials have been investigated. Plastic deformation mechanisms of these systems depend upon the test rate and temperature with high rates and low temperatures being in favor of crazing. The ductility and toughness of these materials are explained in light of the competition between crack formation and the degree of plastic deformation through crazing and shear yielding. The second phase morphology with smaller average rubber particle diameter D appears to be more efficient than that with larger D in toughening PP. Theoretical calculations indicate that the stresses imposed upon the rubber particles due to volume shrinkage of PP during crystallization are sufficient to compensate for the stresses due to differential thermal contraction in cooling from solidification temperature to end‐use temperature. The difference between these two is small, and therefore they provide very little contribution to interfacial adhesion between rubber particle and PP matrix, the adhesion being insufficient for the rubber particles to be effective in controlling craze propagation. The rubber particles, in addition to promoting crazing and shear yielding, can also improve the fracture resistance of PP by varying the crystalline structure of PP (e.g., reducing the spherulite dimensions).
Trifluoroethanol/chloroalkane mixtures: Excellent novel solvents for aliphatic polyamides
Authors: Aharoni Shaul M. , Cilurso Frank G. , Hanrahan James M.
Published: April 2003

Certain mixtures of TFE/CHCl3 were found to be excellent solvents for aliphatic polyamides such as nylon‐6, nylon‐66, nylon‐11, nylon‐12, nylon‐69, nylon‐610, and nylon‐612. Intrinsic viscosities were measured and Mark–Houwink coefficients determined for nylon‐6/TFE/CHCl3, indicating TFE‐rich mixtures to be better solvents than TFE alone. Similar results were obtained for TFE/CH2Cl2. Four ternary phase diagrams were constructed for nylon‐6/TFE/chloroalkanes, of which the ones with CHCl3 and CH2Cl2 are the most interesting. In the nylon‐6/TFE/CHCl3 diagram higher nylon‐6 solubility in TFE‐rich mixtures and a biphasic region in the CHCl3‐rich compositions are evident. In the TFE/CH2Cl2 system, the higher dissolution of nylon‐6 is observed, but no biphasic regions are detected. In certain solvent compositions and/or polymer concentrations the polymer is incompletely soluble, making the phase diagrams rather complicated. Observed thermodynamic excess properties appear to relate to the quality of TFE/chloroalkanes as solvents for nylon‐6. Studies on swelling of nylon‐6 networks immersed in TFE/CHCl3 show a behaviour previously described by Krigbaum and Carpenter for a general case where the formation of contracts between molecules of the two solvents is discouraged and their preferential solvation of the polymer is, therefore, encouraged. The phenomena observed in this work can be qualitatively explained as arising from antagonistic interaction of TFE molecules with chloroalkane ones. The presence of the polyamides in solution reduces such contacts, enchancing the dissolution of the polymer in the (TFE‐rich) solvent mixtures.
Dynamic mechanical measurements on monofilaments
Authors: Rong Shu‐De , Williams H. Leverne
Published: April 2003

Monofilaments were obtained or extruded and drawn to representative degrees. The dynamic mechanical properties of polyether based polyurethane, high density polyethylene, and polycaprolactam monofilaments produced commercially and of laboratory prepared monofilaments of low and high density polyethylene, poly(ethylene terephthalate), and poly(tetramethylene terephthalate) were measured. The data are compared with those from oriented film and amorphous or unoriented film when possible. The effect of orientation on the properties was clearly detectable as was the effect of absorption of water vapor on polycaprolactam.
Effect of a variation in kinetic parameters (rate constant, activation energy) on the vulcanization of rubber sheets in injection molding process
Authors: Ferradou C. , Rochette B. , Vergnaud J. M.
Published: April 2003

As shown previously, a slight variation in the kinetic parameters (rate constant, activation energy) of the cure reaction has a pronounced effect on the vulcanization of rubber. The purpose of this work is to show that this effect is more important when the injection molding process is used and the temperature of injected rubber is higher. Experiments were performed using microcalorimetry for determining the kinetic parameters, and a heated mold pressing a 2 cm thick rubber sheet. The resulting variations in the temperature and state of cure at the midplane of sheets were calculated and compared for different temperatures of injected rubber ranging from 40 to 140°C, while the temperature of the mold was kept constant at 180°C.
Antiinflammatory polymer‐bound steroids for topical applications. I. Synthesis and characterization
Authors: Khue Nguyen Vu , Galin J. C.
Published: April 2003

Covalent binding of hydrocortisone and dexamethasone to hydrophylic biocompatible macromolecular carriers through hydrolizable carbonate linkage was investigated according to two complementary strategies. (a) Radical copolymerization of hydrocortisone‐21C‐vinylcarbonate with N‐vinylpyrrolidone (NVP,60°C), or N‐[tris(hydroxymethyl)methyl]acrylamide (THMMA, 50°C) in dimethylacetamide solution: In spite of a nearly zero reactivity ratio for the steroid monomer which behaves as a degradative transfer agent—CT ∼ 5.7 × 10−2 and 6.8 × 10−3 for NVP and THMMA, respectively–this process may afford fairly high molecular weight polymers (M̄w ≃ 104–105) with high enough hydrocortisone content (0.03–0.10 mole.fraction). (b) Condensation of the hydrocortisone or dexamethasone‐21C‐chloroformates onto poly(oxyethylene glycol) (M̄n = 6220) or hydroxypropylcellulose (HPC, M̄w = 1.35 × 105) in tetrahydrofuran solution (30°C): This straightforward process is of low efficiency (yields >50%), and only HPC derivatives show good chemical homogeneity.
Estimation of interaction between polyanions and bovine serum albumin by means of affinity chromatography
Authors: Kuramoto Noriyuki , Sakamoto Munenori , Komiyama Jiro , Iijima Toshiro
Published: April 2003

The ligand binding of some polyanions to bovine serum albumin immobilized on Sepharose 4B has been studied by column affinity chromatography. Frontal chromatography using a polyanion of low concentration on an affinity adsorbent gave the dissociation constant Kd of the polyanion‐immobilized ligand complex. Kd values determined under various concentrations enabled us to discuss in detail the interactions of bovine serum albumin and polyanions.