bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cured polyesters based upon bisacid A2: Water absorption, toluene resistance, and resistance to 5% aqueous HNO3 and NaOH
Authors: Lenk R. S. 
Published: April 2003

AbstractEarlier papers have described the preparation and purification of bisacid A2,1,2 the preparation and cure of crosslinkable polyesters,3 the thermal properties of cast sheet,4 and the mechanical properties of glass fiber laminates5 which were made from reactants that included bisacid A2 in two series of cocondensates. The present paper details the water absorption and the long‐term effects (up to 12 months) of toluene, 5% aq. HNO3, and 5% aq. NaOH. The effects of the last two were found to be negligible, but the water absorption and the toluene resistance appeared to be capable of correlation with the known composition and the inferred structure of the copolyesters.
Reinforcement factors in fibers from block copolyamides and polyamide blends
Authors: Zimmerman J. , Pearce E. M. , Miller I. K. , Muzzio J. A. , Epstein I. G. , Hosegood E. A. 
Published: April 2003

AbstractThe modulus of a fiber can be increased by plying with it a higher‐modulus fiber. In this case, the modulus of the combination is characterized by a springs‐in‐parallel model, and the modulus of the composite is a linear function of the per cent of the second fiber in the composite. Another method of obtaining reinforcement is to melt‐blend a higher‐modulus polymer with the substrate polymer. With polyamides, this leads to a certain degree of amide interchange and block copolymer formation which depends on the compatibility of the polymers as well as on the usual kinetic factors. If the dispersion of the higher‐modulus polymer is such that aggregate size is relatively large (e.g., ≥500 Å) and if the adhesion between the two polymers is good, a springs‐in‐parallel‐type reinforcement is the best which can be obtained. In melt‐blend polyamides, a “nonclassical” phenomenon in reinforcement has been noted when the diameters of the dispersed aggregates are ≤500 Å and when there are a relatively high number of hydrogen bonding sites on both polymer components. In this case, it appears that moduli appreciably higher than predicted from a springs‐in‐parallel model are obtained as well as higher than expected Tg values. A mechanism is proposed to account for this “nonclassical” behavior along with data to support it. Another type of anomaly is observed when the components of the blend are isomorphous. In this case, the reinforcement is considerably less than expected.
Relations between viscoelastic parameters of hydrophobic fiber and dyeing with disperse dyes
Authors: Supanekar S. D. , Daruwalla E. H. 
Published: April 2003

AbstractExperimental evidence is presented to show that the kinetics of dyeing of hydrophobic fibers with disperse dyes can be represented by an equation of the same form as the well‐known equation giving creep in fibers. A mechanism is proposed whereby one can regard the dye uptake in the fiber at a constant temperature as a viscoelastic phenomenon in the dye‐polymer system. A comparison of these two equations enables the dyeing constants to be interpreted in terms of the viscoelastic parameters of the system. It is also possible to find the upper bounds for the dyeing rate and a condition for rapid dyeing on the same basis.
Formation of an amorphous powder during the polymerization of ethylene in a radio‐frequency discharge
Authors: Kobayashi Hiroaki , Bell Alexis T. , Shen Mitchel 
Published: April 2003

AbstractAn investigation has been carried out to determine the influence of operating conditions on the character of the final product resulting from the polymerization of ethylene in a radio‐frequency discharge. It has been found that low pressures and high ratios of discharge power to gas flow rate lead to the deposition of a powder as well as a film. From visual observations of powder deposition, it has been possible to divide the plane formed by the axis of pressure and flow rate into a region in which powder is deposited together with a film and a region in which only a film is deposited. Numerous physical measurements have been carried out in order to characterize the powder. From these measurements, it has been concluded that the powder is a relatively dense, amorphous, and highly crosslinked polymer composed of short‐chain segments containing no more than two adjacent methylene groups. Many forms of unsaturation have been observed which, together with the high crosslink density, explain the measured hydrogen‐to‐carbon ratio of 2.7 to 2. Evidence of oxidation has been observed through the appearance of hydroxyl and carbonyl bands in the infrared spectrum of the polymer. A mechanism for the formation of the powder has been proposed which suggests that the polymerization of the powder takes place totally in the gas phase.
The influence of the stretch ratio on the rate of diffusion in a wet‐spinning process
Authors: Doppert H. L. , Harmsen G. J. 
Published: April 2003

AbstractThis article describes diffusion experiments on a single filament spinning set. The aim was to find phenomena which may occur in any wet‐spinning process. An alkaline poly(vinyl alcohol) solution containing an indicator was spun out into a coagulation bath containing Na2SO4, after which the filament was guided into an acidic second bath. The first bath served to deswell the filament in order to avoid contamination in the diffusion study. In the second bath the diffusion of H+ and OH− ions was studied by measuring the distance which had to be covered by the filament in order to produce a color change of the indicator at the center of the filament. The equation for cylindrical diffusion was tested at various mechanical adjustments of the spinning set. It was found that the rate of diffusion decreases with increasing stretch ratio. Moreover, the relevant diffusion equation is qualitatively very well applicable to the phenomena considered, provided the applied stretch ratio is taken into account.
Bulk polymerization of methyl methacrylate
Authors: Balke S. T. , Hamielec A. E. 
Published: April 2003

AbstractThis manuscript reports on an experimental investigation of the chemical‐initiated (AIBN) bulk polymerization of methyl methacrylate to limiting conversion at temperatures of 50°C, 70°, and 90°C. The change in the cumulative differential molecular weight distribution (CDMWD) with respect to conversion was measured by gel permeation chromatography (GPC). These CDMWD's were differentiated to determine the instantaneous differential molecular weight distribution (instantaneous DMWD) over the range of conversions investigated. These experimental instantaneous DMWD's were found to agree with theoretical distributions predicted by classical free‐radical kinetics over the entire conversion range and where diffusion control of the termination reactions is dramatic. A correlation of the dimensionless group α (where α = ktdRp/kp2M2) with free volume is proposed. This correlation appears to adequately account for diffusion control of the termination reaction. A kinetic model for the bulk polymerization of methyl methacrylate has been developed. This model should find use in the design, simulation, and optimization of PMMA reactors.
Block copolymers of polycarbonates with several hydroxy‐terminated elastomers to yield thermoplastic elastomers for higher service temperature
Authors: Memon Nazir A. , Williams H. Leverne 
Published: April 2003

AbstractThe synthesis of block copolymers and the study of their morphology were undertaken to find improved thermoplastic rubbers for service at elevated temperatures. The basis was the extraordinary properties possessed by ABA‐type block copolymers in which the terminal blocks are polystyrene and the central block is either polyisoprene or polybutadiene. In these systems it has been well established that the unusual properties are a result of domain formation in which the hard and the soft blocks aggregate separately into distinct phases. The hard segment is thought to act both as a crosslink and as a filler. Block copolymers were synthesized with different soft and hard segments. The effects of these segments and of their properties on the morphology and the stress‐strain properties of the block copolymers were measured and evaluated. Electron microscopy and birefringence were used to determine the morphology. It was found that the glass transition temperatures of the segments, the bulk of the monomer unit in the glassy segment, and the morphology determined the strength of the material. Some of the materials prepared have tensile strengths of 0.1 kg/cm2 or more at temperatures in excess of 180°C and therefore appear promising as elastomers for service at elevated temperatures.
Dynamic mechanical properties of epoxy–rubber polyblends
Authors: Kalfoglou Nikos K. , Williams H. Leverne 
Published: April 2003

AbstractThe dynamic mechanical properties of the epoxy resin of the diglycidyl ether of bisphenol A cured with varying amounts of a carboxyl‐terminated butadiene–acrylonitrile copolymer were determined. Isochronal measurements were made between −90° to 170°C for eight compositions. Mechanical relaxations indicate the degree of interaction and the state of mixing of the two‐phase system. Phase reversal occurs at a volume fraction of 0.5, where an intermediate compound is formed. In the low concentration range of the elastomeric phase, the impact strength improvement correlates well with an increase in the energy absorption of the relaxation. The known morphology of the system at this composition range allowed testing of various phenomenological mechanics models proposed to calculate the tensile properties of composite systems.
The structure and physical properties of anionically polymerized nylon 6 crosslinked by bislactams
Authors: Šimůnková E. , Zelinger J. , Kubánek V. , Králíček J. 
Published: April 2003

AbstractCrosslinked polyamides prepared by copolymerization of ϵ‐caprolactam with bislactams under conditions of activated anionic polymerization proceeding adiabatically below their melting point show differences in physico‐mechanical properties. Owing to varying copolymerization rates of bislactams, depending on the position of the connecting bridge of the bislactam in relation to the amido group, copolymers with different morphological structure are formed. The differences in the mechanical properties of the copolymers are explained on the basis of the differences in the morphological structure. This explanation is supported by results obtained by measuring the thermal and dynamic properties.
Influence of the die entry angle on the entrance pressure drop, recoverable elastic energy, and onset of flow instability in polymer melt flow
Authors: Han Chang Dae 
Published: April 2003

AbstractAn experimental study has been carried out to investigate the effects of die entry angle on the entrance pressure drop, recoverable elastic energy, and onset of melt fracture in the flow of viscoelastic polymeric melts through a capillary die. For the study, capillaries with an L/D ratio of 4 and with varying die entry angles, 15°, 30°, 60°, 90°, 120°, and 180°, were used for extruding low‐density polyethylene and high‐density polyethylene. Measurements were taken of wall normal stresses along the upstream reservoir section, tapered conical section, and straight capillary section.
Molecular weight determination of high polymers by means of vapor pressure osmometry and the solute dependence of the constant of calibration
Authors: Bersted Bruce H. 
Published: April 2003

AbstractData are presented to show that the calibration constant of the vapor pressure osmometer is in fact not a constant, but rather depends on the nature of the solute. It is shown that the assumption of the constancy of the calibration constant is particularly severe when comparing low molecular weight standards and polymeric materials. A model is presented which visualizes either condensation or evaporation taking place at the solution drop surface, depending on the relative magnitudes of the concentration and Thermistor self‐heating. In terms of this model, the solute dependence of the calibration constant is attributed to the formation of a diffusion‐controlled surface concentration of the solution drop that differs from the concentration of the drop as a whole. Experimental evidence consistent with a diffusion‐controlled surface layer is given. A method based on this model is given for operating the instrument so that the solute dependence of the calibration constant disappears. When the instrument is run in this manner, Mn determinations from vapor pressure and membrane osmometry are in significantly better agreement than when the instrument is operated as recommended by the manufacturer.
Gel permeation chromatography. VIII. A study of the effect of column arrangement of resolution at normal and overloading concentrations
Authors: James P. M. , Ouano A. C. 
Published: April 2003

AbstractIn the determination of molecular weight distributions by GPC, the traditional column arrangement is such that the fractionation process proceeds from a high‐permeability limit to a low‐permeability limit column. We report computer comparisons of data obtained from columns in their normal ordering (high‐ to low‐permeability limit), reverse ordering, and random ordering. The columns had a permeability limit range from 1 × 106 Å down to 1 × 103 Å, and the polymers had a molecular weight range of 1.8 × 106 down to 2.1 × 103. The concentrations used varied from 0.05% up to 0.5%. The data show significantly different results, with the random arrangement the preferred ordering. A qualitative model for the separation mechanism is presented to account for the improvement in resolution. Additional data are presented which show that serious errors (as high as 45%, depending on concentration) will be encountered in GPC studies, unless the calibration curve is obtained at the same relative concentration as the samples, with definite overloading effects occurring at the higher concentrations. A new method of curve fitting was used in the higher molecular weight region to give meaningful calibration curves.
Solution polymerization of acrylamide to high conversion
Authors: Ishige T. , Hamielec A. E. 
Published: April 2003

AbstractThe solution polymerization of acrylamide initiated by 4,4′‐azobis‐4‐cyanovaleric acid (ACV) at high monomer concentrations in the temperature range 25–50°C has been studied. Molecular weight distributions were measured by gel permeation chromatography and by electron microscopy. Molecular weight measurements show that transfer to monomer plays a dominant role in controlling the molecular weight averages.
On some rheological phenomena of amorphous polymers
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractThe molecular domain model for flexible macromolecules is presented in brief, and various observations are enumerated, indicating that the model holds true for the solid, melt, and solutions of different concentrations. The four forms in which the domains can exist under shear stress are then presented, and, by referring to them, such rheological phenomena as “die swell,” sudden jumps in flow rate, critical concentrations, and changes in viscosity are qualitatively explained.
Polymerization in an electrodeless glow discharge. II. Olefinic monomers
Authors: Yasuda H. , Lamaze C. E. 
Published: April 2003

AbstractThe rates of polymer deposition from various olefinic monomers in an electrodeless glow discharge were studied. The previously found empirical relationship (with styrene in part I) between the rate of polymer deposition R, the monomer pressure pM, and gas pressure px in a steady‐state flow system (i.e., R = a(pM)2 [1 + b(px)], R being nearly independent of the discharge power) was also found with all monomers investigated. (The effect of gas was examined with nitrogen in this study.) However, it was found that the polymer deposition is controlled by the monomer flow rate and Ro (in pure monomer flow) is proportional to the flow rate of monomer Fw (based on the weight); i.e., Ro = kFw, where k is a characteristic rate constant of the polymerization. Olefinic monomers can be generally classified into two major groups, i.e., type A monomers which predominantly polymerize, and type B monomers which decompose in a glow discharge. Type B monomers have smaller values of a and k compared to type A monomers. The values of a and k for type A monomers both increase with increasing molecular weight of the monomer. The values of k for all monomers investigated are within roughly an order of magnitude, indicating that the reactivity levels of monomers are very similar in a glow discharge polymerization.
Terpolymers. III. Isochronal viscoelastic parameters for terpolymers of vinyl stearate, vinyl acetate, and vinyl chloride
Authors: Jordan Edmund F. , Riser George R. , Artymyshyn Bohdan , Wrigley A. N. 
Published: April 2003

AbstractIsochronal viscoelastic parameters were collected for many of the copolymers, terpolymers, and diluent mixtures whose mechanical properties at ambient temperatures were reported in the preceding paper. In the polymeric systems, vinyl stearate, acting as the primary internal plasticizer, was introduced into terpolymers by displacing vinyl acetate from base copolymers of vinyl acetate and vinyl chloride, across the range of composition. In the diluent mixtures, poly(vinyl chloride) was plasticized by di‐2‐ethylhexyl phthalate across the range of compositions. For direct comparison with the mixtures, vinyl chloride was plasticized by copolymerization with vinyl stearate across the same range of compositions. Moduli for the co‐ and terpolymers reached the low values characteristic of soft materials at room temperature only through a short range of vinyl stearate composition. At higher internal plasticizer compositions, side‐chain crystallization stiffened the samples and raised their moduli. In contrast, moduli for the mixtures decreased steadily with increase in diluent at ambient temperature. The effective use temperature ranges were narrow for the co‐ and terpolymers but broad for the mixtures. Curve broadening was similar for both types of systems, but reached a maximum at about 40 weight‐% plasticizer for the diluent mixtures. The slopes of the glassy modulus with decreasing temperature at 50°C below Tg for the vinyl stearate copolymers were relatively large. However, moduli close to that of poly(vinyl chloride) were reached only near the temperature range associated with the γ‐transition. Consequently, this behavior was attributed to motions of the side chains in the glassy matrix. Room temperature moduli, which could be obtained before the onset of melting, were correlated with the fractional side‐chain crystallinity for polymers having a high vinyl stearate content. From this relation, the modulus for the hexagonal crystal form of the side‐chain crystallites of poly(vinyl stearate) was estimated to be 1.2×1010 dynes/cm2. Moduli for the glassy amorphous phase of this same polymer appeared to have one sixth of this value at 40°C below the glass transition. The glass transition temperature occurred about 10° below the inflection temperature at 109 dynes/cm2, as an average for all of the systems studied.
Molecular weight distributions of standard polystyrene samples by GPC and by sedimentation velocity analysis
Authors: Tung L. H. , Runyon J. R. 
Published: April 2003

AbstractIn precision gel permeation chromatographic (GPC) work, the spreading (zone spreading) characteristics of the instrument must be calibrated. Standard samples of anionic polystyrene have been used for this purpose. The molecular weight distributions of these standard samples, nevertheless, have not been determined carefully. In this work, several standard polystyrene samples obtained from Pressure Chemical Company were examined by GPC and by sedimentation velocity analysis. The results show that (1) the high molecular weight polystyrene samples have skewed molecular weight distributions as has been suspected and that (2) the present data treatment technique for GPC is effective for these very narrow‐distribution samples.
Thermal conductivity of polymer melts
Authors: Ramsey J. C. , Fricke A. L. , Caskey J. A. 
Published: April 2003

AbstractThermal conductivities were measured for melts of a series of polypropylene and a series of polyethylene samples that had been characterized by GPC. Results indicate that thermal conductivity depends upon the molecular weight distribution and degree of branching of the polymers. The results of this work can probably be used to predict the thermal conductivity of a commercially available polypropylene or polyethylene to within 25%.
Thiolation of starch and other polysaccharides
Authors: Trimnell D. , Shasha B. S. , Doane W. M. , Russell C. R. 
Published: April 2003

AbstractThiolated starches with a degree of substitution of 0.01–0.6 were obtained by pyrolysis of starch dithiobis(thioformates) followed by saponification. The pyrolytic decomposition of dithiobis(thioformates) followed two pathways: (1) to thionocarbonate , carbon disulfide, and sulfur, and (2) to dithiocarbonate , carbonyl sulfide, and sulfur. Only the second pathway affords thiolation. Thiol groups were determined by Ellman's reagent, by sulfur analyses, and, following acetylation, by the ratio of O‐acetyl versus S‐acetyl absorption in nuclear magnetic resonance spectra. The poly‐saccharides cellulose, dextran, and xylan were thiolated by the same procedure.
Predicting solubilities of vinyl polymers
Authors: Manning A. J. , Rodriguez F. 
Published: April 2003

AbstractAccurate solubility limits of polymers are best expressed by molecular weight fractionation curves. Individual curves may be obtained for each polymer–solvent (–nonsolvent) system. A method for predicting solubility behavior, based on solubility parameter δ and hydrogen bonding index γ, is proposed here. The correlation is of the form

where [η] = intrinsic viscosity of precipitated polymer; T = absolute temperature; (v.f.) = volume fraction of solvent; R = (δs − δn) − 0.3(γs − γn); Q = (γp − γe)2.2/(δp − δe); p refers to polymer; s refers to solvent; n refers to nonsolvent; e refers to solvent system at theta temperature; and a,b,c, and k are fitted constants. The correlation was derived from data for poly(vinylpyrrolidone) and polyacrylamide. It probably is limited to systems in which the precipitate occurs as a liquid.
Diffusion of water and caprolactam in nylon 6 melts
Authors: Nagasubramanian K. , Reimschuessel H. K. 
Published: April 2003

AbstractThe diffusions of both caprolactam and water from nylon 6 melts have been measured using a semiinfinite geometry. The process involving diffusion and chemical reaction was analyzed utilizing Higbie's penetration model and known kinetic data. The caprolactam and water diffusion coefficients are, respectively, 8 × 10−8 and 2.5 × 10−4 cm2/sec. Using the data, molecular weight profiles were obtained for both semiinfinite and cylindrical geometries as a function of melt depth and time.
Effect of blending on the rheological properties of polystyrene
Authors: Harris Everette K. 
Published: April 2003

AbstractExperimental non‐Newtonian viscosity, primary normal stress difference, complex viscosity, and shear stress relaxation were taken for highly fractionated polystyrene in Aroclor 1248 (a chlorinated biphenyl) as well as for blends differing in molecular weight and concentration. The data are described by three parameters: a zero‐shear rate value, the slope of the log–log plots in the high shear rate region, and a time constant defined as the inverse of the shear rate at the intersection of the low and high shear rate asymptotes. For the functions measured, the low shear rate region is characterized by a dependence on Mw and the high shear rate region by a dependence on Mn. Implications to polymer processing are discussed.