bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐density polyethylene melt elasticity—some anomalous observations on the effects of molecular structure
Authors: Mendelson R. A. , Finger F. L. 
Published: April 2003

AbstractThe die swell behavior of polymeric melts is a manifestation of melt elasticity of these materials and is of considerable commercial as well as fundamental importance. Hence, knowledge of the effect of such molecular variables as molecular weight (MW) and molecular weight distribution (MWD) on melt elasticity is important from both commercial and basic rheological points of view. The effect of these variables on melt elasticity of broad‐distribution polymers in the shear rate region of commercial interest is not unambiguously known, with most published theory and experiment being applicable to the low‐shear behavior of narrow‐distribution polymers and blends thereof. There is indication that die swell increases with increasing MW and broadening MWD. However, the current investigation of carefully characterized broad‐distribution HDPE materials prepared specifically to examine the effects of various molecular variables on melt elasticity does not support this contention and, in fact, provides consistent evidence for the opposite result, i.e., decreasing die swell with increasing MW or broadening distribution. The various samples studies were prepared by fractionation removal or addition of component molecular species or by polymerization designed to provide systematic variation of molecular species or by polymerization designed to provide systematic variation of molecular parameters. Overall MWD's of the samples were characterized, and die swell behavior was determined at 200°C over a wide shear rate region in a high L/D capillary both with and without annealing of extrudates. The results are presented showing effects of specific molecular variables.
Apparatus for torsional braid analysis by a digital data analyzer
Authors: Yano Shoichiro 
Published: April 2003

AbstractAs apparatus for torsional braid analysis (TBA), which is a variant of the torsional pendulum technique, a new method for recording the damped wave electrically, using an electric mater as a transducer, is described. In order to process a large volume of data, an instrument to print out digitally the amplitude and period of oscillation has been developed. The thermomechanical behavior of poly(vinyl chloride) is presented so as to demonstrate the use of the present TBA apparatus.
Fundamental studies on solvent dyeing with tetrachloroethylene. I. Diffusion of disperse dyes in poly(ethylene terephthalate)
Authors: Morita Zenzo , Kobayashi Ritsuko , Uchimura Koji , Motomura Hiromi 
Published: April 2003

AbstractThe diffusion of C.I. disperse Violet 1 and Violet 8 in poly(ethylene terephthalate) (PET) was investigated by the method of cylindrical film roll. The effect of tetrachloroethylene (TCE) on the properties of PET was also studied. The treatment of PET with TCE brought about a strong effect on the thermal properties without degradation of PET. The diffusion of disperse dyes in PET from the TCE dyebath was faster than that from the aqueous dyebath. The activation energies of diffusion in the temperature range of 60° to 95°C from the TCE dyebath were smaller than those from the aqueous dyebath. Some break points were observed in the Arrhenius plots of diffusion coefficients in PET from the TCE dyebath. They were lower than those observed at dry and water‐swollen states.
The influence of extent of polymerization on the thermal behavior of an epoxy‐based polyether resin
Authors: Lopata Eugene S. , Riccitiello Salvatore R. 
Published: April 2003

AbstractA number of studies have been reported in the literature on the polymerization and thermal decomposition of epoxide resins. Lee1 and Anderson2 have both studied the thermal decomposition of epoxy resins, and they concluded that the characteristic exothermic peak (which can occur anywhere between 300° and 400°C) is caused at least partially by some reaction of the epoxide group. We have been investigating the thermal decomposition of an aromatic polyether resin which is produced by curing the diglycidyl ether of bisphenol A (Epon 825) with the catalytic agent trimethoxyboroxine (Fig. 1). DTA studies of the polyether in an inert atmosphere of N2 showed exothermic peaks at approximately 390°, 430°, and 470°C, with the major exotherm being the one at 430°C. Our investigation has shown the important role played by low molecular weight epoxides in these exothermic reactions.
Determination of diffusion coefficients of water in cellulose acetate membranes
Authors: Palin Michael J. , Gittens Gerald J. , Porter G. Brian 
Published: April 2003

AbstractThe determination of the diffusion coefficient for water in various porosity cellulose acetate membranes by a gravimetric method, using a humidified carrier gas, is described. It was found to be impossible to obtain meaningful results for very porous membranes, although dense membranes gave limiting values of diffusion coefficient at high carrier gas velocities. This phenomenon is explained in terms of the dissipation of the heat of sorption by the forced convection provided by the carrier gas. The variation of diffusion coefficient with concentration of water in dense cellulose acetate is explained in terms of clustering of water molecules in the polymer at high concentration.
The structural causes of the dyeing variations of nylon 66 yarn subjected to the false‐twist texturing process
Authors: Warwicker J. O. 
Published: April 2003

AbstractThe structural variations in nylon 66 caused by heat and the mechanical action of the false‐twist texturing process have been studied by measuring dyeing rates with Durazol Blue 2R, the determination of density, x‐ray orientation, and lateral order, and also by consideration of x‐ray small‐angle scattering data. It is concluded that the morphologic units are probably shish‐kebabs with straight‐chain cores between which the dye penetrates.
The determination of solubility parameters of solvents and polymers by means of correlations with other physical quantities
Authors: Koenhen D. M. , Smolders C. A. 
Published: April 2003

AbstractCorrelations of solvent solubility parameters with molar attraction constants and with properties like surface tension, dipole moment, and index of refraction have been explored. From relations found to be valid for solvents, it is possible to calculate the solubility parameters for polymers. A relation between the dispersion contribution to the surface energy of polymers (a measurable quantity) and the dispersion solubility parameter of polymers has been found which is similar to a relation established for low molecular weight substances.
The extensional flow of poly(methyl methacrylate) and high‐impact polystyrene at thermoforming temperatures
Authors: Lai M. O. , Holt D. L. 
Published: April 2003

AbstractThe work described in the present paper was performed to establish stress–strain–time relationships at plastic sheet thermoforming temperatures. The relationships are correlated with sheet‐forming “formability”. Specimens of poly(methyl methacrylate) at 165°C and high‐impact polystyrene at 122°C were extended to large strains at constant cross‐head velocities. Initial strain rates were between 4.2 × 10−3/sec and 1.6 × 10−1/sec. It was found that the flow stress σ was related to the true strain ε and the elapsed time t by a relation σ = Ktm′εn, where K is a constant and n and m′ are indices. The value of n for both materials was approximately one. The value of m′ was −0.052 and −0.33 for poly(methyl methacrylate) and high‐impact polystyrene, respectively. Tests were also performed in which the cross‐head velocity was increased in steps. It was found that the flow stress in these tests followed the same relationship as in the constant cross‐head velocity tests.
Siloxane zwitterions: Synthesis and surface properties of crosslinked polymers
Authors: Litt Morton , Matsuda Takehisa 
Published: April 2003

AbstractThe aminoalkoxysilanes, γ‐aminopropyltriethoxysilane and N‐aminoethyl‐γ‐ainopropyl‐trimethoxysilane, were chemically modified by ring‐opening addition of γ‐propanesultone. Surfaces coated with polymers from these new monomers have, at the surface, zwitterionic functions of sulfobetaines which are attached to the polymeric siloxane backbone. They showed good wettability, with critical surface tensions as high as 50 dynes/cm.
Nuclear magnetic resonance and stereoregularity of PVC
Authors: Abdel‐Alim Ahmed H. 
Published: April 2003

AbstractThe decoupled α‐proton spectrum of PVC was examined using a 220 MHz NMR spectrometer. All of the ten possible pentads were detected and an assignment is given based on Bernoullian statistics. This assignment is in general agreement with conclusions reached by previous workers except for some modifications in the heterotatic resonances. Triad tacticity data were obtained from the pentads and were used to estimate the differential enthalpy and entropy changes for bulk PVC polymerized in the temperature range 70°C to −50°C.
Grafting acrylonitrile onto wood pulp: Influence of process variables
Authors: Lepoutre P. , Hui S. H. 
Published: April 2003

AbstractGraft polymerization of acrylonitrile onto a never‐dried bleached kraft pulp by the ceric ion process was not affected by the presence of air, nor by the use of technical‐grade ceric salt and unpurified monomer. The initial polymerization rate and final degree of conversion to grafted polymer increased with monomer and pulp concentration. An increase in the catalyst concentration also increased the initial rate and final conversion up to a maximum value, after which they leveled off. The amount of catalyst required for a given degree of conversion was minimized when operating at high concentration of pulp and monomer and when the catalyst was added last. Attainable graft level decreased when the pulp was dried but could be brought back to its normal level after the dried pulp was beaten. The molecular weight of the polymer increased with monomer concentration but was independent of ceric salt concentration when the latter was low. The number of grafted sites increased with ceric salt concentration.
Effect of microgels on the viscoelastic properties of poly(dimethylvinylsiloxanes)
Authors: Członkowska‐Kohutnicka Zofia , Raszczuk Alina 
Published: April 2003

AbstractThe course of dynamic viscosity η′ and modulus of elasticity G′ curves versus frequency of oscillations f was compared for poly(dimethylvinylsiloxanes) (PDMVS) samples of similar weight‐average molecular weights containing 0.1–0.2% by weight of microgels and free of microgels. It was found that the presence of microgels considerably changes the viscoelastic properties of PDMVS, particularly in the low‐frequency range. Only for samples with microgels a linear course of the above‐mentioned curves is observed. The content of microgels was determined by the light scattering method, whereas the η′ and G′ versus f values were obtained with the use of the Weissenberg rheogoniometer.
On the modeling of bulk poly(vinyl chloride) reactors
Authors: Ray W. H. , Jain S. K. , Salovey R. 
Published: April 2003

AbstractA detailed mechanism and corresponding mathematical model is suggested for bulk PVC production. The model is more detailed and general than earlier models and is consistent with reported experimental data as well as new experimental evidence presented here. Equations are presented and computations performed showing the evolution of the particle size distribution of the polymer beads. The predicted particle size distributions are in reasonable agreement with the limited experimental data available.
A study of the combination of unsaturated perfluorocarbon binder and perfluoroammonium salt
Authors: Toy M. S. , Stringham R. S. , Rewick R. T. , Lubowitz H. R. 
Published: April 2003

AbstractA composite of poly(perfluorobutadiene) and perfluoroammonium hexafluoroarsenate has been developed that can be used as an efficient source of fluorine atoms because the salt does not react with the polymer. This point has been demonstrated by showing that no more than trace amounts of NF3, which is formed in most reactions of perfluoroammonium salts, are formed by heating the composite to 120°C or by maintaining the composite at 80°C for four days. The small amount of NF3 that is formed can be explained as resulting from reactions with trace impurities.
Characterization of linear polyethylene fractions obtained by preparative GPC
Authors: Peyrouset A. , Prechner R. , Panaris R. , Benoit H. 
Published: April 2003

AbstractA new preparative liquid‐phase chromatograph, operating at a high temperature (160°C), allowed us to fractionate a linear polyethylene sample in narrow fractions (polydispersity about 1.1). These fractions, characterized by viscosity, light scattering, osmometry, and GPC measurements, can be used to calibrate any analytical GPC, i.e., to determine the variation of molecular weight and axial dispersion versus the elution volume.
Hydraulic permeation of liquids through swollen polymeric networks. I. Poly(vinyl alcohol)–water
Authors: Ebra‐Lima O. M. , Paul D. R. 
Published: April 2003

AbstractPoly(vinyl alcohol) membranes were prepared by crosslinking with terephthalaldehyde. Hydraulic permeation of water through this network structure was measured as a function of pressure for temperatures ranging from 18° to 35.8°C. The data were analyzed via a previously developed solution–diffusion theory for hydraulic permeation to give mutual diffusion coefficients. The activation energy for diffusion was found to be 6.5 kcal/mole which compared to the value of 4.3 kcal/mole for viscous flow of water indicates an influence of polymer–liquid interaction on the energetics of the diffusion process.
Biconstituent fibers from segmented polyurethanes and nylon 6
Authors: Saunders J. H. , Burroughs J. A. , Williams L. P. , Martin D. H. , Southern J. H. , Ballman R. L. , Lea K. R. 
Published: April 2003

AbstractThe characteristics of Monvelle, a new biconstituent fiber from nylon 6 and a segmented polyurethane, are reviewed briefly, and some of the technical problems inherent in producing such a fiber are discussed. The characterization of two series of polyurethanes which can be melt spun is given in detail. The chemical composition of the hard segment was maintained constant, being derived from 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol, in all polymers. In one series using poly(butylene adipate) of MW 2000 as the soft segment, the average hard segment content was varied from 33% to 54%. In the other series, the hard segment content was held at 43%, and three additional soft segments, each at MW 2000, were used: poly(ethylene adipate), polycaprolactone and poly‐1,4‐oxybutylene glycol (PBG). Characterizations include molecular weight distributions, thermal analysis, rheological studies, and selected small‐angle and wide‐angle x‐ray diffraction and polarized light microscopy. Crystallinity, melt viscosity, and activation energy of flow increased with increasing hardsegment content. Changes in the polyester soft segments had little effect on the properties studied, but with PBG the crystalline melting point of the polymer, without annealing, was higher and the melt viscosity was slightly higher than corresponding polyester‐based samples, in agreement with previous reports of sharper phase separation in polyether urethanes, compared to polyester urethanes.
Cellulose acetate ultrafiltration membranes
Authors: Kutowy O. , Sourirajan S. 
Published: April 2003

AbstractTwenty‐three different casting solution compositions involving cellulose acetate E‐938‐3 (polymer, P), acetone (solvent, S), and aqueous magnesium perchlorate (Mg(ClO4)2:H2O = 1:8.5) (nonsolvent, N) were studied for making ultrafiltration membranes. These compositions (expressed in weight units) involved N/P ratios of 0.817 to 1.3 and S/P ratios of 3.5 to 5.33. It was found that by adjusting the values of S/P and N/P ratios in the casting solution composition, temperature of the casting solution, temperature of the casting atmosphere, and solvent evaporation period during film formation, a wide variety of cellulose acetate membranes useful for both ultrafiltration and reverse osmosis applications could be obtained. The results of a continuous test run at 50 psig for a period of 250 hr with a typical set of membranes, and their separation characterstics for a group of solutes ranging in molecular weight from 58 to 160,000, are presented.
Temperature effect on polymer mechanochemistry
Authors: Casale Antonio 
Published: April 2003

AbstractThe influence of temperature is a fundamental variable for the mechanochemical processes of high polymers. However, it is generally recognized that the effect of temperature in this process is not always direct, as in normal chemical reactions, but is mainly indirect involving change in the properties (principally elastic and viscous), in the physical state of the system, and consequently in the mechanism of rupture. The negative temperature coefficient has been considered a prime criterion of a mechanochemical reaction by many researchers. Recently, it has been suggested that the negative temperature coefficient is really due to the viscous heating during polymer deformation and the low thermal conductivity of polymers.The aim of this paper is to reevaluate the role of temperature on mechanically induced reactions of polymers. In light of evidences published in the last 30 years, the dependence of mechanochemical reaction on temperature must involve the overlapping of the following factors: (1) the usual positive dependence of rate on temperature, as predicted by Arrhenius equation; (2) the true experimental temperature, which depends on viscous heating and on thermostatting efficiency; and (3) the breaking tension at the center of the polymer chain which is inversely dependent on temperature, i.e., greater at the higher viscosity and the slower relaxation at the lower temperatures, this last factor being dominant in determining the characteristic negative temperature coefficient for polymer mechanochemistry.
Removal of cupric ion from solution by contact with peanut skins
Authors: Randall John M. , Reuter F. William , Waiss Anthony C. 
Published: April 2003

AbstractCertain tannin‐containing agricultural wastes, such as peanut skin, are highly efficient ion exchange materials for the removal of cupric ion from aqueous waste solutions. Concentrations of Cu2+ as high as 200–1000 ppm can be reduced to less than 0.5 ppm by pouring the waste solution through a short column of peanut skin. The column packing can take up greater than 10% of its weight in copper, even from 50 ppm solution. Complete regeneration of the packing is readily achieved by eluting the Cu2+ from the column with 0.1 N HCl. The ion exchange process is pH dependent, with optimum removal of copper from solution occuring in the 5–7 pH range. Two hydrogen ions are liberated into solution for each Cu2+ attached to the peanut skin, so pH decreases as reaction continues, inhibiting the reactions. Thus, a continuous column process would be more efficient than a stepwise batch process.
Reactions catalyzed by soda lime glass. II. Polymerization of methyl methacrylate
Authors: Moustafa A. B. , Diab M. A. 
Published: April 2003

AbstractRates of sodium bisulfite‐initiated polymerization of methyl methacrylate (MMA) in water were determined in the presence and absence of colorless and colored soda lime glass (amber glass). The rate of polymerization increased in the presence of glass. For example, the rate of polymerization increased from 1.3 × 10−5 mole/(1.sec) to 3.9 × 10−5 mole/(1.sec) when amber glass (200 mesh) concentration was varied from 0 to 30 g/l. of the reaction mixture at 40°C. It was found that the finer the particle size of the soda lime glass, the higher was the conversion percentage of monomer to polymer. A glass–polymer combination containing 20 g glass was prepared and subjected to Soxhlet extraction with benzene; the insoluble polymer part was found to increases as initiator concentration was decreased.
Change of polypropylene film surface by chromic acid mixture treatment
Authors: Kato Koichiro 
Published: April 2003

AbstractPolypropylene films were treated with chromic acid mixture. The change in the treated films was investigated by comparing change in amount of 2,4‐dinitrophenylhydrazones formed in the treated films with their change in wettability with water. Oxidation of the film surface zone, partial breakdown of polymer in the film surface zone, and oxidation of surface zone bared from the film inner zone seemed to occur with increase in treatment time or with increase in treatment temperature.
Exclusion chromatography using controlled‐porosity glass. I. Comparison with styrene gels
Authors: Spatorico A. L. 
Published: April 2003

AbstractThe instrumental parameters influencing the calibration of a gel permeation chromatograph (GPC) using column packings of Corning CPG‐10 porous glass have been evaluated. The porous glass system used a set of columns 1.6 × greated in length and 0.6 × smaller in diameter than the Styragel system, which was used for comparison. The dependence of retention volume of polystyrene calibrants on eluent flow rate and on sample size was similar in both systems. Samples of poly(methyl methacrylate), poly(vinyl choloride), and poly(4,4′‐isopropylidenediphenylene 1,1,3‐trimethyl‐3‐phenylindan‐4′,5‐dicarboxylate) fractions were examined, and the molecular weights, obtained by using the hydrodynamic volume concept, were in satisfactory agreement with the light‐scattering data for both chromatographic systems. Corrections for axial dispersion, for the polyester fractions and polystyrene samples, were probably equivalent in these two chromatographic systems.
Effect of temperature on the course of thiuram‐accelerated sulfur vulcanization
Authors: Ducháček Vratislav 
Published: April 2003

AbstractTetramethylthiuram disulfide‐accelerated sulfur vulcanization of styrene‐butadiene rubber has been investigated at temperatures from 100°C to 170°C over 0.5 to 600 min. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Apart from the induction period (ti), the kinetic graphs are satisfactory represented by a rate equation assuming three independent first‐order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for ti−1, for fast crosslinking, and for degradation. The activation energy of slow crosslinking only is significantly greater. Due to the presence of Aerosil, the reciprocal values of the induction periods and the values of the ultimate extents of fast crosslinking are increased, and the values of the rate constants of degradation and slow crosslinking are decreased. Simultaneously, the activation energy of slow crosslinking is also significantly decreased. On the basis of these results, the proposed theory of tetramethylthiuram disulfideaccelerated sulfur vulcanization supposing that zinc dimethyldithiocarbamate is the actual accelerator in this type of curing system is discussed.