bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of cellulose acetate butyrate membranes in hyperfiltration of sodium chloride and urea feed solution
Authors: Wydeven T. , Leban M. 
Published: April 2003

AbstractCellulose acetate butyrate (CAB) membranes gave high salt and urea rejection with a water flux of about 3 gfd (gallons/ft2 · day) during hyperfiltration at 600 psig. Evidence was obtained which indicated that the CAB membranes used in this work were asymmetric. Membrane heat treatment increased urea rejection significantly while salt rejection was invariant, and water flux decreased. An increase in feed solution temperature caused a significant increase in water flux and a small decrease in urea and salt rejection. Increasing the pressure increased water flux and urea and salt rejection. During a 400‐hr life test, the water flux decreased by about 25% while urea rejection increased and salt rejection was invariant. The influence of pressure, membrane heat treatment, and compaction during CAB membranes life testing on urea and salt rejection provided evidence that these two solutes were rejected by somewhat different mechanisms. Salt rejection was consistent with a solution–diffusion mechanism for membrane transport and uncoupled flow while changes in urea rejection with pressure, membrane heat treatment, and compaction during life testing suggested that urea was at least partially rejected by membrane exclusion resulting from geometric factors.
Preparation and copolymerization of polyvalent metal salts of ethyleneglycol–methacrylate–phthalate
Authors: Matsuda Hideaki , Dohi Hidemi 
Published: April 2003

AbstractPreparation of polyvalent metal salts of ethyleneglycol–methacrylate–phthalate (EMP) was investigated by the reaction of the Na salt of EMP and chlorides of polyvalent metals such as Al3+, Cr3+, Fe3+, Ni2+, Co2+, and Cu2+. It was found that, among the metal salts obtained the Cr salt could be obtained in the form of (EMP)2− Cr(OH) in high purity and good yield where EMP means EMP residue: (EMP)2−
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Cr(OH) is soluble in chief organic solvents and vinyl monomers such as styrene (St) and MMA. (EMP)2Cr(OH) was then copolymerized with St and MMA. As for the physical properties of the copolymers obtained, heat distortion temperature, compressive strength, and Rockwell hardness were generally improved by introducing (EMP2)Cr(OH) into the polymers. Tensile strength, flexural strength, and impact strength were also improved by selecting the most suitable concentration of (EMP)2Cr(OH) according to the species of vinyl monomers. Moreover, the physical properties of (EMP)2Cr(OH)–MMA copolymers are generally superior to those of (EMP)2Cr(OH)–St copolymers. TGA and boiling water resistance of the copolymers were also discussed.
Dynamic rheological properties of bromine‐terminated polybutadiene melts
Authors: Dunlop A. N. , Williams H. Leverne 
Published: April 2003

AbstractThe viscous and elastic properties of bromine‐terminated polybutadiene were investigated as functions of temperature, molecular weight, and molecular weight distribution. They were found to depend on these variables in a manner similar to other polybutadienes. It was shown that the effect on the viscous properties due to bromine terminal functionality is not as great as for carboxyl and/or hydroxyl terminal functionality. In this study it was shown that the viscosity resultant from the blending of two samples of the same polymer differing in molecular weight is dependent on the polydispersity of the polymers from which the blend is prepared. A form of the Ninomiya and Ferry theory was modified and compared with experiment. As a result of the experiments involving blending, it was shown that the temperature dependency of elasticity is less for polymers exhibiting greater polydispersity.
Studies of relaxation phenomena in polymers. I. The use of periodic square and triangular stress functions
Authors: Jansson Jan‐Fredrik 
Published: April 2003

AbstractIn order to evolve the methods of mechanical spectroscopy and find new methods of studying the rise of nonlinear viscoelasticity, periodic square and triangular stress functions have been used. A “new” viscoelastic function is defined, log J2 = g{log J1}, where J1 and J2 are the compliances at the time (ζ/2 + 2nζ)n→∞ for an odd, periodic, square function and an even, periodic, triangular function, respectively, with periods of 2ζ. The function shows characteristic shapes for viscoelastic spring and dashpot models. The interrelations between the complex compliance and J1 and J2 are developed; and since the sum of J1 and J2 at the time ζ/2 agrees very well with the creep compliance at the same time, J1 and J2 can be used as an interrelation between complex compliance and creep compliance. Special equipment for measuring the compliances J1 nd J2 is described.
Studies of relaxation phenomena in polymers. II. The behavior of simple polymers in their main transition region
Authors: Jansson Jan‐Fredrik 
Published: April 2003

AbstractIn an earlier paper, a “new” viscoelastic function, log J2 = g{log J1}, was defined. For polymers, the linear viscoelastic behavior of which is characterized by “simple segment movements” in their main transition regions, the following general properties are found: (1) The local maxima of the function for different polymers fall along a straight line width the slope approximately equal to 1.1. (2) A characteristical general shape is noticed for the function after shifting along the straight line and reducing the J1 compliance as regards the “frozen in” compliance J10. (3) J1 reflects the storage and J2, the loss mechanisms of the system. The relation J2/J1 is an expression for the average retardation time.
Studies of relaxation phenomena in polymers. IV. Superimposed transition mechanisms in polymethacrylates
Authors: Jansson Jan‐Fredrik 
Published: April 2003

AbstractThe existence of superimposed transition mechanisms in the “Tg region” of polymethacrylates has been indicated by several authors including Ferry and co‐workers, who also have tried to separate the mechanisms. Using the general properties of the viscoelastic function logJ2 = gα {log J1} and a simple weighting model, the α‐and β‐mechanisms have been separated. The viscoelastic function log J2 = gβ{log J1} is determined and is found to coincide both where different polymethacrylates are concerned and for the calculated as well as the directly measured data.
A statistical method for computer treatment of elastomer flex data
Authors: Derringer George C. 
Published: April 2003

AbstractIn flex testing of elastomers, the length of a cut is measured periodically as a function of the number of flexing cycles. In most cases a large number of measurements is accumulated for each test piece which would lead one to believe that the results should have a high degree of precision. This, however, is not the case, mainly because not all of the measurements are used to express the final result. Instead of being a precise test, flex testing is in fact notorious for its irreproducibility. A new method is proposed for computer treatment of flex data in which all of the flex measurements are fitted to an empirical equation by means of nonlinear regression analysis. From the fitted equation, more precise estimates of rate of growth and growth initiation point can be obtained than is possible using the data treatment procedures proposed by ASTM. Also a new index of flex life is defined which is conveniently scaled from 0–100. This so‐called flex index is a convenient index of overall flex behavior.
Molecular aggregation in poly(vinyl chloride)
Authors: Abdel‐Alim A. H. , Hamielec A. E. 
Published: April 2003

AbstractMolecular weight distributions and molecular aggregation for poly(vinyl chloride) (PVC) polymerized in bulk at −10, −30, and −50°C have been measured using gel permeation chromatography. The aggregate content in PVC polymerized at −50°C was found to be 87 wt‐%. These spherical aggregates of mean diameter of 5000 A are formed preferentially from PVC chains having high molecular weights and long syndiotactic sequence lengths. A temperature of 200°C was used to disintegrate these aggregates into single PVC molecules. In disagreement with measurements of Mn and Mw published in the literature, our measured values do not reach a minimum but rather increase continuously with decreasing temperature of polymerization. This disagreement is most probably due to the phenomenon of molecular aggregation in PVC.
The preparation and acid‐catalyzed hydrolysis of polyoxymethylene isopropyl methyl ethers
Authors: Stanonis David J. , Vail Sidney L. , King Walter D. 
Published: April 2003

AbstractThe first four members of the polyoxymethylene ether series (CH3)2CHO(CH 2O)nCH3 were prepared, separated by fractional distillation and GLC, and characterized by NMR. Rate constants for the aqueous acid hydrolysis of the compounds were determined at 25°, 30°, and 35°C. Although the polyformals (n > 1) in this series hydrolyzed at essentially the same rate, they all hydrolyzed three times faster than the formal (n = 1). It is proposed that a mixed polyformal, (CH3)2CHO (CH2O)n>1CH3, undergoes two concurrent fissions to yield (1) the stem (CH3)2CHOCH2 with CH3O(CH2O)n−1 as the leaving group and (2) the stem CH3OCH2 with (CH3)2CHO(CH2O)n−1 as the leaving group. Most of the fissions occur by the first path. An equation that can aid in predicting the rate of hydrolysis of a mixed polyformal was developed and tested.
A rotating sphere viscometer
Authors: Kelkar J. V. , Mashelkar R. A. , Ulbrecht J. 
Published: April 2003

AbstractThe use of a rotating sphere viscometer for the measurement of parameters in the flow curves of inelastic as well as viscoelastic liquids is examined. An experimental investigation of the primary flow around a sphere rotating in Newtonian and viscoelastic liquids is carried out by using a new “three‐dimensional particle technique.” Currently available theoretical analyses of rotation of a sphere in viscoelastic liquids are shown to be inadequate to describe the experimental primary velocity distribution data. Theoretical results for the primary distribution derived on the basis of a creeping flow of a power law liquid are found to describe the experimental data well. This distribution is then used to derive torque–angular velocity relationships, which are then confirmed experimentally for both inelastic and viscoelastic liquids. The results of this work justify the use of a rotating sphere viscometer as a useful tool for the measurement of parameters of flow curves of inelastic and viscoelastic liquids.
Practical estimation of dilute solution parameters
Authors: Rudin Alfred , Strathdee Glenn B. , Edey W. Brain 
Published: April 2003

AbstractThe concentration dependence of viscosities of dilute solutions of nonpolar polymers can be expressed generally as power series in concentration. Intrinsic viscosity is often estimated from zero concentration extrapolations of the Huggins and Kraemer equations, which are truncated versions of virial expressions in concentration. Neither form is strictly valid at most practical concentrations since real curvilinear relationships are forced into rectilinear forms. Prior methods of overcoming this deficiency by basing extrapolation methods for [η] on more extended power series have attempted to provide graphically useful solutions. This requires reduction of the power series to a two‐parameter (slope and intercept) form and the assumption of certain relations between the various factors in the initial multiparameter expression. In this work, power series expressions in concentration are solved directly by nonlinear regression analysis. It is shown that no two‐parameter solution is generally valid, although each may be of value in a particular context. Three‐parameter power series extensions of the basic Huggins and Kraemer equations represent dilute solution viscosities up to concentrations of 1% or 2% (w/v) very well. The computer‐assisted nonlinear regression analysis is easily extended to higher powers of concentration, and the use of four‐parameter forms is illustrated to represent viscosities of polystyrene solutions with concentrations as high as 9%.
Determination of optimal reactor system configuration for polymerization reactions. II. Effect of chain transfer, autoacceleration, and temperature profile
Authors: Shastry J. S. , Fan L. T. , Erickson L. E. 
Published: April 2003

AbstractThe effect of chaln transfer, diffusion control, and temperature on the optimal design and selection of polymerization reactors was investigated. Chain transfer to the monomer was examined and a parametric study of the corresponding rate constant was carried out. The Trommsdorff effect was included in the model by using a diffusion‐controlled termination process. An optimum temperature sequence was determined for this modified model by incorporating the effect of temperature on the rate constants and on the amount and rate of heat removal. Furthermore, the concept of dividing the plug flow reactor into several constant temperature zones was considered, and the effect of “zoning” on the system performance was determined.
The water absorbency of hydrolyzed polyacrylonitrile‐grafted cellulose fibers
Authors: Lepoutre P. , Hui S. H. , Robertson A. A. 
Published: April 2003

AbstractThe water absorbency of a bleached softwood kraft pulp, as measured by its water retention value (WRV), was increased up to 30 times by graft polymerizing polyacrylonitrile (PAN) and subsequently hydrolyzing it to sodium polyacrylate–polyacrylamide copolymer. WRV was found to be related to the initial PAN graft level rather than to the final sodium polyacrylate content, and was independent of the grafting process used. However, the ceric ion process was found superior to both the cellulose xanthate–H2O2 and ferrous ion–H2O2 redox systems in that it occasioned only a minor loss during the hydrolysis stage and the WRV was less affected by drying. The WRV remained constant as pH was lowered from 9 to 5 but dropped to the level of unmodified pulp at pH 3.5 where the sodium salt is fully converted to poly(acrylic acid). Retention of 1% aqueous NaCl was about 60% of the WRV. The swelling properties of the grafted fibers under various conditions appear to be explained by considering the grafting to act in two ways: (a) the introduction of a potentially hydrophilic component capable of generating swelling pressures and (b) the reduction in the cohesion of the fiber by the interposition of graft polymer chains in the fiber structure.
An analysis for the calendering of non‐newtonian fluids
Authors: Alston Jr. William W. , Astill Kenneth N. 
Published: April 2003

AbstractEquations are derived to predict the one‐dimensional behavior of a hyperbolic tangent fluid model flowing between calendering rollers. The equations were solved numerically on a computer, and results were obtained for maximum roller pressure and the exit thickness of the fluid sheet as a function of roller speed and reservoir size for three polymers. The numerical integration employed Gauss‐Legendre quadrature and a cascading iteration scheme to solve equations in which unknowns appeared in the limits of the integrals. Unlike existing power law solutions, these results show a definite relation between roller speed and exit thickness.
Polymer compatibility
Authors: Schneier Bernard 
Published: April 2003

AbstractBohn has compiled a list of polymer pairs on which compatibility studies have been reported. The list contains 13 polymer pairs for which, according to Bohn, compatibility as solids may be considered to be definitely established, at least within some regions of proportions. The approach used here is based on calculations which provide a value whose magnitude apparently differentiates between mixtures in Bohn's list which are either compatible as solids or incompatible. Data calculated on mixtures of styrene–acrylonitrile copolymers not included in Bohn's list systematize according to the same classification.
Electron irradiation of poly(olefin sulfones). Application to electron beam resists
Authors: Bowden M. J. , Thompson L. F. 
Published: April 2003

AbstractAll the poly(olefin sulfones) examined degraded rapidly under electron irradiation. The dose required to effect a molecular weight distribution completely separated from the original distribution as required for fractional solution development was similar for all polymers, viz., 1–2 × 10−6 coulomb/cm2. This indicates that they all have similar values for G(scission). The film thickness of the exposed area decreased at a rate dependent on olefin structure and temperature. This process, termed vapor development, has been attributed to concurrent chain scission and depolymerization. Factors determining the rate of depropagation are discussed.
Elastic and viscoelastic behavior of ethylene–propylene copolymers
Authors: De Candia F. , Vittoria V. 
Published: April 2003

AbstractThe viscoelastic behavior of an ethylene–propylene copolymer is analyzed. Two different vulcanization procedures were followed; in the first a binary mixture of initiator‐polymer was used, while in the second the polymer was diluted by a solvent. The networks thus obtained show a different viscoelastic behavior depending on the different vulcanization procedure used. Results, analyzed in terms of supramolecular organization being present in the amorphous material, give some important information about the molecular nature of the C2 coefficient of the Mooney‐Rivlin equation, and therefore about the well‐known deviations from the Gaussian theory shown by all rubber‐like networks.
Dynamic mechanical studies of four elastomeric fibers at low, intermediate, and high extensions
Authors: Hourston D. J. , Meredith R. 
Published: April 2003

AbstractA dynamic mechanical study of four elastomeric threads has been made: the threads comprise natural rubber, nitrile rubber, Lycra, and Spanzelle. The dynamic loss modulus (E″) and the dynamic storage modulus (E′) were studied over a wide range of temperature (−110°C to 180°C) and the transitions were interpreted in the light of the chemical composition of the materials. The threads were investigated at 2%, 200%, and 400% static strain at a frequency of 110 Hz.
An equation of state for molten polymers
Authors: Rao Krishna , Griskey Richard G. 
Published: April 2003

AbstractA simple, generalized equation of state has been developed for molten polymers. The equation yielded calculated pressure–volume–temperature data that deviated by 1% or less from experimentally determined data. The use of the equation requires only that the polymer's glass temperature and density at 25°C and 1 atm be known. Polymer glass temperatures can also be estimated with the equation.
On the origin of order‐disorder in drawn polyacrylonitrile
Authors: Hinrichsen Georg 
Published: April 2003

AbstractDrawn polyacrylonitrile can be characterized only insufficiently with regard to its molecular and supermolecular structures which substantially determine the physical properties. This paper points out that the so‐called “superstructure” of polyacrylonitrile fibers can be cleared up after suitable thermooxidative treatment using x‐ray small‐angle scattering technique. The chemical reactions during the thermo‐oxidative treatment lead to a “self‐contrasting” effect so that the fibers as such are severely damaged yet information about the supermolecular structure can be obtained. The investigations show that changes in the course of fiber production (spinning, drawing, and annealing processes) affect alterations of the superstructure. The described method of investigation represents a so far unknown possibility for the purpose of detecting the supermolecular structure of drawn polyacrylonitrile.
Retention of antioxidants in polyethylene by silane coupling agents
Authors: Albarino R. V. , Schonhorn Harold 
Published: April 2003

AbstractAntioxidant additives in polyethylene films have been shown to diffuse to the surface where they are subsequently lost, exposing the polymer to oxidation. Compatibility of antioxidants with polyethylene may be increased by use of silane coupling agents. In this study, three approaches to antioxidant modification are examined: (1) bonding antioxidant directly to silicon, (2) coupling the silane to an antioxidant hydroxyl function, and (3) dissolving antioxidants in silanes. All three approaches are shown to be effective in reducing antioxidant loss by diffusion.
ESR studies of free radicals in photo‐initiated graft polymerization reactions with cotton cellulose
Authors: Reine Alden H. , Hinojosa Oscar , Arthur Jett C. 
Published: April 2003

AbstractElectron spin resonance (ESR) spectra of free‐radical intermediates formed during photo‐initiated graft polymerization reactions of acrylamide, methacrylamide, and diacetone acrylamide onto purified cotton cellulose were recorded. Purified cellulose was saturated with aqueous solutions of the vinyl monomers (0.5M) and then photolyzed under nitrogen by near‐ultraviolet light (3100–4100 Å, peak near 3500 Å) at −196° and 40°C. Other samples of cellulose were saturated with aqueous solutions of the monomers, dried, and then photolyzed at 40°C. In the absence of cellulose, either poorly resolved or no free‐radical spectra were generated on photolysis of the monomers. Photolysis of dried cellulose at 40°C and wet cellulose at −196°C initiated formation of a cellulosic radical that generated a singlet spectrum. Photolysis of wet cellulose at 40°C generated no ESR detectable radical; however, photolysis of wet cellulose that contained monomer at 40°C generated poorly resolved spectra. The ESR spectra of the propagating copolymer radicals recorded were poly(acrylamide), three lines; poly(methacrylamide), five lines; and poly(diacetone acrylamide), two lines (doublet).
Mechanical relaxations of poly(vinylidene fluoride) and some of its copolymers
Authors: Kalfoglou Nikos K. , Williams H. Leverne 
Published: April 2003

AbstractThe dynamic mechanical properties of poly(vinylidene fluoride) have been studied under isochronal conditions and the effect of thermal treatment examined. The results are compared with a product of different molecular weight distribution. The study also included the mechanical relaxation spectra of copolymers of vinylidene fluoride and chlorotrifluoroethylene at four compositions and four frequencies as a function of temperature. The thermodynamic parameters associated with the main relaxations were determined and the results discussed on the basis of available information on the drgree of crystallinity, copolymer heterogeneity, and main chain flexibility.