bluuebunny/crossref_metadata_2025_split huggingface dataset:
The apparent domain structure of polystyrene as revealed by liquid and vapor crazing
Authors: Nielsen Lawrence E. 
Published: April 2003

AbstractDomains, or areas of inhomogeneities and imperfections, may be made visible in polystyrene by treatments of the plastic with certain liquids and vapors. Different types of domains are revealed by different techniques, depending upon the solvent power of the liquids and vapors. One type of domain reveals itself as craze cracks when polystyrene is first soaked in a nonsolvent such as methanol, and then exposed to the vapors of a solvent such as hexane or benzene. A second type of domain may be revealed by exposing polystyrene to certain mixtures of solvents and nonsolvents which produce a rough, whitened surface on the polystyrene. For the first type of crazing, the size of the domains is influenced by the frozen‐in thermal stresses, and the shape of the domains is influenced by molecular orientation. The domains of the second type are due to heterogeneity of molecular orientation and are not found in annealed specimens. A theory has been proposed which explains crack crazing in terms of adsorbed vapors in cracks and areas of imperfections in the polystyrene.
The effect of carbon black on thermal antioxidants for polyethylene
Authors: Hawkins W. L. , Hansen R. H. , Matreyek W. , Winslow F. H. 
Published: April 2003

AbstractAbout 3% by weight of carbon black adequately protects polyethylene against photo‐oxidation and, under accelerated test conditions, slightly inhibits thermal oxidation. As a rule small amounts of organic antioxidants are also added to the polymer for optimum protection. Now many of the common phenolic and amine additives have been found to function much less effectively in polyethylene containing carbon black than in clear polymer. Loss of effectiveness is attributed to adsorption and/or decomposition of the antioxidant by both basic and acidic carbon black.
New thermal antioxidants for polyethylene containing carbon black
Authors: Hawkins W. L. , Lanza V. L. , Loeffler B. B. , Matreyek W. , Winslow F. H. 
Published: April 2003

AbstractCommon secondary aromatic amine and alkylated phenolic antioxidants lose much of their activity in polyethylene containing carbon black. In contrast their thioether derivatives provide more protection against oxidation than the sum of the separate contributions of carbon black and the sulfur compounds. Organic disulfides and some thio‐ethers without amino or phenolic hydrogen also safeguard polyethylene from oxidation but only in the presence of carbon black. Likewise thiols are excellent protectants in combination with carbon black but not in clear polymer. Aliphatic thiols, disulfides, and their polymeric derivatives and related selenium compounds exhibit similar activity.
Some properties of poly(ethylene oxide)1 in aqueous solution
Authors: Bailey F. E. , Callard R. W. 
Published: April 2003

AbstractHigh polymers of ethylene oxide have been shown to have a number of unique properties in water solution. In this study, these properties have been investigated from the view of the behavior of large neutral molecules in media of high dielectric constant. Predictably, these high polymers of ethylene oxide undergo salting‐out effects which are reflected in changes of solution viscosity with salt concentration. Salts vary in effectiveness in a manner similar to that observed in the case of small neutral solute molecules. The salting‐out and viscosity effects are paralleled by the inverse solubility‐temperature relationship in water. Above a minimum molecular weight of about 50,000, the precipitation temperature (the temperature at which polymer separates from solution as a separate phase as the temperature is raised) becomes essentially independent of molecular weight. For these very high polymers the upper temperature limit of solubility in water is independent of polymer concentration over a wide range of concentration. These effects are discussed in terms of the balance of hydrophilic and hydrophobic character in the polymer structure which can be altered by increasing the hydrocarbon content of the polymer through copolymerization of ethylene oxide with other olefin oxides such as propylene oxide. This investigation permits the development of an interpretation of the unusual rheology of high molecular weight poly(ethylene oxide) in water solution.
The viscoelastic behavior of rubber in extension
Authors: Mason P. 
Published: April 2003

AbstractMeasurements of the (complex) dynamic Young's modulus of natural rubber have been made by a wave propagation technique on filaments held at mean extensions up to 600%. It is shown that the real and imaginary parts vary with strain in the same way as the equilibrium modulus obtained from “static” stress‐strain measurements, the behavior up to about 140% extension being derivable from a Mooney‐type stored‐energy function and at higher strains being dominated increasingly by the effects of finite extensibility in the network. The viscoelastic behavior in the region up to 140% strain may then be characterized by four parameters, of which one vanishes and another is constant for the rubber studied. It is shown how these parameters may be used to derive the strain‐dependence of the damping or loss‐factor (tan δ) in this region. The effect of increasing extension upon the relaxation spectra, over the range 100 to 600% extension, is to displace the whole spectrum progressively to longer times.
Relationship between impact strength and spherulite growth in linear polyethylene
Authors: Ohlberg S. M. , Roth J. , Raff R. A. V. 
Published: April 2003

AbstractSamples of Ziegler‐type polyethylene containing no additives were placed in a temperature‐programmed oven, melted, and subsequently cooled at constant rates. Average spherulite size, based on the measurement of fifty spherulites, and impact strength by a falling ball method were determined for different cooling rates and for samples having weight‐average molecular weights of 125,000 175,000, and 300,000. It was found that both the formation of a brittle structure and the growth of spherulites occur over the relatively narrow temperature range in which the molten polymer passes from the liquid to the solid state. The rate of spherulite growth is initially proportional to the square root of time, viz., diffusion controlled, but subsequently becomes linear with time. The spherulite growth rate decreases with increasing molecular weight. There is no change in spherulite size after aging six months at room temperature. The impact strength decreases with increasing average spherulite size; however, the lower the average molecular weight, the greater will be the impact strength for a given average spherulite size. The loss in impact strength is attributed to the rupture of amorphous chain strained by the formation and growth of spherulites.
Viscosity of concentrated polymer solutions. I. Polyvinylchloride in cyclohexanone
Authors: Pezzin G. , Gligo N. 
Published: April 2003

AbstractViscosities of samples of poly(vinyl chloride) in cyclohexanone were measured over a wide range of concentrations, up to polymer weight fractions of the order of 0.4. Polymers with molecular weight from 10,000 to 230,000 and with different molecular weight distributions were studied. The effect of concentration and molecular weight on the solution viscosity is reported and discussed for this systems, as well as for other systems for which data are available in literature. The empirical reduction schemes often applied to the viscometric data of concentrated polymer solutions are discussed.
Viscosity of concentrated polymer solutions. II. Application of a free‐volume treatment to solutions of poly(vinyl chloride) in cyclohexanone and to other polymer solutions
Authors: Pezzin G. 
Published: April 2003

AbstractThe Kelley‐Bueche free‐volume treatment of the viscosity of polymeric solutions has been applied to the previously reported data on poly(vinyl chloride)‐cyclohexanone solutions and to several other polymer‐diluent systems. It has been shown that the theoretical equations, based on the assumption of the additivity of free volumes of the components, are capable of predicting with remarkable accuracy the concentration, temperature, and molecular weight dependence of the viscosity of the investigated solutions over very large ranges of the variables.
Simple theory of stress‐strain properties of filled polymers
Authors: Nielsen Lawrence E. 
Published: April 2003

AbstractBy the use of simple models of filled plastics, approximate equations are derived for the elongation to break in the case of perfect adhesion between the phases and for the tensile strength in the case of no adhesion between the polymer and filler phases. By combining these equations with equations for the modulus (assuming Hookean behavior) all the stress–strain properties can be derived, including rough estimates of the impact strength, as a function of filler concentration. Among other things, the theory predicts a very rapid decrease in elongation to break as filler concentration increases, especially for the case of good adhesion. It is also predicted for the case of good adhesion that the tensile strength of a filled polymer can be greater than that of an unfilled polymer.
Torsional braid as a kinetic tool for the study of the polymerization of viscous materials. I. Initial studies
Authors: Adicoff Arnold , Yukelson Arnold A. 
Published: April 2003

AbstractThe torsional braid experiment of Lewis and Gillham has been so modified that kinetic parameters can be obtained in polymerizations conducted with viscous prepolymers. The relative rigidity curve is interpreted in terms of extent of cure. The activation energy for the polymerization of a carboxyl‐terminated polybutadiene with an aziridinyl compound has been measured.
Change in surface properties of polymers with immersion in sulfuric acid
Authors: Bott T. R. , Harvey A. P. , Palmer D. A. 
Published: April 2003

AbstractBy using a similar apparatus to that described by Baer and McLaughlin but differing in detail, the surface characteristics of samples of polyethylene, polypropylene, and a woven glass fiber/polyester laminate have been studied after periods of immersion in sulfuric acid at 60°C. Results show considerable progressive variation over the range of immersion times employed (up to 170 hr.), suggesting that surface changes might be considered as a measure of the corrosion involved. (No measure of the corrosion was attempted). The presence of a water layer on the surface of the test piece is suggested as being the reason for the plot of sin αs versus V‐2/3 giving an intercept on the sin αs axis whereas in the original work of Baer and McLaughlin the plot passes through the origin.
Stress softening in carbon black‐reinforced vulcanizates. Strain rate and temperature effects
Authors: Kraus G. , Childers C. W. , Rollmann K. W. 
Published: April 2003

AbstractStress softening of carbon black‐reinforced butadiene‐styrene rubber was studied as a function of the rate and temperature of the original tensile deformation. To a good approximation, stress softening depends on the product of the extension rate and a temperature function which is analytically well represented by the familiar Williams‐Landel‐Ferry relationship. When the elongation of the original deformation is also varied, a good correlation is obtained between stress softening and the maximum stress attained in the original extension, irrespective of the particular combination of strain, strain rate and temperature used to achieve this stress. Variables which tend to increase the stiffness of the vulcanizate, such as increased degree of crosslinking or carbon black chain structure, also increase stress softening; dilution by plasticizers decreases it. Prestressing at high strain rates and low temperatures affects the stress–strain curve of the softened vulcanizates beyond the elongation of the original extension. Connections are established between stress softening and viscoelastic and failure behavior. The evidence presented favors the contribution of several mechanisms to the general phenomenon of stress softening. These are thixotropy of transient filler structures, network chain rupture, and breakage of “permanent” filler structure. The latter appears to be most important at high strain rates, low temperatures, and with highly reticulated “structure” blacks.
Diphenolic acid ester polycarbonates
Authors: Fischer Robert P. , Robert Hartranft G. , Heckles John S. 
Published: April 2003

AbstractPolycarbonates of methyl, ethyl, n‐propyl, n‐butyl, and n‐hexyl 4,4‐bis(4‐hydroxyphenyl)pentanoate and copolycarbonates with bisphenol‐A of 0.5‐0.9 intrinsic viscosity in dioxane were prepared by a homogeneous CH2Cl2pyridine method and the physical properties determined. Increasing the number of carbon atoms in the DPA ester alcohol group from 1 to 6 decreased the initial softening temperature of the polycarbonates from 126 to 58°C. ; this change also increased the solubility of the polycarbonates in aromatic solvents and in three ketone solvents. O2 transmission rates were not affected by increasing the ester chain length. CO2 transmission rates increased as DPA ester alcohol chain length increased. Methyl DPA polycarbonate had the highest tensile strength and per cent elongation and the lowest O2 and CO2 transmission rates.
Oxidation and heat aging of carboxyl‐terminated polybutadiene
Authors: French David M. , Rosborough Lawrence 
Published: April 2003

AbstractLiquid carboxyl‐terminated polybutadiene (CTPB) on aging in air increased in viscosity and molecular weight and eventually gelled. Simultaneously, the acid content decreased without formation of anhydride, the changes being a function of the hydrocarbon portion of the molecule. Cured stocks of CTPB underwent changes on heating in air which were largely resinification due to oxidation. However, chain scission or hydrolysis also occurred, resulting in reversion of cure which could be observed in vacuum‐aged material or in the interior of the stocks. Commercial resins were compared, and a difference noted between CTPB prepared by ionic and free‐radical methods. The idea was presented that the greatest depth of oxidation was determined by the plane benetath the surface where the rate of oxidation equalled the rate of arrival of oxygen by diffusion. This idea was devloped mathematically from Fick's diffusion law and an equation derived which related the depth of oxidation to the temperature, the energies of activation for reaction and diffusion, and the rate constants for reaction and diffusion. By using the equation, relative rates of oxidation were determined and the energy of activation for diffusion of oxygen in CTPB was found to be 13.6 kcal./mole.
Cure rates of some epoxy systems
Authors: Jenkins Robert , Karre Lowell 
Published: April 2003

AbstractThe property changes of Epon 828 crosslinked by either diethylenetriamine or m‐phenylenediamine at several temperatures have been studied by two in situ techniques. The mechanical property changes were followed by continuously monitoring the changes in the fundamental frequency of vibration during cure of a resin‐coated substrate acting as a cantilever reed. The disappearance of the reactive epoxy group was followed in situ by continuously monitoring the absorbance of the infrared epoxide band at 915 cm.−1. Correlation of the two techniques was accomplished by normalizing both the mechanical property and infrared data. The apparent energy of activation was calculated to be 10.4 and 11.4 kcal. /mole, respectively, for the m‐phenylenediamine and diethylenetriamine systems by the mechanical technique, and 11.0 kcal./mole for the m‐phenylenediamine crosslinked system by the infrared technique.
Method of calculating molecular weight distribution function from gel permeation chromatograms
Authors: Tung L. H. 
Published: April 2003

AbstractAn integral equation taking account of the limited resolution of the chromatographic columns is given to relate the gel permeation chromatogram and the true molecular weight distribution function. Three approaches to solve the integral equation are described. The first approach provides a special solution for the log‐normal molecular weight distribution function; the other two approaches give two numerical solutions for general distribution functions. The use of these solutions in the treatment of gel permeation chromatography data is discussed.
Effects of nuclear radiations on structure and molecular motions in some crystalline stereoregular polymers
Authors: Baccaredda Mario , Butta Enzo , Frosini Vittorio 
Published: April 2003

AbstractYoung's modulus and the mechanical damping factor have been determined between −180 and +280°C. (at a frequency of several kilocycles), in samples of isotactic polypropylene, isotactic polystyrene, and trans‐1,4‐polybutadiene, subjected to pile irradiation (γ‐rays and neutrons) at γ‐doses from 90 to 4000 Mrad. In isotactic polypropylene no important structural changes are produced by the irradiation, except for a partial destruction of crystallinity. The samples receiving high radiation doses exhibit a low temperature loss region, which is attributed to the formation of a certain number of branches. Isotactic polystyrene shows very slight modifications of the dynamic mechanical properties at room temperature. At low temperature an increase of intensity of the δ relaxation phenomenon (probably due to oscillations of phenyl rings) with increasing radiation dose is observed. Important structural modifications produced by the radiation, destruction of crystallinity accompanied by crosslinking, which transform the material into a crosslinked rubber, are observed in trans‐1,4‐polybutadiene. Unlike conventional (sulfur) vulcanization, crosslinking by radiation does not cause a marked shift of the glass transition point. A secondary low‐temperature relaxation effect, not existing in the unirradiated material, appears in the mechanical loss curves of the irradiated samples; it is attributed to the formation of CH2sequences in the main chains through saturation of CC bonds. The mechanical spectrum of irradiated polybutadiene is very similar to those shown by crosslinked ethylene–butadiene copolymers.
Cast polyacrylonitrile. II. Properties
Authors: Pellon J. J. , Smyth N. M. , Kugel R. L. , Valan K. J. , Thomas W. M. 
Published: April 2003

AbstractPolyacrylonitrile sheet cast by a novel method described in Part I is clear, colorless, chemically resistant, brittle, and rather weak. It undergoes irreversible thermal changes above about 80°C., but if heated quickly, it can be oriented to give greater strength parallel to the direction of orientation. Some improvement in strength can be achieved by the use of fibrous fillers. Certain copolymers are stronger than the homopolymer but have lower softening temperatures.
An effect of moisture content on successive changes in the load‐elongation curve for paper
Authors: Harrington K. J. 
Published: April 2003

AbstractChanges in the stress‐strain curve for paper undergoing cyclic loading have been studied as a function of moisture content. It has been found that the extensional stiffness of the paper progressively decreases at both low and high moisture levels but progressively increases at intermediate moisture levels. The moisture content at which the transition from decreasing to increasing stiffness occurs (when passing from low to intermediate moisture content) has been determined and for the particular paper used in these experiments has been shown to correspond to a relative humidity of approximately 60%. It is postulated that at low and high moisture levels, conditions are not favorable for interfiber bond re‐formation, whereas conditions are favorable for such reformation at intermediate moisture levels.
A novel parameter of polymer structure
Authors: Bahary William S. 
Published: April 2003

AbstractA need exists for a simple and reliable heterogeneity index to determine the presence of high molecular weight components which may be branched in complex polymers and copolymers. On the basis of theoretical considerations, a proposal is made to employ the ratio of concentrated solution to intrinsic or Mooney viscosity as a heterogeneity index. The basis for the index is that the concentrated solution or melt viscosity is a function of a higher moment of the molecular weight distribution than either the intrinsic or Mooney viscosity. Experimental evidence in the form of light‐scattering measurements and osmometry support the validity of the index when the range of intrinsic viscosities is narrow and other assumptions cited are justified. It is further shown that the heterogeneity index correlates well with the processibility of cis‐polybutadiene.
Melt viscosity of polyethylene: Shear dependence
Authors: Ram A. , Narkis M. 
Published: April 2003

AbstractApparent viscosities of linear polyethylene melts may be simply related to molecular weight at various shear stresses. One gets constant slopes on a log–log scale with higher critical M̄w at higher shear stresses. The validity of Ferry's equation and the dependence of its coefficients are extensively analyzed.
Investigations of the kinetics of maleate–fumarate isomerization during the polyesterification of maleic anhydride with different glycols
Authors: Szmercsányi I. Vancsó , Maros L. K. , Zahran A. A. 
Published: April 2003

AbstractThe rate of isomerization during the polyesterification of maleic acid or maleic anhydride depends on the structure of the glycol used: the longer the chain of the glycol, the lower the isomerization rate. The rate constants differ greatly from one case to another. Thus, the difference in the reaction rate constants depends mainly on the steric effects caused by the different types of glycols used in the polycondensation. The isomerization approaches a constant value, which after a certain time depends on the structure of the glycol and the temperature of the condensation. The activation energies calculated from the rate constants would fall at about 20 ± 4 kcal./mole. This value for the activation energy corresponds to that reported in the literature for the transformation of maleic acid into fumaric acid. The reaction apparently follows second‐order kinetics due to the catalytic effect of the maleic acid on the isomerization.
Proposed mechanism for the curing of epoxy resins with amine‐lewis acid complexes or salts
Authors: Harris James J. , Temin Samuel C. 
Published: April 2003

AbstractThe common assumption in the literature is that amine complexes of Lewis acids (particularly boron trifluoride) cure epoxy resins by virtue of their dissociation to liberate the Lewis acid which then functions as the “true” catalyst. Evidence is presented to indicate that this picture of amine–Lewis acid complex curing may be incorrect. Another mechanism is proposed which is consistent with (a) lack of correlation between adduct stability and reactivity, (b) a similarity in reactivity of BF3 adducts and the corresponding fluoroborate salts, (c) the relationship between reactivity of BF3 and PF5 adducts, (d) a correlation between reactivity and structure of the amine in the complex, and (e) the effect of the anion on reactivity of amine salts. The relative reactivity of the catalysts has been equated with the temperature at which gelation occurs on heating at a fairly constant rate.