bluuebunny/crossref_metadata_2025 huggingface dataset:
The apparent domain structure of polystyrene as revealed by liquid and vapor crazing
Authors: Nielsen Lawrence E.
Published: April 2003

Domains, 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

About 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

Common 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

High 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

Measurements 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

Samples 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

Viscosities 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

The 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

By 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

The 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

By 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

Stress 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

Polycarbonates 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

Liquid 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

The 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

An 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

Young'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

Polyacrylonitrile 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

Changes 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

A 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

Apparent 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

The 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

The 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.
Effect of γ‐radiation on the dynamic mechanical properties of silicone rubbers
Authors: Traeger R. K. , Castonguay T. T.
Published: April 2003

Dimethyl‐, trifluoropropyl‐, and high phenyl content polysiloxanes were irradiated in a 60Co source to doses of 100 Mrad. The hardness of the specimens increased with dose. Crosslink density changes did not directly reflect the hardness changes. The crosslink density of the dimethyl polymer increased significantly and that of the trifluoropropyl polymer increased only slightly. There was a slight decrease in the crosslink density of the aromatic material. The storage moduli reflected the changes in crosslink density. Loss moduli of the dimethyl‐ and trifluoropropylpolysiloxanes initially decreased and then increased on continuing irradiation. Dynamic moduli of the high aromatic content polymer were essentially unchanged by the radiation. All the dynamic data were correlated by the WLF time–temperature relationship.
Effect of crosslinking on flatspotting of nylon 6 tire yarn
Authors: Cipriani C. , Papero P. V. , Moore M. S. , Menkart J.
Published: April 2003

Tires containing nylon tire cord exhibit a temporary deformation upon standing under load. The delayed recovery from this deformation, due to the fact that the yield point of nylon is exceeded under normal inflation pressures, results in the phenomenon of “flatspotting.” Previous attempts to improve the viscoelastic characteristics of nylon by crosslinking have been discouraging on account of the general degradation of properties caused by the treatment. It has now been found that short, vapor‐phase treatments with diisocyanates, particularly tolylene diisocyanate, produce nylon 6 of greatly improved flatspotting resistance, without undersirable side effects. The development of this procedure, the evaluation methods employed, and the proposed mechanism are discussed.
Properties and structure of nylon fibers in relation to drawing and aqueous phenol treatments
Authors: Sakuma Yasuhiko , Rebenfeld Ludwig
Published: April 2003

The changes in nylon 66 fiber structure and properties which take place during drawing and aqueous phenol treatments were studied by means of measurements of length, birefringence, density, moisture regain, x‐ray diffraction, stress–strain behavior, and sound velocity. Drawing was found to establish molecular orientation along the fiber axis predominantly in the early stages, whereas the development of lateral order occured primarily after a certain level of orientation had been achieved. Treatments in aqueous phenol solutions caused longitudinal contractions which depended on phenol concentration (1‐5%), draw ratio (1‐6), and the tension on the fiber during the treatment. The treatments resulted in an increase in the lateral order, decrease in orientation and corresponding changes in mechanical properties. Moisture regain was inversely related with density for the untreated fibers of various draw ratios, but the relationship became complex after treatments in phenol. The data are interpreted in terms of changes in the lateral order distributions, which permits an increase in the fibers' sorptive capacity despite an increase in the mean lateral order.
Tensile properties of TiO2‐filled poly(vinyl acetate) in the transition region
Authors: Galperin I. , Kwei T. K.
Published: April 2003

The stress–strain properties of TiO2‐filled poly(vinyl acetate) have been studied at filler percentages of 0, 10, 20, 30, and 40% TiO2 over a strain‐rate range of 100–5000%/ min at 24°C. Tensile strength, Young's modulus, and offset yield strengths all were found to increase with higher strain rates and higher TiO2 contents. Ultimate elongations decreased with greater TiO2 content and higher strain rates. Shift factors for volume fraction of filler were estimated for tensile properties as function of test rate. Stress relaxation studies have shown a reduction in relaxation times with increasing TiO2 content. Calculations of the out‐of‐phase Young's modulus were made as a function of filler content employing a box‐type of distribution of relaxation times. A possible explanation for the stress–strain behavior observed is that introduction of TiO2 changes the internal viscosity of the system, similar to the effect of temperature. This would also mean that the ultimate properties would be dependent on filler content and strain rate because viscous resistance to chain deformation would be altered. The effect of filler on stress relaxation could be thought of being due to an increase in short‐range chain motion.
Equilibrium of water between gelatin solution and ice
Authors: Tanner J. E.
Published: April 2003

The equilibration of water between aqueous gelatin solution and physically separate cakes of ice was observed. Typically, the water content of the solutions reached a nearly steady value several times before final equilibrium, reasons for which are discussed. The equilibrium gelation concentrations were found to be 72 ± 1%, 77 ± 2%, and 80 ± 3% at −10, −21, and −33°C., respectively, in moderately good agreement with predictions based on the vapor pressure measurements of Bull at higher temperatures.
Experimental determination of ultrasonic wave velocities in plastics as functions of temperature. III. Rigid epoxy foam
Authors: Asay James R. , Guenther Arthur H.
Published: April 2003

The velocity and attenuation of longitudinal bulk waves in a solid epoxy foam were measured by an acoustic pulse technique in the frequency range of 0.667–4.0 Mc./sec. and in the temperature range from ambient to 150°C. The measurements are reported with the density of the solid epoxy and with aluminum impurity loading as parameters. Over the indicated temperature and frequency ranges, complete attenuation and velocity measurements are reported for one foam corresponding to a density of 0.325 g./cc. In the density range of 0.088–0.325 g./cc. for the unloaded foams, attenuation is reported at room temperature. It is observed that the longitudinal velocities for all the densities decrease with temperature by about 40% in a span of 100°C. and that an approximately linear relation exists with temperature. The velocities in the foams loaded with small percentages of aluminum and heat‐treated at 250°C. exhibit temperature behavior which is dependent upon the combined effects of loading, density change, and epoxy properties. For the loaded foam with the highest density (1.068 g./cc.), velocity is reported to a temperature of about 250°C. The velocities of all the various density samples with the exception of the loaded foams exhibit inflections at a temperature of about 110°C. The attenuation–temperature measurements on the 0.325 g./cc. sample show similar behavior at this temperature except that the effect is much more pronounced than the velocity inflection, hence a better indication of the transition. The precision of the measurement is about 2% for the relative longitudinal velocities and about 20% for the attenuation.
Universality of the temperature‐independent viscosity characteristic of polymer melts and some of its consequences
Authors: Malkin A. Ya. , Vinogradov G. V.
Published: April 2003

It is shown that some results of recent publications (of Longworth and Piesky and of Bartoš) can be treated as particular consequences of the principle of universality of temperature‐independent viscosity characteristics of polymer melts, earlier found by these authors. This concerns the method of determination of molecular weight by means of melt index measuring and supposition that the definite value of apparent viscosity to initial Newtonian viscosity ratio can be considered to be a criterion of elastic turbulent flow emerging.
Isothermal permeabilities from thermo‐osmosis experiments
Authors: Bearman Mirion Y. , Bearman Richard J.
Published: April 2003

With the use of strain‐gauge pressure transducers, an improved constant volume apparatus has been constructed for the measurement of isothermal permeabilities of gases from thermo‐osmosis experiments. Permeabilities are reporducible to about ±5% accuracy and compare favorably with those obtained by alternative techniques. Revised values are presented for the permeability coefficients of the noble gases in rubber.
Chloride‐sulfate equilibria and transport processes in benzidine‐formaldehyde and other anion‐permeable membranes
Authors: Gregor Harry P. , Bruins Paul F. , Kramer Richard M.
Published: April 2003

Exchange equilibria, ohmic resistances, concentration and bi‐ionic potentials, diffusion coefficients, and transport numbers were measured for the chloride–sulfate–oxalate system in anion‐permeable membranes with quaternary ammonium and benzidine exchange sites. The benzidine membranes showed a greater selectivity for sulfate than chloride as compared with the quaternary ammonium membranes, but a lower transport number. These phenomena were interpreted in terms of an ion‐binding mechanism. Fair agreement was observed between measured transport numbers and those calculated from selectivity coefficients, diffusion coefficients, and equivalent conductances.
Application of DTA traces to polymer pyrolyses
Authors: Reich Leo
Published: April 2003

Various expressions are presented for the estimation of kinetic parameters during pyrolysis from DTA traces. These expressions are applied to polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, isotactic poly(propylene oxide), and poly(methyl methacrylate). The results obtained are compared with reported values, and advantages and disadvantages of the various methods are given.
Continuous heterogeneous polymerization. I. A laboratory‐scale stirred tank reactor
Authors: Stuetz D. E.
Published: April 2003

Design, calibration, and operation is described of a unique, 2‐liter laboratory‐scale continuous stirred tank reactor for the heterogeneous stereospecific polymerization of α‐olefins under pressure.
Thermal oxidation of thermoplastics
Authors: Kelleher P. G.
Published: April 2003

Commercial thermoplastics may be classified by the types of rate curves obtained on thermal oxidation. The rate of oxidation of an acrylonitrile‐butadiene‐styrene plastic is affected by sample thickness and appears to be diffusion‐controlled. Pigmentation increases the reaction rate of this compound in all the cases studied because of the catalytic effect of the metals present. Carbon black adversely affects the oxidation rate of stabilized polypropylene. The acetal plastics decompose under oxidative condition at 140°C. Of the thermoplastics examined, polytetrafluoroethylene, fluorinated ethyleneproplyne copolymer, poly(vinylidene fluoride), poly(ethylene terephthalate), and polysulfone are the most resistant to thermal oxidation at 140°C.
Water–formaldehyde–hydrogen sulfide system. II. Formation and growth of thiomethylenic chains.
Authors: Credali Lino , Mortillaro Luigi , Russo Mario , De Checchi Carlo
Published: April 2003

A linear polymer with a high melting point is obtained from the water–formaldehyde–hydrogen sulfide system in the presence of sulfuric acid. This polymer is substantially formed by a polythiomethylene chain with a few oxymethylene units. Its formation involves a topochemical reaction of the mercaptomethanol present in solution on the first separation solid of the system. On heating, the polymer loses oxymethylene units; in the same way, the first solid product separated from the system loses formaldehyde and undergoes a morphological and chemical transformation to polythiomethylene.
Effect of processing conditions on the gloss of polypropylene films
Authors: Schael G. W.
Published: April 2003

A study of the effect of three processing variables, melt temperature, quench temperature, and air pressure, on the gloss of polypropylene films shows that although these processing parameters are used to control this property they do not constitute the primary cause of gloss variations. The main causes of gloss variations were found to be changes in the polymer melt index, i.e., melt roughness, and film crystallinity, both of which can be controlled by changing the processing conditions.
A study of the morphology and physical properties of polypropylene films
Authors: Schael George W.
Published: April 2003

Data are presented showing that rapidly quenched polypropylene films contain a paracrystalline phase in addition to crystalline and amorphous phases. The density of the paracrystalline phase was found to vary between 0.8890 and 0.9080 g./cm.3. Other data show that the density of quenched polypropylene films increases during aging, the increase being a linear function of the logarithm of the film age. The physical properties of the films, secant modulus, impact strength, and coefficient of friction, were found to vary not only with crystallinity, i.e., composition‐dependent density, but also to vary during aging when the density was increasing with little change in crystallinity. An example of this dependence is the increase in secant modulus of 10.9 × 106 psi/g./cm.3 during aging and only 3.7 × 106 psi/g./cm.3 as the crystallinity increased. Because of the three phases and the density–time change, it is possible to have films with the same density and different physical properties and, conversely, films with the same physical properties and different densities.
Graft copolymers of starch. I. Copolymerization of gelatinized wheat starch with acrylonitrile. Fractionation of copolymer and effect of solvent on copolymer composition
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E.
Published: April 2003

The starch–polyacrylonitrile graft copolymer prepared from gelatinized wheat starch with ceric ammoninm nitrate as the initiator has been freed of ungrafted polyacrylonitrile and separated into fractions by extraction with dimethylformamide, γ‐butyrolactone, and dimethyl sulfoxide. The copolymer fractions obtained differed appreciably in level of add‐on, molecular weights of grafted chains, and grafting frequency. To determiue the molecular weights of grafted chains, the starch part of the copolymer was effectively removed by hydrolysis with α‐amylase. It was necessary to dissolve or swell the polymer in dimethyl sulfoxide and freshly precipitate it by addition to water before enzymatic hydrolysis. In studying the effect of reaction medium on copolymer composition, there was less ungrafted homopolymer formed and a higher yield of graft copolymer possessing more frequent grafts with water than with aqueous dimethylformamide or aqueous ethylene glycol. Polymer solubility, the results of control polymerizations of acrylonitrile in the absence of starch, and the detection of glucose endgroups on the polyacrylonitrile liberated from the fractionated polymer by hydrolysis are presented as evidence that the copolymers obtained are true grafts rather thau intimate mixtures.
Hyperfiltration studies. III. Effect of certain metal ions on the salt filtration properties of cellophanes
Authors: Kuppers J. R. , Harrison Neva , Johnson James S.
Published: April 2003

The salt rejection properties of cellophanes are substantially increased, and permeation rates decreased, by pretreatment with certain metal ions or presence of these ions at low concentration in feed solutions. In a typical case, a cellophane which initially rejected about 20% of salt from a 0.05M NaCl solution rejected over 70% in Presence of 10−3M ThCl4. Permeation rates were decreased, usually be a factior of 2 or 3. Additives found to have a marked effect were Fe(III), Th(IV), U(VI), Cu(II), and hydrolyzed pb(II). Mg(II), Ba(II), La(III), and unhdrolyzed Pb(II) had little effect. The mechanism by which the additives affect the cellophane is not clear.
Molecular weight distribution in alkyd resins. Part II. Castor oil and hydrogenated castor oil alkyds
Authors: Solomon D. H. , Hopwood J. J.
Published: April 2003

Alkyds prepared from castor and hydrogenated castor oils have been prepared direct from the oil and by first subjecting the oil to a glycerolysis reaction. The molecular weight distributions of the alkyds have been measured in solvent systems designed to separate predominantly on polarity and molecular weight. The properties of the alkyds in stoving enamels have been evaluated. The results are discussed in relation to existing theories relating processing conditions to molecular weight distribution in alkyd resins. Previous suggestions regarding the reactivity of the hydroxyl groups in the oil molecules are not consistent with the results obtained in this study.
Milling behavior of gum elastomers: Experiment and theory
Authors: Tokita Noboru , White James L.
Published: April 2003

When an uncompounded elastomer is processed on a two‐roll mill, four different regions of mechanical behavior are observed, depending upon the temperature and the severity of the nip deformation. this behavior is observed on materials with a wide variety in chemical composition, through the severity varies. The flow at high temperatures is typical of melt or polymer solution behavior. At lower temperatures unstable flow and elastic solidike regions are observed. By presuming the elastomer to be an isotropicviscoelastic medium, the stress and velocity fields were computed in the polymer melt region. The unstable regime was found to correspond to a critical value of the ratio of viscoelastic to viscous forces. The mathematical analysis, done interms of the Green‐Rivlin‐Noll theory of viscoelastic media, extends earlier studies of deformation in this geometry by Gaskell and Bergen.
Ultrasonic degradation of macromolecules in solution. Study of degradation kinetics by estimation of free‐radical scavenger DPPH and solution viscosity measurements
Authors: Chandra (Mrs.) Sarswati , Roy‐Chowdhury Phanibhusan , Biswas A. B.
Published: April 2003

The kinetics of degradation of butyl rubber in two solvents, cyclohexane and toluene, was studied by two independent techniques: viscosity measurements and free‐radical estimation as a function of DPPH consumed. The general shape of the rate curves in the two cases is similar, but not identical. The rate given by estimation of DPPH is faster than that obtained from solution viscosity data. This has been attributed to the inherent limitations of the two methods for the quantitative determination of the number of breaks occurring in the polymer molecules. The rate is also reduced as the viscosity of the solution medium is increased, which may be correlated with the reduction of the cavitation effect responsible for degradation. The degradation rates in two solvent media initially having the same viscosity were unequal. This may be due to different solvent–solute characteristics, which means that the viscosity and cavitation change to different extents in the two cases throughout the course of degradation. The limiting degree of Polymerization (DP)∞ obtained after prolonged irradiation has been found to be dependent on parameters such as intensity of irradiation, solution viscosity, and initial DP of the molecules.
Cold flow in high‐impact polystyrene
Authors: Arends C. B.
Published: April 2003

Eyring's theory of viscous flow has been applied to some mechanical properties of rubber‐modified polystyrenes. Yield strength as a function of orientation, temperature, of transition from ductile to strain have been shown to be consistent with the theory. The temperature of transition from ductile to brittle fracture as a function of orientation has also been measured and found to be consistent with theoretical predictions.
Heptane‐soluble material from atactic polypropylene. II. Interaction with liquids
Authors: Moore W. R. , Boden G. F.
Published: April 2003

Reduced melting point and swelling measurements, involving heptane‐soluble material from atactic polypropylene and over thirty liquids of differing chemical type, are reported. A value of 578 ± 40 cal. is obtained for the molar heat of fusion of a crystalline repeat unit which is much lower than values given for isotactic polypropylene. Some reasons for the low value are considered. Values of the polymer‐solvent interaction parameter χ1 for systems involving alkylbenzenes and n‐alkanes suggest a solubility parameter of 7.9 ± 0.1 (cal./cc)1/2 for the polymer. These values of χ1 decrease with increasing molar volume of liquid. Polar liquids of comparable solubility parameter or molar volume are associated with higher values of χ1. Intrinsic viscosities and values of the slope constant k′ are given for fractions in the molecular weight range 3,000–25,000 and six solvents at 25°C. The results suggest the following order of solvent power: cyclohexane ≈ cyclohexene > methylcyclohexane > trichloroethylene > decalin > carbon tetrachloride. Intrinsic viscosities are higher than those generally obtained for flexible polymers of comparable molecular weight, and the values of the Mark‐Houwink exponent appear to be high. Some reasons for these high values are considered.
On the complex poisson's ratio of a urethane rubber compound
Authors: Thomson Ker. C.
Published: April 2003

The complex Poisson's ratio of a urethane rubber compound was determined for frequencies up to 700 cps. It is shown that the assumption made by earlier workers using this material, that Poisson's ratio is a numerical constant slightly less than 1/2, while approximately correct at low (creep) frequencies is definitely invalid in certain more elevated frequency bands.
Accuracy of approximations in kinetic data circulation
Authors: Haber Václav
Published: April 2003

Kinetic data can be determined from the relation of two kinetic equations in their integrated form. For the calculation of the exponential integral, approximations are generally used, which allow a simple calculation of the activation energy. With respect of the most frequently used approximations, an evaluation of error produced by their application has been calculated. The best results can be achieved by using the equation

equation image

which permits determination of E to within 1% accuracy.
Absorption of water by proteins and related compounds
Authors: Ramsden D. K. , Wood F. , King G.
Published: April 2003

Isotherms have been obtained for the absorption of water by proteins and polyamides and by simple amides closely related to the repeat chemical unit of the polymers. The differential heat of absorption of water at zero water content has also been determined for these substances, from isosteres and from heats of mixing. In addition the nature of the hydrogen bonding of water to these compounds has been investigated by infrared spectroscopic methods. The large differences found between the heats of absorption by the polymers and the simple model compounds are discussed.
Stress softening in natural rubber vulcanizates. Part IV. Unfilled vulcanizates
Authors: Harwood J. A. C. , Payne A. R.
Published: April 2003

Stress softening (Mullins effect) is observed in gum natural rubber vulcanizates. The magnitude of this softening is similar to that in carbon black‐filled vulcanizates. The amount of stress softening is slightly greater in vulcanizates cured to produce predominantly polysulfide crosslinks than in those containing monosulfide or carbon–carbon crosslinks. The total recovery of stress softening in the vulcanizates containing monosulfide or carbon–carbon crosslinks suggests that the phenomenon is attributable to a quasi‐irreversible rearrangement of molecular networks due to localized nonaffine deformation resulting from short chains reaching the limit of their extensibility. This non‐affine deformation results in a displacement of the network junctions from their initial random state.
Peel strength of polyurethanes from oxypropylene polyols II. Effect of additives, isocyanate structure, and other factors
Authors: Reegen S. L.
Published: April 2003

The study of factors influencing the adhesion properties of polyurethane coatings to aluminum has been continued. The data indicate that the addition of additives to polyurethanes can affect their peel strengths. The addition of epoxy resins, chlorinated paraffins, or sulfonamide–formaldehyde resins results in increased peel strengths; the use of a mixture of fatty acids resulted in reduced values. The isocyanate structure can also play an important role; those producing more flexible films (such as m‐xylylene di‐isocyanate) result in higher peel strength values. Other factors found to be of importance included the concentration of aromatic and aliphatic groups, the type of solvent used in casting the films, the crystallinity of the polyether glycols and the presence or absence of certain substituents, such as fluorine, in the polyurethane chain. Tracer studies have indicated that the mechanism of adhesion failure involves the breaking of the polymer‐polymer as well as polymer–substrate bonds.