bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractionation of acrylonitrile copolymers. I. Development of a method
Authors: Cotten G. R. , Schneider W. C.
Published: April 2003

The mechanism of precipitation of acrylonitrile polymers was investigated using different nonsolvents. The effect of the dielectric constant and the polarity of individual bonds in the molecule of precipitant is discussed briefly. A methyl methacrylate–acrylonitrile copolymer was successfully fractionated from dimethylformamide solution, using a two‐stage fractionation technique, and a mixture of (2 parts n‐hexane + 1 part ether) as a precipitant. The molecular weight distributions of primary fractions were skewed to the left and overlapped each other. A large, 100‐g. sample of the same copolymer was separated into eight primary fractions, which on refractionation gave a result substantially the same as that obtained by the small scale experiment. An experimental terpolymer of methylvinylpyridine–vinyl acetate–acrylonitrile, prepared by suspension polymerization, was carefully fractionated by the same method. The polymer was shown to have a double‐peak molecular weight distribution in agreement with the earlier suggestion that acrylonitrile in aqueous suspension polymerizes by two simultaneous mechanisms: (1) homogeneous polymerization of single radicals in solution, and (2) heterogeneous growth of radicals present in stable suspended polymer particles. The above conclusion was further supported by methylvinylpyridine analysis on secondary fractions. It was found that the low molecular weight fractions contained appreciably more of the water‐soluble monomer (M.V.P.), than the high molecular weight fractions.
Measurement of triboelectric position
Authors: Webers Vincent J.
Published: April 2003

A convenient technique is presented for determination of triboelectric characteristics of a film sample relative to a group of reference surfaces and to other film samples, with the use of inexpensive, easily assembled equipment. It consists of pressing a number of reference surfaces into contact with a test film, determination of the sign and intensities of the charges generated, by spraying with an indicating powder, and estimation of tribo‐electric position of the test sample by the distribution of positive and negative charges generated. With this technique, relative triboelectric characteristics were determined for films of various polymers. The measurements give some insight into the relation between polymer structure and triboelectric characteristics.
Characteristic viscoelastic parameters for amorphous polymers
Authors: Tobolsky A. V. , Takahashi M.
Published: April 2003

By use of a reference value of modulus equal to 109 dynes/cm.2 and a reference value of time equal to 10 sec., characteristic viscoelastic parameters are defined from stress relaxation master curves and from modulus–temperature curves. Values of these parameters are tabulated for several linear amorphous polymers and slightly crosslinked amorphous polymers.
Stress relaxation in molten polymers. II
Authors: Mussa C. , Tablino V.
Published: April 2003

A new analytical method is suggested for the evalution of the stress relaxation phenomena arising when a viscous flow of molten polymers is suddenly stopped. This method is based on the consideration of the relaxation isochronism and of other most typical features of the experimental stress–time relationships. Such features can be deduced by means of an analysis in elementary non‐Hookean bodies in series having a stress–time low of a particular analytical type. Such an analysis is applied to four samples of high and low pressure polyethylenes and natural rubber. The new parameters difined in this way are discussed in order to state some correlations with the structural features. Attention is drawn on the importance of an elasticity number defined as the ratio of the relaxation area to the corresponding Newtonian viscosity.
Stress‐strain behavior of irradiated polyurethane elastomers
Authors: Fritz E. G. , Johnson Peggy M.
Published: April 2003

The applicability of the Martin‐Roth‐Stiehler stress‐strain relationship to a number of reactor‐irradiated (gamma‐ray dose range 0–1.9 × 1010ergs/g. in carbon) polyurethane elastomers has been demonstrated. For each level of dose and irradiation temperature, the stress‐strain values showed remarkably good agreement with the behavior predicted by this relationship, thus permitting a realistic characterization of the stress‐strain curves up to extension ratios of 3 by two parameters: the tangent modulusE0and a coefficientK. While the available data did not justify conclusive inferences regarding the explicit nature of the functionsE0(D) andK(D), it appears from this analysis thatE0varies exponentially with doseDand thatKis a slowly varying function of dose.
The fraction of effective sulfur crosslinking in SBR vulcanizates
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V.
Published: April 2003

Shear modulus measurements as a function of temperature have been made for SBR vulcanized with sulfur in amounts between 6 and 34% of the recipe. The shape of the modulus–temperature curves are typical of crosslinked amorphous polymers and there is a consistent displacement of the curves toward higher temperatures as the percentage of sulfur in the mixture is increased. The rubbery plateau modulus also increases with increasing sulfur, and from its magnitude the concentration of crosslinks is computed. The ratio of crosslinks to total sulfur atoms is below 0.20 in all cases. The results lend support to the conclusions of Bateman and of Bloomfield that a high proportion of cyclic structures is formed during sulfur vulcanization.
The fraction of effective sulfur crosslinking in high sulfur–natural rubber vulcanizers
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V.
Published: April 2003

Shear modulus measurements as a function of temperature for smoked sheet natural rubber vulcanized with sulfur in amounts between 2 and 34% show the crosslinking efficiency of sulfur to be much lower in natural rubber than in SBR‐1000, at least for the particular curing recipe here used. The ratio of crosslinks to total sulfur atoms computed from the rubbery plateau modulus is below 0.07 for all of the natural rubber mixtures. Ratios up to 0.20 were found in SBR mixture. The shape and slope of the modulus–temperature curves of natural rubber vulcanizates are similar to those of SBR mixtures and are typical of crosslinked amorphous polymers. Consistent displacement of the curves toward higher temperatures and higher rubber modulus as the percentage of sulfur in the recipes is increased also follows the same general pattern found for SBR. Cyclization is concluded to be the primary cause of the low sulfur efficiency in crosslinking both polymers, although polysulfide formation in natural rubber may further reduce the ratio of crosslinks formed per atom of sulfur combined.
A direct infrared estimation of cyclic oligomers in water extract of nylon 6
Authors: Anton Anthony
Published: April 2003

Methods described in the literature for the estimation of the cyclic oligomer content (which includes cyclic dimer, trimer, etc.) of nylon 6 are indirect determinations, generally based on weight differences, and require the prior extraction of ϵ‐caprolactam (monomer) from the sample. Infrared studies show that all of the cyclic oligomers have a strong NH deformation band at 6.45 μ, whereas the monomer does not exhibit such a band. This difference in the infrared is the basis of a direct determination of the cyclic oligomer content in the presence of monomer. In the method, the residue obtained after evaporation of the water extract of nylon 6 is dissolved in tetrafluoropropanol, and the absorbance at 6.45 μ is determined by the base line method. If the per cent moisture in the original nylon 6, the per cent water extractables, and the per cent oligomers in the water extract are known, one can also estimate the monomer content of the sample.
Stress relaxation in molten polymers. III
Authors: Mussa C.
Published: April 2003

The parabolic law, according to the equation , of the elasticity in the relaxation phenomena of molten polymers can be deduced from the consideration of the feature that the experimental stress relaxation curves show log–log plots which are often linear in a broad field. A general analysis, only on the basis of the viscoelastic equation permits calculation of relaxation functions, which are suggested as possible means of polymer characterization.
Polymeric ligands IV.1 Polyvinyl β‐ketoesters
Authors: Berninger C. J. , Degeiso R. C. , Donaruma L. G. , Scott A. G. , Tomic E. A.
Published: April 2003

Copolymers were prepared by ester interchange of polyvinylalcohol with ethyl acetoacetate, ethyl benzoylacetate, and ethyl 4‐nitrobenzoylacetate. Reaction of ethyl 2,4,6‐trimethylbenzoylacetate with polyvinylalcohol yielded a homopolymer. The polymers functioned as chelate ion exchangers. Ion exchange capacities were determined for the polymer derived from polyvinylalcohol and ethyl acetoacetate.
Dynamic properties of butyl containing attrited black
Authors: Gessler A. M. , Payne A. R.
Published: April 2003

The dynamic modulus and loss angle of butyl vulcanizates containing both normal and attrited carbon black (HAF) have been studied over a wide strain amplitude range. Large changes are observed in the modulus with the attrition of the black. Hot milling treatment accentuates these changes. The decrease of modulus with the logarithm of the strainwork is shown to be sigmoidal in form. When the modulus is normalized between, G0, the shear modulus at very low strains and, G∞, the shear modulus at high strains, the resulting plots with respect to strainwork are independent of the concentration of the black and the condition of the vulcanizate.
Vinyl oil monomers. I. Vicinal methacryloxy‐hydroxy soy oils
Authors: Nevin C. S. , Moser B. F.
Published: April 2003

New vinyl oil monomers have been prepared by combining epoxidized unsaturated oils with vinyl carboxylic acids. This is accomplished by heating the reactants in the presence of free radical inhibitors and appropriate reaction catalysts. The reaction consists of cleavage of the oxirane ring followed by addition of the vinyl acid through its carboxylic group. By varying the reactants and the conditions of reaction, a large family of related, but different, vinyl oil monomers can be prepared. Vicinal methacryloxy‐hydroxy soy oil monomers are clear, yellow, medium viscosity (2000–2500 cpoise), high molecular weight (1300–1500) liquids. Chemical analyses are presented for typical preparations. The monomers readily homopolymerize by a free radical mechanism to clear, solid, thermoset resins. They are compatible with a variety of commercial vinyl monomers and form copolymers which range from highly viscous liquids through soft gels, to tough rubbery products and hard resins. Data are presented on physical properties of copolymer castings of several specific vicinal methacryloxy‐hydroxy soy oil monomers.
The effects of electron radiation on the properties of ziegler polyethylenes
Authors: Wright B.
Published: April 2003

An investigation has been made of the effects of electron radiation on the properties of stabilized Ziegler polyethylenes. Radiation was applied at dose levels of 0, 2, 5, 10, 25, 50, and 75 Mrad to polymers of various molecular weights and densities. The properties most affected were flow behavior and stress‐cracking resistance. Radiation reduces the melt index of the polymers rapidly and no flow is observed at doses of 10 Mrad or more. A corresponding increase in environmental stress‐cracking resistance is evident and in every case this property reaches a value of 2000 hr. at a dose of 10 Mrad. Changes in other properties are not very great until the radiation dose becomes large. At a dose of 50 Mrad, softening point is increased on the average by 7°C., yield strength is increased on the average by 140 psi, elongation is reduced to a common value of about 200% and impact strength is increased to a common value of about 20 ft. lb./in. notch. Power factor rises to a maximum as the dose is increased to 10 Mrad and diminishes at larger doses. Flex resistance, in the one case examined, diminishes as radiation dose is increased.
Ionic crosslinking of chlorosulfonated polyethylenes
Authors: Maynard John T. , Johnson Paul R.
Published: April 2003

It is shown that chlorosulfonated polyethylenes heated with divalent metal oxides or hydroxides and rosin acids in the presence of trace amounts of free‐radical scavengers crosslink exclusively by formation of metal–sulfonate bonds. Vulcanizate properties are independent of the nature and concentration of free‐radical scavengei, and it is suggested that these agents prevent decomposition of the sulfonyl chloride crosslinking sites, thus allowing efficient reaction with the salt‐forming components of the system. This technique allows the curing of chlorosulfonated polyethylenes in direct contact with copper and lead without development of the adhesion or discoloration usually encountered in sulfur‐containing systems.
Study of epoxy compounds. Part II. The gelation point of the epoxy resin–acid anhydride system
Authors: Tanaka Yoshio , Kakiuchi Hiroshi
Published: April 2003

Equations are derived by means of Flory's original method for the gelation point of epoxy resin/acid anhydride/polyhydric alcohol systems containing various epoxy resins, acid anhydrides, and polyhydric alcohols. The resultant equations take no account of the reactivities of the various carboxyl, epoxy, and hydroxyl groups and are applied satisfactorily to epoxy resin/acid anhydride/polyhydric alcohol systems. The difference between the observed and calculated gelation point is about 2–3% when the acid anhydride used in HHPA and 4–5% when the acid anhydride used is tri‐ or tetrafunctional, such as TMA and PMDA. There is a little difference between resins E‐828 and E‐1001 for the gelation point. The discrepancy is beleived to be due to the reactivity difference between epoxide and hydroxyl to carboxyl groups and to the occurrence of intramolecular condensation, and it is contended that the degree of intramolecular condensation in these branching systems obtained is a function of the branch unit functionality of reactant, in this case, acid anhydride or epoxide.
Friction and deformation of nylon. II. Theoretical
Authors: Adams N.
Published: April 2003

It was concluded in the preceding paper that there was a significant difference between the indices m and n in the expression A = βWm and F = αWn by which the contact area A and the friction F were found to be related to the load W when nylon 610 slid on glass. A discussion of published adhesion theories of the friction of elastic bodies shows that the difference n – m is too small to be attributed to roughness of the nylon surface. It is concluded that under the contact pressures used the nylon surface was effectively smooth and that the friction of a unit area of “true” (i.e., molecular) contact between nylon and glass increased with pressure P as about P1/4. A theoretical treatment is given of the dependence of friction on load for a rough‐surfaced elastic body which covers the load range in which the surface asperities become completely flattened. It is shown that from measurements of the elastic properties of the body and feasible measurements of its surface texture one can estimate the load at which the dependence of friction on load changes from that for a rough to that for a smooth surface. Comparison with a published experiment is satisfactory.
The rheological behavior of a filled viscoelastic material
Authors: Spurr R. T.
Published: April 2003

The time‐temperature superposition principle appears to apply to filled materials, a change in the proportion of filler being equivalent to a shift along the time axis.
Some aspeots of the microetructure of polyblends of poly(vinyl chloride) and butadiene–acrylonitrile copolymer rubber with and without talc fillers
Authors: Rovatti Walter , Bobalek Edward G.
Published: April 2003

Fracture and microtome sections of polyblends, prepared from varying proportions of poly(vinyl chloride) and an elastomer (with and without talc fillers) and with the use of different conditions of mixing, were examined with the electron microscope. In general, the structures observed in cut and in fracture sections were very similar when taken from the same polymer at the same reference planes with respect to direction of process‐induced orientation. Optimal tensile behavior seems to occur when the degree of mixing establishes a structure resembling a fibrous interweaving of continuous domains. Undermixing or overmixing seems to establish more random dispersions of more or less large and discrete particles of rubber in a continuous poly(vinyl chloride) phase. Introduction of fillers changes the microstructure of the fracture patterns. Particularly in polymers containing talc fillers, the influence of prior strain history on microstructure is very evident. Thirty‐eight figures are shown to demonstrate how differences in composition, mixing process, and strain history can alter the microstructure produced by fracture or cutting of the plastic.
Effect of rate and temperature on the tensile properties of double‐base propellant
Authors: McAbee E. , Chmura M.
Published: April 2003

The tensile properties of two cast and two extruded solid rocket propellants were studied at 25°C. and 50% R.H. over a range of failure times from 0.005 to 2500 sec. The effects of temperature were also investigated at the highest rate and at 0.1 in./in./min. over a range of −60 to 80°C. The results indicate that both temperature and rate of loading greatly affect the tensile properties of double‐base propellants.
High speed tensile testing as an index of the oxidative degradation of polyethylene resins
Authors: Meltzer Theodore H. , Supnik Ross H.
Published: April 2003

A study was made of the tensile properties of two polyethylene resins incrementally oxidized on a two roll mill at 160°C. Changes in tensile parameters were related on a theoretical basis to the net effect of crosslinking and chain scission, and compared with solution viscosity measurements for the same materilas. It was shown that polymeric oxidative degradation was affected by molecular weight distribution and by crystallinity. In addition measurement of properties over 5 decades of time revealed a “critical velocity,” reflecting a relatively sensitive measure of degradation. High speed tensile tests provided a useful diagnostic tool for detecting early evidence of molecular decomposition in the materials studied.
High speed puncture testing of thermoplastics
Authors: Furno F. J. , Webb R. S. , Cook N. P.
Published: April 2003

An extensive study has been made of a broad range of polymeric materials, by the instrumented high speed puncture method. The range of strain rates prevalent in these tests has been related to the strain rates in parts subjected to normal abuse. It has been further demonstrated that at some critical test speed each material exhibited a load maximum which is accompanied by a change in the mode of failure and loss of ductility. This “critical speed” has been shown to be characteristic of the material under test.
Factors influencing izod impact properties of thermoplastics measured with the autographic impact test
Authors: Wolstenholme W. E. , Pregun S. E. , Stark C. F.
Published: April 2003

The standardization of notched Izod impact test data to normalized values of foot pounds per inch of notch is based on the assumption of a 1:1 increase in breaking strength with increasing notch width. This assumed relation is not supported by experimental tests on commercial thermoplastics. As notch width was increased from 1/8 to 1/4 to 3/8 to 1/2 in., nine of ten thermoplastics tested showed a decrease in normalized impact strength. Each material appears to show a characteristic loss in breaking strengths as the notch width increases. A technique developed for calibration of pendulum impact testers has been used to examine the variation of impact breaking strength in relation to the total kinetic energy of the hammer. Experimental tests show practically no change in impact strengths up to values that take 2/3 of the available hammer energy. Experimental work on the comparison of the impulse transferred by the hammer during breaking with impulse curves photographed by the Autographic Impact test show very good agreement for catastrophic breaks and fair agreement for plastic type breaks. The reduction in recorded impulse is attributed to the degrading of the sample during the plastic portion of the breaking cycle. The peak force of thermoplastics as measured by the Autographic Impact test increases as the temperature decreases from 100°C. or above to 0°C. Over the same temperature range flexural tests on small cantilever samples of these thermoplastics show the same thermal dependence for the flexural yield or permanent distortion stress. Plots of the impact peak forces and flexural yield stress at corresponding temperatures give a linear correlation. Each thermoplastic material exhibits a unique relation for this correlation between impact yielding and flexural yielding. This correlation between the impact and flexural tests over the range of temperatures is the first known experimental indication of a direct relation between impact properties and standard physical tests.
Rapid bursting of tubular specimens
Authors: Noyes R. B.
Published: April 2003

Burst tests on thin wall circular cylinders of aluminum, brass and magnesium alloys, mild steel and polymethylmethacrylate plastic are described in which stress and strain are measured at impact velocities of 14–31 ft./sec. The apparatus consists of an hydraulic cylinder and piston assembly attached to the inside of the specimen, with a falling weight producing a pressure pulse. Measurement problems inherent in the technique are analyzed: e.g., local instability leading to blister formation. An increasing amount of uniform deformation occurs in the specimen as strain rate is increased.
Techniques for studying strain rate effects in brittle materials
Authors: Abbott B. W. , Cornish R. H. , Weil N. A.
Published: April 2003

Techniques for studying brittle fracture over a strain rate range of 10−7–101 in./in./sec. and at temperatures from 75 to 1800°F are discussed. Techniques for achieving a uniaxial tensile stress in prismatic bars via a reflected stress wave method at strain rates up to 103 in./in./sec. at room and elevated temperatures are presented. Results of the aforementioned effects in flexure, and experimental verification of the stress‐time‐position history for the stress wave loading technique are presented along with applicable theoretical explanations. Applications of the above techniques to a broader spectrum of brittle and semi‐brittle materials are described.
Effect of strain rate on the viscoelastic properties of high polymeric fibrous materials
Authors: Dogliotti Eugene C. , Yelland William E. C.
Published: April 2003

Stress‐strain measurements have been made at a relatively low strain rate (100%/min.) and at relatively high strain rates (approximately 260 × 103%/min.) on a series of high polymeric materials of different chemical composition in textile yarn form. The series comprises the following classes of materials: polyacrylic, polyamide, polyester, polymodacrylic, polyolefin, polypeptide, polyurea, polyurethane, polyvinylidene chloride, rubber, and glass. The yarns, with a few exceptions, were conventional continuous filament, low twist structures of varied filament count and denier. Polyvinylidene chloride was tested both as a monofil and also in the form of a slit film. Polyethylene was tested as a monofil. Two polyurethanes and the rubber were tested as monofils with and without cotton covering. From the results of the stress‐strain measurements there were calculated values for the following properties at two strain rates: tenacity and elongation at break, work‐to‐break, and initial modulus. The effects of increased strain rate on these properties are shown. In general, increased strain rate increases the tenacity and initial modulus. These changes are usually, but not always, accompanied by decreases in elongation at break, so that the work to break may either decrease or increase with increasing strain rate. The physical form in which the yarns were tested (denier, number of filaments, conventional yarns versus slit film type) appeared to have only slight effect on their behavior at different strain rates. However, the chemical nature of the polymer molecules and their physical organization within the yarn filaments both have appreciable effects on yarn behavior at different strain rates. The first effect, that due to chemical nature, is exemplified by silk. The behavior of this natural polypeptide, which contains an appreciable number of side chains attached to the main polymer chain, differs markedly, as the strain rate is increased, from the behavior of polyamides which do not contain such side chains. The side chains evidently tend to keep the main polymer chains apart and thus the interchain forces in the polypeptide differ greatly from the interchain forces in polyamides which do not have such side chains. The second effect, that due to the physical organization (crystallinity and degree of orientation) of polymer molecules within a fiber, is demonstrated by a comparison of the behavior of undrawn and regular nylon at low and high strain rates. The stress‐strain behavior of the other polymers in yarn form at different strain rates is discussed in the light of their chemical structure and macromolecular organization.
Single and repeated snatch loading of textile yarns, and the influence of temperature on the dynamic mechanical properties
Authors: Swallow J. E. , Webb M. W.
Published: April 2003

Yarns of nylon and polyethylene–terephthalate were subjected to snatch loadings of quarter period 5 × 10−2 sec. and stress amplitudes up to break, by impacting at several known levels of energy. Force developed was measured as a function of time by means of a capacitance gauge, and the extension by photographing the movement of a small torch attached to the yarn. The equivalent linear modulus, calculated from the period of longitudinal oscillation at low energy input, agreed broadly with the initial modulus of the dynamic load‐extension curves. In repeated impact at a given energy level, the total deformation increased logarithmically with time, but the extension attributable to individual impacts decreased. There was a corresponding progressive increase in dynamic tension, but the breaking tension was not apparently affected either by the number of previous impacts or by the energy level. Breaking loads of a nylon yarn, reached in 10−2, 10, and 103 sec., were compared at temperatures from 20 to 250°C. Tenacity decreased with temperature at a rate depending on the time to break, but the tenacity at a temperature of about 240°C. was substantially independent of rate of loading. Strain‐time relationships, obtained at various temperatures using a photoelectric technique, were compared and analysed.
Novel curing systems for chlorosulfonated polyethylene
Authors: Nersasian A. , King K. F. , Johnson P. R.
Published: April 2003

Polyfunctional alcohols, acyclic, cyclic, and heterocyclic imines, and organotin oxides have been studied as crosslinking agents for chlorosulfonated polyethylene. Mechanisms for the crosslinking reactions involving the sulfonyl chloride moiety have been proposed. Differences in curing activity have been correlated with structural modifications of the curing agents consistent with classical chemical reactions for nonpolymeric systems. Of the curing systems examined, the polyols provide nontoxic, low cost, safe‐processing formulations offering excellent physical properties which have found use in practical commercial applications.
Generalized approach to adhesion via the interfacial deposition of amphipathic molecules. III. Adhesion of polyethylene to stainless steel
Authors: Schonhorn Harold
Published: April 2003

Oriented monolayer adhesives of stearic acid have been employed to bond polyethylene to stainless steel. Bonding time, bonding temperature, and rate of peel are several of the parameters that here varied to determine their effect on the final peel strength. Peel strengths of about 90 lb./in. width were obtained for monolayer coated specimens. When the specimens were fabricated properly, only cohesional failure of the polyethylene resulted. Irradiation of the bonded specimens resulted in considerable lowering of the peel resistance of the nonmonolayer coated specimens, relatively small differences being noted for those prepared with the oriented monolayer adhesive.
Stress relaxation in molten polymers. IV
Authors: Mussa C. , Sacerdote P. , Guglielmino P. , Tablino V.
Published: April 2003

After a survey of suggested analytical methods, data are given for ten polymer samples (high and low pressure polyethylenes, atactic and isotactic polypropylenes, and of natural rubbers). It appears that the suggested methods of plotting the stress relaxation data after cessation of steady flow, as well as the quantities defined from such analysis, in the case of the given polymers can yield qualitative and semiquantitative information on such structural features such as average chain length, polydispersity, chain regularity, long branching, and crosslinking.
Rheologic behavior of epoxy resins in the transition region
Authors: Theocaris Pericles S.
Published: April 2003

Master curves of log Q(t/K) against log (t/K) were constructed from experimental data on creep compliance, relaxation modulus, stress‐optical and strain‐optical coefficients of two types of epoxy resins at a series of temperatures in the transition region. The characteristic creep or relaxation time K for each temperature was defined and tabulated. The master curves were fitted to the reduced equation of the Gauss error integral form and the following characteristic parameters were calculated: Q1, the glassy‐state parameters (creep compliance, relaxation modulus, stress‐optical or strain‐optical coefficients); Q2, the rubbery‐state parameters; Td, the distinctive temperature; Kd, the characteristic creep or relaxation time at Td; and the parameters ht and hg of the steepness of master curves at the transition and glassy regions, respectively. The investigation was extended to the determination of the distribution functions of mechanical and optical retardation and relaxation times L (log τ) and H (log τ), respectively, representing the differential contribution to instantaneous compliance, stress‐optical or strain‐optical coefficients associated with retardation times and instantaneous modulus, stress‐optical or strain‐optical coefficients associated with relaxation times.
Photopolymérisation du nitrile acrylique en présence des sels de lanthane
Authors: Simionescu Cristofor , Feldman Dorel , Oprea Spiridon
Published: April 2003

Data are given for the photopolymerization of acrylonitrile in the presence of some lanthanium salts, as initiators of the polymerization. The activity of these salts with respect to the photopolymerization of acrylonitrile indicates the following series: LaCl3 · H2O > La2(SO4)3 · 9H2O > La(NO3)3 · 6H2O > La(CH3COO)3. The kinetics of the process have also been considered.
Study of polymers applicable to insulation systems
Authors: Torossian K. A. , Jones S. L.
Published: April 2003

In recent years thermosetting polymeric systems have been used extensively as binders in electrical insulation and composite plastic structures with excellent success. However, such properties as post‐cure gassing, thermal stability, and high temperature bond strength have always been stumbling blocks for the insulation engineer. Experience has shown that these properties can ultimately affect the dielectric endurance of an insulation when subjected to high voltage stresses. The above‐mentioned problems are generally controlled by the organic binders present in the insulation. Test methods have been developed whereby the behavior of the polymers under certain conditions can be predicted, thus increasing the effectiveness of the design engineer.
Mechanical behavior of some lightly crosslinked rubbers
Authors: Nielsen Lawrence E.
Published: April 2003

The creep and dynamic mechanical properties of rubbers with a wide range of degree of crosslinking have been correlated with the swelling properties of the rubbers. Both butyl and styrene–butadiene rubbers were studied. Mechanical damping steadily decreases as the crosslinking increases. A damping test could replace the usual swelling tests as a measure of the tightness of the network structure. Lightly crosslinked rubbers have a minimum in the damping‐temperature curve while highly crosslinked rubbers do not. Very small degrees of crosslinking dramatically decrease the creep rate, however, even for highly crosslinked rubbers, creep does not completely stop. The Nutting equation often gives a very good correlation between damping and creep rate.
Some implications of the gel point concept to the chemistry of alkyd resins
Authors: Bobalek E. G. , Moore E. R. , Levy S. S. , Lee C. C.
Published: April 2003

This study explored the effects of chemical composition, extent of polyesterification and possible side‐reactions upon the rheological behavior of a variety of oil‐modified, glyceryl phthalate alkyds in both melt and in dilute solutions with several solvents. Correlative data were obtained on molecular weight and on other aspects of solubility and drying properties important to paint technology. Viscometric data proved very useful in relating variances of reaction degree with usage properties of these polymeric materials. Those data suggest a viewpoint of the gel point mechanism which enhances practical utility of polyesterification theory. This hypothesis proposes that alkyd synthesis is not a homogeneous reaction throughout, and that phase separation creates a colloidal dispersion in the reacting mass long before gelatification occurs. Classical polyesterification theory can predict the event of initial phase separation; other process variables affect the relative stability of the transition colloid which ultimately coalesces into the final gel structure. Practical properties of alkyds in paint vehicles can be adjusted to satisfy varying requirements by arresting the reaction at different levels before or in the transition region. Measurements of melt viscosity and intrinsic viscosity are especially sensitive and convenient probes for control of process and product in terms of this concept.
Molecular weight distribution in alkyd resins. Part I
Authors: Fletcher J. R. , Polgar L. , Solomon D. H.
Published: April 2003

The factors which could affect the molecular weight distribution of a fatty acid modified polyester (alkyd) are discussed. Specific studies on a 33% coconut oil/glycerol/phthalic anhydride polymer are described, and the effect of monoglyceride composition on alkyd distribution and film properties of an automotive baking enamel are considered.
Experimental study of the mechanism of film formation
Authors: Brodnyan John G. , Konen Thomas
Published: April 2003

The temperature above which a polymer latex forms a continuous film, i.e., the minimum film formation temperature (MFT), was studied as a function of particle size, surface tension, and stiffness of the polymer. The MFT was found to occur in the region where the modulus of the polymer G is decreasing very rapidly with increase in temperature. The MFT appears to be independent of particle size but very strongly dependent on polymer stiffness. The random error in MFT measurement, however, is equivalent to a change in polymer modulus of the same order of magnitude as the particle size variation investigated. Thus the ratio Gr/γ, where r is the particle radius and γ the surface tension, may be constant as predicted by Brown for a given chemical composition but the instrumentation used was not sensitive enough to prove it. The value of that ratio, however, depends markedly upon chemical composition going from an average value of 0.58 for a nonpolar copolymer (75% styrene, 25% n‐butyl acrylate) to an average value of 260 for a more polar copolymer (50% ethyl acrylate, 50% methyl methacrylate). The quantity (MFT‐Tg), where Tg is the glass temperature of the polymer, also depends upon the chemical composition going from a value of 10°C to −3°C. when changing from the nonpolar copolymere to the more polar copolymer mentioned above.
Effect of organic sulfur compounds on the autoxidation and stress relaxation of peroxide vulcanizates of natural rubber
Authors: Cunneen J. I. , Lee D. F.
Published: April 2003

The effect of various sulfur compounds on the oxidizability and stress relaxation of peroxide vulcanizates of natural rubber has been investigated. Many of the sulfur compounds reduce the rate of stress relaxation and oxygen absorption, but in general their inhibitory powers are considerably less than those observed when they are added to squalene.
Anomalous flow of cellulose solutions during spinning
Authors: Reeves E. V.
Published: April 2003

An apparatus is described for measuring the flow rate of cellulose xanthate solutions at known pressure gradients across spinning jets. It is shown that the jet hole behaves more like a capillary than an orifice in its effect on flow and that similar relationships exist for flow through spinning jet holes and a narrow pipe characterized by an equation of the form Q = Apb, where b has a value of approximately 1.5 for the high rates of shear strain found in spinning jets and 1.4 for the lower rates found in the pipe. A fundamental approach shows a similar discontinuity when comparing the relation between apparent viscosity coefficient and rate of shear strain, between low and high rates of shear. Experimental results are given for the effect of certain chemical factors in viscose solutions and the effect of spinning jet hole size, on the flow rate/pressure gradient curve.
Acrylic latex film formation in the critical temperature range
Authors: Myers Raymond R. , Schultz Ray K.
Published: April 2003

A shear wave of 15 megacycle frequency and four microsecond duration was made to impinge on the under‐side of a series of ethyl acrylate‐methyl methacrylate copolymer films on fused quartz. Reduction in the reflection coefficient of the pulse provided a direct measure of the increased viscosity and elasticity of the film as it dried, as well as the loss in adhesion which occurred in some cases. Upon reducing the minimum film‐forming temperature (MFT) from 54 to 32°C. by increasing the ethyl acrylate content from 35 to 50%, the adhesion loss was reduced, eventually to zero, depending on the drying rate. Despite the fact that elasticity of the latex particles is the controlling parameter in film quality, a dependence on their viscosity was revealed by this work.
Hard rubber polyblends: Shear modulus–temperature relationships
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V.
Published: April 2003

Polyblends which undergo two distinct modulus transitions between glassy and rubbery behavior have been made from sulfur‐vulcanized diene rubbers. In these blends butyl rubber or polyisobutylene is used to form the rubbery phase of a mixture in which an appropriate diene polymer is converted to resinous hard rubber by sulfur vulcanization. Data are given to illustrate the modification of modulus produced in polyblends bsaed on hard rubber mixtures and to show the importance of marginal compatibility in determining the properties of the product.
Temperature coefficient of vulcanization and equivalent cures for SBR hard rubber polyblends
Authors: Meltzer T. H. , Dermody W. J.
Published: April 2003

The temperature coefficient of vulcanization for SBR hard rubber polyblends has been determined to be approximately 2.0 for 10°C. intervals of temperature. Higher percentages of sulfur give faster rates of cure and higher glass transition temperatures. Ti at 109 provides a convenient index to the degree of vulcanization of the mixtures. The response of hard rubber polyblends to variations in time and temperature of vulcanization and to changes in the proportion of sulfur in the recipe are similar to those found for conventional rubber recipes. Vulcanization parameters for hard rubber polyblends may therefore be estimated according to procedures found valid for nonpolyblend hard rubber mixtures.
Antistatic polystyrene
Authors: Gechele Giovanni Battista , Convalle Giovanni
Published: April 2003

Mechanical blends of polystyrene with small amounts of poly(2‐methyl‐5‐vinyl‐pyridine) furnish molded objects which acquire by means of a surface treatment with chemical agents (which react with the pyridic nitrogen) satisfactory antistatic protection. Methods of measure of the static charge are discussed along with the conditions of applications of the quaternizing agents.
A study of the effect of branching on certain physical and mechanical properties of stereoregular polypropylene
Authors: Huff T. , Bushman C. J. , Cavender J. V.
Published: April 2003

The properties of stereoregular polypropylene have been modified by the introduction of controlled branching into the polymer chain backbone. Branching is achieved by copolymerizing propylene with certain long‐chain 1‐olefins by using a standard Ziegler Natta low pressure catalyst. Physical and mechanical properties of the copolymers are related to the degree and length of branching. It was found that ultimate strength properties of moderate molecular weight polymers could be improved at some expense in short‐range deformation properties by adjusting the degree of branching to a suitable level. The copolymers did not show a good combination of low temperature brittleness characteristics along with higher temperature strength properties. It is suggested that the branching technique described will allow the tailoring of polypropylene resins for specific end use applications.
Stress relaxation after steady shearing: Applications and empirical representation
Authors: Menefee Emory
Published: April 2003

The measurement of stresss relaxation following steady‐state shearing is particularly useful in the terminal relaxation zone, where the rheological properties are molecular weight dependent. This paper contains a description of the method as applied to molten polymers, and an empirical function found to be useful for fitting the data. Three examples are given to demonstrate some direct and simple applications. First, the decrease of viscosity with increasing shear rate may be estimated by simply replotting the experimental data. Second, extrapolation of calculated viscosities to very high shear rates is shown to lead to a possible explanation for melt fracture. Third, the true Newtonian viscosity can be estimated from measurements conducted at a nonzero shear rate.
Effect of molecular weight distribution on the sprayability of poly(methyl methacrylate)
Authors: Elgood E. J. , Heath N. S. , O'Brien B. J. , Solomon D. H.
Published: April 2003

Factors which influence the sprayability of poly(methyl methacrylate) lacquers are discussed. A method of prediction this property based on considerations of the molecular weight distribution of the polymer is presented.
The relative inhibitory effect of various compounds on the rate of polymerization of vinyl acetate. II. Effect of conjugated and unconjugated acetylenes and olefins
Authors: Georgieff K. K. , Blaikie K. G. , White R. C.
Published: April 2003

The relative inhibitory effects of hexene‐1, hexyne‐1, trans‐hexene‐2, cis‐hexene‐2, hexyne‐2, 1,5‐hexadiene, 1,5‐hexadiyne, 1,7‐octadiyne, 1,8‐octadiyne, 1‐hexen‐5‐yne, 4‐chloro‐1,2‐butadiene, chloroprene, 2,5‐dimethyl‐2,4‐hexadiene, 2,4‐hexadiyne, 2‐methyl‐1‐buten‐3‐yne, styrene, ethynylbenzene, hydroquinone, and p‐methoxyphenol on the bulk polymerization of vinyl acetate were measured. Polymerization was carried out at 70°C. in a test tube in the presence of benzoyl peroxide. A comparison was made of the magnitude of the inhibitory effect due to isolated and conjugated, double and triple bonds as well as cumulative double bonds. A brief comparison between aliphatic and aromatic compounds was also made.
Measurement of photochemical degradation in certain plastics by color reactions with phenylenediamines
Authors: Gray Vannie E. , Wright James R.
Published: April 2003

Samples of polyester plastics, upon exposure to solar or carbon‐arc radiant energy, were found to form oxidation products which, when reacted with N,N‐dimethyl‐p‐phenylenediamine (DMPDA), produced yellow to brown reaction products. The extent of the reaction was determined directly by the amount of diamine reacted or indirectly by differential colorimetry. Research with this color reaction was extended into the development of tests for measuring the photooxidative degradation of polyesters, rigid poly(vinyl chloride), acrylics, and cellulose acetate–butyrate plastics. The basic colorimetric method was modified as needed for each of these plastics types, by directly measuring the absorbance of the DMPDA solution instead of measuring the amount of DMPDA reacted, by the use of o‐, m‐, and p‐phenylenediamines as replacements for DMPDA in the color reaction, or by a change in the solvent. The reliability of “yellowness” as an indicator of the photochemical stability of plastics was examined.
Viscoelastic properties of plasticized poly(vinyl chloride)
Authors: Taylor R. B. , Tobolsky A. V.
Published: April 2003

Master curves in stress relaxation for several samples of poly(vinyl chloride) plasticized by varying proportions of dioctyl phthalate [di(2‐ethylhexyl phthalate)] are reported and discussed in terms of plasticizer concentration and polymer structure. Modulustemperature curves derived from the data are also shown. Comparisons are given of plasticized compositions of poly(vinyl chloride) and polystyrene. The useful commercial properties of poly(vinyl chloride) are discussed in the light of data on the polymer structure and plasticizer action.
Temperature–strain rate transformations with isotactic polypropylene at finite strains
Authors: Hall I. H.
Published: April 2003

The possibility of applying Ferry's superposition principle to the entire stress‐strain curve of oriented isotactic polypropylene is studied. Sufficient data to prove the applicability of the principle is not available, but from published information it is shown that if superposition is valid for this material, then the shift factors are independent of strain and apply to the breaking extension as well as points along the stress–strain curve.
Ozone oxidation of corn starch
Authors: Szymanski C. D.
Published: April 2003

The oxidation of granular corn starch with ozone under various conditions was investigated. The reaction was found to be influenced by water, with the highest degree of oxidation being obtained at 23°C. in an aqueous solution of acetic acid as the suspending medium. In each medium investigated, approximately 65–75% of the total carbonyls generated were found to be aldehydes. Approximately similar results were obtained when aqueous solutions of the sugar alcohols sorbitol and mannitol were ozonized.
Use of sol‐gel analysis to estimate chain scission during vulcanization. Part II. Peroxide vulcanization of synthetic cis‐polyisoprene
Authors: Bristow G. M.
Published: April 2003

Sol‐gel analysis indicates that in the vulcanization of synthetic cis‐polyisoprene by dicumyl peroxide there are only 2–3 sites of scission per 100 crosslinked isoprene units, a value closely comparable with that observed for natural rubber.