bluuebunny/crossref_metadata_2025_split huggingface dataset:
Examination of the oxidative degradation of polyacrylonitrile using infrared spectroscopy
Authors: Conley Robert T. , Bieron Joseph F. 
Published: April 2003

AbstractThe oxidative thermal degradation of polyacrylonitrile has been examined using infrared spectroscopy. It was found that the generally accepted mechanism for the thermal degradation of polyacrylonitrile in air, which involves direct interaction of neighboring nitrile groups, and alternate proposals, involving azomethine crosslinks through reaction of the nitrile group and a neighboring tertiary hydrogen atom, do not satisfactorily represent an initial degradation scheme accounting for the observed infrared spectral changes. Rather, it must be concluded that these reactions take place after the initial degradation, to produce highly complex pyridinoid systems, and are not observable under the experimental conditions employed here. By detailed interpretation of the spectral changes using, in part, a difference spectral examination technique, an alternate route for the oxidative degradation involving the introduction of double bonds in the polymer chain could be formulated. This reaction can best be visualized as occurring via the attack of molecular oxygen at the activated tertiary carbon–hydrogen bond adjacent to the electron‐withdrawing nitrile group. The nitrile group was shown to remain unreacted during the course of the initial oxidation. After the introduction of the double bond, a number of secondary degradative reactions, of which the previously proposed routes of degradation are representative, take place; these include degradation reactions of the nitrile groups to form acid and amide groups. It was observed that the accumulation of oxygenated intermediates on the surface of the polymer film is a rapid reaction and that the initial degradation process is controlled by the concentration of these species.
Friction and deformation of nylon. I. Experimental
Authors: Adams N. 
Published: April 2003

AbstractAn apparatus which permits the simultaneous measurement of kinetic friction and contact area between polymer hemispheres and a smooth glass surface has been used to study the dependence of friction and contact area on load, specimen radius, sliding speed, and loading time. Hemispherical nylon 610 specimens of radii 0.12–0.58 cm. have been used with loads of 0.7–200 g. and sliding speeds from 10−7 to 3 × 10−2 cm./sec. All measurements were performed in air at 20°C. and 66% r.h. The contact area was estimated from optical interference fringes (Newton's rings) between the surface of the specimen and that of the glass plate, by means of a theoretical expression, experimentally verified, for the shape into which an elastic hemisphere is deformed when pressed against a rigid plane. The contact area was negligibly affected in size or shape by the presence of the tangential force of friction, in accord with the theory for the contact of elastic spheres. The deformations of the specimens were, within experimental error, completely recoverable but depended on the time of loading. The effects of changes in the four variables, load, radius, speed, and time were found to be essentially independent. Subsidiary experiments showed that both friction and contact area increased by about 10% for each factor‐of‐10 increase in loading time in the range 5–1000 sec. and that friction increased by a factor of 3 as sliding speed increased from 10−7 to 3 × 10−2 cm./sec. The main series of measurements (at constant sliding speed and loading time) showed that the dependence on load W of both the contact area A and the friction F could well be represented by the expressions: A = βWm and F = αWn (where α and β were constants for a given specimen). The values of m and n were almost independent of specimen radius and their mean values, for 15 specimens, were 0.708 ± 0.006 and 0.781 ± 0.012, respectively. The difference between these values, 0.073 ± 0.013, is statistically highly significant and in the following paper is interpreted as implying that the friction per unit area of true contact between nylon and glass increases with pressure. The dependence of A on the specimen radius R (which is included in β) was found to be as R0.576. The value of this index of R and the value of m are both consistent with a power‐law dependence of mean contact pressure on deformation (measured by the ratio of contact to specimen radius) with index 0.82. The values of α for specimens of the same radius showed too much variation for a useful estimate of the dependence of F on R to be obtained.
Polymer structure and gas permeation II. Permeation studies
Authors: Roberts R. W. , Kammermeyer K. 
Published: April 2003

AbstractA series of gas permeability studies of plastic membranes demonstrated the strong dependence of gas transport on structural aspects of the membrane. Films of cellulose acetate butyrate, silicone rubber, polyethylene, polypropylene, and vinyl chloride, were used in these studies. The effect of elastic and nonelastic stretching, orientation, plasticization, and phase changes were shown to be detectable by gas permeations. Interpretation of the permeation response, as a function of temperature, is compatible with a thermodynamic appraisal of the permeation process.
Determination of carboxyl groups in the presence of carbonyl groups in oxidized polyolefins by using sulfur tetrafluoride
Authors: Heacock J. F. 
Published: April 2003

AbstractA simple analytical technique has been developed to determine the amount of carboxyl groups present in degraded polyethylene film. This procedure is based upon the relative reactivities of the various carbonyl groups present, in oxidized polyethylene film, to sulfur tetrafluoride gas. The quantity of the carboxyl groups in the film is then measured as a function of the absorption at 5.45 μ.
Cut growth and fatigue of rubbers. I. The relationship between cut growth and fatigue
Authors: Gent A. N. , Lindley P. B. , Thomas A. G. 
Published: April 2003

AbstractThe relationship between the cut growth and fatigue failure of natural rubber vulcanizates under repeated loading is examined. The cut growth behavior has been investigated using several types of test piece, and the results are shown to be consistent when interpreted in terms of the tearing energy concept developed previously. The most comprehensive data have been obtained by measuring the growth of a small cut in the edge of a strip cycled in simple extension. It is found that the cut growth per cycle is approximately proportional to the square of the maximum tearing energy attained during the cycle. Using this relation, the fatigue life of a specimen containing a small cut is deduced from elasticity theory as a function of initial cut size and maximum strain. Experimental results give good agreement with theory. A similar strain dependence is found for the fatigue life of die‐stamped dumbbell test pieces with no intentionally produced flaws; this is consistent with the mechanism of failure being cut growth from small flaws present in the specimens. Their effective size is estimated to be about 2 × 10−3 cm, which is compatible with the observed superficial imperfections of the cut edges.
Crystallite orientation in regenerated cellulose filaments. II. Effect of degree of polymerization and stretch
Authors: Ellis K. C. , Warwicker J. O. 
Published: April 2003

AbstractMeasurements of the degree of orientation in cellulose filaments prepared from fractions of secondary cellulose acetate having a very limited range of degree of polymerization have shown that the degree of orientation produced by a given effective stretch increases as the degree of polymerization increases. The orientation distributions of the (101) and (020) planes have been compared with those predicted by Kratky's theory for the deformation of a material containing rod‐shaped crystallites, and it has been shown that the shapes of the observed and theoretical distributions are the same if the appropriate value of the degree of stretch is used. This value is always less than that calculated from the changes in the dimensions of the filaments produced by stretching. Kratky's theorv cannot however account for the variation with degree of polymerization and does not account for the observed shape of the curves for orientation as a function of stretch. Consideration of the process by which the filaments were produced shows that the filaments were subjected to stretches additional to those intentionally applied to them. The results of the orientation measurements are compared with published figures for the birefringence and tenacity of similar filaments, and linear relations are found between birefringence and orientation and between tenacity and orientation.
Evaluation of poly(2,6‐dimethyl)‐1,4‐phenylene oxides and related copolymers for high temperature adhesive application
Authors: Hoyt H. E. , Halpern B. D. , Tsou K. C. , Bodnar M. , Tannar W. 
Published: April 2003

AbstractPoly‐(2,6‐dimethyl)‐1,4‐phenylene oxides and related copolymers have been evaluated for high temperature adhesive applications. Because of the high‐melting character of these polymers, proper wetting was found to be difficult to achieve. Where such conditions can be obtained, good tensile strength values have been reached up to 600°F. The introduction of allyl group and epoxy group into such polymers provides sites for thermosetting. The fast setting rate of these groups, however, introduces difficulty in bonding procedure. Problems and ways to improve the initial bonding of specimens are discussed.
Partial specific compressibility of polystyrene
Authors: Nomura Hiroyasu , Miyahara Yutaka 
Published: April 2003

AbstractThe partial specific compressibilities of polystyrene at infinite dilution in such solvents as methyl ethyl ketone, toluene, dioxane, and a mixture of methanol and toluene were determined by ultrasonic velocity measurements and were compared with the intrinsic viscosities. The limiting partial specific compressibility decreased with decreasing solvent power. The variation of this quantity was ascribed to the increase in the segment‐segment contacts on the basis of a macroscopic model. The limiting partial specific compressibility is a measure of the compactness of the polymer molecule.
Light‐sensitized crosslinking of polyvinyl alcohol by chromium compounds
Authors: Duncalf B. , Dunn A. S. 
Published: April 2003

AbstractThe insolubilization of polyvinyl alcohol by potassium dichromate on exposure to light has been investigated. Ultraviolet spectrometry shows that secondary hydroxyl groups are oxidized to ketone groups but insolubilization is attributed to crosslinking of polymer chains by co‐ordination of alcohol groups to “nascent” chromic ions formed by reduction of the dichromate. Exposure to air saturated with water vapor eliminates the carbonyl absorption maxima from the ultraviolet spectrum of polyvinyl alcohol film but the spectrum can be restored by heating: this phenomenon is independent of the crosslinking reaction.
Phenolic‐formal resins
Authors: Heslinga A. , Schors A. 
Published: April 2003

AbstractA new method of curing phenolic novolac resins by means of cyclic formals under the catalytic influence of strong acids is given. It was proved that the formals react with the novolac molecules to form a highly crosslinked resite structure. As a practical consequence of this novel curing process it is possible to use the new resins at low or contact pressures in molding operations. The physical properties of the end products in general resemble those of the standard phenolic casting resins.
Acid–base properties of fibers. Part I. Nylon
Authors: Mathieson A. R. , Whewell C. S. , Williams P. E. 
Published: April 2003

AbstractThe acid‐base titration curves of solid nylon 6 resins and nylon 66 fibers have been measured, and isoionic points and endgroups determined. Five nylon 6 polymers of different molecular weights and two commercial nylon 66 yarns have been studied. Titration curves of these materials with hydrochloric acid and sodium hydroxide in the absence of added salt, and of nylon 66 in the presence of added salt, at three different temperatures, and with benzenesulfonic, trichloroacetic, and naphthalene‐2‐sulfonic acid, allowed the effect of polymer molecular weight, salt, temperature, and anion affinity on the titration curves to be determined. All the results are consistent with the view that nylon possesses a zwitterion structure at neutral pH, carboxyl groups being protonated on acid titration. A proportion of the endgroups is not available to titration in the solid polymers. Existing theories of the acid–base combination of solid polymers fail to explain all the results. The titration curves and elastic properties of the following modified nylon 66 yarns have also been determined and interpreted: nylon deaminated by nitrous acid, dinitrophenylated, acetylated, carboxymethylated, hydrolyzed, and dihydrophenylated nylons, and nylon treated with alkaline hypochlorite, boiling water, and boiling benzene. In all cases the increase in the work to stretch the filament is independent of pH.
Capillary viscometry of molten polycaprolactam
Authors: Pezzin G. , Gechele G. B. 
Published: April 2003

AbstractA study was made of the rheological behavior of 35 samples of nylon 6 polymers of molecular weights varying from 4,000 to 40,000. A capillary extrusion rheometer was employed, and flow curves extending over a large range of shear rates were obtained. The effect of temperature, shear rate, and molecular weight on viscosity is reported, and some peculiarities of the flow behavior of nylon 6 polymers are discussed.
Partial specific compressibility of dextran
Authors: Nomura Hiroyasu , Yamaguchi Sadao , Miyahara Yutaka 
Published: April 2003

AbstractThe limiting partial specific compressibility (LC) of low molecular weight dextran in aqueous solution was determined by the measurements of ultrasonic velocity and density. The negative value of LC was ascribed to hydration. The amount of bound water calculated from LC and its temperature dependence were in accord with those of sugars in order of magnitude.
Column fractionation of polymers. IV. Large‐scale polyester column fractionation
Authors: Cantow Manfred J. R. , Porter Roger S. , Johnson Julian F. 
Published: April 2003

AbstractA small‐scale fractionation of 9 g. and a large‐scale fractionation of 90 g. of a polyester were carried out. The polymer was prepared by condensation of isophthalic acid, maleic anhydride, and propylene glycol in the mole ratio 1:2:3. Results from the two fractionations were in good agreement despite different fractionation conditions. By proton magnetic resonance measurements the fractions were found to have nearly constant chemical compositions. The Huggins' constant and the Staudinger relation for this polyester were determined from data on fractions in chloroform at 30°C. Integral and differential molecular weight distributions as well as various molecular weight averages for the polyester were obtained by a computer program. The fractionation data were applied to several popular distribution correlations. The experimental distribution was found to be in good agreement with that expected from the theory of polycondensation kinetics.
Semipermeable membranes of cellulose acetate for desalination in the process of reverse osmosis. I. Lyotropic swelling of secondary cellulose acetate
Authors: Kesting Robert E. 
Published: April 2003

AbstractThe role of certain inorganic salts in increasing the flux of water through semipermeable membranes of cellulose acetate is related to the capacity of the component ions to swell the cellulosic substrate. The mechanism whereby ions which are high on the Hofmeister lyotropic series swell and dissolve secondary cellulose acetate has been investigated. Swelling is effected by the formation of metastable complexes involving the highly hydrated cationic fraction of the salt and both the hydroxyl and acetate groups of the cellulose acetate. Whereas effective anions possess large ionic radii and cause a breakdown in the structure of water which results in increased hydration of the cation, ineffective anions possess higher charge densities and tend to pair with the cation and decrease the latter's electrophilicity and hence hydratability. Ionic charge density is the factor of prime importance both with respect to the hydratability of the cation and the tendencies toward water disaggregation and ion association of the anion. The mechanism involved in the swelling of secondary cellulose acetate is related to swelling phenomena in many other polymers containing polar groups.
Electrochemical properties of thin parlodion membranes
Authors: Lakshminarayanaiah N. , Shanes Abraham M. 
Published: April 2003

AbstractThin membranes (50‐800 A. thick) formed by spreading a solution of Parlodion in isoamyl acetate on the air‐water interface have been characterized. The electrical resistance and capacitance of these membranes prepared from each of the three Parlodion concentrations viz., 5, 10, and 20 mg./ml. solution, have been measured as functions of both membrane thickness and external electrolyte (KCI) concentration. Capacitance values corroborate the thickness inferred from the weight of material transferred to cover a fixed area. Membrane resistance drops with increase in thickness. Resistivity of a membrane 100 A. thick rises with decrease in external electrolyte concentration. Acid and alkaline solutions of KCI lower membrane resistance due to increased porosity of the membrane brought about possibly by the hydrolysis of the membrane material. Membrane potentials arising across these membranes also have been measured as functions of both membrane thickness and external electrolyte concentration. The bi‐ionic potentials confirmed the usual order of penetrability of alkali metal ions observed in artificial membranes. A study of the effect of pH on membrane potentials indicates that the electrochemical activity of the membrane may be attributed to the presence of odd and terminal carboxyl groups in the nitrocellulose matrix of the membrane.
Effects of molecular weight distribution and branching on rheological parameters of polyethylene melts. Part II. Fractions and blends
Authors: Guillet J. E. , Combs R. L. , Slonaker D. F. , Weemes D. A. , Coover H. W. 
Published: April 2003

AbstractStudies of the rheological properties of fractions of linear and branched polyethylenes have shown that the melt recovery of linear polyethylene fractions is very small and independent of molecular weight over a wide range. Fractions containing high degrees of long‐chain branching, on the other hand, have high melt recoveries. The melt recovery of a fraction can therefore be used as an index of long‐chain branching. Alternatively, if no long‐chain branching is present, the melt recovery is a unique function of the molecular weight distribution. This effect is illustrated by blends of fractions. The log of the critical shear rate is a linear function of the log melt viscosity of the fraction for both linear and branched polyethylenes. This would indicate that the critical shear rate of polydisperse samples would depend primarily on the weight‐average of Z‐average molecular weight of the polymer. This is confirmed by previous studies on polydisperse samples. It also appears that critical shear rate is highly dependent on the homogeneity of the sample. Blends of the same fractions had quite different critical shear rates, depending on the procedure used to prepare them, even though their molecular weight distributions were identical. The change in viscosity with shear rate is not a unique function of molecular weight or melt viscosity. Fractions of linear polyethylene show a greater change in viscosity with shear rate than branched fractions of similar low shear melt viscosity. This suggests that the effect is related to chain entanglement or coordinated segmental motion.
Formulas for the dielectric constant and dissipation factor of mixtures and their application to the cellulose system
Authors: Venkateswaran A. 
Published: April 2003

AbstractFormulas for the dielectric constant and dissipation factor of a dielectric mixture of many components have been derived assuming (1) that the dipoles can point only in two definite directions, along and opposite to the directions of the applied field, and (2) that the dipole is a highly anisotropic body having a needle shape. The formula for the dielectric constant is applied to calculate the dielectric constant of cellulose at any sheet density. The application of the Clausius‐Mosotti relation for the dielectric constant‐density relation is discussed.
Spin casting of polymer films
Authors: Kaelble D. H. 
Published: April 2003

AbstractA versatile technique for spin casting of small polymer films within a cylindrical open faced mold is described. The high centripetal acceleration, about 500g, provides outstanding thickness uniformity and freedom from interior defects. The casting apparatus may be provided with pressure, temperature, and atmosphere control. A compact unit for simultaneous casting of four films is illustrated.
Reactions catalyzed by minerals. Part I. Polymerization of styrene
Authors: Solomon D. H. , Rosser M. J. 
Published: April 2003

AbstractThe polymerization of styrene on neutral mineral surfaces has been studied. It has been shown that the polymerization has characteristics expected for both a radical and cationic reaction, and a mechanism involving a radical‐carbonium ion is proposed to explain this evidence. A range of mineral catalysts have been investigated and a tentative theory proposed to relate the variation in activity with catalyst structure. Experiments have also been carried out to define the specific portion of the mineral surface responsible for the catalyst activity.
Preparation and characterization of thin parlodion membranes
Authors: Lakshminarayanaiah N. 
Published: April 2003

AbstractParlodion membranes 95 to 500 A. thick have been prepared on a glass surface by dipping a clean glass plate into the Parlodion solution and subsequently evaporating the solvent under controlled conditions by keeping the glass plate vertical in a metallic frame and covered with an inverted beaker. The membrane may be floated off on to an aqueous surface. Capacitance measurement established the thickness of the membrane. Electrical resistance and isothermal diffusion potentials arising across them when they separate different salt solutions have also been measured at room temperature.
Kinetics of emulsion polymerization
Authors: O'toole J. T. 
Published: April 2003

AbstractThe quantitative theory of free radical mechanisms in emulsion polymerizations is reexamined. It is suggested that existing descriptions are not entirely consistent with physically realizable situations. The proposed modifications result in a closer resemblance to homogeneous systems. Explicit expressions for the distribution of radicals are also given. The importance of interphase transfer is emphasized.
Transport properties of cellulose acetate osmotic membranes
Authors: Lonsdale H. K. , Merten U. , Riley R. L. 
Published: April 2003

AbstractDiffusion and distribution coefficients of water and sodium chloride have been measured in cellulose acetate osmotic membranes. These coefficients have been found to vary with the degree of acetylation of the cellulose ester. The diffusion coefficient of water varies from 5.7 × 10−6 to 1.3 × 10−6 cm.2/sec., and the diffusion coefficient of salt varies from 2.9 × 10−8 to 3.9 × 10−11 as the acetyl content is increased from 33.6 to 43.2 wt.‐%. A homogeneous diffusion model is proposed which describes the observations in terms of Fick's law.