bluuebunny/crossref_metadata_2025_split huggingface dataset:
ESR spectra of copper complexes of cellulose
Authors: Baugh Peter J. , Hinojosa Oscar , Arthur Jett C. , Mares Trinidad 
Published: April 2003

AbstractThe ESR spectra of complexes of fibrous cotton cellulose and cupriammonia dihydroxide or cupriethylene diamine dihydroxide under various experimental conditions were determined. The spectra of both complexes with cotton cellulose were almost identical at −100 and 25°C. The spectrum of the complex of cupriethylene diamine dihydroxide with cellulose was stable to temperatures as high as 100°C. The sum of the linewidths of the hyperfine components of the spectra for each complex was about 180 gauss. Cotton fibers were combed and aligned with their axes (lengths) parallel to the magnetic field (B∥); after formation of either of the complexes with cellulose a minumum of hyperfine structure of components centered at H∥ was observed. A maximum of hyperfine structure of these components was observed when the complexed fibers were aligned with their axes perpendicular to the magnetic field (B⊥). The opposite was true of components centered at H⊥. For a complex of cupriethylene diamine dihydroxide and cellulose at 25°C. and at high pH the g∥ was 2.2127 and the g∥ was 2.0476. It was suggested that the alignment of most of the complex was its axis of symmetry at a maximum angle to the axes of the cotton fiber, when the axes of the fibers were in the parallel alignment with the magnetic field. At high pH these observations were even more marked. When ramie was used with cupriethylene diamine dihydroxide at high pH, the contribution of components centered at H∥ to the spectra was zero. Spectra for the copper compounds alone and complexed with cellobiose are also reported.
Flow properties of molten ethylene–vinyl acetate copolymer and melt fracture
Authors: Fujiki Tokio , Uemura Masaru , Kosaka Yujiro 
Published: April 2003

AbstractIn an investigation of the behavior and formation mechanism of melt fracture the flow properties of molten ethylene–vinyl acetate (EVA) copolymer in the region of high shear rate were measured with a capillary‐type rheometer. EVA copolymer differs slightly in flow curve from low‐density polyethylene (LDPE); it seems, however, that the difference is due to the difference in molecular weight distribution (MWD) rather than to the materials themselves. The fluidity of molten EVA copolymer having a narrow MWD is equivalent to that of LDPE having a broad MWD and, generally, EVA copolymer has a higher fluidity than LDPE. It is expected that the fluidity increases with incorporation of vinyl acetate at the same MWD and the same M̄w. The critical shear rate increases with melt index and temperature. It cannot be found that the materials themselves and the MWD directly influence the critical point of melt fracture formation when the melt index is taken as a parameter. The critical viscosity (ηc) at which melt fracture forms decreases in an almost straight line with an increase of melt index. It was found from the studies of end correction and behavior of melt fracture formation that melt fracture occurs at the inlet of the die, and it is supposed that the melt fracture formation is caused by the elastic turbulence in the flow pattern due to a failure of recoverable shear strain at the die inlet.
Abrasion, fatigue, and smearing of rubber
Authors: Schallamach A. 
Published: April 2003

AbstractThe abrasion of rubber on tracks without sharp‐pointed asperities is dominated by fatigue failure. This is demonstrated by the effect of certain antioxidants on the abrasion of natural rubber compounds in air, which largely disappears in nitrogen. The experimental results obtained in air can be obscured by smearing which seems to originate from the abrasion process itself. In addition, the relative humidity of the surrounding atmosphere has a great, and little‐understood influence on the rate of abrasion. The bearing of these findings on the interpretation of road test results is discussed.
Oxidative aging of natural rubber vulcanizates. Part III. Crosslink scission in monosulfidic networks
Authors: Colclough T. , Cunneen J. I. , Higgins G. M. C. 
Published: April 2003

AbstractA natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert‐butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress–strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75°C., the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.
Kinetics of continuous addition emulsion polymerization
Authors: Wessling Ritchie A. 
Published: April 2003

AbstractAn analysis of the kinetics of continuous addition emulsion polymerization is presented. For systems that follow the Smith‐Ewart mechanism, this analysis predicts that the reaction will approach a steady‐state condition if the rate of monomer addition Ra is constant. In the steady state, the rate of polymerization depends on Ra according to a reciprocal relationship, 1/Rp = (1/K) + (1/Ra), where K depends on the number of particles and the propagation rate constant. Above a critical value of Ra, the particles will become saturated with monomer and Rp will be constant and independent of Ra.
Radiation chemical studies of protein reactions: Radiation dose and viscosity change
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractWhen protein was irradiated by gamma rays from a cobalt 60 source, an activated state was caused. An empirical equation for the viscosity change was obtained, and the phenomena were explained on the basis of the molecular mechanism. The general equation for the viscosity change is given by ηred = (b + a log R)(1 − e−kt), where ηred is the reduced viscosity of the solution, R is the gamma radiation dose, and t is time.
Separation and characterization of the vinyl side chains from grafted polyacrylonitrile–cotton copolymers
Authors: Morris Nelle J. , Blouin Florine A. , Arthur Jett C. 
Published: April 2003

AbstractA method of separation of polyvinyl side chains from grafted polyacrylonitrile–cotton copolymers was developed in order to study the effect of length of side chain on copolymer properties. The method consists of dispersion of the copolymer (1 g.) containing 20% polyacrylonitrile in 75% aq. ZnCl2 (100 ml.), addition of 6N HCl (100 ml.), heating for 1 hr. at 100°C., and precipitation and purification of the resulting vinyl polymer. The effect of hydrolysis on the intrinsic viscosity, the nitrogen content, and the infrared absorption spectra of the polyacrylonitrile polymers was investigated. It was concluded that this method of separation of the grafted polymers permitted a comparison of samples grafted by various techniques. A series of grafted copolymers was hydrolyzed, and the molecular weights of the isolated products were determined by measurements of intrinsic viscosity. Copolymer samples prepared by a post‐irradiation grafting technique had the longest polyacrylonitrile side chains (molecular weight, 1 × 106). Samples grafted by a simultaneous irradiation technique varied in side‐chain length, depending upon the monomer‐solvent system used in the preparation of the copolymer (molecular weight, 3 × 104−5 × 105). Chemically initiated grafting to cotton resulted in a copolymer containing relatively short side chains (molecular weight, 9 × 104).
Preparation and properties of films and fibers of disordered cellulose
Authors: Jeffries R. 
Published: April 2003

AbstractThe preparation and properties of films and fibers of highly disordered cellulose are described; the basis of the preparation is the regeneration of cellulose from cellulose derivatives in non‐aqueous media. These cellulose are at least 97% hydrogen‐bond disordered (as measured by the infrared‐deuteration technique), give x‐ray diagrams showing poor three‐dimensional order, and are practically completely accessible to swelling agents such as water and formic acid. The crystallization of these disordered celluloses is described. The effects on native cellulose of ball milling, mercerization, amine treatment, swelling in acid and salt solutions, and swelling in solutions of potassium hydroxide in non‐aqueous solvents are described with reference to changes in fine structure as measured by the infrared‐deuteration technique.
The alcoholysis of cellulose
Authors: Heath J. E. , Jeffries R. 
Published: April 2003

AbstractThe alcoholysis of cellulose in solutions of sulfuric acid in ethanol and n‐butanol is described; emphasis is placed on the reactions of a cellulose that is 97% disordered, as measured by an infrared‐deuteration technique, but the reactions of several partially ordered celluloses are also investigated. Alcoholysis produces only very slight increases in hydrogen‐bond order, and the rate of reaction is roughly related to the degree of hydrogen‐bond disorder in the starting material. The reactivity of the 97% disordered cellulose is dependent upon the method of freeing the film from the non‐aqueous media used in its preparation. This variable reactivity is not associated with differences in hydrogen‐bond order or in the surface area of internal voids, capillaries, etc., as measured by nitrogen sorption and a nonswelling oxidation technique, but could be due to the existence of a very fine pore structure in some of the films.
Transition‐metal complex formation with phenyl isocyanate
Authors: Rand Leon , McLean John A. 
Published: April 2003

AbstractComplex formation between phenyl isocyanate and cobalt or manganese naphthenate in benzene was determined by the mole ratio method. Complex of 3:1 for cobalt and 2:1 for manganese were found. The method of analysis in this study utilized the characteristic transition‐metal visible absorption spectra. Effects of time and metal‐salt solution stability are noted.
Effect of orientation and trace crosslinking on the properties of high wet‐modulus rayon
Authors: Daul G. C. , Muller T. E. 
Published: April 2003

AbstractTechnology is now available to produce superior quality rayon fibers with a wide range of tenacity, elongation, and modulus. In‐process modification results in rayon fibers suitable for a great variety of end uses as continuous filament yarn or staple, either in 100% construction or blended with synthetics. In addition to versatility, such modified rayons have unique dimensional stability and chemical resistance. The developments leading to a method for preparation and the characteristics of such a highly oriented rayon, modified through trace crosslinking, are described here. The discovery of a triple modifier system utilizing poly(ethylene glycol)–dimethylamine in the viscose and small amounts of formaldehyde in a low zinc sulfate‐containing acid spin bath, has made possible the production of rayon fibers with high strength (ca. 6 g./den.) and adequate elongation (ca. 10%) for good processability and which are highly resistant to caustic soda. Among the variables studied were spin bath composition, especially the relationship between formaldehyde and zinc sulfate concentration, and bath temperature. Optimum modifier concentrations are defined with regard to particular fiber properties desired. The effects on orientation and fiber physical properties of spinning modified viscose into formaldehyde‐free and formaldehyde‐containing spinning systems are described. High orientation coupled with trace crosslinking provides greatly improved resistance to caustic soda over that resulting from orientation alone.
Sorption and diffusion of water in a rubbery polyurethane
Authors: Schneider N. S. , Dusablon L. V. , Spano L. A. , Hopfenberg H. B. , Votta F. 
Published: April 2003

AbstractUnsteady‐state water sorption measurements have been carried out over the temperature range 27–40°C. on a polyurethane elastomer composed of MDI, 1,4‐butanediol, and polybutylene adipate (MW 2000) in the mole ratios 3.2:2:1. The sorption isotherm is concave upward above an activity of 0.6, reaching a saturation water concentration of 1.6 g./100 cc., the heat of mixing is zero, and the diffusion constant decreases slowly and linearly with increasing water concentration. The overall behavior is attributed to the immobilization of sorbed water in clusters. Analysis of the sorption process in terms of the cluster integral reveals that the interaction of water with specific polymer sites occurs at the lowest concentrations but that clustering dominates for water activities greater than 0.45. Since the activation energy for diffusion decreases with increasing water concentration, from 11,000 cal./mole at zero concentration to about half that value at saturation, plasticization of the polymer also affects the transport process.
Mechanism of reinforcement in rubber‐modified polystyrene systems studied by use of a miniature dart drop test
Authors: Schmitt J. A. 
Published: April 2003

AbstractA miniature dart drop test was used in a study of the mechanism of reinforcement in impact resistant rubber‐modified polystyrene. A typical SBR‐polystyrene system was diluted with varying amounts of polystyrene, and thin compression moldings were made from each blend. The impact‐whitened areas were observed directly under the microscope and photomicrographs are presented. The whitening is caused by scattering of light from interfacial separation of portions of many rubber particles from polystyrene and by formation of a multitude of microcracks and/or crazes, starting at the partially separated particles. The absorption of energy by this mechanism can be very large. The driving force for the initial separation appears to be the triaxial tension under which the rubber particles exist, and this results from the higher volume shrinkage rate of rubber compared to that of polystyrene. Included also are photomicrographs taken of specimens after tensile stretching, and the mechanism derived from the impact case is extended to explain the increased elongation and corresponding whitening.
Effect of proccessing on flow properties of some linear polyethylene resins
Authors: Ford R. W. , Scott R. A. , Wilson R. J. B. 
Published: April 2003

AbstractChanges in flow properties of polyethylene resins have often been observed during processing operations. Studies in this laboratory show that melt viscosity of polyethylene normally increases when the resin is heated in a compression mold at temperatures below 300°C. At the same time, the solution viscosity actually decreases in some cases. During extrusion, on the other hand, both melt viscosity and solution viscosity are shown to decrease. In addition, the logarithm of melt flow rate is seen to deviate markedly from the expected linear dependence on reciprocal of absolute temperature. The results suggest that both crosslinking and chain‐scission reactions occur during processing, the former predominating at low or zero shear, the latter at high shear.
Dependence of the thermal conductivity on mechanical stress in polymers
Authors: Fox J. S. , Imber M. 
Published: April 2003

AbstractAn examination of the theory of thermal conductivity of amorphous dielectrics as applied to polymeric materials indicates that it is reasonable to expect that the conductivity is stress dependent. An experimental investigation was undertaken to determine the validity of this hypothesis for a number of plastics at temperatures below their respective glass transition points. Poly(methyl methacrylate), nylon, and Delrin were chosen as representative of a wide range of percentage crystallinity and were tested at compressive stresses up to 140 kg./cm.2 and temperatures between 4 and 38°C. The results indicate that the conductivity may increase as much as 20% and that the dependence on stress is a function of temperature and the type of polymer examined.
Novel thermally stable and chemically resistant epoxy polymers derived from phenylene oxides
Authors: Neville Roy G. , Mahoney John W. , MacDowall Kenneth R. 
Published: April 2003

AbstractThermogravimetric and differential thermal analysis data are presented for three novel bisepoxy monomers and formulated coatings derived therefrom. The coatings were insensitive to impact in liquid oxygen and showed excellent resistance to liquid nitrogen tetroxide, concentrated nitric acid, and a variety of organic solvents. All coatings showed excellent adhesion to metals and oxidation resistance superior to any known commercial epoxy polymer. Thermal resistance was excellent at 500°F. for periods of at least 500 hr. in air. Other data on these novel epoxy polymers are also presented.
Sur la dégradation thermique du polychlorure de vinyle. V. Stabilité thermique de polyméres semicristallins
Authors: Guyot A. , Bertet M. , Tho Pham Quang 
Published: April 2003

AbstractThe thermal dehydrochlorination of semicrystalline, but rather low molecular weight, PVC fractions, prepared by ionic polymerization catalyzed by tert‐butylmagnesium chloride was studied under an inert atmosphere and compared with that of commercial polymer. When the samples are in powder form, the crystallinity of some fractions, which are insoluble at room temperature in all the usual solvents for PVC, induces a tremendous thermal stability, which is observed so long as the temperature is under the melting point of the sample. In dilute solution, the dehydrochlorination of all the samples is much slower, but the differences between the samples are less important; besides, a catalytic effect of some metallic impurities is observed. This catalytic effect is chiefly relative to a process of intermolecular condensation which causes the formation of a labile tertiary chlorine structure and so initiates or accelerates the purely thermal chain dehydrochlorination. It is suggested that, besides the crystallization and the catalytic effects, the configuration of the structural units could be an important factor in the course of the dehydrochlorination process.
Preparation of polysaccharide solutions for electron microscope investigations of supermolecular morphologic formations of the solid component
Authors: Rak J. 
Published: April 2003

AbstractA new preparation process, which preserves the original morphological state of polysaccharides in solution during removal of the solvent and so makes possible direct electron microscope investigations, has been developed. The process consists of lyophylization of the sample (in very low concentration of water solution) by freeze‐drying, modified for the purpose of electron‐microscopic examination. Water‐soluble mixture of the polysaccharides of hemicelluloses isolated from the wood tissues of beech and the water solution of the mannan from Saccharomyces cerevisieae treated by means of the new preparation process (preparation with freeze‐drying) and, for comparison, these same samples treated without the application of freeze‐drying (by means of drying at laboratory temperature and atmospheric pressure, standard preparation process) are introduced as instance from many polysaccharides electron microscopic examined after this preparation process. This method allows one to make direct electron microscope investigations of the water‐soluble polysaccharides in no way stained or otherwise shadowed with good resolutions of details in the supermolecular range.
Relationships between surface wettability and glass temperatures of high polymers
Authors: Lee Lieng‐Huang 
Published: April 2003

AbstractThe adhesion between a polymer and a solid substrate may be considered to be one type of complex liquid‐solid interaction. Relationships between surface wettability and bulk properties of liquidlike polymers are discussed. A new and direct empirical relationship between the glass temperature (Tg) and critical surface tension of a polymer (γc) is established:

where n = degree of freedom, defined by Hayes, Vm = molar volume, and Φ = interaction parameter, or the ratio between reversible work of adhesion and geometrical mean of the work of cohesion. The effect of polarity and hydrogen bonding on this relationship is also discussed. The calculated γc's are much closer to the observed values than those calculated on the basis of parachor. With this new wettability relationship the wettability of polymers, especially of those forming no hydrogen bonds, can be related to thermal, rheological, mechanical, and relaxational properties.
The effect of strain rate on the stress–strain curve of oriented polymers. II. The influence of heat developed during extension
Authors: Hall I. H. 
Published: April 2003

AbstractThe temperature changes which take place in a yarn during extension are considered. From thermodynamical considerations and the heat‐transfer coefficient it is shown that extension of the yarns studied will take place isothermally at strain rates below 0.04 sec.−1 and adiabatically at rates above 4 sec.−1 It is not possible to make an accurate estimate of the magnitude of the temperature rise during adiabatic extension, because of the lack of information on internal energy changes during irreversible extension, but by assuming these to be zero it is estimated that the temperature is likely to rise by 20–30°C. at strains above 10%. Results from a study of the effect of strain rate on the stress‐strain curves of five different yarns show in all these materials a range of strain rate in which the stress that produces a given strain increases less rapidly with strain rate than elsewhere. For viscose and poly(ethylene terephthalate) this effect occurs in the expected range of strain rate, and its magnitude is of the correct order for it to be attributed to the temperature rise resulting from the transition from isothermal to adiabatic extension. For the other materials the transition does not seem likely to provide a complete explanation of this effect. There is no evidence that the transition significantly affects the breaking properties.
Melting points of cellulose nitrates
Authors: Colborne R. S. 
Published: April 2003

AbstractFresh determinations and estimations of the melting temperatures of cellulose nitrates have been found to be much lower than previously reported and to be in line with those of other cellulose derivatives, varying from 200°C. for the dinitrate to 280°C. for a sample approaching the trinitrate in composition. The heat of fusion of at least 3000 cal./unit is also similar to values of other cellulose derivatives. The paper contains some observations on the applicability of Flory's theory of the effect of diluents on the crystalline melting temperature of polymers.
Prediction of long‐term ABS relaxation behavior
Authors: Malpass V. E. 
Published: April 2003

AbstractThe applicability of time–temperature superposition to tensile stress relaxation of ABS plastics has been verified at strains from 0.5 to 5% for temperatures in the range of 10–50°C. Master curves have been compiled to predict the long‐term stress relaxation at 23°C. and a stress–strain–reduced time surface has been constructed. A comparison of relaxation times and activation energies has confirmed that a strain increase facilitates stress relaxation up to yield. The decay of relaxation modulus at linear viscoelastic strains was shown to be equivalent to that of tensile creep modulus. By normalizing the master curves to originate at yield stress and then converting them into multiaxial from the strain which gives the best data fit with long‐term hydrostatic pipe‐burst strength was shown to be at yield or beyond. The ABS yield‐strain master curves at 23°C. were shown to match satisfactorily the long‐term pipe‐rupture data. Activation energies for ABS relaxation have been compared below and above the rigid matrix Tg, to assess the degree of stiffening of the polymer in the solid state.