bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of thin films in ultraviolet studies of cellulose xanthate
Authors: Phifer Lyle H. 
Published: April 2003

AbstractA procedure for the study of the chemistry of viscose based on ultraviolet measurements of a film of cellulose xanthate has been developed. To illustrate the range of usefulness of the technique, spectra of various compounds formed with cellulose xanthate, including metal salts, organic derivatives, and an acid form, the influence of solvation on several cellulose xanthate compounds, and formation and decomposition curve of cellulose xanthate derivatives are presented. Possible applications of the technique include a study of the acid decomposition of cellulose xanthate, the influence of additives, new derivatives, and the xanthation mechanism. It is also probable that the method can be used in the study of other systems where fast reaction mechanisms are involved and suitable absorption characteristics are present.
Reaction of formaldehyde with cellulose xanthate
Authors: Phifer Lyle H. , Ticknor Leland B. 
Published: April 2003

AbstractFormaldehyde reacts reversibly with cellulose xanthate in aqueous acid to form a product having an absorption maximum at 280 mμ and an extinction coefficient of 11,600. The fraction of the original xanthate converted to the formaldehyde form is related to the formaldehyde concentration. The aqueous acid decomposition rate of the formaldehyde derivative is pseudo first‐order and is inversely proportional to the formaldehyde concentration. At high acidities the decomposition rate is independent of acid concentration, but the rate decreases with decreasing acidity in the pH range of 1–4. On the basis of the data obtained in these studies, the equilibrium constant for the formation of the formaldehyde derivative was found to be of the order of 10.4.8. The activation energy for the decomposition of the formaldehyde derivative is 18,600 cal./mole.
Mechanism for the aqueous acid decomposition of the formaldehyde derivative of cellulose xanthate
Authors: Phifer Lyle H. , Dux James P. , Ticknor Leland B. , O'shaughnessy M. Thomas 
Published: April 2003

AbstractKinetic equations for the decomposition of S‐hydroxymethyl cellulose xanthate in the presence of acid and formaldehyde are derived. The assumed mechanism involves an equilibrium between the S‐hydroxymethyl cellulose xanthate and cellulose xanthic acid and xanthate ion. Decomposition appears to proceed via interaction between the cellulose xanthate ion and hydrogen ion which form an activated complex that subsequently decomposes to cellulose and carbon disulfide. The equations derived show the proper dependence on acid and formaldehyde concentrations. An estimate of the equilibrium constant between cellulose xanthate and S‐hydroxymethyl cellulose xanthate is calculated from the rate constants.
Effect of ethylamine treatment on the dielectric properties and crystallinity of cellulose. I
Authors: Venkateswaran A. , Akker J. A. Van Den 
Published: April 2003

AbstractA study of dielectric properties and crystallinity by x‐ray diffraction was made of ramie, cotton linters, bleached sulfite pulp, and cellophane. These cellulosic materials were treated with various concentrations of ethylamine in water. A linear relationship was found to exist between dielectric constant and crystallinity. The results also indicated that both dielectric constant and loss factor of ethylamine‐treated cellulose obeyed anomalous dispersion and absorption. The difference in density of untreated and treated samples was not significant for the range of crystallinity change observed by ethylamine treatment. In calculating the intrinsic dielectric constants of cellulose of different crystallinities the density of crystalline cellulose was used for the purposes of comparison.
Measurement of the smectic content in undrawn polypropylene filaments
Authors: Farrow G. 
Published: April 2003

AbstractBy the use of x‐ray diffraction techniques a method is proposed for the measurement of the “smectic” content (interpreted here as material of intermediate order) of undrawn polypropylene filaments. The method involves two estimates of crystallinity by x‐ray methods. One is considered to measure the amount of diffraction from the normal crystalline monoclinic lattice and the other the total amount of diffraction from crystalline, “smectic” and noncrystalline material. By separation of these various quantities the amount of “smectic” polypropylene can be deduced. It was found by this technique that the “smectic” content of quenched polypropylene samples decreased from 40°C. onward and approached zero at about 85°C.
Studies in hard rubber reaction. Part II. Effect of organic accelerators
Authors: Bhaumik M. L. , Banerjee D. , Sircar Anil K. 
Published: April 2003

AbstractThe method of differential thermal analysis has been applied to the study of thermal effects accompanying exothermic vulcanization reaction in hard rubber compounds accelerated with common rubber accelerators. Exothermic reaction was found to start at about 1% sulfur, in the case of CBS‐accelerated compound which increases linearly up to 32% and then decreases, probably due to predominance of a dehydrogenation reaction. 68/32 Rubber‐sulfur compounds containing increasing amounts of combined sulfur evolve decreasing quantity of heat and a plot of ΔH vs. combined sulfur of the precured compounds shows three stages of reaction. Accelerators were found not to affect the heat of reaction of the compounds to a great extent except in the special cases of those containing MBT and ZDC. The beneficial effect of certain accelerators is to be traced in the lowering of initiation temperatures and a decrease of slope values whereby the reaction becomes more regulated and spread out. Increase of concentration of accelerators (CBS and TMT) was found to have little effect.
Some unusual properties of graft copolymers and polyblends of β‐vinylnaphthalene and ethylene oxide
Authors: Cuddihy E. , Moacanin J. , Rembaum A. 
Published: April 2003

AbstractIt was found that poly‐β‐vinylnaphthalene and poly(ethylene oxide) (54:46% by weight) form homogeneous blends or graft copolymers when prepared under conditions which inhibit the crystallization of poly(ethylene oxide). Such preparations can be obtained from solutions in a good solvent for both components, either by precipitation procedures which lead to coacervation rather than fractionation, or by freeze‐drying. Preparations containing more than 46 wt.‐% poly(ethylene oxide) were characterized by modulus versus temperature curves exhibiting a minimum at about 60°C. This behavior was interpreted as due to microphase separation taking place with increasing temperature, a process which becomes irreversible above 120°C. A graft copolymer having the 54:46 composition was rubbery at room temperature, and in contrast to polyblends did not exhibit the poly‐β‐vinylnaphthalene glass transition at 138°C. The marked difference in behavior between polyblends and graft copolymers is due to the fact that in the latter irreversible microphase separation cannot take place. The above described properties seem to be peculiar to poly‐β‐vinylnaphthalene. Similar properties could not be reproduced in preparations of poly(ethylene oxide) with polystyrene, poly‐4‐vinylbiphenyl, or polyacenaphthylene. These preparations exhibited a behavior characteristic of mixtures of two incompatible polymers.
Relation between stress–strain behavior and equilibrium volume swelling for peroxide vulcanizates of natural rubber and cis‐1,4‐polyisoprene
Authors: Bristow G. M. 
Published: April 2003

AbstractData are reported for the elastic behavior, as described by the parameters C1 and C2, and the equilibrium swelling in n‐decane, vr, for dicumyl peroxide vulcanizates of natural rubber and cis‐1,4‐polyisoprene. For natural rubber vulcanizates the correlation between C1 and vr can be described in terms of the original Flory‐Rehner equation with χ = 0.41. Tentative evidence is presented which favors this equation rather than the later modified form in which the term in vr1/2 is replaced by one in (vr1/2 − vr/2).
Effects of mixing variables and talc fillers on tensile and impact fatigue properties of some thermoplastic blends of poly(vinyl chloride) with acrylonitrile‐butadiene copolymer rubber
Authors: Lee C. C. , Rovatti W. , Skinner S. M. , Bobalek E. G. 
Published: April 2003

AbstractAn apparatus is described which measures simultaneously a relative change in vibrational damping and in transient electrical charging of a wafer specimen of plastic during the interval immediately following an impact blow. When impacting cycles are repeated regularly (at an energy less than the destructive level for nonfatigued specimen), the curves relating either electrical or mechanical responses to the number of impact blows show significant changes of slope at coincident intervals of the impact fatigue history, and either of these correlated effects can be used to indicate successive changes in microstructure which lead to the ultimate fracture endpoint of the fatigue test. These fatigue tests were used to study the effect of compositional and mixing variables on the properties of some heterophase thermoplastics. This study demonstrated that impact fatigue resistance can be poor in some plastic compositions which are rated to have superior impact resistance by tensile testing. Also, some special fillers in the correct quantity may improve fatigue resistance even though such filler loading will degrade other desirable tensile properties.
Polyacrylonitrile fiber behavior. II. Dependence on structure and environment
Authors: Rosenbaum Shlomo 
Published: April 2003

AbstractThe effect of comonomer, draw ratio, and annealing temperature on the glass transition temperature Tg and on a number of properties of polyacrylonitrile fibers has been examined. The coefficients of axial thermal expansion above Tg were found to be positive and unusually high. In water, they increased with increasing draw ratio and annealing temperature, but these effects could not (or hardly) be observed in decalin. The axial thermal expansion is compared with that of polyamide fibers, where the coefficient was positive on unstretched fibers but negative on drawn ones throughout the temperature range (25–150°C.) examined. Implications for the structure of polyacrylonitrile fibers and a number of peculiarities in their glass transition are discussed. Most of the results were in line with a structure based on stiff molecules twisted out of a straight conformation by intramolecular repulsive interaction between adjacent dipoles. An unexpectedly large proportion of compounds examined were found to exert a plasticizing action which could be related most readily to the dipole moments. The effect is attributed to a reduction in molecular stiffness and is compared with the solution behavior of the polymer. An increase in “yield point” with increasing molecular size of tensile testing medium provided evidence for an increase in volume during initial extension.
Polyhexaallylmelamine and related polymers
Authors: Gillham John K. , Petropoulos John C. 
Published: April 2003

AbstractThermoset polymers result when hexaallylmelamine and related monomers, such as 2,4‐bis(diallylamino)‐6‐piperidino‐s‐triazine, are polymerized with di‐tert‐butyl peroxide or 2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)‐n‐hexane. Advantageous properties of the new systems when filled with glass fabric include high mechanical strength and modulus at elevated temperatures, solvent resistance, and excellent electrical properties, especially dielectric constant, dissipatio factor, and arc resistance. Although glass cloth‐reinforced laminates of the resins are stable to almost 400°C. in nitrogen, oxidatively they are much less stable. Nevertheless, these new resin systems have certain advantages in comparison with silicone resins and should be useful for structural and electrical applications in air to above 200°C.
Tensile stress relaxation behavior of a mechanical mixture of two polymer components
Authors: Horino Tzuneo , Ogawa Yasuo , Soen Toshiichi , Kawai Hiromichi 
Published: April 2003

AbstractAs one in a series of studies relating the rheological properties of mechanical mixtures of two polymer components to the degree of mixing, the temperature dependence of tensile stress relaxation behavior of two types of mixed systems, i.e., poly(methyl methacrylate)–poly(vinyl acetate) system and lightly crosslinked poly(methyl methacrylate–poly(vinyl acetate)) system, was investigated over a temperature range covering the glass transition temperatures of both polymer components. The time–temperature superposition procedure was carried out for comparison of several parameters, such as fractional free volume and its thermal expansion coefficient, which were determined on the basis of the free volume concept from the viscosity in relation to the William‐Landel‐Ferry equation, with those of the individual polymer components. Although the fractional free volume and its thermal expansion coefficient thus determined for the mixed systems were apparent values, the results may, at least qualitatively, deny the simple additivity of the free volumes of the two‐polymer mixed phases and suggest the existence of a sort of physical interaction between the phases, i.e., the internal pressure induced by one phase or the other due to a difference in thermal expansion coefficient between the phases.
Stress—strain behavior of rubber‐reinforced glassy polymers
Authors: Newman Seymour , Strella Stephen 
Published: April 2003

AbstractThe main objective of this work has been to develop some rational hypothesis for the toughness of rubber‐modified glassy polymers as defined by the energy to rupture in a tensile measurement. It is shown that the rigid phase yields and that the toughness is a result of the large energy absorption involved in the cold drawing of the matrix. The rubber phase acts principally to induce a yielding in the matrix. A triaxial stress field in the environment of the dispersed particles results in local increases in free volume which aid in the initiation of cold drawing and provides the rubber with sufficient breaking stress to prevent premature crack propagation.
Polyurethane latex
Authors: Suskind Stuart P. 
Published: April 2003

AbstractA technique has been developed for preparing stable, film‐forming, polyurethane latices without the use of emulsifying agents. The reaction of an alkyl diethanolamine with a stoichiometric excess of an isocyanate terminated prepolymer yields a relatively low molecular weight urethane which is readily dispersed with 3% aqueous acetic acid. When small amounts of triethanolamine are employed as a third reactant, the selfemulsifiable urethane is branched. In either case, water diffuses into the suspended globules of the latex and chain‐extends the urethane to a linear or crosslinked high polymer via reaction with isocyanate endgroups. Upon drying, the creamy, white latices yield strong, elastic films which exhibit low swelling when immersed in water for extended periods. Cationic polyurethane latices were prepared from both polyester‐ and polyether‐based materials, and, in general, the expected structure–property relationships were obtained. A major stabilizing factor in these polyurethane latices is the positive charge on the particles arising from the tertiary amine salts. The latices were compatible with nonionic pigmenting and thickening agents, and they could be blended with a nonionic poly(vinyl acetate) emulsion.
Investigation of thermal oxidation and photooxidation of acetal plastics by infrared spectroscopy
Authors: Kelleher P. G. , Jassie L. B. 
Published: April 2003

AbstractInfrared spectroscopy was used to study the thermal oxidation, accelerated and natural photooxidation of acetal homopolymer and copolymer. Chain scission is the predominant reaction, as revealed by changes observed in the hydroxyl, carbonyl, and methylene absorption regions of the infrared spectra. Photolysis accelerates the degradation of both plastics. Reaction mechanisms are presented to explain the behavior of these materials under oxidative conditions.
Effect of mounting technique on the laboratory weathering of polypropylene monofilaments
Authors: Forsman James P. 
Published: April 2003

AbstractA comparative study was made of two methods of mounting yarns in the Weatherometer. In the first, in which test materials are wound continuously around separated halves of wooden hubs, the yarns tend to bunch. In the second, the sample is constrained from bunching but is free to relax or to shrink. Use of the second method of mounting significantly shortens exposure time and greatly improves the repeatability of tensile and elongation tests performed on exposed yarns.
Fine structure of regenerated cellulose films as revealed by dye accessibility
Authors: Wellisch Eric , Gupta M. K. , Marker Leon , Sweeting Orville J. 
Published: April 2003

AbstractWe have demonstrated the utility of dyeing techniques, using Solophenyl Fast Blue Green BL, to characterize a variety of regenerated cellulosic films. Measurement of the optical density ratio and the rate and magnitude of dye uptake show that differences in structure exist in regenerated cellulose films processed under different conditions. These differences are attributed to differences in lateral order and orientation of cellulose chains and are believed similar to the so‐called skin and core observed in rayon fibers. These differences have been found related reproducibly to differences in regenerating and processing conditions. Diffusion of dye into a film is very rapid initially, slowing later to an almost constant rate, depending on the dye concentration in solution and on the type of film. A modified diffusion equation of the form In C/C0 – (1 – C/C0) = Dγ2‐tC0/Cf has been found adequate to express the non‐steady state of the observed absorption process, where C0 is the initial dye concentration of the test solution, C is the instantaneous dye concentration at time t, Cf is the dye concentration in the film, γ2 is the area of film per unit volume of dye solution, and D is the diffusion coefficient. Thus, a mathematical basis is provided for structural differentiation in cellulosic films processed in various ways. Plate‐cast viscose films appear to have a dense surface (skin) exposed to the regenerating bath and a porous surface (core) on the side touching the plate, whereas machine‐cast viscose films have a dense surface on both sides.
Relationships between chemical structure and properties of polyether urethane sealants
Authors: Damusis A. , Ashe W. , Frisch K. C. 
Published: April 2003

AbstractStress relaxation and swelling measurements were carried out and the data used for determination of the effective crosslink densities of one‐ and two‐component urethane sealants. These crosslink densities were compared with calculated values. The results were correlated with the structure of the urethane sealants. Two sealant structures were evaluated: one based on mixtures of triol prepolymers and diol adducts, and the other on triol adducts. Both one‐ and two‐component sealants were investigated. The two‐component sealants had a tendency to be undercured even when quite effective catalysts were used. The one‐component sealants, because of moisture cure and of biuret or allophanate formation, produced in most cases a higher crosslink density than the calculated triol crosslink density. It was also observed that curing efficiencies of the two‐component sealants decreased with increasing molecular weight per crosslink. Deviations from these correlations were noted when a short poly(oxypropylene)glycol of 400 molecular weight was used for curing purposes. These anomalies were detected by stress relaxation and by swelling techniques as well as by measurement of torsional modulus. Stress relaxation studies were carried out to determine the influence of temperature, catalysts, and strain on stress decay. The results again indicated that the two‐component sealants did not cure completely, and that the type of catalyst had a significant influence on degradation of urethane sealants at elevated temperatures.
Properties of semicrystalline polyolefins. IV. Crystallization phenomena in poly‐3‐methyl‐1‐butene
Authors: Kirshenbaum I. , Feist W. C. , Isaacson R. B. 
Published: April 2003

AbstractA study has been carried out of the physical and mechanical properties and crystallization behavior of poly‐3‐methyl‐1‐butene (poly‐3‐MB). The melt behavior of poly‐3‐MB was examined by means of the depolarized light intensity (DLI) technique. These birefringence studies indicated the onset of motion in the crystalline phase of poly‐3‐MB at about 100°C. (over 200°C. below the melting point). These studies also showed that limited molecular motion may occur at room temperature, i.e., about 25°C. below the glass transition temperature of poly‐3‐MB.
Fraction of effective sulfur crosslinking in polybutadiene rubber vulcanizates
Authors: Meltzer T. H. , Dermody W. J. , Tobolsky A. V. 
Published: April 2003

AbstractShear modulus measurements as a function of temperature for the high cis‐ and high trans‐isomers of 1,4‐polybutadiene, vulcanized with sulfur in amounts between 2 and 44% of the recipe, show the crosslinking efficiency of sulfur in these systems to be slightly lower than in SBR‐1000, but higher than in natural rubber. Two distinct modes of mechanical behavior are noted with these stereo regular rubbers. There is pronounced crystalline behavior at low degrees of vulcanization. After crystallinity has been destroyed by increased crosslinking, both polymers behave as typical crosslinked amorphous materials. Additional evidence is found to support the conclusion that polymer structure, as well as chemical reactivity, plays an important role in the chemistry of vulcanization.
Network characterization of silicone rubber vulcanizates. Part I. solvent, temperature, and specimen shape effects on effective crosslink density determinations
Authors: Seeley R. D. 
Published: April 2003

AbstractThe effective crosslink densities were determined for four silica‐filled silicone rubber vulcanizates which represent different degrees of crosslinking. The determinations were made from compression‐deflection measurements of rubber specimens at an equilibrium swelling condition. Nine solvents representing a wide range of dilatant strengths were investigated at four equilibrium temperatures (8, 23, 41, and 60°C.) for their effect on the crosslinking determinations. Specimen shape effects were also investigated. Explicit equations of state were derived empirically and were found to be similar to the well‐known Mooney‐Rivlin equation in which two independent parameters are required for the definition of a dilated rubber network.