bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of copper on the autoxidation of cellulose suspended in sodium hydroxide solution
Authors: Michie R. I. C. , Neale S. M. 
Published: April 2003

AbstractA kinetic study has been made of the depolymerization of cotton cellulose immersed in aerated solutions of sodium hydroxide and in solutions of sodium hydroxide containing dissolved copper. In absence of (added) copper the reaction rate is proportional to the thermodynamic molal activity of the sodium hydroxide over the concentration range 2–14N. Addition of copper causes an increase in the rate but to an extent which depends on the alkali concentration; with constant copper concentration and with increasing alkali concentration the rate now passes through a maximum at approximately 6N sodium hydroxide. The decrease in rate above 6N alkali has been ascribed to the increasing importance of oxygen solubility and of diffusion which become rate determining factors at the higher alkali concentrations. In 4N sodium hydroxide and at low copper concentration diffusion is taken to be unimportant; under these conditions the rate is proportional to the concentration of copper in the solution external to the cellulose but is relatively insensitive to the total amount of copper absorbed by the cellulose. However, it has previously been shown that the overall absorption of copper is probably due to contributions from two different sorbing sites in the cellulose anhydroglucose unit. The rate is found to be approximately proportional to the calculated extent of absorption by the site postulated to form the less stable complex with copper. There is some indication that copper bound in this latter position is responsible for the catalytic depolymerization.
Main‐chain degradation and thermal stabilization of polyoxymethylene by ionizing radiation
Authors: Torikai Sadao 
Published: April 2003

AbstractPolyoxymethylene dihydrate was irradiated in vacuum and in air at room temperature by γ‐rays from Co60, and the change of its thermal stability was examined. The logarithm of viscosity number decreased linearly with the logarithm of dose both in vacuum and in air. The decomposition curve of irradiated polyoxymethylene in vacuum at 200°C. can be divided into two components. The percentage of stable polymer of the irradiated polyoxymethylene dihydrate increased with decreasing solution viscosity, attained a value of 80–95%, and was expressed approximately as function of η/η0. In case of irradiation in air, the stabilization was often invalidated by oxygen. The after‐effects of irradiation on the stabilization could not be detected under the irradiation conditions examined in the present study. In decomposition in vacuum at 250°C., the irradiated polyoxymethylene dihydrate showed a curve of three components. It seems certain that the irradiated polyoxymethylene dihydrate consists mainly of three kinds of polymer differing in their thermal stabilities. The most stable polymer comprises about one‐fourth of total stable polymer. These facts might be explicable with the formation of formyloxy and methoxy endgroups by the disproportionation reaction of radicals produced primarily by main chain scissions. The inclusion of stable polymer before irradiation was noted in the case of the polyoxymethylene produced in the post‐polymerization of irradiated solid formaldehyde.
Effect of molecular weight and its distribution on stretching of polyacrylonitrile gel
Authors: Kobayashi Hidehiko , Sasaguri Kiichiro , Fujisaki Yoshisato , Amano Toshihiko 
Published: April 2003

AbstractThe present studies were designed to secure information about the effect of molecular weight and its distribution on the hot‐stretchability (defined as maximum hot draw ratio possible without breakage under given condition) of the coagulated gel obtained by extruding a concentrated solution of polyacrylonitrile dissolved in 70% nitric acid into dilute nitric acid solution. After washing, the coagulated threads thus obtained were stretched at 100–140°C. In the case of fractionated polyacrylonitrile, the results obtained under the above conditions showed a maximum hot‐stretchability at M = 80,000. Below this point, hot‐stretchability was lowered with decrease of molecular weight. For polymers having a molecular weight larger than this value, it was also depressed as molecular weight increased and approached a certain value. For whole polymers, hot‐stretchability distribution curves obtained from molecular weight distribution curves by substituting molecular weight with corresponding hot‐stretchability were studied. It was found that the maximum stretchability of a whole polymer was the weight average value of those of its constituent polymer species. The effect of molecular weight of the polymer on the mechanical properties of fibers and their fine structure was investigated by means of tensile and x‐ray measurement.
Diffusion and sorption of vapors in ethylene–propylene copolymers. I. Equilibrium sorption
Authors: Frensdorff H. K. 
Published: April 2003

AbstractEquilibrium sorption of cyclohexane, n‐hexane, carbon tetrachloride, n‐pentane, benzene, trichlorotrifluoroethane, and methylene chloride in ethylene‐propylene copolymers at 10°, 23°, and 40°C. has been measured. These penetrants range from most soluble to least, in the order given. The propylene content of the copolymer has very little effect on equilibrium sorption, and the heats of dilution are small. The concentration dependence of the results is discussed in terms of the Flory‐Huggins equation. Correlation between sorption and solubility parameter is considered.
Diffusion and sorption of vapors in ethylene–propylene copolymers. II. Diffusion
Authors: Frensdorff H. K. 
Published: April 2003

AbstractThe diffusion rates of methylene chloride, benzene, n‐pentane, n‐hexane, and cyclohexane in a copolymer of 51 mole‐% propylene and 49% ethylene at 23°C. and penetrant concentrations of up to 10 vol.‐% have been measured, as have the rates of benzene diffusion in copolymers containing 31–100% propylene units at 10, 23, and 40°C. Integral diffusion coefficients were calculated from the initial diffusion rates; differential diffusion coefficients from the final rates. Comparison of the two types of diffusion co‐efficients leads to the conclusion that their concentration dependence flattens out at the very lowest penetrant concentrations. The diffusion coefficients fall and the activation energies rise as the propylene content of the copolymers increases. Diffusion in low‐propylene copolymers occurs at rates comparable to those in natural rubber, while the rates in atactic polypropylene are slower by about an order of 1 magnitude. Even so, the latter are about 10 times faster than in polyisobutylene.
Cationic polymerizations of 3‐methylbutene‐1. II. Polymerizations at extremely low temperatures
Authors: Kennedy J. P. 
Published: April 2003

AbstractThe cationic polymerization of 3‐methylbutene‐1 has been studied at extremely low temperatures e.g., −130°C. and below. Practically no polymerization occurs, even at high catalyst concentrations, and the system lies “dormant” at −150°C. The molecular weight‐conversion curve obtained with AlCl3 is a straight line which can be extrapolated through the origin. The slope of this line is determined by monomer concentrations. Higher molecular weights are obtained at the same conversion with higher monomer concentrations. With boron trifluoride catalyst, the linear part of the curve does not extrapolate back through the origin. Product molecular weights were higher in ethyl chloride than in pentene with BF3 at the same conversion level at −130°C.
Preparation and reactions of p‐cyanostyrene–styrene copolymers
Authors: Beckerbauer Richard , Baumgarten Henry E. 
Published: April 2003

AbstractCopolymers of p‐cyanostyrene and styrene were prepared by heating p‐iodostyrenestyrene copolymers with cuprous cyanide in N‐methylpyrrolidinone. The p‐cyanostyrene copolymers could not be hydrolyzed to the benzoic acid derivative but were converted to the methyl p‐vinylbenzoate‐styrene copolymer by reaction with methanol and hydrogen chloride. This methyl ester copolymer was partially hydrolyzed to the free acid. A p‐cyanostyrene(11%)‐styrene copolymer was treated with n‐butyl and methyl Grignard reagents to yield the corresponding n‐butyl‐ and methyl‐p‐styryl‐ketone copolymers. In the reaction with n‐butylmagnesium chloride, the intermediate n‐butyl‐p‐styrylketimine copolymer was isolated.
Crosslinked and noncrosslinked diisocyanate‐linked elastomers containing substituted urea groups
Authors: Havlik A. J. , Smith Thor L. 
Published: April 2003

AbstractA study was made of the preparation and properties of diisocyanate‐linked elastomers prepared from polyoxypropylene glycol (POPG), toluene‐2,4‐diisocyanate (TDI), and toluene‐2,4‐diamine (TDA). The chemical structure and gelation of a series of prepolymers were investigated first. Next, many series of elastomers were prepared at 60°C. in open molds and at 110°C. in closed molds from mixtures in which values of the ratio of isocyanate groups to the sum of the hydroxyl groups and amino groups (R1) and the ratio of the amino groups to hydroxyl groups (R2) were systematically varied. Cure at 60°C. gave tough, noncrosslinked elastomers, the properties apparently resulting from interchain attractive forces, while cure at 110°C. gave covalently crosslinked elastomers having rather similar properties. Glass‐transition temperatures increased linearly with the concentration of substituted urethane groups but were independent of the concentration of substituted urea groups. An explanation for the surprising behavior is presented. The noncrosslinked elastomers were soluble in N,N‐dimethylacetamide (DMA) and similar solvents. Intrinsic viscosities in DMA were found to increase with R1 at constant R2. Young's modulus, tensile strength, and ultimate elongation were determined between −23 and 82°C. At elevated temperatures, the crosslinked elastomers showed near‐equilibrium moduli, while the noncrosslinked ones did not. The number of chains per milliliter for the crosslinked elastomers was calculated from the quantities of excess isocyanate and urea hydrogens, along with an assumed topology for the network. The moduli for both types of elastomers were related to chemical composition. Various relationships between the ultimate properties and equilibrium moduli were evaluated. Extensions up to 5000% with elastic recoveries of better than 90% were noted.
Estimation of copolymer reactivity ratios: An example of nonlinear estimation
Authors: Behnken D. W. 
Published: April 2003

AbstractThe first portion of the paper consists of a brief statement of the statistical procedures involved in obtaining efficient estimates of parameters from experimental data, determining their precision, and selecting optimum experiments. Emphasis is primarily directed toward models in which the parameters appear in a nonlinear fashion. Some of the difficulties and pitfalls which are encountered are discussed; primary among these are the problems arising from linearization schemes and transformations affecting the error structure. References are given which supplement the necessarily cursory discussion given here. Utilizing this background, the second half applies itself to the problem of estimating the reactivity ratios in the copolymer equation. Approximate and exact estimation schemes are described which both guarantee most efficient use of the data and allow objective probabilistic statements to be made about the reliability of the estimates. A graph is presented which allows the experimenter to select the two initial feed ratios for his experiments which provide the most information for the estimation scheme. Use of the graph presumes that order of magnitude estimates of the reactivity ratios can be made in advance. A sequential scheme can be followed when prior information is lacking or is not very precise. When more than two different initial feed ratios are to be used, the optimum ratios for two‐point experiments give a good indication of the proper range to cover.
Phase changes in fibrous macromolecular systems and associated elasticity. Model phase diagrams
Authors: Ciferri A. , Smith K. J. 
Published: April 2003

AbstractIn order to illustrate the concepts of solid–solid and solid–melt first‐order transitions and associated elasticity for an ideally homogeneous fiber where different conformational arrangements of the macromolecules in the crystalline state are possible, phase diagrams were arbitrarily constructed on the basis of reasonable estimates of the variables involved. With some limitations, these diagrams illustrate several situations which might be expected to occur in real systems and the conditions under which one crystalline modification can be expected to be stable or metastable and under which a transition to another crystalline form or to the amorphous rubbery state can be observed. The variables which determine the state of the system were considered to be the external tensile force and temperature, pressure being regarded as a constant. Thermodynamic concepts and relationships used under such conditions were only a generalization of those established by Flory and Gee. Large changes of length of the fiber were assumed to occur during the reversible phase changes. A unified schematic picture of the elastic behavior of a fiber in its different physical states (single phase: crystalline or amorphous; two co‐existing phases: crystal–crystal or crystal–amorphous) is afforded by the construction, on the basis of the phase diagram, of stress–strain isotherms, length–temperature curves at constant load, and stress–temperature curves at constant length.
Photoelastic properties of tightly crosslinked networks
Authors: Blumstein Alexandre 
Published: April 2003

AbstractThe photoelastic properties of tightly crosslinked networks formed from expoxy resins were investigated in the rubbery and in the glassy states. The following resins were used: bisphenol–diepoxy, resorcinol–diepoxy, and trisphenol–triepoxy resins. The anisotropy Δa of the links, the degree of crosslinking N, and the rigidity of the network were varied independently and the variation of the stress‐optical constant with these parameters measured at different temperatures. The results indicate the strong influence of a parameter g depending upon the interactions between the links of the network. g and Δa contribute to the value of the stress‐optical constant in opposite directions and can partially compensate each other. If this parameter is introduced in order to account for the interchain interactions, the theory of rubber photoelasticity can account qualitatively for the photoelastic behavior of these networks.
Polyurethane sulfides containing cyclohexane ring in the polymer chain
Authors: Iwakura Yoshio , Sakamoto Munenori , Awata Yasuhira 
Published: April 2003

AbstractPolyurethane sulfides of high molecular weight containing trans‐1,4‐cyclohexylene groups were successfully obtained by both methods of polymerization, polyaddition of trans‐1,4‐cyclohexylenebis(N,N‐ethyleneurethane) or trans‐hexahydro‐p‐xylylenebis(N,N‐ethyleneurethane) with polymethylene dimercaptans and polycondensation of bis(chloroformates) with polymethylenebis(β‐aminoethyl thioethers) prepared by reaction of ethylenimine with polymethylene dimercaptans. Comparison of physical properties of the polymers prepared by both methods of preparation indicated that (1) polymer repeating units of polyaddition and polycondensation products were quite equivalent; (2) polycondensation polymers had chloroformyl groups as terminal groups.
Hydration and ion binding of polyelectrolytes
Authors: Ikegami Akira 
Published: April 2003

AbstractThe counterion binding of polyelectrolytes has been investigated with special attention to the change of the structure of water in the neighborhood of charged polymer skeleton induced by the binding. The molar volume change due to this structural change of water was obtained by the method of refractivity measurement. Systems employed were polyacrylic acids neutralized to varying degrees by tetra‐n‐butyl‐ammonium hydroxide or sodium hydroxide in the presence and absence of simple low molecular salts such as NaCl and BaCl2. The results indicate that there are two regions of water around the polyion. In the first “intrinsic” hydration region, water molecules are oriented to individual charged groups. In the second region, water molecules are rearranged by the cooperative action of two or more charged groups on the polyion. The binding of Ba++ or La+++ to the polyion destroys not only the second region but also the first intrinsic region. On the other hand, Na+ ions are bound only in the second region without effect on the first region. The amount of bound Na+ ions estimated by refractivity measurement changes with the charge density of the polyion, showing the characteristic feature as a condensation phenomenon.
Rheo‐optical properties of polymers. V
Authors: LeGrand D. G. 
Published: April 2003

AbstractA theory of the rheo‐optical properties of polyerystalline polymers has been developed. It is based on a model similar to that used by Debye for his theory of dielectric relaxation. Using the theory, sized of crystals in various types of polyethylene are calculated from rheo‐optical data and compared with results obtained by x‐ray techniques.
Rheo‐optical properties of polymers. VI. Dynamic birefringence
Authors: LeGrand D. G. 
Published: April 2003

AbstractIn previous papers we have presented data on the dynamic birefringence and light scattering from polyethylene. New studies of the dynamic birefringence of polytetrafluoroethylene, silicone rubber, polycarbonate, polymethyl methacrylate, and polyethylene as a function of frequency and temperature have been made. The results are presented and interpreted in terms of various proposed theories. The relationships between the mechanical and optical relaxation spectrum are discussed.
Linear free energy relationship in the diffusion of gases through polymer films
Authors: Kwei T. K. , Arnheim W. M. 
Published: April 2003

AbstractThe general correlation between ΔH†/T and log D0 in the diffusion of gases through polymers is discussed in terms of a linear free energy relationship. It is shown that the diffusion constant D can be expressed as log D = kα + constant, where k is a parameter characteristic of the diffusing gas and α is a parameter characteristic of the polymer. The relationships between structural characteristics of gases and polymers and the respective parameters k and α are discussed. The possible application of similar linear free energy relationships for the purpose of expressing the permeability constant (P) and the solubility coefficient (S) is also suggested.
Mechanism of the mechanical degradation of cellulose
Authors: Ott Ronald L. 
Published: April 2003

AbstractFrom electron spin resonance spectra of a ball‐milled cellulose sample, it was established that the mechanical degradation of air‐dry cellulose was characterized by the formation of free radicals. It was shown that iodine increased the rate of mechanical degradation, presumably by preventing the recombination of at least some of the radicals formed during grinding. Since no difference in iodine consumption during grinding was observed between air‐dry and oven‐dry cellulose samples, it was concluded that heterolytic cleavage of cellulose molecules did not occur. The formation of benzyl iodide and cyclohexyl iodide was observed when cellulose was ground with iodine in toluene and cyclohexane, respectively. It is possible that either chain transfer reactions between cellulose radicals and solvent molecules account for the halogenation of the solvent or that the halogenation is due to a hypoiodite structure formed by the reaction of cellulose alkoxy radicals with iodine.
Copolymerization of diethyl phosphonoalkyl acrylates
Authors: Overberger C. G. , Sarlo E. 
Published: April 2003

AbstractDiethylphosphonomethyl acrylate, diethylphosphonomethyl methacrylate, and 1‐diethylphosphonoethyl acrylate were copolymerized by radical catalysis with methyl methacrylate and, in one case, methyl acrylate. The reactivity ratio values indicate that the phosphorous‐containing monomers enter into the copolymer somewhat less readily than methyl acrylate or methyl methacrylate. Both electronic and steric effects may be operative.
Cold‐drawing of acetone‐crystallized polyethylene terephthalate
Authors: Blakey P. R. , Sheldon R. P. 
Published: April 2003

AbstractThe room‐temperature cold‐drawing behavior of acetone‐crystallized polyethylene terephthalate film has been compared with that of amorphous and heat‐crystallized film. X‐ray diffraction photographs give good resolution in the case of the acetone‐crystallized sample with evidence of molecular orientation in every case. The order of the magnitudes of the yield stresses is acetone‐crystallized < amorphous < heat‐crystallized. Heating of the drawn samples produces disorientation for the amorphous drawn film with an improved resolution of the diffraction photograph for the heat‐crystallized film. It is suggested that the results are in agreement with a picture of a drawing mechanism involving molecular mobility in the amorphous regions and that acetone influences the yield stress by lowering the softening temperature.
Aliphatic polyhydrazides: A new low temperature solution polymerization
Authors: Frazer A. H. , Wallenberger F. T. 
Published: April 2003

AbstractHigh molecular weight polyhydrazides have been prepared by a new low temperature polymerization technique from equimolar amounts of a dihydrazide and a dicarbonyl chloride in dialkyl amide solvents. All‐aliphatic polyhydrazides were insoluble in dimethyl sulfoxide, had polymer melt temperatures ranging from 200 to 300°C. Films could be pressed and fibers could be pulled from the melt. Aliphatic‐aromatic and oxalic‐aromatic polyhydrazides which undergo dehydration at different rates had polymer melt temperatures ranging from 250 to 300°C. and inherent viscosities ranging from 0.3 to 1.5. They were soluble in dimethyl sulfoxide, a solvent from which tough films could be cast.
Clay‐catalyzed reactions of olefins. I. Polymerization of styrene
Authors: Bittles James A. , Chaudhuri A. K. , Benson Sidney W. 
Published: April 2003

AbstractQualitative observations are reported on the polymerization of styrene with acid clay cracking catalysts. Molecular weights were 500–2000, depending on solvent, catalyst quantity, monomer concentration, and temperature, monomer conversions approached 100%. The reaction rate is rapid at 0°C. and at ambient temperatures and is severely inhibited by water and other proton acceptors. The polymer was structurally the same as polystyrene and contained saturated endgroups formed by solvent termination and by a competitive cyclization reaction. The chain termination products and polymer end‐groups were identified.
Die sekundäre keimbildung bei polyäthylen‐sphärolithen
Authors: Heber I. 
Published: April 2003

AbstractThe growth of two dimensional polyethylene spherulites has been followed in the range of 115° to 125°C. The radial growth velocity vr has been assumed to be determined by the rate of formation of secondary nuclei on the nuclei on the spherulite border. Thus the nucleation theory gives the expression

The critical free energy ΔF* has been calculated for rectangular nuclei ΔF* = x(4σeσe/Δf). This nucleus according to the calculation consists of a single layer of attached chain segments. Specific surface tensions σe/σs of the critical nucleus derived from the radial growth rate on the base of the theory agree with the values obtained for polyethylene single crystals with folded chains. On the base of the known folding length in polyethylene the secondary nucleus consists of three closely arranged folded chain segments 100 A. in length. The satisfactory agreement between the values derived from growth rates of two‐dimensional spherulites and the results obtained on polyethylene single crystals confirms the assumption that the growth velocity of spherulites is determined by the rate of formation of secondary nuclei on their surface.