bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structure of the γ‐form of nylon 6
Authors: Arimoto H. , Ishibashi M. , Hirai M. , Chatani Y. 
Published: April 2003

AbstractThe crystal structure of the γ‐form of nylon 6 (polycaproamide) obtained by the iodine treatment of the α‐from of nylon 6 has been determined by x‐ray diffraction. The unit cell contains four repeating units \documentclass{article}\pagestyle{empty}\begin{document}$ [\rlap{--} ({\rm CH}_2 \rlap{--})_5 {\rm CONH \hbox{---}}] $\end{document} and is monoclinic with a = 9.33 A., b = 16.88 A. (fiber axis), c = 4.78 A., β = 121°. The space group is P21/a. There is considerable deviation from the planar configuration in the amide group of the chain. The plane of the CH2 chain zigzag lies nearly parallel to the (001) plane. The crystal is composed of the pleated sheets of the parallel chains joined by hydrogen bond between the adjacent chains. The chain directions are opposite in alternating sheets. The hydrogen‐bond length is 2.83 A., a reasonable figure for an NH·. O chains joined by a hydrogen bond between the adjacent chains. The direction of the hydrogen bond makes an angle of 12° with the (100) plane, and the CO and NH bonds are nearly colinear. The amide groups lie at the same level in the cell.
An improved method of calculating copolymerization reactivity ratios
Authors: Tidwell Paul W. , Mortimer George A. 
Published: April 2003

AbstractA nonlinear least‐squares method for solving forr1andr2the copolymerization reactivity ratios, is explained. This new method is superior to all other methods that have been used heretofore in the following ways: (1) a unique pair of values is obtained which does not depend on the judgment of the person examining the data; (2) this pair of values can be shown mathematically to be the best pair obtainable from the data at hand; (3) the errors are quantitatively defined in meaningful terms: and (4) the data are checked to see how well they fit the copolymer equation. A basis for selecting experimental conditions which will provide data from which precise values of the reactivity ratios can be obtained is explained, and experimental conditions appropriate for obtaining these precise values over a wide range ofr1,r2values are presented in tabular form.
Polybenzimidazoles. IV. Polybenzimidazoles containing aryl ether linkages
Authors: Foster Robbie T. , Marvel C. S. 
Published: April 2003

AbstractSome polybenzimidazole polymers which have aryl ether linkages between the recurring units have been prepared in order to study their thermal stability and their film‐ and fiber‐forming properties. All of the polymers prepared were soluble, high molecular weight materials with very good thermal stability.
Thermal oxidation of deuterated polypropylenes
Authors: Beachell H. C. , Beck D. L. 
Published: April 2003

AbstractThis paper describes some of the aspects of the thermal oxidation of deuterated isotactic polypropylenes. Several polymers of propylene, deuterated at different sites along the polymer chain, were subjected to a kinetic treatment designed to establish the comparative rates of oxidation at different temperatures. Infrared spectroscopy was used to follow the kinetics over the temperature interval 100–130°C. These experiments have shown the existence of a deuterium isotope effect for the thermal oxidation of polypropylene.
Thermal conductivity of high polymers
Authors: Hansen David , Ho Chong C. 
Published: April 2003

AbstractThe thermal conductivities of linear high polymers were studied experimentally and theoretically. A theory of thermal conductivity in linear amorphous high polymers was derived based on a simple model of molecular structure. Predictions on the effects of molecular weight and molecular orientation on thermal conductivity taken from the theory agree with available experimental data. New data on the thermal conductivity of linear polyethylene and some polyethylene–wax blends are presented. Temperature dependence of the thermal conductivity in polyethylene was analyzed by the per cent crystallinity concept to obtain results which are in accord with the phonon theory of thermal conductivity in dielectric crystals.
Gel formation in polyolefins exposed to ionizing radiation
Authors: Lyons B. J. 
Published: April 2003

AbstractIt is shown that a reasonable value for the ratio of main chain scission to crosslinking rates in a number of polyolefins at infinite dose is close to zero. Moreover, the sum of the sol fraction (s) and its square root \documentclass{article}\pagestyle{empty}\begin{document}$ (\sqrt s) $\end{document} in almost all of the polymers studied is proportional to some fractional power of reciprocal dose. There is some slight evidence to suggest that \documentclass{article}\pagestyle{empty}\begin{document}$ s + \sqrt s $\end{document} in relatively low molecular weight polyolefins, which initially contain small amounts of reactive carbon–carbon unsaturation and have random distributions, may be proportional to the square root of the reciprocal dose. There is already good evidence that main chain scission rates in polypropylene and poly‐1‐pentene decrease with increasing dose: such a variation may account for the observed relationship in these polymers and presumably also in polyethylene. Another possible explanation is that the chance of a molecule becoming attached to the crosslinked network depends not only on the number of monomer units it contains, but also on the chance that a previous radiation event (such as trans‐vinylene formation) has already occurred in that molecule.
Dye‐sensitized photopolymerization. II. Enhanced sensitization by combination of a cationic and an anionic dye
Authors: Chen Catherine S. Hsia 
Published: April 2003

AbstractIn dye‐sensitized photopolymerization of the redox type, enhanced rates and quantum yields of polymerization were achieved by employing suitable combinations of a cationic and an anionic dye. The enhancement could be attributed to the more reactive new species of the sensitizing dye molecules produced as a result of an interaction between the cationic and the anionic dyes. In a combination of two cationic dyes where practically no interaction between the dyes was indicated, essentially no effect on the polymerization was observed.
Dye‐sensitized photopolymerization. IV. Enhanced rates of polymerization of acrylamide in ethylene glycol, sensitized by thiazine dyes with triethanolamine
Authors: Chen Catherine S. Hsia 
Published: April 2003

AbstractThe polymerization of acrylamide, in ethylene glycol, induced by visible light, with methylene blue–triethanolamine as the sensitizing system, was found to follow a steadystate kinetic scheme after an induction period. The rate was proportional to the half power of the absorbed light intensity and to the second power of the initial monomer concentration. In an experimentally convenient range of dye concentration the rate increased with the dye concentration. The molecular weights of the polymers were in the range of 3.0 × 104–2.5 × 105; they were insensitive to the absorbed light intensity; they increased with the initial monomer concentration and decreased with the initial dye concentration. The induction period was inversely proportional to the first power of the light intensity. Polymerization in the ethylene glycol systems was found to proceed at considerably faster speed than in the aqueous systems. The faster polymerization was attributed primarily to the fact that methylene blue at all concentrations employed existed principally in the monomeric form in the ethylene glycol systems. New methylene blue N–triethanolamine and methylene green–triethanolamine also were investigated as the sensitizing systems for the polymerization of acrylamide in ethylene glycol. Similar results as with methylene blue–triethanolamine were obtained.
Thermal degradation of poly(methyl methacrylate) in a closed system
Authors: Clark J. E. , Jellinek H. H. G. 
Published: April 2003

AbstractThe thermal degradation of poly(methyl methacrylate) has been studied with unfractionated and fractionated polymer samples over a temperature range of 275–400°C. in a closed system by a new technique. Kinetic data have been obtained at temperatures about 100°C. higher than was possible previously. The results are compared with those obtained in open systems. Two main degradation reactions are operative. It is shown that the energies of activation for these reactions do not vary with polymer chain length in accordance with what is to be expected from the usually assumed depolymerization mechanisms. The termination reactions are diffusion‐controlled. Hydrogenation by Adam's catalyst and bromination of the polymers have only moderate effects on the rate of degradation.
Shear dependence of viscosity–molecular weight transitions. A study of entanglement effects
Authors: Chinai Suresh N. , Schneider William C. 
Published: April 2003

AbstractThe flow behavior of concentrated polymer solutions covering molecular weights up to 150,000 were examined at shear rates up to 200,000 sec.−1. The viscosity–molecular weight–shear rate results of previous workers recognizing only single critical molecular weight M*, above which ordinary Bueche entanglements dominated the flow, were compared with our findings in which two distinct critical molecular weights, upper M* and lower M** exist. These results are compared with the theory, and new interpretations are presented.
Analysis of oligomerization kinetics of styrene on the electronic digital computer
Authors: Tsuchida Eishun , Mimashi Setsuo 
Published: April 2003

AbstractThe mechanism of radical oligomerization by chain transfer reaction was studied in connection with the distribution of molecular weight of the obtained oligostyrene. In this case, the styrene–CCl4 system was selected as model for this purpose. The kinetics of the chain transfer reaction is difficult to analyze because the concentrations of components in the system varies along with oligomerization. The rates of component reactions expressed by the simultaneous differential equations were solved by utilizing an electronic digital computer (IBM 650). Consequently, the analytical values and the experimental data showed good agreement, and the correlation among the coefficients of kinetic velocity in the system was clarified, yielding much information regarding the control of oligomerization.
Scission reactions in some vinyl and vinylidene polymers
Authors: Tobolsky Arthur V. , Norling Parry M. 
Published: April 2003

AbstractRates of autocatalyzed oxygen absorption and chain scission were measured at 160°C. and 1 atm. oxygen pressure for copolymers of ethyl acrylate–methyl methacrylate and ethyl acrylate–methyl α‐chloroacrylate. The crosslinked homopolymers of both the vinylidene‐type monomers were very resistant to oxygen uptake and oxidative scission. Increasing amounts of ethyl acrylate in the copolymer systems increased the rate of oxygen absorption and chain scission. Slightly crosslinked poly(methyl methacrylate) containing 5% of dicumyl peroxide showed rapid chain scission at 140°C. in the absence of oxygen and negligible chain scission in the presence of oxygen. The same experiment carried out with poly(ethyl acrylate) shows the reverse behavior: crosslinking and little scission in the absence of oxygen and efficient chain scission in the presence of oxygen. Chemical mechanisms are presented to account for these results.
Kinetic study of the polymerization of α‐d‐styrene and/or styrene by homogeneous catalysis. Part II
Authors: Overberger C. G. , Jarovitzky P. A. 
Published: April 2003

AbstractInitial rates of polymerization using the (C5H5)2TiCl2Al(C2H5)2Cl homogeneous catalyst system, were determined for homo and copolymerizations of styrene, styrene‐α‐C14, α‐d‐styrene, p‐methylstyrene, and m‐methylstyrene. Homopolymerization rates of styrene as a function of Al/Ti ratio indicate three rate maxima of apparently equal magnitude near Al/Ti ratios of 3.0, 11.0, and 16.0. Copolymerizations of gE; 97.5% α‐d‐styrene and styrene as a function of Al/Ti ratio yielded no rate maxima but appeared to be a linear function of the Al/Ti ratio employed. α‐d‐Styrene yielded higher initial polymerization rates than styrene under all tested experimental conditions. These rate increases as a function of monomer deuteration at the α position are related to a higher concentration of active centers. A reaction scheme is proposed in which the predominant mode of formation of active centers occurs via alkylation of titanium but by a cationic mechanism. The observed isotope effect with the use of α‐d‐styrene is related to the stability of the cationically formed active centers. Destruction of these active centers is is suggested to result in either an α‐alkylated new monomer and/or low molecular weight oligomers. An isotopically controlled unimolecular decomposition step is suggested as a mode of termination and/or destruction of potential active centers resulting in divalent titanium; probably (C2H5)2Ti. The predominant mode of termination and/or destruction of active centers appears to occur by a bimolecular mechanism which is related to the experimentally observed monomer dependence of the initial rate of polymerization.
Hydrodynamic friction coefficients for cellodextrins in water
Authors: Kurath Sheldon F. , Bump Donald D. 
Published: April 2003

AbstractThe diffusion coefficients for the cellobiose through cellohexaose members of the cellodextrin series were determined in water. The molecular friction coefficients calculated on the basis of the Einstein diffusion equation can be represented by, ζN = N ζa + 2ζe, where ζa is the monomeric friction coefficient of an anhydroglucose unit, ζe is a friction coefficient assigned to a terminal monomer unit due to its additional hydrodynamic surface, and N is the degree of polymerization. For the cellodextrins, ζa is 1.25 × 10−9 dyne‐sec./cm., and ζe is 2.42 × 10−9 dyne‐sec./cm. The monomeric friction coefficient of the anhydroglucose unit was found to agree with the value calculated from literature data on the diffusion of cellulose in cadoxen. The calculations were based on the Ptitsyn‐Eizner theory for the hydrodynamic behavior of the “wormlike” chain. The partial specific volumes of the cellodextrins were found to decrease from glucose to cellotriose and then to increase from cellotriose to cellohexaose.
Poly(chloroaldehydes). II. Polymerization of chloral
Authors: Rosen Irving , Sturm C. L. , McCain G. H. , Wilhjelm R. M. , Hudgin D. E. 
Published: April 2003

AbstractChloral was polymerized by means of cationic and anionic initiators and the products compared. Anionic catalysts readily produce high molecular weight polymer (DP ∼ 300–600), but a DP of only 200 could be produced with cationic catalysts. The anionic system apparently initiates and propagates polymerization much more readily than the cationic system. This effect is attributed to the inductive effects of the chlorine atoms on the chloral. Little difference was found when products of similar DP were compared as to x‐ray diffraction pattern, infrared spectrum and tractability. This is believed due to the single type of structure which is sterically favored. Various cyclic compounds of chloral could not be made to undergo polymerization under cationic initiation. The conditions required to effect ring opening were too rigorous to enable polymerization to take place.
Infrared spectra of polybutadienes
Authors: Binder John L. 
Published: April 2003

AbstractIt is shown, by analytical resolutions of the spectra of isomerized cis‐1,4‐polybutadienes, that the band due to hydrogen out‐of‐plane vibrations of cis‐CHCH groups appears at 740 cm.−1 and that the apparent shift of this band to lower frequencies, as the amount of cis‐CHCH decrease in a polybutadiene, is due to the presence of other bands in this region. Some possibilities as to the origins of these other bands are discussed. It is also shown that there are some bands in the 10–11 μ region of polybutadiene spectra which are probably connected with vibrations of cis‐CHCH groups and that there probably are others which are not due to either cis‐CHCH or trans‐CHCH or CH2CH. Some possibilities regarding the origins of these bands are discussed. The bands found here explain in large measure the appearance of polarization spectra of high‐cis 1,4‐polybutadienes.
Polymerization of 4‐vinylcyclohexene by the cyclic polymerization mechanism
Authors: Butler George B. , Miles Marion L. 
Published: April 2003

Abstract4‐Vinylcyclohexene is an example of a 1,5‐diene and is functionally capable of under‐going cyclic polymerization. Polymerization to soluble polymers was accomplished by cationic and Ziegler‐type initiators. Cationic initiation resulted in 28% conversion to polymer, of which 85% was soluble, having intrinsic viscosity of 0.11 dl./g. Infrared and nuclear magnetic resonance analyses led to the conclusion that cyclization of the monomer occurred to the extent of almost 50%. Ziegler‐type initiation resulted in 20% conversion to polymer of which 45% was soluble, essentially saturated, and having intrinsic viscosity of 0.04 dl./g. X‐ray diffraction studies on these polymers indicated no appreciable degree of crystallinity.
Radiation‐induced polymerization and other reactions of n‐perfluoropentadiene‐1,4 at high temperature and pressure
Authors: Brown D. W. , Fearn J. E. , Lowry R. E. 
Published: April 2003

AbstractThe radiation‐induced polymerization of n‐perfluoropentadiene‐1,4 was studied at temperatures of 100–170°C. and pressures of 8,000–15,000 atm. Kinetic evidence indicates that polymerization occurs by a free radical reaction; the activation energy is between 14 and 17 kcal./mole and the activation entropy is −8 ± 5 e.u./mole. Transfer with monomer limits the number‐average degree of polymerization to values of 40 or less except in special circumstances. Dimerization and double bond migration occur to some extent; n‐perfluoropentadiene‐1,3 is formed in the latter process. It and the 1,4‐diene copolymerize; the latter undergoes cyclic addition so that the polymers are soluble and have little perfluorovinyl unsaturation. The polymers are brittle if the fraction of 1,3‐diene in the polymer is less than 0.1. They are rubbery and of considerably higher molecular weight if the fraction of 1,3‐diene is greater than 0.4. The thermal stability of the polymers decreases as the content of 1,3‐diene increases.
Stress relaxation of γ‐irradiated fluorocarbon elastomers
Authors: Yoshida T. , Florin R. E. , Wall L. A. 
Published: April 2003

AbstractPoly(vinylidene fluoride), polytrifluoroethylene, and two rubbery copolymers with vinylidene fluoride were crosslinked by γ‐irradiation in vacuum. Radiation‐induced chain scissions in the copolymers were studied by observing the relaxation of stress at constant extension during further irradiation at 27°C., at 0.31–2.7 Mr./hr. in nitrogen and in air. From gel content, swelling, and elasticity, the values of Gc (crosslinking) and Gd (scission) were respectively; for CF2CFH, Gc = 2.2 and Gd = 0.4; for CF2CH2, 2.0 and 0.3; for CF2CH2 + C3F6, 3.4 and 1.3; for CF2CH2 + CF2CFCl, 1.8 and 1.4. The Gd values from stress relaxation were variable; the lowest were: for CF2CH2 + C3F6, 4.6 in nitrogen and 8.4 in air; for CF2CH2 + CF2CFCl, 1.9 in nitrogen and 3.6 in air.
Mechanism of fracture in glassy polymers. I. Fracture surfaces in polymethyl methacrylate
Authors: Kambour R. P. 
Published: April 2003

AbstractThe interference colors on poly(methyl methacrylate) fracture surfaces have been shown to arise from a layer of craze material. The order of interference can be determined in various ways for most areas on the fracture surface and craze layer thicknesses determined. Layer thickness is a function of fracture velocity; at zero velocity where the Griffith criterion may be applied with the least error an average surface layer thickness of 6800 A. is calculated. The plastic work of this amount of craze formation corresponds to 13–20% of the nominal Griffith energy.
Etude de la polymérisation des oléfines catalysée par les oxydes métalliques. II. Influence des impuretés sur la cinétique de polymérisation du propylène par le système catalytique phillips
Authors: Guyot Alain , Daniel Jean‐Claude , Durrieu Marc , Ptack Marius 
Published: April 2003

AbstractA study was made of the influence of oxygenated impurities probably present in propylene on the polymerization kinetics and on the paramagnetic properties of the Phillips catalysts which contain about 2.5% chromium. Only a fraction of chromium atoms are active centers, which could be the pentavalent atoms.
Macroreticular redox polymers. I. Hydroquinone–quinone redox polymers
Authors: Kun Kenneth A. 
Published: April 2003

AbstractRedox polymers based upon the hydroquinone–quinone redox system are prepared by the addition of hydroquinone and hydroquinone derivatives to preformed polystyrene matrices. Conventional gel and macroreticular styrene–divinylbenzene copolymers were chloromethylated with chloromethyl ether by using a Friedel‐Crafts catalyst and the reaction products were treated, by a second Friedel‐Crafts reaction, with hydroquinone, benzoquinone, or alkyl homologs of these materials or with the dimethyl ether or the diacetoxy derivatives of hydroquinone to give polymeric vinylbenzylhydroquinones. Macroreticular redox polymers show greater reactivity and better stability than resins having redox systems on conventional gel‐type matrices. These redox polymers convert iron III to iron II, cerium IV to cerium III, iodine to iodide, and remove dissolved oxygen and peroxides from aqueous and organic liquids when the resins are in the reduced form. When in the oxidized form, the resins are reduced with titanium III, sodium sulfite, sodium bisulfite, sodium dithionite, sulfur dioxide, and sodium borohydride.
Use of a capillary extrusion rheometer to measure curing of thermosetting plastics and rubbers
Authors: Salyer I. O. , Heyd J. W. , Brodbeck R. M. , Hartzel L. W. , Brown L. E. 
Published: April 2003

AbstractBy use of a modified, small‐bore, capillary extrusion rheometer (MCER) with an Instron tensile testing machine, the flow and set‐up properties of thermosetting plastics and rubbers were characterized. The majority of the experiments were performed with diallyl phthalate, where the rate of curing was also followed by infrared determination of the reduction in unsaturation as the polymerization‐curing proceeded. Phenol–formaldehyde was also characterized. Finally, the curing of ethylene–propylene and ethylene–vinyl acetate copolymer rubbers with peroxide was studied and correlated with the type of peroxide used. The MCER data are shown to be of practical use for predicting the time–temperature–pressure relationships for processing thermosetting plastics and rubbers. Moreover, the history of the curing, as obtained by analysis of the continuously extruded strand, is also of theoretical interest for studying reaction kinetics and for evaluating the effectiveness of various curing systems. It is predicted the MCER will be widely used for studying the curing of thermosetting plastics and rubbers.
Kinetics of the polymerization and styrene copolymerization of m‐ and p‐divinylbenzene
Authors: Wiley Richard H. , Devenuto Giovanni 
Published: April 2003

AbstractThe rate of polymerization and copolymerization with styrene of m‐, 2:1/m : p‐, commercial, and p‐divinylbenzene in tert‐butylbenzene decreases in the order listed at 65 and 80°C. The copolymerization of the para isomer at 80°C. accelerates more rapidly than does that of the other isomers. The overall activation energies increase from 14.9–20.8 kcal./mole to 23.5–26.9 kcal./mole in the polymerizations and from 9.0–12.1 to 13.0–17.6 kcal./mole in the copolymerizations over the time interval involved. The differences in rates and autocatalytic effects are attributed to differences in relative reactivities of the m‐ and p‐vinylstyrene‐derived radicals, the m‐ and p‐alkyl styrene structures, and to the different distribution of divinyl units in the copolymers.