bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactions of low molecular weight polypropylene induced by titanium compounds
Authors: Kresta J. , Majer J. , Veselý K. 
Published: June 2010

AbstractThe thermal and thermooxidative reactions of polypropylene oligomer in the presence of α‐TiCl3, TiOCl2, Ti(O‐i‐Pr)4, and HCl were studied. HCl is formed during the reaction of α‐TiCl3with hydrocarbon; the rate of formation is a function of the C–H bond strength. In the oxidation reactions of the polypropylene oligomer Ti3+acts as a terminator of the oxidation chain and, if its concentration is higher than that of the hydroperoxides, it inhibits the process. Ti4+(TiOCl2, Ti(O‐i‐Pr)4) retards oxidation, and HCl acts as catalyst.
Photodestruction and photooxidative destruction of polyurethanes
Authors: Tarakanov O. G. , Nevskji L. V. , Beljakov V. K. 
Published: June 2010

AbstractThe ultraviolet‐irradiation stability of polyurethanes synthesized on different diisocyanate bases was estimated in this work. The composition of the gaseous products formed during the photolysis of different polyurethanes was analyzed. The quantum yield of CO2 into the gaseous phase was evaluated. It is shown that the formation of gaseous products in photolysis proceeds through the breaking of NC and CO bonds in the urethane group of the polymer. From the electron spin resonance spectra of irradiated polyurethanes it was concluded that the strong delocalization of unpaired electrons takes place along the conjugation system formed in polyurethanes based on aromatic diisocynates. Kinetic oxygen absorption curves in ultraviolet irradiation of polyurethanes based on different diisocyanates were obtained. It is shown that the amount of absorbed oxygen depends primarily on the degree of crystallinity of the polyurethanes. The accumulation of peroxidates in polyurethane photooxidation was studied.
Molecular structure and nmr spectra of stereoregular poly(methyl acrylate) models
Authors: Doskočilová D. , Sýkora S. , Pivcová H. , Obereigner B. , Lím D. 
Published: June 2010

AbstractNMR spectra of the meso and d,l isomers of methyl‐2,4‐pentanedicarboxylate and of isotactic, heterotactic, and syndiotactic methyl‐2,4,6‐heptanetricarboxylate have been measured and analyzed. From the values of vicinal coupling constants the energy differences between various conformational structures of these isomers were estimated. The limitations of the procedure are discussed.
Dielectric properties of polytetrafluoroethylene and tetrafluoroethylene‐hexafluoropropylene copolymer
Authors: Koizumi Naokazu , Yano Shinichi , Tsuji Fukuju 
Published: June 2010

AbstractPrecision measurements of dielectric properties of polytetrafluoroethylene and copolymers of tetrafluoroethylene and hexafluoropropylene were made over a temperature range of –40 to +180°C. at frequencies of 10 Hz to 300 kHz. Polytetrafluoroethylene exhibited the typical dielectric behavior of a nonpolar substance: no dielectric loss peak was found over the experimental range of temperature and frequency. The dissipation factor remained constant, being about 2 × 10−5. Copolymers of tetrafluoroethylene and hexafluoropropylene showed two dielectric loss peaks: one occurred at about 100°C. and the other at about −20°C. There was a break point, or an abrupt bend, near 60°C. in the curve of dielectric constant versus temperature, indicating the existence of a transition point. The high‐ and low‐temperature loss peaks correspond to the α and γ relaxations, respectively, which have been found for the mechanical behavior of this copolymer. The dielectric relaxation in the copolymer was attributed to the slightly polar nature of the perfluoromethyl side groups. The activation enthalpy and entropy are 80 kcal./mole and 180 eu for the α relaxation and 12 kcal./mole and 15 eu for the γ relaxation, respectively. The σ and γ relaxations are discussed in connection with the molecular motion of the copolymer chain.
Diffusion behavior of polymer molecules in solution
Authors: Kotera Akira , Matsuda Hideomi , Konishi Katsutoshi , Takemura Kenji 
Published: June 2010

AbstractDiffusion experiments were carried out with a decalin solution of polystyrene at temperatures from room temperature to 110°C., to establish an experimental technique at higher temperatures. Values of diffusion constants obtained were checked by substituting them in the theoretical equations of diffusion behavior of polymer solutions. Results were satisfactory. For example, effective bond length of polymer chain calculated from Miyake's theory compares with those obtained by light‐scattering measurement. The apparent activation energy of diffusion is about 3 kcal./mole.
Polymerization of 3,4‐dihydro‐2H‐pyran‐2‐carboxyaldehyde (acrolein dimer). Part I. The homopolymerization
Authors: Kitahama Yoshiharu , Ohama Hiroshi , Kobayashi Hidehiko 
Published: June 2010

AbstractPolymerizations of 3,4‐dihydro‐2H‐pyran‐2‐carboxyaldehyde (acrolein dimer) were investigated under several conditions. Polyacrolein dimer obtained at room temperature was found to have structural units (III) of 6,8‐dioxabicyclo[3,2,1] octane produced by an intraintermolecular reaction, in addition to the ordinary structures (I) produced by the unsaturated ether‐group polymerization and those (II) produced by the aldehyde‐group polymerization. The lower the polymerization temperature, the higher the selectivity of (II). The stronger the acidic character of initiators, the higher the selectivity of (I) and (III). With anionic catalysts, such as Al(C2H5)3 and dibenzene chromium, acrolein dimer gave a polymer containing only recurring structural units (II) at −78°C., while it did not give any polymer above –20°C. There consequently seems to be a ceiling temperature in the polymerization with anionic catalysts. The solubility of the polymers increased with increasing amounts of the bicyclic structure (III).
A study of cellulose trinitrate structure
Authors: Watanabe Sadayoshi , Hayashi Jisuke , Imai Kiyoshi 
Published: June 2010

AbstractThe structure of cellulose trinitrate was studied by x‐ray analysis and polarized infrared spectroscopy. Its meridional reflections and fiber period suggest that the molecule is approximately in the 5‐fold screw structure. If a glucose residue of the molecule is of the chair form, no molecular conformation satisfying these requirements can exist. The hydroxyl groups on adjacent carbons C2 and C3 of the glucose residue will be transformed from the gauche conformation to the trans conformation during nitration because of bulkiness of nitrate groups. As a consequence, the glucose residue is transformed from the chair form to the half‐boat form, and the molecule is changed from the 2‐fold screw structure to the 5‐fold screw double‐helix structure. Then it can satisfy the requirements. Screw sense is left‐handed in the direction from C1 to C4. The change of absorption bands related to the skeletal structure of glucose residue during nitration suggests the transformation of the configuration of glucose residue. Orientations of CH2 and NO2 groups were studied by polarized infrared spectroscopy.
Chlorination of ethylene–propylene copolymer
Authors: Ramp Floyd L. 
Published: June 2010

AbstractCleavage of ethylene propylene rubber by oxygen may occur during chlorination at 25°C. Peroxy groups are first introduced without chain cleavage. Chain cleavage occurs only after all chlorine has been consumed. Vanadium, required to give cleavage under these conditions, is probably reduced and in turn cleaves the peroxy linkages. The distribution of tertiary chlorine along the chain was determined by dehydrohalogenation and oxidative cleavage.
Computer calculations of dimensions of linear alkanes and their use in the theory of diffusion in liquid solution
Authors: Burkhart R. D. , Merrill J. C. 
Published: June 2010

AbstractThe method of Flory was used to calculate unperturbed mean‐square dimensions of linear alkanes at 25°C by utilizing the assumption of three‐fold rotational isomerism and allowing, but giving small statistical weight to, configurations involving successive gauche rotations of opposite sign. The necessary 15 × 15 matrix multiplications were made with an IBM 1620 computer. The reciprocal square root of these calculated dimensions were assumed equal to <1/R>Av, and diffusion coefficients of pentane through dotriacontane were then computed by means of the Kirkwood‐Stokes equation. These coefficients were then compared with experimental values from four different solvents and with self‐diffusion measurements. In general, it may be said that theory and experiment agree well for solvents of low viscosity. For more viscous solvents (tetralin and decalin) experimental diffusion coefficients are about 80% larger than those calculated for pentane. As chain length increases, however, better agreement is observed.
Electronic computations of light scattering functions for heterodisperse systems of isotropic spheres
Authors: Yajnik M. , Witeczek J. , Heller W. 
Published: June 2010

AbstractFortran programs were developed to compute light scattering functions for heterodisperse systems that can be described by a biparametric, uni‐modal, exponential distribution function. The programs had to include the evaluation of the Mie functions for angular scattering for any arbitrary values of the size parameter α. This involves the calculation of the Riccati‐Bessel functions and Legendre polynomials. Several methods of numerical integration of the expressions containing the products of the Mie functions and the distribution function were investigated. Gaussian quadrature could yield the results of integration with better precision, but its use required a considerable amount of machine time, and thus it was adopted only for part of the results obtained. The simpler Simpson's rule allowed one to store the Mie functions needed in the integration and, as some of our studies have shown, its results come close (within the limits of experimental error of light scattering methods) to those obtained by the Gaussian method. The computer has also been used for fitting the experimentally obtained light scattering data with the theoretical ones.
Polymer science & technology (POST): A computer‐based information service
Authors: Siegel H. , Veal D. C. , McMullen D. A. 
Published: June 2010

AbstractThe integration of computer support into information processing provides many services for workers in science and technology. These services result from the simultaneous generation of printed text and machine records in the processing of data for publication, in effect, producing a complete information system rather than simply a publications system. Polymer Science & Technology (POST), a new service of the American Chemical Society's Chemical Abstracts Service (CAS), exemplifies such a multifaceted, computer‐based information system. POST consists of two units: POST‐J covers the journal and report literature, and POST‐P covers patents. Each unit is available in both computer language and printed journal form. This new system serves the needs of the practicing scientist for current, deeply indexed, subject‐oriented, printed information which has been specially formatted to simplify scanning and searching. The computer tape version of POST is supplied along with well‐documented search programs for use in the subscriber's computer installations or, if the subscriber wishes, computer searching can be done at CAS. This paper describes the POST information system in relation to the total CAS operation.
Structure‐property relationships for styrene‐diene thermoplastic elastomers
Authors: Morton Maurice , McGrath James E. , Juliano Peter C. 
Published: June 2010

AbstractA study has been carried out on block polymers of the A‐B‐A type, the thermoplastic elastomers, where A represents polystyrene and B polybutadiene or polyisoprene. The objective was to relate the mechanical properties of these elastomers to their molecular architecture. For this purpose a series of styrene‐butadiene and styrene‐isoprene block polymers were synthesized by means of organolithium initiators, in which the block lengths of the polystyrene and polydiene were varied. It was found that the stress‐strain properties of styrene‐butadiene polymers are mainly dependent on the polystyrene content, regardless of the block sizes, and that the center, elastic block does not appear to behave as the “molecular weight between crosslinks” of these networks. However, the monodispersity of the chain length of these elastic blocks does appear to contribute substantially to higher tensile strengths. The polystyrene appears to be aggregated in small domains, of the order of several hundred angstrom units, and these undergo an irreversible deformation under stress, which is, however, completely recoverable above the Tg of the polystyrene. At high polystyrene contents (∼40%) these elastomers exhibit an irreversible yield point at very low elongations, and this is ascribed to the presence of a continuous phase of connected polystyrene domains, which can be re‐formed by raising the temperature above the Tg of the polystyrene. Although the stress‐strain curves are not affected by the thermal history of the sample, the tensile strength, especially at high styrene contents, is strongly dependent on “annealing” of any frozen stresses in the polystyrene phase. The useful range of block molecular weights is about 10,000–20,000 for polystyrene and 40,000–80,000, respectively, for polybutadiene. The lower limit is probably governed by the minimum polystyrene chain length required to insure the formation of a heterogeneous phase; while the upper limit is set by the high viscosity of both blocks, which might seriously hamper domain formation.
Developments in self‐reinforced elastomers
Authors: Brunwin D. M. , Fischer E. , Henderson J. F. 
Published: June 2010

AbstractUntil recently it has been believed that either stress‐crystallization or the presence of reinforcing filler is necessary for the development of high strength in elastomers. Now it has been observed that gum vulcanizates of isoprene/acrylonitrile copolymers have tensile strengths in the order of 3000–4000 psi in the absence of fillers. In this case crystallization does not occur and the strength is associated with the ability of the polymer molecules to become highly oriented on stretching. Similar observations have been made with ABA block copolymers polystyrene‐polybutadiene‐polystyrene which are highly elastomeric in the absence of chemical crosslinks. The elastomeric properties and high strength of the block copolymers are attributed to the mutual incompatibility of the A and B blocks which leads to phase separation on a microscopic scale. The effective network structure can be temporarily destroyed by heating the polymer above the softening temperature of the resinous blocks which makes the material readily processable. The initial decrease in retractive force with increasing temperature up to 60–70°C is attributed to an increase of mobility of the resinous domains in the rubbery matrix. At higher temperatures the crosslinking effectiveness decreases markedly due to softening of the resinous regions. The process of yielding, hysteresis effects, and delayed elastic creep arise because of viscous forces which oppose the motions of the colloidal polystyrene domains. The strength and effectiveness of physical crosslinks in block copolymers shows a similar temperature dependence as has been observed for other filled and unfilled vulcanizates. The process of self‐reinforcement in isoprene‐acrylonitrile copolymers and polystyrene‐polybutadiene‐polystyrene block copolymers is attributed to viscous effects which make possible the alignment of a large number of polymer chains in the stretching direction.
Anionic emulsion polymerization of siloxanes
Authors: Weyenberg D. R. , Findlay D. E. , Cekada J. , Bey A. E. 
Published: June 2010

AbstractIn 1959, Hyde and Wehrly described an emulsion polymerization of permethylcyclosiloxanes. This unique example of an emulsion polymerization proceeding via an ionic mechanism involved base catalysis with a cationic surfactant. An analogous acid‐catalyzed anionic emulsion polymerization has now been developed which employs dodecylbenzene‐sulfonic acid as the catalyst and surfactant. Polydimethylsiloxane emulsions with particle diameters of 500–5000 Å are obtained on heating aqueous dispersions of permethylcyclosiloxanes with dodecylben‐zenesulfonic acid at 50–100°C. Polymerization is completely arrested by neutralization of the catalytic surfactant. As in the earlier cationic emulsion polymerization, the molecular weight of the polymer is easily controlled by the temperature of polymerization via the equilibrium between siloxane, water, and silanol. Polymers with molecular weights of 49,000 and 172,000 are obtained at 90°C and 25°C, respectively. The use of alkyltrimethoxysilanes in this anionic emulsion polymerization makes available a new system of colloidal silsesquioxanes with extremely small and uniform particle size. Colloidal methylsilsesquioxanes with particle diameters of 70–1000 Å are obtained by the addition of methyltrimethoxysilane to an aqueous dodecylbenzenesulfonic acid solution. Methylsilanetriol and methylsiloxanols were shown to be intermediates in this latter reaction.
Emulsion polymerization: A stochastic approach to the polymer size distribution
Authors: Saidel Gerald M. , Katz Stanley 
Published: June 2010

AbstractThe dynamic behavior of emulsion polymerization is described both stochastically and deterministically. A partially stochastic approach is taken when the rate of radical arrival at the emulsion particles is much less than the rate of termination. In this case, the radical arrival which alternately starts and stops a growing polymer is considered to be random, but the growth of polymers and particles are treated deterministically. When the rate of radical arrival is much greater than the rate of termination, many growing polymers may coexist in a given particle. Under these conditions a (completely) deterministic model is found applicable. Both these models show how the reactant concentrations, the number of emulsion particles, and the reaction and transport rate coefficients effect the moments of the polymer size distribution and the rate of polymerization.
Relationship between electric conductivity, thermally stimulated currents, thermoluminescence and polymer structure
Authors: Kryszewski M. , Kasica H. , Patora J. , Piotrowski J. 
Published: June 2010

AbstractIn order to study the relation between polymer structure and their d.c. conductivity the measurements of current‐ voltage characteristics, thermally stimulated currents /TSC/ and thermoluminescence /TL/ measurements of poly (ethylene terephthalate) films were carried out. The PET samples were subject to different thermal treatment and deformations (unixial stretching). The degree of crystallinity of the thermally treated films was determined on the basis of density measurements and their supermolecular structure by means of light scattering technique. It was found that PET samples exhibit non ohmic behaviur and different TSC curves depending on crystallinity degree and orientation. The TSC curves analysis allowed establishing of the trap levels energy depth and trap densities. The shallow trap levels energy was also calculated from TL glow curves. The trap depth was correlated with the structure of the investigated specimen. The observed behaviour of PET films in d.c. field and the related phenomena were interpreted in terms of the injected current carrier theory.
Influnce of the chemical structure on the morphology and physical properties of crosslinked macromolecules synthesized by polyaddition reaction
Authors: Schmid R. , Lohse F. , Fisch W. , Batzer H. 
Published: June 2010

AbstractThe investigations in epoxy resins and other polymers have shown that by selecting the structure of the segments between the crosslinks it is possible to vary to a great extend the morphology and the physical properties. In a survey, a classification of 7 systems is given, cach of them characterized by specific morphological and physical properties. It is demonstrated that conventional epoxide resins show a distinct maximum of the mechanical damping and elongation at rupture nearly at the same temperature. The toughness‐temperature characteristic however shows a maximum 20°–30°C below the glass transition temperature. One system, the slightly crosslinked epoxy resins e.g. obtained by reacting long chain acid polyesters and diepoxides show a very high toughness in the transition range, compared to the conventional high crosslinked polymers.
The adsorption behavior of polymer mixtures
Authors: Botham Ruth , Thies Curt 
Published: June 2010

AbstractThe interfacial behavior of several mixtures of incompatible polymers has been examined at 24°C using finely divided silica as the adsorbent and trichloroethylene as the solvent. Displacement experiments have shown that poly (ethylene‐vinyl acetate) (EVA) (20.4% by wt. vinyl acetate) completely displaces polystyrene (PS) from silica within 1 hr. while poly (vinyl acetate) (PVAc) displaces ethyl cellulose (EC) within 3 hrs. A given EVA copolymer displaces one of lower vinyl acetate content; EVA (44.2% vinyl acetate) is displaced by EC. EC tends to displace poly (methyl methacrylate) (PMMA), but the process is slow and incomplete. The fraction of adsorbed polymer segments attached directly to silica, as determined by infrared spectroscopy, can be correlated with the displacement results. Experiments with PS/PVAc, PS/PMMA, and polydimethylsiloxane/EVA (20.4% vinyl acetate) mixtures have shown that adsorbance values of the preferentially adsorbed PVAc, PMMA, and EVA are increased by the second polymer, when polymer concentrations which cause phase separation are approached. Increases in adsorbance are accompanied by lower infrared bound fraction values, implying formation of a more extended adsorbed layer.
Enzymes covalently bound to various polymers and the effects on the properties of these enzymes
Authors: Manecke G. , Günzel G. , Förster H. J. 
Published: June 2010

AbstractIt was investigated how polymers which carry 2,4‐dinitro‐fluorobenzene or isothiocyanate groups could be used for preparing protein and enzyme resins. Furthermore it is demonstrated that the quantities of covalently bound enzymes as well as the properties of the enzymes themselves are dependent on the structure and chemical composition of the polymer matrices.
Comparative lethal action of ethyl methanesulfonate, nitrogen mustard, myleran and diepoxybutane on T7 coliphage
Authors: Brakier L. , Verly W. G. 
Published: June 2010

AbstractInterstrand crosslinks can be shown in phage T7 DNA after treatment by nitrogen mustard or DL‐diepoxybutane, but not after treatment by myleran. Lethality increases after an ethylmethanesulfonate or myleran treatment; this increase is related to the increase of depurinations. Lethality first increases after the nitrogen mustard treatment, then decreases and finally increases again. Crosslinks account for the whole lethality at the end of the treatment, and the evolution of lethality with time can be related to the evolution of crosslinks; the subsequent increase could be correlated to the appearance of fragmentations. Lethality remains constant after the DL‐diepoxybutane treatment; the number of crosslinks is smaller than the number of dead phages; the disappearance of the crosslinks would compensate the biological effect of the increase of depurinated sites so that the lethality remains constant during the first hours after the end of the treatment. The inactivation of the T7 phage by any of these agents is a one‐hit process.