bluuebunny/crossref_metadata_2025_split huggingface dataset:
Study of the inhibition effect of stable iminoxy radicals on the oxidation degradation of polymers
Authors: Matisová‐rychlá L. , Lazár M. , Rychlý J. , Karpukhin O. N. 
Published: June 2010

AbstractThe chemiluminescence method was used to study the reaction of peroxy radicals with stable radicals of X2NO. type where Corresponding courses of chemiluminescence intensity were followed either in low molecular solvents (ethyl benzene, dioxane) or in benzene solutions of polystyrene and in poly(ethylene oxide). The ratio ki/kt0.5 of rate constants of peroxy radicals and stable radicals recombination (ki) and mutual peroxy radicals termination (kt) was measured at 60°C. This value for ethyl benzene is 54.2 (1. mole−1 sec−1)0.5, for benzene 27.7 (1. mole−1 sec−1)0.5, and for 5% benzene solution of polystyrene 19.3 (1. mole−1 sec−1)0.5, respectively.Similar systems in dioxane and poly(ethylene oxide) exhibited different courses of chemiluminescence intensity than those in ethyl benzene and benzene.
Metal compounds in free radical processes. I. Effect of copper (II) ion on the ligand reactivity in transfer reactions
Authors: Barton J. , Horanska V. 
Published: June 2010

AbstractThe reactivity of (‐)‐ephedrine, free or bonded in copper complex, in the transfer reactions with free radicals was studied. The reactivity of the ligand functioning as a hydrogen donor was expressed by the ratios of the rate constants of the interaction of 2,2′diphenyl‐1‐picrylhydrazyl (DPPH) with bis‐(−)‐ephedrine copper(II) chelate (k1), (−)‐ephedrine (k2), and cumene (k3). Thus the values 100 mole0.5 1.−0.5 and 2.5 mole0.5 1.−0.5 were found for the ratios k1/k2 and k1/k3, respectively. These data indicate a significant effect of copper ion on the reactivity of (–)‐ephedrine in the transfer reactions with DPPH radicals.
Chemical stabilization of polymers by unsaturated derivatives of 2‐mercaptobenzothiazole and 1, 2, 3‐benzotriazole
Authors: Saidov B. , Shakirova E. , Askarov M. , Bank A. 
Published: June 2010

AbstractStatistic copolymers of methyl methacrylate, allyl‐2‐mercaptobenzothiazole or allyl‐1,2, 3‐benzotriazole, containing up to 10 mole % of the latter were studied. Using viscosimetric and infrared spectrometry methods it was shown that the increased content of certain stabilizing agents brings about an increased light stability effect in the polymer product.Moreover, such properties were found to survive in graft copolymers of poly(vinyl chloride) and 2‐mercaptobenzothiazole and 1, 2, 3‐benzotriazole acrylic derivatives in the form of films and fibers.
Antioxidants and stabilizers. XXXVIII. Effect of the side initiation on the antioxidative activity of the hydroquinone derivatives
Authors: Lisá E. , Pospíšil J. 
Published: June 2010

AbstractThe stoichiometric factor of (2‐alkoxyalkyl), pivaloyl, hydroxy, methoxy, and alkyl derivatives of hydroquinone during the inhibited oxidation of tetralin has been determined. The differences observed in the antioxidative activity of the individual hydroquinone derivatives has been interpreted on the basis of different participation of the aryloxy radicals derived therefrom in the side initiation reaction leading to a reduction of the stoichiometric factor. The aryloxy radicals of hydroquinones with an intramolecular hydrogen bond in the molecule have been found to participate in this reaction to a limited extent only. This is one of the causes why these inhibitors have a higher stoichiometric factor than the alkyl derivatives of hydroquinone which does not form intramolecular bonds.
The sorption and diffusion of small molecules in amorphous and crystalline polybutadienes
Authors: Brown W. R. , Jenkins R. B. , Park G. S. 
Published: June 2010

AbstractDiffusion coefficients of methylene chloride, chloroform, benzene, and 2,2,4‐trimethyl‐pentane in 1,4‐polybutadiene having trans contents between 2 and 100% have been obtained from vapor sorption and desorption kinetics. For amorphous polymers (trans content less than 70 to 80%) the diffusion coefficient at zero penetrant concentration decreases with increasing trans content and with increasing size of the diffusant. The activation energies for diffusion are independent of temperature and increase with trans content and diffusant size. Comparison with the activation energies for viscous flow give values for the B factor in Fujita's free volume theory and this increases with diffusant size towards a value of unity. At trans contents above about 80% a sudden drop in the diffusion coefficient and in the equilibrium vapor sorption occurs accompanied by a large increase in the concentration dependence of the diffusion coefficient. These changes result from the onset of crystallinity but the absence of any sudden change in the activation energy suggests that the main effect is a geometric one due to the inaccessibility of the crystalline regions with little change in the basic mechanism of diffusion in the amorphous regions. Vapor sorption enables calculation of the accessibility of the crystalline polymers and this is found to decrease with increasing size of the diffusant. Variations in crystallinity produced by different heat treatments give the expected variations in the diffusion coefficient and equalibrium vapor sorption.
Anionic copolymerization of methacrylates
Authors: Vlček P. , Doskočilová D. , Trekoval J. 
Published: June 2010

AbstractAn investigation was carried out of the anionic copolymerization of methyl methacrylate (M1), 2‐methoxyethyl methacrylate (M2), and 2‐(N, N‐dimethylamino) ethyl methacrylate (M3) in benzene solution at 20°C initiated with lithium tert‐butoxide. The monomer reactivity ratios (M1–M2) r1 = 1.51 ± 0.05, r2 = 2.10 ± 0.10, (M1–M3) r1 = 1.20 ± 0.10, r3 = 0.40 ± 0.05, (M2–M3) r2 = 1.40 ± 0.15, r3 = 0.60 ± 0.15 show that the reactivities of the individual monomers M1, M2, and M3 do not differ too much from each other. A study of the microstructure of copolymers M1–M2 by the NMR method revealed that at low conversions the tacticity of the copolymers depends on the concentration of 2‐methoxyethyl methacrylate in the starting monomer mixture; in the initial stage of copolymerization it is strongly dependent on conversion. Already a low content of M2 in the starting monomer mixture (below 1%) strongly affects the tacticity of the forming copolymer by depressing the content of the isotactic component.
Semi‐empirical calculation of reactivity ratios
Authors: Albert Richard , Malone William M. 
Published: June 2010

AbstractFrom the specific refractive index, the UV absorption maximum is calculated which measures the difference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). Subtracting the HOMO‐LUMO energy from the π–π° transition energy of ethylene renders an estimation of the total π‐energy. The difference between the sum of the total π‐energies of reactants and the energy of the transition state approximates the activation energy and relates to the reactivity ratio.
The mechanism of cationic polymerization of β‐propiolactone
Authors: Ludvig E. B. , Khomyakov A. K. , Sanina G. S. 
Published: June 2010

AbstractThe mechanism of cationic polymerization of β‐propiolactone (PL) in methylene chloride under action of magnified image has been studied by the kinetic method. In the absence of additives, the process proceeds steadily via the active centers–acyl ions–and it involves the following reactions: 1. chain propagation, and 2. reversible combination of the active centers and carbonyl groups of monomer and polymer.The dielectric constant of the medium affects the reaction in the range of low monomer concentrations. In the presence of ether and ester additives another combination reaction between the active centers and additives is observed. Kinetical treatment of the results was performed, and the ratios were determined for the respective equilibrium constants and the rate constant of chain propagation which are a measure of relative basicity of ethers and esters. Ketones were shown to be inhibitors of the process. The rate constants of chain termination were estimated for different ketones on the basis of kinetic data.
Influence of acids on the reaction rate of transesterification of dimethyl terephthalate
Authors: Šitter E. , Jalovecký J. 
Published: June 2010

AbstractThe reaction rate of transesterification of dimethyl terephtalate by ethylene glycol was investigated in the presence of some organic acids. The reaction rate decreased only slightly in the presence of monocarboxylic acids, usually forming anions of used catalysts; however the decreasing reaciton rate is very strong in presence of dicarboxylic acids. These acids can be present in ethylene glycol (oxalic acid), dimethyl terephtalate (terephtalic acid), or in any modifier. The monoester of terephtalic acid has a similar influence. The decrease of rate constant of a second order reaction during the reaction can be explained by the forming of carboxylic groups in the transesterification.
On the mechanism of hardening of resorsinol‐formaldehyde polyconden‐sates
Authors: Kurachenkov V. I. , Matyukhina O. S. , Silling M. I. , Stalnova M. A. , Igonin L. A. 
Published: June 2010

AbstractThe study of novolac resorcinol formaldehyde resin hardening was effected by means of the differential thermal analysis (under pressure) and IR‐spectroscopy methods. Two types of polycondensate were investigated. Paraformaldehyde and hexamethylene tetramine were used as hardeners. The existence of two regions of hardening, a low temperature range (100–120°C) and a higher temperaturer range (220–250°C) was revealed. Moreover, the influence of molecular weight, isomeric composition, and free resorcinol content on the hardening process was investigated. It was suggested that the existence of two regions of hardening is related to the different reactivity of β and γ positions in the resorcinol nucleus.
Copolymerization of propylene and complexed acrylonitrile by TiCl3–AlEt3 catalyst system
Authors: Dankovics A. , Szentivínyi Zs. , Kissin Ju. V. , Szöllösy I. 
Published: June 2010

AbstractIt was found that an equimolar complex is formed from acrylonitrile with triethylaluminum. The complex formation was verified by infrared spectroscopy. The original bands of acrylonitrile at 2235 cm−1 shifted and the new bands appeared at 2225 and 2275 cm−1. Copolymerization of acrylonitrile with propylene was proved to be possible with a TiCl3–AlEt3 catalyst system.Kinetic studies on copolymerization of propylene with acrylonitrile showed that composition of the starting monomer mixture markedly influenced the course of the reaction and the acrylonitrile content of the copolymer.Optimum conditions of the copolymerization reaction were as follows: temperature, 70°C; reaction time, 30 min; molar ratios of acrylonitrile to the metal alkyl and Al to Ti, 1:1 and 2;1, respectively, concentration of the total amount of monomers. Conversion is influenced by the aging time of the acrylonitrile‐metal alkyl complex; the yield is a linear function of the aging time. Composition of copolymers was determined by chemical analysis.
Zwitter‐ion polymerization of methacrylonitrile initiated by triethylphosphine
Authors: Ranogajec F. , Kotchetov E. V. , Markevitch M. A. , Enikolopyan N. S. 
Published: June 2010

AbstractThe mechanism of polymerization of methacrylonitrile initiated by triethylphosphine in dimethylformamide was investigated. It has been shown by elemental analysis that phosphorus is chemically bound to polymeric molecules. Analysis by NMR spectroscopy, as well as conductivity measurements prove that in the initiation process the following zwitterion structure: magnified image has been formed. Monomer addition to carbanion leads to macrozwitter‐ion. The role of free ions and ion pairs in macrozwitter‐ion polymerization are discussed. In the case of intramolecular formation of ion pairs, monomolecular equilibrium constant ion pairs‐free ions depends on the length of macrozwitter‐ion. Consequently, the polymerization rate depends on the length of the growing chain due to different reaction activity of ion pairs and free ions. By addition of salt, Ph3MeP+J−, in the polymerization system, i.e., by bimolecular formation of ion pairs the polymerization rate does not depends on the length of macrozwitter‐ion. Kinetics of polymerization in the presence of the salt was investigated. It was shown that terminated polymer also influences the polymerization rate and yield.
Modelling of the x‐ray scattering of polymers by light diffraction
Authors: Bodor G. , Samay G. 
Published: June 2010

AbstractThe x‐ray patterns of solid phase polymers are widely used to characterize the structures. They can be used, among others things, to calculate the degree of crystallinity, the crystalline particle size, and the lattice distortions. However, it is not perfectly clear how the characteristics of the structure effect the obtained diffractograms. The main aim of the present work is to explain what kind of diffraction patterns can be obtained from a hypothetical structure of a polymer. The effect of the following structural parameters were investigated: degree of crystallinity, crystalline particle size, lattice distortions of the first and second kind, and amorphous background. The changes of the diffraction patterns depending on these varied factors were followed.The light diffraction patterns were produced by a modified Schlieren 80 apparatus. The polymer segments were modelled by point‐like scattering centers. From these, the models of an ideal crystal and the lattice distortion of the first and second kind were prepared. The crystalline particle size was varied by cutting the original mask. In the amorphous background the minimum distances of two scattering centers were altered. The light diffraction patterns were produced also by rotating the mask, and the x‐ray diagram of the unoriented polycrystalline samples could be reproduced. The intensities of the obtained patterns were measured by a microdensitometer. With the help of the diagrams, both qualitative and quantitative conclusions can be obtained about the relation between the mask and its diffraction pattern.
Selective interactions between macro‐molecules and two‐component solvents
Authors: Munk Petr , Allen Robert G. , Halbrook Michael E. 
Published: June 2010

AbstractA new method of measuring the refractive index increment of a macromolecular solution while it is at equilibrium with a composite solvent is presented. A synthetic boundary is formed in the ultracentrifuge cell between the solution and composite solvent, which was not dialyzed against the solution. The solvent components equilibrate much faster than the macromolecules, and by proper extrapolation the refractive index increment of the macromolecules is obtained. Refractive index increments of a series of solutions of bovine serum albumin in guanidinium chloride solutions were measured and the amount of preferentially bound guanidinium chloride was calculated.
Influence of fillers on ethylene‐vinyl acetate copolymer degradation
Authors: Romanov A. , Marcinčin K. , Pollák V. 
Published: June 2010

AbstractMechanical degradation of ethylene‐vinyl acetate copolymer under use of oxalic acid, sodium chloride, basalt, and poly(vinyl chloride) as fillers has been studied. It has been found that the degree of degradation is affected by the reinforcement of the polymer matrix by the filler.
A mass spectrometry study of a connection between the mechanical and thermal degradation of polymers
Authors: Regel V. R. , Amelin A. V. , Pozdnyakov O. F. , Sanfirova T. P. 
Published: June 2010

AbstractThe influence of the “weak links” of real macromolecules on the kinetic parameters of thermal degradation and mechanical breakdown processes is suggested. This conclusion was made on the basis of studing and comparing the activation energies of these two processes for a number of polymers. The activation energy of the thermal degradation process was found by the mass spectrometry technique and the activation energy of mechanical breakdown was found by the results of mechanical tests.
Thermal degradation of vinyl copolymers as a function of their composition and sequence length distribution
Authors: Jaćović Mihailo S. , Milošević Danica 
Published: June 2010

AbstractIn order to study thermal degradation of copolymers and homopolymer mixtures of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and styrene mild pyrolysis on a hot filament, followed by gas chromatography, was used. For each of the eight monomer pairs, at least eleven copolymers and eleven homopolymer mixtures of different composition were prepared for the study. It was suggested to present the results by plotting weight fraction of a monomer in the mixture of regenerated monomers vs. weight fraction of the same monomer in the copolymer or in the mixture of homopolymers. Ratio of the degrees of regeneration of two monomers can be obtained directly from such graphs. Taking the degree of monomer regeneration as an indication of the relative importance of depropagation and transfer, conclusions were made about the mutual influence of homopolymer sequences of two monomers in thermal depolymerization. A cosequence of this influence is the tendency for equalization of the degrees of regeneration of two monomers in the thermal degradation of the studied copolymers.
Dextran: A branched polymer and plasma expander
Authors: Cerny L. C. , Mc. Tiernan J. , Stasiw D. M. 
Published: June 2010

AbstractThe method of Flory and a modification of the method proposed by Elias and Cornet and van Ballegooijen were used to determine theta conditions for samples of dextran and poly(vinyl pyrolidone). Light scattering and viscosity measurements made at the theta condition for dextrans of widely ranging molecular weights showed the second virial coefficient to be zero and were in agreement with the theory of Zimm and Kilb for branched polymers. Viscosity and osmotic pressure measurements were made on various mixtures of dextran and poly(vinyl pyrolidone) in water and the theta solvents determined by the above methods. Osmotic pressure measurements for various mixtures of high‐molecular‐weight dextrans and poly(vinyl pyrolidone) made in water showed a minimum in the number‐average molecular weight and osmotic second virial coefficient at all three temperatures. This minimum did not occur in blends of a lower molecular weight dextran and poly(vinyl pyrolidone).
The supermolecular structure of viscose fibers and its dependence on spinning conditions
Authors: Nikonovich C. V. , Kerimova N. G. , Burchanova N. D. , Usmanov Kh. U. 
Published: June 2010

AbstractThe supermolecular structure of viscose fibers (VF) has been studied by electron microscopy and some other physical methods. Experimental and industrial VF samples were selected at different spinning stages and served as the objects of investigation.Coagulation conditions (bath composition) were shown to affect significantly VF surface structure. Besides, the latter essentially depends on VF swelling and shrinkage in the course of spinning. In the case of tire cord fibers the surface reveals no significant changes after bath stretching; on the contrary, the structure of the surface and inner regions of the VF, spun according to the Lilienfeldt process (in concentrated sulfuric acid) shows noticeable changes after bath stretching.Electron micrographs of isotropic VF reveal a loose fibrillar network with pore dimensions and homogeneity depending on the coagulation bath composition and its component ratio (H2SO4/ZnSO4). While increasing the ZnSO4 content in the coagulation bath, some decrease of the network pore diameter was observed to take place.Stretching leads to the orientation of VF structural elements in the direction of the fiber axis, followed by formation of lamellar structures.Investigations of crystallites isolated by hydrolysis and estimation of their dimensions allow to come to conclusions on changes in the fine structure of microfibrils in the course of spinning.Electron microscopy data and some other VF structural characteristics are shown to be in good agreement.
Hardness as a rapid, reliable measure of polymer crystallization
Authors: Wilkes Charles E. , Walters Maxie R. 
Published: June 2010

AbstractSince polymer crystallization rate is such a universal measure of backbone stereo structure, side chain structure, crosslinking, and the effect of additives, we have developed a routine, easily used method for its measurement. Normalized plots of the time‐honored measurement of hardness vs time compare well with results obtained by dilatometry, x‐ray diffraction, and light absorption (or optical birefringence). Sample preparation, surface roughness (especially important in the case of “nervy” rubbers), shortcuts to round‐the‐clock testing, temperature control and fine points of hardness measurements are discussed.
Differential scanning calorimetry of polypentenamers: Correlation of thermal properties with cis/trans content
Authors: Wilkes Charles E. , Pekló Mária J. P. , Minchak Robert J. 
Published: June 2010

AbstractFirst and second order thermal transitions have been characterized for a number of cis/trans‐polypentenamer copolymers, for blends of high cis and high trans polymers, and for high trans polypentenamer containing oil and carbon black. The extrapolated value of Tg for 100% trans polypentenamer is −91°C at a heating rate of 10°C/min. At the same heating rate the maximum, equilibrium melting point is estimated to be 44°C. Correcting for the thermal lag in the experiment (i.e., extrapolating to infinitely slow heating rate), the above value is 40°C. The heat of fusion of trans‐polypentenamer is 1.93 ± 0.11 K cal/mole. The presence of crystalline polypentenamer slightly raises the glass transition temperature of the amorphous phase. This effect becomes measurable when the trans content is greater than 80%. Once calibrated by infrared or other spectroscopic determination of composition, thermal analysis is a rapid, precise method for measuring cis/trans contents in polypentenamers.
Viscoelastic measurement of polybutenes and low viscosity liquids using ultrasonic strip delay lines
Authors: Knauss Carl J. , Leppo Dale , Myers Raymond R. 
Published: June 2010

AbstractA new method for measuring the shear mechanical properties of liquids in the 1–20 MHz range is used to obtain data for low‐viscosity liquids at approximately 2 MHz. The results obtained agree with literature data reported for these samples at 40 MHz. The technique involves the propagation of a pulsed, shear wave in a thin strip of metal, and measurements of the phase shift and increased attenuation of the wave by a sample at the metal‐liquid interface. The method is then extended to measuring the properties of polybutenes, whose average molecular weights range from 250–920. The relationship between average molecular weight and the dynamic viscosity and elasticity is studied for these polymers.
A role of internal viscosity in the intrinsic hydrodynamic and rheooptical properties of polymer solutions
Authors: Peterlin A. 
Published: June 2010

AbstractExact treatment of intrinsic viscosity and streaming birefringence is possible for the limiting case of zero gradient where the coil dimensions are not yet perturbed by the flow. Experimental data on streaming birefringence in solvents of low viscosity suggested an internal viscosity characteristic for the polymer and independent of the viscosity of the solvent. More recent data on frequency dependence of viscosity in very viscous solvents unequivocally demand an internal viscosity proportional to the viscosity of the solvent. By reconsiderations of the possible origins of internal viscosity one indeed finds two contributions one prevailing at low and the other one at high solvent viscosity in good agreement with experimental data. The former is the original Kuhn‐Cerf term based on energy barriers opposing rapid conformational changes. The latter is caused by the coupling of lateral and longitudinal displacement of chain elements as a consequence of conformational limitations by valency angles and bond orientation (g,g′,t).