bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studium der Polymerisation von Bis(glycerinmonoallyläther)fumarat mittels Infrarot Spektroskopie
Authors: Vlček Jiří Klaban Jaroslav , Mleziva Josef 
Published: June 2010

AbstractBis(glycerin monoallyl ether)fumarate (I) was prepared by a reaction of fumaric acid with an excess of allyl glycidyl ether. This compound has proved to be a reactive monomer in a blend with the unsaturated polyester resins for the preparation of lacquers which after suitable initiation dry in air into a hard film. In this work the role of the double bonds in the polyfunctional monomer in the network and the nature of the relative reactivity of the allyl and fumarate bond with and without oxygen. The problem was studied by infrared spectroscopy on model compounds and the bis(glycerin monoallyl ether)fumarate. To trace the fumarate trans‐bond we used the 773 cm.−1 bond; for the allyl bond, that at 930 cm−1. As an internal standard for the quantitative valuation we chose the carboxyl zone. It was ascertained that the allyl and fumarate bonds polymerize with each other and that the copolymerization is influenced by the presence of oxygen.
Initiator—Cocatalyst Interaction in Trioxane Polymerization
Authors: Kučera Miloslav , Hladký Eduard , Majerová Karla 
Published: June 2010

AbstractPolymerization of trioxane dissolved in an organic solvent is kinetically a very complex process. The polymerization proper is influenced by the initiator–cocatalyst interaction. The usual cocatalyst, practically always present in trioxane, is water. This compound, however, takes part in several reactions simultaneously; in the absence of any other cocatalyst its presence is necessary for initiation and propagation. It takes part also in chain transfer and is removed from the system by the transfer reaction. Loss of water is accompanied by changes of the overall rate of polymerization of trioxane melt. The actual concentration of initiator decreases in the course of polymerization. Another factor which can seriously complicate the polymerization is the change of the dielectric constant of the medium, if it differs from that of trioxane. The loss of water and of initiator has been analyzed, and relationships have been derived describing with sufficient accuracy certain cases of polymerization of trioxane in the presence of a solvent.
Low‐Temperature Relaxation of Some Polyamides
Authors: Bareš J. , Janáček J. 
Published: June 2010

AbstractThe low‐temperature relaxation process of polycaprolactam, methyl‐substituted poly‐caprolactams, and other linear polyamides was studied by dielectric methods in the temperature range from – 140°C. to +50°C., and in the frequency range from 100 cps to 10 Mc./sec. In some of these polymers the temperature dependence of the complex shear modulus of elasticity was also measured at a frequency of about 1 cps. The methyl substituent provokes an increase of relaxation times of dielectric dispersion in poly‐γ‐methylcaprolactam and a decrease of relaxation times in poly‐ϵ‐methylcaprolactam. This decrease is ascribed to the increase in steepness of the potential barrier owing to a close attachment of dipole to the methyl‐substituted group. Irrespective of its position, the methyl substituent has been found in all cases to cause an extension of the distribution of relaxation times of shear modulus towards lower temperatures, as compared with the dispersion of nonsubstituted polyamides. The dependence of the widths of the distribution of dielectric relaxation times upon the temperature and the degree of crystalline arrangement have been discussed. For the copolymer of caprolactam. 7‐aminoheptanoic acid, and aminoundecanoic acid, which possess the same concentration of polar groups per unit of chain length as poly(hexamethylene sebacamide), a narrower distribution of relaxation times has been found. On the basis of ideas concerning low‐temperature dispersion it is possible to explain also higher relaxation times of low‐temperature dispersion occasioned by low molecular weight substances by an increase of the mean friction factor.
Inhibited Thermooxidative Degradation of Polyesters. Oxidation of Poly(ethylene Adipate) and Poly(ethylene Sebacate)
Authors: Gömöry I. , Štímeľ J. , Reya R. , Gömöryová A. 
Published: June 2010

AbstractThe noninhibited and inhibited oxidation of poly(ethylene adipate) and poly(ethylene sebacate) polyesters was studied at temperatures of 130–200°C. Oxygen absorption curves, typical for autocatalytic processes, were obtained. Hydroperoxides formation was not confirmed even at lower temperatures. Induction periods and maximal rates of oxygen absorption were estimated. Activation energies calculated from temperature dependence of induction periods and of maximal rates were 19–22 kcal./mole. Addition of 0.5% of 2,2′‐methylene bis(4‐methyl‐6‐tert‐butylphenol), N,N′‐diphenyl‐p‐phenylene‐diamine, and tri‐octylphenyl phosphite extends induction period 5–50 times. Inhibitor concentration changes during the induction period led to the conclusion that after inhibitors' consumption the reaction is inhibited by the products of direct attack of oxygen on the inhibitor. This supposition was verified on using oxidized inhibitors and it was proved that these are more effective than the inhibitors of original structure.
Structure and Solution Properties of Radical‐Initiated Poly(vinyl Chloride)
Authors: Kolínsk M. , Kolínský M. , Ryska M. , Bohdanecký M. , Khatochvíl P. , Šolc K. , Lím D. 
Published: June 2010

AbstractThe dependence of the structure of poly(vinyl chloride) on precipitation conditions during polymerization was investigated. Properties of polymers prepared in 2,4,6‐trichloroheptane, 2,4‐dichloropentane, sec‐butyl chloride, and isohexane were compared. The character of the polymerization ranged from homogeneous to heterogeneous. The polymers were fractionated in the system tetrahydrofuran–water. Molecular weights of the fractions were determined by osmometry and light scattering in cyclohexanone and tetrahydrofuran. The ratio M̄w/M̄n of the fractions varied in the range 1.1–1.8. It was found that for all the polymers investigated the same relation between [η] and M̄w is valid. Samples prepared by heterogeneous polymerization to a low conversion do not therefore exhibit an appreciable amount of branching with long side chains. These results are compared with the behavior of high‐conversion polymers and of branched samples prepared by copolymerization of vinyl chloride with divinyl adipate.
Solubility and Diffusion Behavior of Benzene in a Vinyl Acetate‐Methyl Acrylate Copolymer
Authors: Garrett T. A. , Park G. S. 
Published: June 2010

AbstractEquilibrium sorption and the kinetics of sorption of benzene have been obtained in a 46% vinyl acetate‐54% methyl acrylate copolymer at temperatures from 25 to 55°C. and at equilibrium concentrations up to 0.19 volume fraction of benzene (V). The ther‐modynamic diffusion coefficient (Dt) obtained from the sorption rates can be fitted by a relationship of the kind suggested by Wilkens and Long: In Dt = In Do + AV ‐ BV2 but the data are not accurate enough for the A/B ratio to give useful information about the system. By using suitable values for Ao and Bo the relationship Dt = RT/Ao exp { ‐Bo/fv} due to Fujita enables the temperature and concentration dependence of the free volume fv to be calculated. The resulting relationship fv = 0.025 + 0.00043[T ‐ (21 ‐ 280V)] suggests a glass transition of 21°C. for the copolymer. The Flory‐Huggins interaction parameter x is calculated from the equilibrium data and the figure obtained, 0.36, is much closer to the value for polyvinylacetate than to polymethylacrylate. This is also true of the Do values.
Structure and properties of rubber networks. Part I
Authors: Meissner B. 
Published: June 2010

AbstractThe relationship between the concentration VG of elastically effective network chains and structural parameters of the network (the concentration CG of chemical crosslinks in the gel and number‐average molecular weight Mn,G of primary macromolecules in the gel) has been studied on dicumyl peroxide vulcanizates of natural rubber, both undiluted and diluted with paraffin oil prior to crosslinking. On assuming the polymer distribution of molecular weights to be of the Schulz type, the relations between the two network parameter, the sol fraction and the degree of polydispersity of the initial polymer have been derived and used for the calculation of CG and Mn,G from sol fraction data. An equation relating VG to CG, Mn,G and to the concentration E of potential entanglements has been proposed and compared with experimental data. Very good agreement has been obtained in the whole range of variables both for undiluted and diluted natural rubber, the value of E being lower in the presence of the diluent. Published experimental data on isobutyleneisoprene rubber likewise have been shown to conform to the proposed equation. A structural interpretation consistent with this equation is attempted.
Formation and properties of preswollen networks. I
Authors: Bates R. F. , Howard G. J. 
Published: June 2010

AbstractA copolymer of allyl alcohol and styrene has been crosslinked in solution by reaction with diacid chlorides. The reaction rate is first order in acid chloride but of complex order in hydroxyl. Measurements are reported of the extent of reaction at gelation and of gel time as a function of concentration and of the size of the crosslinker. The fraction of crosslinks formed intramolecularly is calculated: the value of this fraction depends strongly on dilution and, to a lesser extent, on the length of the crosslinker chain. The swelling and compressional modulus of gels prepared in solution (preswollen networks) depend on dilution and crosslinker size in the same general manner as does the fraction of intramolecular links.
Cationic polymerization of 2,5‐dimethyl‐l,5‐hexadiene
Authors: Marek M. , Roosová M. , Doskočilová D. 
Published: June 2010

AbstractThe polymerization of 2,5‐dimethyl‐l,5‐hexadiene, catalyzed with boron trifluoride and titanium tetrachloride, has been studied. The reaction was followed up in the temperature range of −78 to 20°C. in a solution of heptane, of dichloroethane, and without solvent. The polymers obtained were soluble in heptane, dichloroethane, and ether, showing only a low content of double bonds. The course of the polymerization depended on the type of catalyst and the polarity of the medium. On the basis both of the properties and the structure of the polymer it is possible to assume an intra‐intermolecular growth reaction which is cationically initiated.
The nonlinear response and rupture of lightly crosslinked elastomers
Authors: Halpin J. C. 
Published: June 2010

AbstractRecently a molecular treatment of nonlinear rubberlike viscoelasticity was advanced which centers around the precept that the nonlinear response is due to the nonlinear character of the stress‐strain curve while the relaxation mechanism remains invariant to large stress or deformations. Excellent agreement was found for highly crosslinked systems, the result being in substantial agreement with classical kinetic theory. The experimental and theoretical work presented here extends this treatment to lighter cross‐linked systems where substantial disagreement is found between classical theory and experiment. Attributing this disagreement to a deficiency in the treatment of the mechanics of long‐range motions in imperfect network structures, it is possible to outline an integrated treatment of the long time creep in the plateau region, the “C2 effect,” the tensile strength maximum as a function of the crosslink density and the so‐called “unique” properties of salt cured carboxylic rubbers. Experimental evidence is presented which shows that lightly crosslinked SBR exhibits properties indistinguishable from the salt‐cured carboxylic vulcanizates.
A modified apparatus for the fractionation of polymers by precipitation chromatography
Authors: Poláček J. , Schulz L. , Kössler I. 
Published: June 2010

AbstractA modified precipitation chromatography apparatus, designed to operate with periodie temperature changes of the entire column, permitted fractionation of larger amounts of polymer. To verify the efficiency, 5 g. of a poly(methyl methacrylate) specimen were fractionated.
Non‐newtonian viscosity of dilute polymer solutions
Authors: Subirana Juan A. 
Published: June 2010

AbstractA model is developed to calculate the influence of the shear rate on the intrinsic viscosity of dilute solutions of nondraining polymer coils. The polymer molecule is substituted by an equivalent ellipsoid with internal flow currents such that the macromolecule yields to the liquid flow and follows it up to a certain extent. The dimensions of the ellipsoid are obtained by equating the hydrodynamic deforming forces to the statistical restoring forces of the polymer chain. The intrinsic viscosity of the solution can then be calculated as a function of the shear rate.
Kinetic study of aminolysis of poly(vinylene carbonate) and related model compounds
Authors: Nemirovsky V. D. , Skorokhodov S. S. 
Published: June 2010

AbstractThe kinetics of poly(vinylene carbonate) (PVC) and ethylene carbonate (EC) aminolysis with n‐butylamine (BA) in DMF solution was investigated. The EC aminolysis is catalyzed by final product and by BA itself but the reaction kinetics follows satisfactorily the equation –d[BA]/dr = k[BA][EC]; k2 increases with an increase in the [BA]0. The rate of the PVC aminolysis is considerably higher than that of EC aminolysis under the same conditions. Comparison of these data with those on the aminolysis kinetics for several model compounds and for EC in the presence of carbamates enables one to conclude that the catalysis occurs by the opened monomeric unit adjacent to the reacting one. The catalytic action is likely to be connected with the carbamate groups.
Copolymerization of fluoroketones with vinyl acetate
Authors: Litt M. , Bauer F. W. 
Published: June 2010

AbstractWe have studied the free‐radical copolymerization of vinyl acetate (VAc) with hexa‐fluoacetone (6FK) and symdichlorotetrafluoroacetone (4FK) through the carbonyl group. The carbon of the carbonyl group is attacked by the growing radical. A strong penultimate effect was found for both copolymerizations (fluoroketone does not homopolymerize). Reactivity ratios were as follows: VAc/6FK − r1 = 0.12 ± 0.01, r1′, = 4.1† 0.5; VAc/4FK ‐ r1, = 0.41 ± 0.02, r1′, = 5.6 ± 0.3. The mechanism of chain termination is also discussed. We conclude that the main transfer step is dismutation of the fluoroketyl radical to a trihalomethyl radical and a trihalomethyl ketone polymer end.
Effect of artificial nucleating agents on polymers structure and properties
Authors: Kargin V. A. , Sogolova T. I. , Rapoport N. Ya. , Kurbanova I. I. 
Published: June 2010

AbstractThe possibility of forming and stabilizing a supermolecular structure and properties of polymers by adding small amounts of dispersive solids to them is shown. Some problems concerning the mechanism of actions of artificial nucleating agents are discussed.
Eine Neue Rechnung zur Röntgenkleinwinkelstreuung an Fadenmolekulen. Die Ermittlung der Segmentgestalt
Authors: Kirste R. G. 
Published: June 2010

AbstractThe scattering function of chain molecules in the x‐ray small‐angle range depends on the shape of the segments. For instance, one obtains quite different scattering curves from solutions of isotactic and syndiotactic poly(methyl methacrylate) (PMMA) in the same solvent. From several models of statistically coiled polymer chains, the scattering functions were calculated with the aid of the Monte Carlo method. Again, a considerable difference between the functions obtained is observed. If the curvature of a thread varies statistically from one point to another, the mean curvature can be determined from the scattering function. A suitable measure for the mean curvature is the persistence length; i.e., the chain length of which the end points form an angle whose average cosine is equal to 1/e. If the curvature is nonrandom, one can detect this from the scattering function. From the position and amplitude of the waves that appear one can determine the degree of preferred curvature. The mean curvature of a thread need not be connected strictly with the radius of gyration or with the statistical chain element of the coil. In real molecules the x‐ray optical center line is essential for the scattering behavior. On syndiotactic PMMA in solution a preferred curvature has been found. It can be interpreted by assuming the presence of helix fragments in the coils.
Some aspects of the polymerization in the solid state
Authors: Berlin Al. Al. , Trofimova G. M. , Pakhomova L. K. , Prut E. V. , Barkalov J. M. , Kuzmina S. S. , Enikolopyan N. S. , Goldanskiǐ V. I. 
Published: June 2010

AbstractThe formal kinetics of the solid‐state polymerization allowing for the specificity of the solid state as such (the long times of diffusion, anisotropy, and inhomogeneity of the solid phase) was considered. All possible changes in inhomogeneity of the system in the course of polymerization were taken into consideration. The applicability of this kinetic scheme was shown for radiation‐induced post‐polymerization and cationic polymerization of trioxane in the solid state. The occurrence of chain transfer to polydioxalane in cationic solid‐state polymerization of trioxane was proven.
The crystallization of high molecular weight poly‐(tetramethylene oxide) and related polymers
Authors: Trick G. S. , Ryan J. M. 
Published: June 2010

AbstractUsing dilatometric techniques, detailed investigations have been made of the crystallization and melting behavior of high molecular weight poly(tetramethylene oxide), low molecular weight poly(tetramethylene oxide) glycol, and a high molecular weight copolymer prepared by the chain extension of the glycol. The degree of crys‐tallinity is expressed as a function of time and temperature. Using fast melting rates, the apparent melting point of the bulk polymers has been found to depend on both the temperature of crystallization and the level of crystallization allowed to develop before melting. Extrapolation gave an estimated equilibrium melting point for high molecular weight homopolymer of about 51°C. The highest experimentally observed melting point was 43°C. Visual observations have been made on crystallization of these materials from dilute solution (⪕3%) in toluene. Under some experimental conditions crystallization was accompanied by gel formation while under other conditions two distinct and separable phases were formed. Measurements were made on the dissolution temperatures of solutions crystallized under different experimental conditions.
Bonding in Macromolecular Crystals
Authors: Livingston H. K. 
Published: June 2010

AbstractCrystallographic data show that many inorganic crystals are inorganic polymers in which chemical bonds extend across the boundaries of the crystallographic unit cell. Crystals with metallic bonds form space‐network (3‐dimensional) polymers, as do ionically bonded crystals unless there is a great disparity in ionic radii. Covalently bonded inorganic crystals may form space‐network, sheet (two‐dimensional), or linear polymers. Organic macromolecular crystals have only been fully characterized for those cases in which bonding is covalent and the structure is linear. Where ionic bonding is involved, organic macromolecules probably form “scrambled salt structures.” The relation between crystal structure and polymer structure for macromolecular crystals can be characterized by the ratio between c, the number of atoms per crystallographic unit cell, and p, the number of chain atoms per polymer repeat unit. The ratio c:p is 1:1 for many space‐network polymers, including most crystals of low symmetry. For linear polymers c:p is usually greater than 1:1. Factors contributing to the higher ratio are the number of chains passing through the unit cell and the number of substituent atoms that are attached to the polymer chain. In considering macromolecular crystals, the distinction between bond types (e.g., ionic versus covalent) is more significant than the distinction between chemical types (e.g., organic versus inorganic). Some of the most challenging problems exist in characterizing the crystals of macromolecules with intermediate bond type. Examples are gold iodide, where both covalent and metallic character must be recognized, and nylon, where hydrogen bonding is important.
Polymerization and spinning of PBI
Authors: Conciatori Anthony B. , Chenevey Edward C. , Bohrer Thomas C. , Prince Arthur E. 
Published: June 2010

AbstractThe polybenzimidazole polymer prepared by Vogel and Marvel from diaminobenzidine and diphenyl isophthalate has been scaled up and dry spun from DMAc for a full‐scale evaluation of the fiber for end uses requiring thermal stability. A process has been developed for the purification of diaminobenzidine suitable for making high molecular weight PBI. A nitrogen sweep process run at atmospheric pressure was substituted for the difficult vacuum cycle of the literature polymerization. Polymers prepared by this process had equivalent molecular weight, better solubility in DMAc, and less gel structure than those prepared in vacuum. Inherent viscosities of 0.75–0.85 and plugging values >1.0 in 97% sulfuric acid have been obtained consistently. An increase in the temperature of solutioning in DMAc was required to dissolve the higher molecular weight fractions of the polymer. Solutioning at 230°C. under pressure dissolved 95–100% of the polymer. 1–2% lithium chloride was required to prevent solution instability or “phasing‐out” of the polymer in DMAc. PBI fiber was dry spun from DMAc into a hot nitrogen atmosphere and steam stretched in tandem with spinning. Yarn was pressure washed on perforated bobbins with hot water, air dried, and oven dried prior to drawing. Drawing was performed at 520°C. and a 2:1 draw ratio. Final physical properties average 5.0 g./den. tenacity, 23% elongation, and 115 g./den. initial modulus. Small‐scale spinning of a high molecular weight fraction of polymer (ηinh = 1.2) gave fiber properties superior to those obtained from the same whole polymer (ηinh = 0.72). The bulk polymer and amorphous fiber were crystallized with phenol under pressure. An oriented and crystalline fiber was obtained by treatment of oriented fiber under pressure with phenol and water.
Continuous silicon carbide filaments
Authors: Hough Ralph L. 
Published: June 2010

AbstractCubic silicon carbide continuous filaments are prepared by vapor deposition from suitable gases upon tiny resistance‐heated tungsten wires. Homogenous deposits are prepared whenever the silicon is derived from silicon tetrachloride by utilizing hydrocarbons containing a carbonyl functional group such as acetone as the carbon source. If halogenated organosilanes are used, those with the higher halogen content produce superior deposits. The silicon carbide is near theoretical density, is highly resistant to air oxidation, and is of nominal 75–100 μ in diameter. The modulus of elasticity measures above 60,000,000 psi. Current tensile strength range above 100,000 psi with potential strengths over 400,000 psi. These filaments are intended for use as reinforcements in high strength, structural plastic composites with improved air oxidation resistance.
Preparation of graphite fibers from polymeric fibers
Authors: Ezekiel Herbert M. , Spain R. G. 
Published: June 2010

AbstractThe preparation of high tensile strength, high modulus of elasticity graphite fibers from polymeric fibers was investigated. Several polymeric yarns were subjected to TGA to 1000°C., the carbon yields of which indicated that polyacrylonitrile, an aromatic polyamide, and an aromatic polyimide were promising graphite precursors. Commercially available rayon‐derived carbon yarns from three sources were graphitized by a continuous process. Application of stress to the carbon yarns during graphitization was found to stretch the fibers and to induce high tensile strength and high moduli in the products. The increase in tensile strength and modulus were shown to be related to the degree of orientation along the fiber axis by x‐ray diffraction.