bluuebunny/crossref_metadata_2025_split huggingface dataset:
Decomposition mechanism of the cumyl hydroperoxide‐sodium methyl sulfite catalytic system in the low temperature bulk polymerization of vinyl chloride
Authors: Patron L. , Mazzolini C. , Moretti A. 
Published: June 2010

AbstractThe redox system cumyl hydroperoxide (C)‐sodium methylsulfite (A) is a very effective initiator for radical low‐temperature polymerizations. In previous works a mechanism for the decomposition of this catalytic system was suggested, but not supported by experimental evidence; owing to the high decomposition rate of the catalyst the polymerization kinetics were followed using an adiabatic reactor working as a calorimeter. The experimental results give evidence for a bimolecular mechanism of reaction between C and A giving place to oxycumyl and sulfonic radicals. The rate constant of the bimolecular reaction resulted to be 0.85 mole−1 liter sec−1 at −30°C. The activation energy, measured in the range −20 to −50°C, was calculated as 8.3 kcal/mole, in agreement with the proposed decomposition mechanism.
Über die mit titanchlorid‐triäthylaluminium katalysator initiierte propylenvinylchlorid copolymerisation
Authors: Dankovics A. 
Published: June 2010

AbstractThe copolymerization of propylene and vinylchloride with a TiCl3–Et3Al system is possible in the presence of polar complex‐forming additives. The presence of diphenylamine is nessesary but not enough to complete the reaction. If the complex‐forming ether‐amine mixture has a high mole ratio, the composition of the copolymer can be changed only in a small range. But when the ether‐amine mole ratio is low, one can change composition of the copolymer at will. The presence of the complex‐forming additives increase the conversion considerably. It is very important that the vinyl chloride be neat. If the vinyl chloride is contaminated with other chlorinated hydrocarbons, the reaction does not take place. If the vinyl chloride has a small acetylene content, it does not disturbe the copolymerization. Several properties of the copolymers change proportional to the composition. The copolymers have lower heat stability than the homopolymers.
The analysis of four point diagrams of branched, cold stretched polyethylene
Authors: Loboda‐Čačković J. , Čačković H. , Hosemann R. 
Published: June 2010

AbstractA combined analysis of small and wide angle X‐ray scattering (SAXS and WAXS) is carried out on cold stretched rods of bulk polyethylene (PE) with various branching rates (BR). If the BR is higher than 0.6%, all crystalline layer domains are always tilted against the fiber direction by about 25° around the b‐axis. For smaller values of BR, a component appears which is not tilted. This tilt is explained by the branches which are predominately located in the “amorphous phase” of the ultrafibrils. Under these assumptions, a formula is derived which shows that the 25°‐turn takes place if the mean distance between neighboring branches in a chain is so small that not more than one backfolding can take place without a branch. With increasing BR the theory predicts that the thickress of the amorphous layers becomes larger. The lateral size of the microparacrystals is always about 50 Å and defines the diameter of the ultrafibrils. During annealing, families of ultrafibrils aggregate and build up paracrystals of ∼ 100 Å lateral size and more, which turn around the b‐axis by 25° as a whole, to form paracrystalline layer domains orthogonal to the fiber.
Some peculiarities of the reaction of sulfur with rubber
Authors: Markov V. V. , Privalikhina N. P. , Zanemonets N. A. 
Published: June 2010

AbstractThe allotropic transformations of sulfur considerably affect the amount of the vulcanization heat and its changes under different phases of reactions. Heat effect depends on the chemical contents of oil plasticizers, though the last do not enter the chemical reaction with sulfur in the presence of rubber.It was supposed that plasticizers affect the nature of allotropic changes of sulfur in the initial phases of the reaction.
Study of the compatibility of plasticizers with poly(vinyl chloride) by dielectric spectroscopy
Authors: Kisbényi Mária 
Published: June 2010

AbstractDielectric spectroscopy has been applied for studying the compatibility of plasticizers with poly (vinyl chloride) as well as for detecting the phase‐inhomogeneities of plasticized systems.Commercial plasticizers having different polarity and compatibility with the polymer have been investigated. The effect of insufficient processing as well as storage and annealing on the physical structure of the compounds are also discussed.For obtaining dielectric spectra, the real and imaginary parts of the dielectric permittivity of liquid plasticizers and plasticized compounds were recorded continuously as a function of temperature in the range from −170 up to +200°C at fixed frequencies and heating‐cooling rates. Exudation, the weight loss of the plasticizer, as well as mechanical properties were measured comparatively.It is a generally accepted fact that the compatibility of a plasticizer with a given polymer depends upon their dielectric properties. According to our observations, the temperature dependence of the dielectric permittivity of the plasticizer is of great importance from this point of view, especially in the range of application of the plasticized system. Comparing the dielectric dispersion spectrum of a liquid plasticizer to that of the corresponding plasticized compound, conclusions about the compatibility can be derived. A special polarization is found to be originated from the phase‐separation and from the inhomogeneities.Besides the dielectric polarization arising from the polymer chain and plasticizer dipoles, the dielectric spectra show the existence of an interfacial, Maxwell‐Wagner type polarization, which is found to be dependent on the inhomogeneities of the texture of the compound.
Investigation of the binary system of a crystalline monomer and its polymer
Authors: Hardy Gyula , Cser Ferenc , Takács Erzsebet 
Published: June 2010

AbstractSystems formed by crystalline monomer and polymer can be characterized by their phase diagram. From the view point of the composition, this diagram can be divided into two main parts at a certain ratio designated here as Mkr. At polymer contents higher than Mkr, the system shows the behavior of plasticized polymers. At polymer ratios lower than this value, crystalline monomer appears in the system. In this latter case the phase condition means the thermodynamic relationship of the crystalline monomer and the plasticized Mkr composition polymer therefore can be explained as a solubility function.
Bicomponent fiber structures on polypropylene basis
Authors: Geleji Frigyes , Druzsbaczky Gabor 
Published: June 2010

AbstractBicomponent fibers were spun in a combination of two different polypropylene polymer melt streams. The different polymers were prepared from a single polymer by dividing the polymer flow into two streams and exposing them to different thermal influences. Individual fibers also were spun from the different polymer streams in order to investigate their molecular and mechanical properties. Mechanical properties of the bicomponent fibers and the molecular characteristics of their components were correlated.
Studies of single spherulite deformation. I
Authors: Pakuła T. , Gałeski A. , Kryszewski M. 
Published: June 2010

AbstractIn this work a mechanical model of deformation of two‐dimensional spherulites is proposed taking into consideration its two phase structure (amorphous and crystalline phase) as well as the internal radial correlation of orientation of crystalline elements. On the basis of the proposed model, assuming specific properties of amorphous and crystalline phases, the changes in shape and in internal orientation within the spherulites, related to a given strain, have been calculated. Using the derived relations the distribution of the intensity in low angle light scattering patterns on deformed spherulites has been obtained. Theoretical results were compared with these obtained from experimental low angle light scattering and optical microscope studies on deformed spherulites in polyoxymethylene.
Polymer configuration in bulk: Neutron diffraction by deuterated polymers in a nondeuterated matrix
Authors: Cotton J. P. , Farnoux B. , Jannink G. , Picot C. , Summerfield G. C. 
Published: June 2010

AbstractSmall‐angle neutron scattering (SANS) by mixtures of labeled and unlabeled polymers is determined by the “contrast factor”. A formulation of this factor and its value for deuterated‐nondeuterated polystyrene and polyethylene systems are given. Some examples of neutron scattering by these systems in the bulk and liquid states indicate that the labeled‐chain signal is important and clearly allows the determination of the single‐chain characteristics.
Property‐structure relationships in poly‐urethanes: Infrared studies
Authors: Macknight W. J. , Yang M. 
Published: June 2010

AbstractTemperature dependent infrared studies have been carried out on three series of poly‐urethanes previously synthesized and characterized. The repeat units of the three series may be schematically represented as follows: magnified image In each case n varies from 2 to 10. The H and DP series are partially crystalline while the 4M series is entirely amorphous.It was possible to draw several conclusions concerning the hydrogen bonded NH and Cbond;O groups in these polymers. These conclusions are: (1) The aromatic polyurethanes of the DP and 4M series are hydrogen bonded in the amorphous phase below the glass transition temperature, (Tg), to the extent of 75% or less whereas the aliphatic H series is completely hydrogen bonded below Tg. (2) Both the DP and H series are completely hydrogen bonded in the crystalline phase below the melting point, (Tm), regardless of the value of n. (3) A temperature dependent equilibrium between free and hydrogen bonded NH groups occurs in the amorphous phase above Tg in all three series. (4) The temperature dependences of the total area of the NH stretching bands exhibit transitions corresponding to Tg, Tm, and, in the case of the H series, to a first order crystal‐crystal phase transition, Tt. (5) The temperature dependences of the frequencies of the hydrogen bonded NH stretching vibration also exhibit transitions corresponding to Tg and Tm.
Investigation of conformations of macro‐molecules and crystalline structure of aromatic polyimides
Authors: Koltsov A. I. , Baklagina Yu. G. , Ginzburg B. M. , Korzhavin L. N. , Koton M. M. , Mikhailova N. V. , Nikitin V. N. , Sidorovich A. V. 
Published: June 2010

AbstractThe structures of four stretched polymides obtained by chemical and thermal imidization of the condensation products of pyromellitic acid dianhydride with diamines [4,4′‐diaminodiphenyloxide (PI‐2) and bis‐4‐aminophenylhydroquinone ether (PI‐3)] and of the condensation products of paraphenylene‐bis‐trimellitate dianhydride with the same diamines were studied by x‐ray analysis, polarized IR spectroscopy, and pulsed magnetic resonance. The crystalline unit cell parameters have been determined. Polymer chain conformations suggested on the basis of x‐ray analysis were supported by IR and PMR spectra. The PMR data allow us to accept the torsional oscillations of aromatic rings around their bonds with neighboring O and N atoms as the main form of molecular mobility at room temperature.
Solution behavior of ethylcellulose in organic solvents
Authors: Meyerhoff G. , Sütterlin N. 
Published: June 2010

AbstractEthylcellulose has been investigated by osmotic pressure, sedimentation‐diffusion, and light scattering measurements in dilute solutions of acetone, ethylacetate, 2‐butanol, n‐butylchloride, and benzene. Combining the results of different measuring techniques allowed the recognition and elimination of the influence of microgels present in the solution. The observed second virial coefficients are high as compared with those of the vinyl polymers and do not show a pronounced dependence on the type of solvent. On the other hand, the radius of gyration is nearly proportional to the root of the molecular weight. This behavior is discussed in connection with results on other cellulose ethers reported in the literature.
Excess functions in polymer solutions
Authors: Rätzsch Margit , Krahn Gerhard 
Published: June 2010

AbstractBy means of a modified Scatchard‐Hildebrand equation the excess Gibbs energies will be calculated for systems consisting of aromatic compounds and saturated hydrocarbons from molar volumes and solubility parameters and they will be compared with experimental data. A way of calculating the solubility parameters of high molecular hydrocarbons from solubility parameters of low molecular hydrocarbons will be suggested and the applicability of the Scatchard‐Hildebrand equation to polymer solutions will be studied.
Mechanism of the thermal degradation of poly(vinyl chloride)
Authors: Troitskii B. B. , Troitskaya L. S. , Myakov V. N. , Lepaev A. F. 
Published: June 2010

AbstractThe kinetics for dehydrochlorination and benzene formation has been studied during the degradation of two samples of poly(vinyl chloride) (PVC) at 180–200°C under vacuum with and without the removal of hydrogen chloride. The effects of various additives, such as organic phosphites, mercury, silver, gold, and glass upon the thermal degradation of PVC were investigated. Mercury, silver, and glass decrease the rate of autocatalytic dehydrochlorination of the polymer in the presence of hydrogen chloride but silver and glass do not affect PVC degradation rate in the absence of HCl. PVC thermal decomposition under vacuum with removal of HCl mostly proceeds by a molecular mechanism. At the same time, radical reactions take place. But there are some very endothermic stages of chain propagation, this is why in this case, the radical mechanism of PVC dehydrochlorination does not compete with the molecular one. In the presence of HCl, the rate of radical reactions increases and predominates over rate of molecular reactions.
Relation between thermal degradation and tacticity of PVC
Authors: Millan J. , Carranza M. , Guzman J. 
Published: June 2010

AbstractThe thermal degradation up to 0.3% at 180°C of sets of PVC prepared in such a way that samples have different tacticity has been studied by conductimetric methods. The degradation rates of PVC were found to depend on the syndiotacticity content; the plots of degradation rates as function of a tacticity parameter show a minimum at which the corresponding polymers are very stable. The kinetic results as well as the shape of UV‐visible spectra of degraded polymers suggest an influence of tactic sequences on propagation step.The degradation of vinyl chloride copolymers with diethyl fumarate, isobutylene, and vinyl bromide, having the same composition but very different tacticity in PVC sequences, was also studied under the same conditions. For each pair of copolymers, the higher degradation rate was always that of the sample having more syndiotactic sequences.
Aggregation of polyoxyethylene in dilute solutions
Authors: Carpenter Dewey K. , Santiago German , Hunt Ann H. 
Published: June 2010

AbstractLight scattering as a function of scattering angle, concentration, and temperature reveals that polyoxyethylene (POE) forms large aggregates in benzene and chloroform, while in methanol and dioxane almost complete molecular dispersion occurs. Although the solutions containing large aggregates contain a distribution of molecular weights, the angular envelopes of c/R (θ) versus sin2θ/2 exhibit pronounced upward curvature, indicating that the aggregates are dense structures such as spheres or highly branched coils. In methanol, the angular envelopes exhibit moderate downward curvature, reflecting the essentially molecularly dispersed character of the solution and the breadth of the molecular weight distribution. In filtered solutions of dioxane, a tendency exists for minima to occur in the angular envelopes; this can be rationalized in terms of the anisotropy of the scattering. The polarized components of the scattered intensity VV, HV, VH, and HH were studied in the scattering plane. For the large aggregates HV is angular dependent, while in methanol and dioxane HV is independent of angle. Heating or cooling a POE solution in benzene followed by a study of the angular envelope, shows that the aggregates are stable. Hydrodynamic measurements fail to detect the existence of the aggregates. Taking all the data into consideration, the large aggregates appear to be compact, extensively branched, anisotropic, and stable.
Kinetic discussion on the catalysis of copper‐partially‐quaternized poly‐(vinylpyridine) complexes
Authors: Tsuchida Eishun , Nishide Hiroyuki , Nishiyama Toshio 
Published: June 2010

Abstract2,6‐Xylenol was oxidatively polymerized by Cu‐poly (vinylpyridine) (PVP) complex or Cu‐partially‐quaternized PVP (QPVP) complex in a homogeneous dimethylsulfoxide solution, and the mechanism of the catalysis of the polymeric Cu complexes was discussed. The polymerization rate increased in the following order: Cu‐pyridine <Cu‐PVP<Cu‐QPVP. The catalytic activity of the Cu‐QPVP complex exhibited a maximum in the region where the percentage of quaternization of QPVP was 20‐50% and tended to increase with the degree of polymerization of QPVP. Considering through the kinetic constants of the polymerization, the neutral salt effect, and the influence of the monomer species, it was cleared that the higher activity of the Cu‐QPVP catalyst was attributed to the electrostatic interaction between the QPVP complex and the anionic monomer. That is to say, the intermediate complex, to which xylenol is coordinated, is enthalpically stabilized due to the electrostatic field of the QPVP complex. Activation entropy ΔS† of the polymer catalyst was larger in comparison with the monomeric analog, and the larger ΔS†S was observed in the PVP system and the neutral‐salt‐added QPVP system, of which structures were compact. It is considered that the frequency factor of the dissociation step of the activated monomer increases because of the high density of cupric ion in the polymer complex.
Butadiene‐propylene alternating copolymers
Authors: Furukawa Junji 
Published: June 2010

AbstractA general account is given of the alternating copolymer of butadiene with propylene. The copolymerization can be carried out at low temperature in the presence of V‐ or Ti‐based, modified Ziegler‐Natta catalyst which is prepared at a very low temperature (‐70°C). The structure of the copolymer was investigated by ozonolysis and 220 MHz NMR spectroscopy. A high degree of alternation, more than 97%, has been confirmed. For copolymerization a mechanism involving alternating coordination of olefin and diolefin is proposed. Finally, physical properties such as green strength, dynamic moduli, processability, etc., are illustrated in an application as a synthetic elastomer. The copolymer exhibits high strength and elongation at break perhaps because of induced orientation. The stress‐strain behavior is discussed in terms of a theory of elasticity and it is concluded that the alternating copolymer may have a flexible chain in spite of the trans‐structure of the butadiene unit.
Effects of gamma radiation on copolymers of styrene and methyl methacrylate in the solid state
Authors: Busfield W. K. , O'Donnell J. H. 
Published: June 2010

AbstractRandom copolymers of styrene and methyl methacrylate, prepared by free radical polymerization in bulk at 60°C, were irradiated under vacuum at 35°C with 60Co gamma rays to doses up to 200 Mrad. The flexural strength, with failure occurring in all cases by brittle fracture, decreased with radiation dose; the rate of this decrease increased with increasing methyl methacrylate content. Compressive strength measurements showed a transition from yield to fracture after a radiation dose which increased with styrene content and then a rapid fall in fracture stress for higher doses. Viscometry measurements showed a good correlation between changes in flexural strength and molecular weight.
Hydrobromation des Polyalcadiènes par les Réactions Couplées D'Hydroboration et de Bromation
Authors: Pinazzi C. P. , Derouet D. , Brosse J. C. 
Published: June 2010

AbstractL'hydrohalogénation spécifique totale, à l'aide des réactions couplées d'hydroboration et de bromation a été étudiée sur des polybutadiènes et des polyisoprènes de synthèse, de faible masse moléculaire et de microstructure définie. L'hydrohalogénation, à l'aide de ce type de réactions, comprend d'abord l'hydroboration des doubles liaisons carbone‐carbone à l'aide du bora‐9 bicyclo [3.3.1] nonane et, ensuite, la bromation par le brome de l'organoborane macromoléculaire formé. Le brome se fixe en position Anti‐Markovnikoff, par rapport à l'alcène de départ.Les résultats obtenus ont permis de noter que les doubles liaisons carbone‐carbone internes (microstructures‐1,4) étaient beaucoup plus réactives que les doubles liaisons carbone‐carbone terminales (microstructures‐1,2 et ‐3,4) et que, plus le polyalcadiène de départ était riche en motifs‐1,4, plus le taux de motifs hydrobromés était élevé. En outre, les polymères hydrobromés formés à partir de polyalcadiènes de microstructure‐1,4 prédominante sont beaucoup plus faciles à isoler et à purifier.
Polycondensation, D'Acides α‐Aminés à L'Aide D'Un Couple Oxydant‐Reducteur (Hg++ OU I2 — Phosphites)
Authors: Guilly Lionel Le , Spach Gerard 
Published: June 2010

AbstractOn a montré que l'action d'un couple d'agents, l'un oxydant (Hg++ ou I2) et l'autre réducteur (phosphite de diéthyle) sur des acides α‐aminés libres en milieu pyridine conduit à la formation de polypeptides. La signification prébiotique d'un tel système est discutée.
Synthesis and characterization of heat‐resistant aromatic and benzothiazolic linear polyethers
Authors: Blaise C. , Bouanane A. , Brembilla A. , Lochon P. , Neel J. 
Published: June 2010

AbstractA series of high molecular weight polyethers has been prepared by polycondensation of alkaline bisphenoxides with various reagents containing two 2‐chlorobenzothiazolic moieties. A general scheme for the synthesis of these heterocyclic bifunctional derivatives is given and a preliminary kinetic study is reported which demonstrates that they are sufficiently reactive to polycondense readily with bisphenoxides. Details are given of the polycondensation procedure (solvent, concentration, temperature, polycondensation period, yield in polymer recovered). The assumed structures of the resulting polymers were corroborated by elemental analysis and infrared spectroscopy (by comparison with the spectra of low molecular weight analogous model compounds). The new polyethers generally display a good solubility in solvents such as tetrachloroethane, dichloroacetic acid, N‐methyl‐2‐pyrrolidone, sulfolane, quinoline, and pyridine. Colorless and transparent films were readily cast from these solutions. Thermal properties of these materials were evaluated by thermogravimetric analysis and differential thermal analysis carried out with powdered samples. Most of them proved to be stable when heated in air around 350°C.
Utilisation De La Chromatographie Sur Gel Dans Le Domaine Des Molecules Organiques De Forte Masse Et Des Macromolecules De Faible Masse
Authors: Aurenge J. , Gallot Z. , de Vries A. J. , Benoit H. 
Published: June 2010

AbstractOn a cherché à étendre l'utilisation de la chromatographie sur gel au domaine des molécules organiques de forte masse et des macromolécules de faible masse. On a montré que l'etalonnage universel en volume hydro dynamique et l'etalonnage en volume molaire peuvent ětre utilisés dans le cas des petites molécules si la séparation sur le support chromatographique n'est pas perturbée par des phénomènes d'adsorption.