bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on polymerization of N‐vinylcarbazole in the presence of some hydrogen halides
Authors: Pielichowski Jan 
Published: June 2010

AbstractStudies on N‐vinylcarbazole polymerization were carried out in the presence of HF, HCl, HBr, and HJ using a variety of solvents. It was found that in the CCl4 solvent, each of the hydrogen halides cause polymerization of N‐vinylcarbazole, the obtained polymer including equimolar proportions of hydrogen halide and of N‐vinylcarbazole.To determine the influence of solvent polarity, some studies on the polymerization of N‐vinylcarbazole influenced by HCl were carried out in the following solvents: carbon tetrachloride, acetone, and methanol. A pronounced contribution of the solvent to the polymerization course was found. A polymerizate including a small proportion of the complex‐bonded HCl was obtained when using acetone or methanol solvent.Irrespective of the nature of the solvent used, the appearance of a green color was observed in all instances; hereafter the solution turned brown accompanied by the polymer precipitation.The polymerization proceeds without any disturbances in the presence of some species that capture the radicals, this being evidence for the ionic nature of the mechanism.Based on the UV and ESR spectra analyses, it was found that some change‐transfer complexes are formed during polymerization. The result obtained make us accept the following mechanism of N‐vinylpolymerization in the presence of hydrogen halides, depending on the reaction medium.Based on the results given, the following conclusions referring to the N‐vinylcarbazole polymerization process in the presence of some hydrogen halides can be drawn. In the early stage of polymerization of N‐vinylcarbazole, the initiation by means of HX occurs and hereafter the polymer is formed. Then, in a nonpolar medium, a charge‐transfer complex of the polymer with hydrogen halide is formed. On the other hand, in a polar medium, this complex cannot be formed.
Synthesis and characterization of poly (phenyl methacrylates)
Authors: Wesslén Bengt , Gunneby Gunilla , Hellström Gunnar , Svedling Per 
Published: June 2010

AbstractPhenyl methacrylate (PMA), as well as its 2‐ and 4‐methoxy analogs (2‐MeOPMA and 4‐MeOPMA, respectively) were polymerized by free radical and anionic polymerization reactions. On anionic polymerization in toluene termination reactions occurred, and polymers were obtained only from PMA and 4‐MeOPMA. Polymers with relatively narrow molecular weight distributions were formed on anionic polymerization in tetrahydrofuran.The steric structures of the polymers were determined from 100 MHz NMR spectra. Polymers obtained by free radical polymerization were found to be predominantly syndiotactic. Anionic polymerization in toluene produced highly isotactic polymers, while the use of tetrahydrofuran as a solvent gave syndiotactic polymers. Glass transition temperatures of the syndiotactic polymers were generally higher than those of the isotactic ones.
Adsorption of polymers on clays
Authors: Schamp N. , Huylebroeck J. 
Published: June 2010

AbstractAdsorption of polyacrylamide with varying molecular weight on clays has been measured. Adsorption on peptized versus flocculated clays differs in amount, in kinetics, and in dependence on molecular weight and temperature. Therefore, distinction is made between surface adsorption and pore adsorption. Adsorption isotherms fit Langmuir equation but contain a minimum, which is explained by a kind of phase transition in polymer solution between an inhomogeneous system with separate polymer coils and a homogeneous system where all of the space is filled with coils.
Renforcement des elastomeres par des particules spheriques
Authors: Evrard G. , Nottin J. P. 
Published: June 2010

AbstractIn the course of a systematic investigation of reinforcement of elastomers, we studied the properties of model composites made of a rubbery matrix and spherical particles with several diameters and various level of adhesion to the matrix. Mechanical properties measured at very small strain are independant of particle size and adhesion, but under large extension reinforcement is more effective with smaller spheres and stronger adhesion. A partial correlation is found between dewetting of particles and loss of reinforcement efficiency.
Some peculiarities of relaxation and structure‐forming processes in polymer boundary layers
Authors: Malinsky Yu. M. , Prokopenko V. V. , Titova N. M. , Areshidze M. G. , Epelbaum I. V. 
Published: June 2010

AbstractThe relaxation processes are retarded when the polymer interlayer in adhesive joints is diminished to a few microns. This retardation shifts the maximum on the temperature vs strength curve of such joints (under considerable overstresses) toward higher temperatures, and secondly, reduces the effectiveness of “rest” responsible for the partial strength recovery of the specimen in which rupturing crack propagates.In many systems the rate of polymer spherulite linear growth (G) diminishes with decreasing thickness of the polymer film (δ) from 15 to 30 μ. This was observed for isotactical polypropylene (PPr) and polystyrene, polyformaldehyde, cellulose tribenzoate, guttapercha, polypropyleneoxide (PPO), and polyethylenesebacynate (PES) on silica glass; PPr on copper, low‐melting metal alloys (in crystalline or liquid state), various crystallo‐graphic planes of NaCl, and planes (100) of CaF2 and LiF. The magnitude of G did not depend on δ in the crystallization of PPr, PPO, and PES on polyvinylacetate, polyvinylbutyral, crystalline and liquid low‐melting mixtures of inorganic salts. Inhibition of spherulites growth in polymer boundary layers is strongly influenced by the surface energy irrespective of the phase or aggregate state of the substrate. The retarded growth of spherulites is probably due to the reduced density and lower mobility of polymer in the boundary layers.
Effect of pressure on the crystallization of polyethylene
Authors: Kanetsuna H. , Mitsuhashi S. , Iguchi M. , Hatakeyama T. , Kyotani M. , Maeda Y. 
Published: June 2010

AbstractCrystallization of polyethylene under pressure has been studied systematically with regard to the structure of the resultant crystal. It was found that in the isothermal crystallization under pressure, alteration of the form of the crystals from folded to extended occurred above certain pressures within a relatively narrow temperature range. The highest temperature that allows isothermal crystallization increases linearly with the pressure, while the lowest temperature to give the extended‐chain crystals increases rather slowly with pressure, widening the temperature range to give the extended‐chain crystals. The least pressure required was found between 2000 and 3000 kg/cm2 for the polymer studied in this work. It is considered that control by a particular nucleation or growth mechanism, different from the ordinary folded‐chain type crystallization and possibly the formation of bundle‐type nucleus is more likely than the effect of annealing or secondary growth of once folded molecules.
Diffusion of gas through polymer bulk: Computer simulation approach
Authors: Jagodic F. , Borštnik B. , Ažman A. 
Published: June 2010

AbstractThe diffusion of a gas through the polymer (polyethylene) bulk is calculated in two steps. In the first part, the amorphous phase of the polymer chains, at appropriate temperature and density, is generated using the Monte Carlo method on the tetrahedral lattice. The ground state is then obtained by the inclusion of the interchain forces. Using the energy surfaces from the first part, the energy barriers, modified by the interaction detween gas molecules (argon) and the polymer chains, are deduced. These values are the basis for the calculation of the diffusion coefficient.
Light scattering, turbidity, and conservative dichroism of suspensions of anisotropic particles in an electrical field
Authors: Ravey J. C. 
Published: June 2010

AbstractUsing the Rayleigh‐Gans approximation and expressions for the mean amplitudes (Evv,…,EHv) induced in rigid anisotropic particles which are arbitrarily oriented, one can calculate the four “components” of the light scattered in an arbitrary direction of space. Likewise, using these relations, the turbidity and the “conservative dichroism” of suspensions of anisotropic particles, partially of fully oriented, are studied, and in any case are calculated.
Thermal stability of melamine formal‐dehyde resins
Authors: Manley T. R. , Higgs D. A. 
Published: June 2010

AbstractThe temperatures given for the decomposition of melamine formaldehyde (MF) resins cover a wide range. An investigation of this decomposition using DTA, TG, EGD, and infrared techniques has shown that these variations are due to different criteria of stability and to errors in interpretation of thermoanalytical results.There is considerable loss of formaldehyde at 200°C which makes this the maximum temperature for the use of MF resins in paints. Contrary to earlier results the triazine ring is not decomposed below 400°C and the main decomposition reaction is the breaking of methylene bridges around 380°. Under oxidative conditions the decomposition occurs at lower temperatures but the mechanism is not yet clear.
Study of destruction process of organotin derivatives of copolymers on basis vinyl‐chloride and unsaturated acids
Authors: Rzaev Z. M. , Mamedova S. G. 
Published: June 2010

AbstractRadical copolymerization has been investigated between vinylchloride and organotin (lead) derivatives of unsaturated acids (bis‐triethyl‐stannylmaleate, β‐phenyl‐tri‐n‐butylstannylacrylate, and tri‐n‐butylstannylmethacrylate and their organic analogs (maleic anhydride andn‐butylmethacrylate). The esterification has been studied of copolymers of vinyl‐chloride and unsaturated acids by organic, organotin (lead) hydroxyl containing compounds and the latter dehydration productsbis‐trialkyltin oxides. The probabilities of forming various compositions (F(M)n, fM1‐M1, fM2‐M2fM1‐M2, or fM2‐M1) in copolymers have been calculated as well as probability of distributing monomer units along the macromolecular chain. Symbat relationship has been established between the probability of forming fM1‐M2and fM2‐M1compositions and thermo‐ and light‐stability of copolymers. The compositions of organotin comonomers and their copolymers with vinylchloride have been investigated. The stabilizing effect of organotin (lead) comonomers in their copolymers with vinylchloride has been revealed, consisting in coordinate interaction of metal atoms with chlorine substituents. The method has been worked out for examing light‐ and thermo‐stability of organotin (lead) copolymers. The stabilizing action of the side organotin (lead) groups on the starting temperature of copolymers, as well as on the induction period duration and the total rate of HCl isolation, has been determined. The occurrence of intermolecular coordinate bonds in the synthesized copolymer macromolecules has been revealed, this fact being the cause of a marked decrease in the copolymers dehydrochlorination rate.
Thermal relaxation and glass transition in polyethylene
Authors: Chang Shu‐Sing 
Published: June 2010

AbstractThermal relaxations in the glass transition region can be observed as spontaneous temperature drifts of the sample under adiabatic conditions. Upon the heating of a quenched glass, positive drifts are observed reaching a peak at some temperature just below its Tg. An annealed glass produces a peak in the negative drift at temperatures just above its Tg. Heat capacity measurements have been made on three linear polyethylene samples having 71 to 96% crystallinity and on one branched polyethylene sample, in an adiabatic calorimeter from 2 to 360 K. In all four samples, temperature drifts were detected with peaks occurring around 235–240 K. The temperature of the peaks is not significantly affected by the degree of crystallinity. However, the magnitude of the peaks decreases as the crystallinity is increased.
Experiments for teaching polymer characterization
Authors: Collins E. A. , Baresš J. , Billmeyer F. W. 
Published: June 2010

AbstractA laboratory manual has been published containing over twenty experiments on polymer characterization, including measurement of molecular weight and distribution, thermal properties, morphology, and mechanical properties. Although written for immediate use in a polymer science laboratory course, the book should find wide use for the instruction of industrial laboratory assistants and by the chemist or engineer who wishes to familiarize himself in further detail with the field.This paper will discuss both the philosophy of the book and the details of selected experiments, all of which have been tested in a graduate laboratory. The main text of the book provides background information on synthesis (experiments in synthesis are also included), a minimal scheme for the characterization of a new polymer, and equipment, theory, data treatment, and limitations for each characterization method for which there is an experiment. Wherever appropriate, a numerical data set is worked through in complete detail from instrument readings to final results. The format of the experiments proper, like those of ASTM and many industrial methods, is kept free of nonessential material and is written in simple stepwise form for direct reference during the experiment. Alternate procedures are included in some cases where more than one type of commercial equipment is in widespread use.
Effect of copolymers containing imidazole and mercaptan functions on ester hydrolyses
Authors: Overberger C. G. , Pacansky Thomas J. , Lee J. , St. Pierre T. , Yaroslavsky S. 
Published: June 2010

AbstractCopolymers containing imidazole and mercaptan groups were investigated as possible synthetic models for the proteolytic enzymes, ficin and papain. Three different types of thiol‐protecting groups were screened to prepare the polymers containing free mercaptan functions: a base‐sensitive group (vinyl thiolacetate), an acid‐sensitive group (methoxy‐methyl vinyl sulfide), and a heat‐sensitive group (S‐vinyl‐O‐f‐butyl thiocarbonate). Removal of the acetyl group occurred in water at neutral pH, presumably due to some intramolecular imidazole catalysis. Similar deacylation steps might follow the acylation of the thiol groups for the copolymers containing imidazole and thiol functions during ester hydrolysis. Acylation rates (rates of ester hydrolysis) for poly(vinyl mercaptan) and several copolymers were studied as a function of pH and copolymer composition. Indications for cooperative effects and apolar binding effects are discussed.
Reactions of epoxide groups of glycidyl methacrylate copolymers
Authors: Kalal J. , Švec F. , Maroušek V. 
Published: June 2010

AbstractAn investigation was made of polymer‐analogous reactions of the epoxide ring bound to the polymer chain with a number of agents such as amines, diamines, hydroxyamines, carboxylic acids, phosphoric acid, phosphorus pentoxide, thiourea, etc. The polymers used were homogeneous or slightly reticular gels. All reactions were considerably affected by the type and thermodynamic quality of the solvent. Reactions with the amino compounds were greatly dependent on their basicity and on the size of the alkyl groups. By using diamines one can obtain a material containing free amino groups capable of further reactions. A sufficiently high conversion of the reaction of the epoxide group with carboxylic and mineral acids could be achieved only in an anhydrous medium. In other media acid‐catalyzed hydrolysis predominated, along with the required addition reaction. If the reaction mixture was treated with thiourea and then left to react with hydrogen sulphide, a polymer gel was formed containing two vicinal thio groups able to bind heavy metals.The reactions described show that the epoxide group bound in the copolymer allows a number of reactions which lead to products with properties markedly different from the starting material.
Dynamic viscoelastic behavior of polybutadiene networks
Authors: Kraus Gerard , Rollmann Kent W. 
Published: June 2010

AbstractDynamic viscoelastic properties of polybutadiene networks, prepared by conventional sulfur vulcanization of polymers differing in primary molecular weight, molecular weight distribution, long‐chain branch content, and branching pattern, were measured in the region of the viscoelastic spectrum of principal interest in dynamic applications of rubbers. At lower frequencies, the storage compliance was found to correlate closely with the fraction of free (terminal) chains in the network, while the loss compliance could be correlated with either the free end fraction or with the fraction of chain entanglements not trapped into the network by primary valence crosslinks. At higher frequencies, approaching the plateau region of the viscoelastic spectrum, effects of network structural features diminished as contributions of untrapped entanglements became more pronounced. Networks prepared in presence of a diluent exhibited the same trends as pure gum vulcanizates. Carbon black produced a leveling effect, ascribed to a second entanglement entrapment mechanism by adsorption sites on the filler surface.
A collaborative study of capillary flow of a highly lubricated unplasticized poly (vinyl chloride)
Authors: Wales J. L. S. 
Published: June 2010

AbstractViscometric measurements carried out by ten members of the IUPAC Working Party “Structure and Properties of Commercial Polymers” is summarized and discussed. The participants in the study carried out steady flow measurements with capillary, slit, cone‐and‐plate and concentric cylinder apparatuses. Dynamic viscosities were determined with the Contraves Balance Rheometer.In this study a highly lubricated material with a relatively low molecular weight was chosen: highly lubricated to aid slip, low molecular weight to obtain a thermal transition at a relatively low temperature.The influence of capillary length and diameter on the flow curve has been the main subject of this study. Information supplementary to this was obtained with the other equipment.Above 180°C it was found that the flow curves obtained by the participants were consistent when account was taken of the lengths and radii used by the respective participant. The reason for this seemed to lie in the effect of hydrostatic pressure on the viscosity. There was no evidence at these temperatures of slip at the capillary wall. A change in the radius of the capillary did not alter the measured flow curve except at high shear rates when the effect of shear heating could be seen.Below 180°C there were indications that wall slippage or other, possibly structural, changes were taking place. However, strong evidence for this was not found by all participants and in some cases the findings were even contradictory.
Recent advances in ziegler polyolefin processes
Authors: Weissermel K. , Cherdron H. , Berthold J. , Diedrich B. , Keil K. D. , Rust K. , Strametz H. , Toth T. 
Published: June 2010

AbstractThe present status and future aspects of polymerization of ethylene and of propylene are reviewed. Main emphasis is directed towards catalyst development, but the general features of some new polymerization processes are also described.
Étude Spectroscopique De La Formation De Complexes Par Liaison Hydrogène Entre La Polyvinylpyrrolidone Et Des Acides Carboxyliques Perfluorés
Authors: Léty‐Sistel Chantal , Sébille Bernard , Quivoron Claude 
Published: June 2010

AbstractNous avons étudié par spectroscopie infra‐rouge, la formation de complexes par liaison hydorgène entre la polyvinylpyrrolidone et les acides trifluoroacétique, perfluoropropionique et perfluorobutyrique en solution dans des solvants halogénés. L'association est quantitative et aboutit à la formation de complexe 1:1 dans tous les cas. L'augmentation du nombre d'atomes de fluor tend à favoriser l'etablissement d'une structure particulière du complexe.
Curing of epoxy resins. I. Statistics of curing of diepoxides with diamines
Authors: Dušek K. , Ilavský M. , Luňak S. 
Published: June 2010

AbstractThe curing of epoxy resins with amine curing agents has been statistically treated as irreversible alternating polyaddition with the aid of the theory of cascade processes for cases when the polymerization of epoxy groups and cyclization are negligible. The coefficients of vectorial generating functions are obtained by solving kinetic differential equations. The solution has been carried out for the reaction of diepoxide with diamine with an independent reactivity of epoxy groups in diepoxide and amino groups in diamine, but with a different reactivity of hydrogen atoms in the primary and secondary amino group. Relationships have been derived for changes in the molecular weight averages, in the sol and gel fractions and their composition, and in the concentration of elastically active network chains as a function of conversion. The conditions for the gel point have been determined. The structural parameters depend on the ratio of the rate constants of hydrogen atoms in the primary and secondary amino group, k2/k1 = r, and on the stoichiometric ratio of functionalities. In a stoichiometrically equivalent system the critical conversion at the gel point increases from 1/2 for r → oo up to (1/2) (51/2 – 1) for r → 0. The critical stoichiometric ratio for gel formation at full conversion of (epoxide) functionalities in deficiency is < 3 or > 3 for r < 1 or r > 1, respectively.
Cyclization in crosslinking polymerization. I. Chain polymerization of a bis unsaturated monomer (monodisperse case)
Authors: Dušek K. , Ilavský M. 
Published: June 2010

AbstractCyclization in the chain polymerization of bis unsaturated monomers has been treated by cascade formalism based on primary chains for a kinetically controlled reaction. The primary chains consist of repeat units bearing an unreacted (pendent) double bond and units engaged in effective branchings (crosslinks), or cycles. Calculation of the participation of the units of individual types is based on the probability for growing macroradicals of different lengths to react with double bonds of the monomer, or attached to other (branched) macromolecules, or with double bonds on the same growing macroradical and on primary chains already attached to it (multiple crosslinking). The cyclization probability is controlled by the conformational statistics of the linear sequence of bonds between the reacting functionalities. Correlations due to already existing cycles are not considered. Differential increments of units of different types are integrated. Relationships have been derived which characterize the degree of unsaturation, cyclization, and effective branching as a function of the degree of polymerization of the primary chains, chain flexibility, dilution, and conversion up to the gel point, and conditions for the gel point. In this part, systems with monodisperse primary chains have been treated, two variants for the calculation of the cyclization probability based on the average and variable composition of the growing macroradical have been discussed, and the effect of multiple crosslinking has been evaluated.