bluuebunny/crossref_metadata_2025 huggingface dataset:
Effet de la Tacticité de l'Acide Polyméthacrylique sur la Vitesse de Formation de Chelates avec les Ions Cu2+
Authors: David C. , De Pauw A. , Geuskens G.
Published: June 2010

A kinetic study of chelate formation between polymethacrylic acid (PMA) and Cu2+ ions has been done to determine the influence of tacticity on reactivity. The metallic‐ion concentration was kept very low and constant during the reaction by means of an ion‐exchange resin. The experimental results show that isotactic PMA is about 1.5 times more reactive than syndiotactic PMA. The activation energies are respectively 6 ± 1 and 7 ± 1 kcal./mole.
Préparation et Caractérisation d'Hétéropolymères Greffés
Authors: Gallot Yves , Grubisic Zlatka , Rempp Paul , Benoit Henri
Published: June 2010

An anionic grafting process that operates by means of a reaction between a carbanionic endgroup of a living polymer and an electrophilic grouping located on another polymer chain has been applied to the synthesis of graft copolymers of extremely high molecular weights. The polymers obtained have been characterized and fractionated. Their radii of gyration are small compared with those of linear macromolecules of the same molecular weight but higher than those of the backbone chain from which they derive. The same method has been applied to the synthesis of heterograft polymers; in that case a three‐block copolymer is chosen as backbone, the two outer blocks bearing electrophilic groupings. The grafting degrees which were reached here are higher than those obtained in the case of homopolymeric backbones. Nevertheless, fluctuations in composition and polydispersities remain of the same order of magnitude. The highly branched structure of the macromolecules obtained is shown by viscosimetric measurements and by the retention times of gel permeation chromatography. The “viscosimetric volumes” of the solvated particles are correctly located on the GPC calibration curve.
Polymerization by Visible Light
Authors: Bleha M. , Lím D.
Published: June 2010

Photopolymerization of methyl methacrylate initiated by labile azo compounds absorbing in the range of visible light was studied. The activation energy of the decomposition of the initiators used is much lower than the energy corresponding to the light absorbed. The results were compared with diacetyl‐initiated polymerization and made possible the conclusion concerning the relation between the structure and the initiation capability.
Molecular changes in the high‐temperature degradation of gelatin
Authors: Donnelly T. H. , Kauffman F. L. , Arendovich P.
Published: June 2010

In a search for a correlation of commercial gelatin test results (Bloom jelly strength and viscosity) with molecular properties, molecular weight distributions were estimated and related to intrinsic viscosities on separate gelatin solutions heated at 95°C. and pH 3.9 for graded periods of up to 48 hr. Number‐average molecular weights based on the estimated distributions were used for estimating the number of groups available for formol titration as a check on the procedure, while solution viscosities were compared with those calculated from the distributions. The need for further work and also the necessity of recognizing the essential polyelectrolyte character of much commercially tested gelatin is apparent.
Thermal degradation of poly(α‐methyl styrene) in a closed system
Authors: Jellinek H. H. G. , Kachi H.
Published: June 2010

Poly(α‐methyl styrene), produced in various ways, was degraded in a closed system over a range of temperatures from 260 to 320°C. in the absence of air. Except for the initial parts of the degradation reaction (up to about 20% conversion to monomer), all samples had a random initiation reaction, followed by a depropagation step with a number‐average kinetic chain length larger than the number‐average polymer chain length. The energies of activation, after the initial part of the degradation, were all of similar magnitude (ca. 63 kcal./mole) and agreed with values found by previous workers. A few samples showed distinct maxima during the first 20% conversion in their curves of rate of monomer versus conversion, whereas others showed only constant rates or slowly decreasing rates during the initial periods of the reaction. The latter rates can be accounted for by chain‐end initiation (kinetic chain length ≫ polymer chains) or by a random initiation process followed by depropagation and disproportionation as termination reaction. The initial maxima found in some samples could be accounted for by a theory of random initiation in conjunction with a number‐average kinetic chain length larger than the polymer chains, which is inhibited by a reaction of polymer radicals with catalyst fragments. The inhibitor is consumed during the reaction.
The role of anomalous addition reactions in copolymerization processes
Authors: Lyubetzky S. , Goldenberg A. , Duntoff F. , Erussalimsky B.
Published: June 2010

The presence of anomalous sequences of the type CH2CHXCH2CH2CHXCH2 in copolymers of ethylene with vinyl chloride, vinyl acetate, and trifluoropropylene is established. A kinetic scheme is proposed, which takes into account the propagation reactions of anomalous growing chains. With the use of this scheme an equation for the copolymer composition is obtained and compared with the Mayo equation. The concentrations of single CH2 groups and of the sequences (CH2)2 and (CH2)3, found by infrared spectra, are used for calculating the constants of the above‐mentioned equation. The calculated values are in satisfactory agreement with the experimental ones.
Copolymerization of ε‐caprolactam with C‐methylcaprolactams
Authors: Čefelín P. , Schmidt P. , Šebenda J.
Published: June 2010

In polymerizations ε‐caprolactam and C‐methylcaprolactams differ by their equilibrium parameters. In the copolymerization of caprolactam with α‐methylcaprolactam in the amorphous phase the equilibrium concentrations of monomers do not change proportionally to the composition of the initial mixture and show a wide minimum. If in copolymerization the respective monomer were in equilibrium with the corresponding structural unit, this finding could be explained by a change of the number of structural units forming the average unit of the macro‐Brownian motion (segment). In the composition range where block grouping of the same structural units does not occur in random copolymer, the segment concentration acquires a characteristic constant value.
Polymerization of p‐methacrylyloxybenzoic acid in mesomorphic and in liquid states
Authors: Amerik Yu. B. , Konstantinov I. I. , Krentsel B. A.
Published: June 2010

The polymerization of p‐methacrylyloxybenzoic acid in the liquid crystalline state (dissolved in p‐cetyloxybenzoic acid) and in the liquid state (solution in dimethylformamide) was studied. The polymerization of p‐methacrylyloxybenzoic acid in the liquid phase is characterized by regularities usual in the radical homogeneous polymerization of vinyl monomers in isotropic mediums. At temperatures above 100°C. incomplete conversion is observed, which is explained by polymerization–depolymerization equilibrium. The polymerization of p‐methacrylyloxybenzoic acid in the liquid crystalline phase is characterized by a considerable increase in polymerization rate and polymer molecular weight (Mw = 6 × 105) over the liquid‐phase polymerization in DMFA (Mw = 5 × 104). The polymerization rate in liquid crystalline state does not depend on conversion degree and remains constant up to 70–75% conversion. The rate of polymer formation depends only slightly on the initial monomer concentration at the change of [M0] from 1.3 to 3 moles/l. The molecular structure of the mesomorphic phase also creates favorable thermodynamic conditions for the formation of macromolecules. At all T < Tceiling practically complete conversion of monomer into polymer is observed, which is impossible with homogeneous polymerization in solution.
Photochemical synthesis of block copolymers
Authors: Dhanraj J. , Guillet J. E.
Published: June 2010

A new photochemical synthesis of block copolymers is described. Polyesters are prepared containing γ‐keto pimelic acid. This provides ketone carbonyl functions along the backbone of the polymer chain. When irradiated with ultraviolet light in the presence of a vinyl monomer such as methyl methacrylate, free radicals are formed by the scission of the main chain of the polyester at the ketone groups. These radicals initiate the polymerization of the vinyl monomer to form a block copolymer. If light is used which is absorbed by the ketone group but not the vinyl monomer, and no transfer occurs, only block polymer is formed. The quantum efficiency for initiation (2.4 × 10−4) is low compared with that for chain breaking (4.0 × 10−3) indicating the possibility that the addition of polymer radicals to the vinyl monomers may be a relatively inefficient process. The activation energy for the block copolymerization of methyl methacrylate is 3.7 kcal./mole which is very similar to that observed in the photopolymerization of this monomer with conventional sensitizers.
Solution properties of chlorinated stereoregular polybutadienes
Authors: Takeda Masatami , Endõ Ryūichi , Matsuura Yoshikatsu
Published: June 2010

Commercial samples of cis‐1,4‐polybutadiene and trans‐1,4‐polybutadiene have been chlorinated with chlorine gas in a chloroform solution and precipitated with methanol. The precipitates were thoroughly washed with a large amount of methanol and dried in vacuum at 40°C. The samples were fractionated with the tetrahydrofuran‐water system at 40°C. The viscosity measurements were made at 30°C. in various solvents. The light‐scattering measurements were made with a modified Brice‐type light‐scattering photometer with unpolarized blue light and with a cylindrical cell, over the angular range from 35° to 145°, at room temperature. The relation between the intrinsic viscosity and the molecular weight was obtained for each sample. The unperturbed mean‐square end‐to‐end distance was estimated by the Stockmayer‐Fixman equation, and was used for calculating the conformational parameter \documentclass{article}\pagestyle{empty}\begin{document}$ \sigma = \;(\overline {r_0 ^2 } /\overline {r_{0f} ^2 })^{1/2} $\end{document} for each chlorinated sample. The relation between the chemical configuration and the chain conformation for each chlorinated sample was discussed in terms of the unperturbed molecular dimension and rotational isomers of model compounds for a rotation around the CC bonds in the main chain.
Osmotic pressures of moderately concentrated polydimethylsiloxane solutions
Authors: Kuwahara Nobuhiro , Okazawa Tadahiro , Kaneko Motozo
Published: June 2010

Osmotic pressures of polydimethylsiloxane in chlorobenzene, toluene, and cyclohexane were measured over a wide range of concentration (0 < v2 < 0.25). A peculiar behavior of an apparent second virial coefficient, observed by others, was not observed in a transition region (c ≈︁ 0.05). The data were used for evaluating the excluded‐volume parameter z. The theories of the excluded‐volume effect were tested with the z values estimated. In the limit of z examined the modified Flory‐Fox relation seems to fit the observed dependence of the expansion factor α03 on z.
Critical factors affecting chemical reactions on polymers
Authors: Gaylord Norman G.
Published: June 2010

Chemical reactions on polymers are influenced not only by the reactivity of a funtional group but also by its accessibility. Although intrachain steric factors that result in neighboring‐group effects are well recognized, the interchain interactions that determine the availability of a potential reaction site have not been adequately considered. The factors that influence polymer reactions include amorphous or crystalline content, orientation, solubility, and compatibility. The interchain interactions involved are not only those between chains of the initial polymer but, more significantly, those between polymer chains that have reacted or partially reacted and polymer chains that have not. Chemical reaction may change solvent‐polymer interactions so that either chain extension or coiling occurs with resultant changes in the accessibility of reaction sites. Incompatibility between polymer that has partially reacted and polymer that has not may result in phase separation. Increased compatibility may result from the generation of block copolymers, due to localized or segmental reaction, which then act as compatibilizing agents and make the separation of reaction products, such as by extraction of unreacted material, extremely difficult.
Polymers with peroxidic functional groups. I. Copolymers of di(t‐butylperoxy) fumarate
Authors: Mageli O. L. , Light R. E. , Gallagher R. B.
Published: June 2010

Di(t‐butylperoxy) fumarate was copolymerized with styrene, butadiene, acrylonitrile, methyl methacrylate, vinyl chloride and vinyl acetate to give copolymers containing pendant peroxyester functions. Another peroxide was generally used for initiating polymerization; however, experiments were carried out with di(t‐butylperoxy) fumarate as both initiating species and comonomer. The active oxygen contents and intrinsic viscosities were determined for these copolymers. A copolymer of styrene and di(t‐butylperoxy) fumarate synthesized from monomers in equal weight ratio had an active oxygen content of 5.3% and a peroxide half‐life of 7.7 hr. at 85°C. in benzene. This peroxide was used as a catalyst for the curing of polyester resins and as an initiator for styrene bulk polymerization. The monomer reactivity ratios for the monomer pair styrene–di(t‐butylperoxy) fumarate were determined. Graft copolymers were made by grafting methyl methacrylate on a styrene–di(t‐butylperoxy) fumarate copolymer and also by grafting styrene on a vinyl acetate–di(t‐butylperoxy) fumarate copolymer. These graft copolymers were used to enhance the stability of homopolymer–solvent mixtures. A novel ABS type of resin was synthesized by grafting styrene and acrylonitrile on the copolymer system butadiene–di(t‐butylperoxy) fumarate. Another novel resin was synthesized by grafting butadiene on the terpolymer system styrene–acrylonitrile–di(t‐butylperoxy) fumarate. A homopolymer of di(t‐butylperoxy) fumarate was also prepared and used as a catalyst for the curing of polyester resins.
Sulfur crosslinks in polybutadiene vulcanizates
Authors: Gregg Earl C.
Published: June 2010

For the first time the crosslink terminus structure of monosulfide crosslinks and the amount of that structure in an elastomer vulcanizate has been determined directly from a sample of the vulcanizate. By measuring the rate of swelling of vulcanizates, immersed in either methyl iodide or methyl bromide, the rate of crosslink cleavage was measured. Comparison of this cleavage rate with the cleavage rate of model monosulfide compounds permits a measure of the terminus structure of the monosulfide crosslinks. The fraction of each monosulfide structure was determined from the cleavage rate equation for the vulcanizate. The monosulfide crosslink terminus structure in a particular polybutadiene vulcanizate was saturated, having secondary carbon atoms on both sides of the sulfur atom, i.e., it was a saturated, tetrafunctional crosslink. Polysulfide crosslinks in 1,4‐polybutadiene vulcanizates are readily cleaved at room temperature by a solution of phenyl lithium in benzene. The number of polysulfide crosslinks was estimated from a measure of the volume swelling of the vulcanizate before and after treatment with phenyl lithium. This reagent does not cleave the monosulfide crosslinks in polybutadiene vulcanizates.
Computer calculations of binary and ternary copolymerization behavior
Authors: Chan Richard K. S. , Meyer Victor E.
Published: June 2010

Computer programs in use in our laboratory for the calculation of binary and ternary copolymerization behavior are reviewed. In the case of binary copolymerization an analytical equation is available, allowing rapid and precise calculations of various parameters of interest. In the case of ternary and higher component systems numerical methods of integration are required. The application of the Runge‐Kutta method to ternary copolymerization systems is outlined. Examples and some of the difficulties encountered with both systems are presented.
A FORTRAN II program for conducting sequence distribution calculations
Authors: Harwood H. James
Published: June 2010

A FORTRAN II program for calculating copolymer compositions, run numbers, diad, triad, tetrad, and pentad distributions, and sequence number distributions and sequence weight distributions for addition type copolymers is described. The program is applicable to both instantaneous and high‐conversion copolymers.
Viscoelastic and ultimate tensile properties of styrene‐butadiene‐styrene block copolymers
Authors: Smith Thor L. , Dickie Ray A.
Published: June 2010

A study was made of the stress–strain and ultimate properties in simple tension of an elastomeric styrene‐butadiene‐styrene block copolymer (Kraton 101) and also of a similar material (Thermolastic 226) that contains about 35% plasticizer as well as inorganic pigments. Stress–strain data were obtained at crosshead speeds from 0.02 to 20 in./min at temperatures from ‐40 to 60°C. The relaxation rate, derived from the data at constant extension rates, was about 8% per decade of time for both materials at temperatures from −40 to about 40°C and at extensions from about 20% up to 400%. Above −30°C, the shift factor log aT was found to vary linearly with temperature. These findings indicate that the time and temperature dependence of the mechanical properties results primarily from the plastic (or viscoelastic) characteristics of the styrene domains. The tensile strength for Kraton 101 below 40°C is somewhat greater than 4000 psi, sensibly independent of extension rate and temperature. For the highly plasticized Thermolastic 226, the tensile strength at an extension rate of 1.0 min−1 increases from 2200 psi at 0°C to 3600 psi at −40°C. Above 40°C for Kraton 101 and above 0°C for Thermolastic 226, the tensile strengths are quite dependent on extension rate and temperature owing to the increased ductility of the styrene domains. The high strength of these materials results from the uniformly dispersed styrene domains of colloidal dimensions. To obtain a crack of sufficient size to satisfy an energetic criterion for self‐sustained high‐speed propagation, domains must be disrupted. The plastic characteristics of the domains have a controlling effect on crack growth and thus on the ultimate properties of the materials. The strength and extensibility of other elastomers are considered in relation to those of the block copolymers.
Half‐life measurements in emulsion polymerization
Authors: Ley Gregor J. M. , Schneider Christel , Hummel Dieter O.
Published: June 2010

Intermittent 60Co γ‐radiation was used in a study of emulsion polymerization of styrene, methyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, vinylidene chloride, vinyl acetate, and chloroprene. A sensitive recording dilatometer was used to follow the build‐up and decay of polymerization rate and radical concentration. Reaction rate versus time curves of these emulsion systems with intermittent irradiation are given and the values of the apparent half‐life times of the monomers are compared. Apparent half‐life of the propagating radicals in emulsion ranged from below 1 min in the case of vinyl acetate up to about 80 min in the case of styrene. Variation of half‐life of the styrene radical with conversion, temperature, monomer and emulsifier concentration, and transfer agents added was determined. Calculation of the apparent termination rate constant of styrene yielded values of about 1 × 103 1/mol‐sec in emulsion as compared to literature data of about 1 × 107 1/mol‐sec in homogeneous systems.
Synthesis of conjugated Schiff‐base polymers
Authors: Hodgkin J. H. , Heller J.
Published: June 2010

Attempts to synthesize conjugated polymers with cyanine dyes attached to the conjugated backbone are described. The experimental approach is to prepare and characterize conjugated polymers with attached quinolinium ions and then to convert these to dyes by reaction with lepidinium methiodide. Aromatic Schiff‐base polymers were chosen as the conjugated backbone. Since unsubstituted Schiff bases show very little conjugation, a series of model compounds and model polymers were prepared and their electronic spectra were determined in order to correlate the effect of substituents on electron delocalization. Efforts are being made to prepare high molecular weight polymers by a Schiff‐base exchange reaction. The syntheses of various monomers for the Schiff‐base exchange reaction are described.
Applications of many body methods to large molecules
Authors: Gutfreund H.
Published: June 2010

The work which I am going to report on was performed about a year ago at Stanford in collaboration with Professor W. A. Little.1‐3 The motivation was the same as for this entire Symposium, but it differs from the other works reported here in the sense that it ignores the question of superconductivity and deals only with properties of the normal π‐electron system. We felt that a better understanding of the normal π‐electron system is an important factor in the theoretical investigation of organic superconductivity. To give an example, let me remind you that the most severe criticism of Little's original paper on organic superconductivity comes from Kuper.4 Kuper shows that in a narrow cylinder the screening of the Coulomb potential is much weaker than in an unrestricted geometry, so that the net potential remains always repulsive. It is thus of utmost importance to be able to calculate the screening of the interaction between two π‐electrons by the other π‐electrons in the medium.
The instabilities of the hartree‐fock solutions for cyclic polyenes with respect to the spin and charge density fluctuations
Authors: Paldus J. , Čížek J.
Published: June 2010

The stability conditions which ensure that the Hartree‐Fock (HF) determinant minimizes locally the energy expectation value are formulated. These conditions are then specified for the closed‐shell electronic systems with spin independent Hamiltonian, which enables classification of the instabilities into the so‐called “singlet” and “non‐singlet” ones. In the case that the HF solution is unstable, another single determinantal HF solution with lower energy expectation value must exist. Moreover, if the original HF solution is singlet unstable, the new HF solution is again a pure singlet function, but has a lower spatial symmetry than the original Hamiltonian. This leads to the electron density waves, while the non‐singlet instability leads to the spin‐density waves in the system considered. Generalization of these results to simple open‐shell systems is briefly mentioned. The numerical results for pi‐electronic models of cyclic polyenes using the three different semiempirical parameterization schemes, which are commonly used, are briefly reviewed. It is shown that for cyclic polyenes, both singlet and non‐singlet instabilities occur if a large enough polyene is considered. The equations determining new HF solutions may be expressed in a form resembling BCS‐Bogoliubov equations of superconductivity. Further, the singlet instability may lead, in this case, to either the atomic‐charge alternating solutions or the bond‐order alternating solutions. It is shown that in cases where both solutions are possible, the latter have the lowest energy while the former is again singlet unstable. The implications of the existence of singlet instabilities for the occurrence of an energy gap and for the occurence of bond‐length alternation as well as for the applicability of some many body techniques are briefly discussed.
Osmotic, viscometric and light scattering studies of polymers dissolved in a mixture of two non‐solvents (cosolvents)
Authors: Sarkar Dilip Kumar , Palit Santi R.
Published: June 2010

Polystyrene has been found to be completely soluble in the following binary mixture of non‐solvents, viz. nitrobenzene and acetone, heptane and acetone, cyclohexane and acetone, nitrobenzene and diethyl oxalate, hexane and diethyl oxalate, cyclohexane and diethyl oxalate. Polymethyl methacrylate has similarly been found to be soluble in carbon tetrachloride and methanol, and in carbon tetrachloride and ethanol. These two polymers have been studied viscometrically, osmometrically and with respect to light scattering property. An optimum composition with a minimum in osmotic μvalue and viscometric Huggins constant, a maximum in [η]‐value and a maximum in dissymmetry coefficient has been found to exist. The above observations are considered to indicate that the composition showing maximum solvent power is a true optimum composition and the dissolved unit is laterally more extended in this optimum composition than at any other composition of the two non‐solvents. Five samples of polymers have been studied in a number of ø‐mixtures near room temperature with a view to obtain the Kø values of Flory‐Fox equation, [η] ø = K o M̄v0.5. It has been found that Kø values vary widely with the chemical nature of the theta mixture indicating solvent dependency of unperturbed polymer dimension.
Thermal degradation of polystyrene
Authors: Wegner J. , Patat F.
Published: June 2010

Living polystyrene samples, both solid and in dilute toluene solution, were thermal degraded under extremely clean conditions in a range of temperatures from 200 to 325°C. The degradation was found to be a first‐order reaction. Pyrolyzed samples were analyzed with regard to the change in molecular weight as well as in molecular weight distribution. For the latter, an extraction method is described, which permits, in addition, the activation energy of thermal degradation (48 kcal/mole for the overall reaction) to be obtained. The results are discussed with a view to earlier outlined degradation theories. The presence of weak links in polystyrene as well as the propagation of degradation by reverse polymerization could be excluded. A radical chain reaction is assumed to be the mechanism of degradation.
Upper and lower solubility gaps in the system butanone‐acetone‐polystyrene
Authors: Wolf B. A. , Breitenbach J. W. , Senftl H.
Published: June 2010

Depending on the solvent‐nonsolvent ratio r of a quasibinary section through the binodial surface of the system butanone‐acetone‐polystyrene, two different cases for the resulting cloud‐point curve (CPC) can be distinguished: (1) separated solubility gaps at relatively high values of r with intermediate temperature region of complete miscibility; (2) overlapping solubility gaps at lower values of r with no temperature of complete miscibility observable. A thermodynamic interpretation is given on the basis of the free‐volume concept. The influence of preferential adsorption on the position of the critical points on the CPC is discussed.
Rotational isomerism, microstructure and molecular motion in polymers
Authors: Pechhold W.
Published: June 2010

In the first part the microstructure of polymer melts and semicrystalline bulk material is treated on the basis of the bundle model and with molecular parameters. The meander‐shaped arrangement of the bundles in the amorphous phase can be founded thermo‐dynamically and leads to a radius of the meander of 50 Å. Based on this model a molecular theory of the relaxation processes (α, β, γ) is given and experimentally proved for linear polyethylene. In the last part both limiting cases of the deformation behavior are quantitatively derived in a molecular picture: the ideal plasticity illustrated by the yield stress of linear polyethylene and the ideal para‐elasticity illustrated by the stress‐strain curve of the drawn polyamide fiber.
Rheological properties of dilute and concentrated solutions of polyvinylchloride branched by irradiation
Authors: Palma G. , Pezzin G. , Zaramella S.
Published: June 2010

Following a previous study of two commercial poly(vinyl chloride) polymers, with Mw values of 130,000 and 70,000, the influence of γ radiation on the concentrated solutions of two other polymers in tetrahydrofuran was investigated. Their Mw values were 51,000 and 700,000, respectively; the second sample being crosslinked by copolymerization with a polyfunctional monomer.

The irradiation‐induced changes were investigated by osmometry, light‐scattering, gel permeation chromatography and dilute and concentrated solution viscometry. From the experimental data obtained, it can be seen that the viscosity‐molecular weight relations are strongly affected by the molecular weight distribtuion and the presence of branching in the samples. By assuming the Stockmayer distribution, and using the equations developed by Kilb, the viscosities of the irradiated samples have been described satisfactorily.
Effects of internal stress on the yielding of oriented poly(vinyl chloride)
Authors: Rawson F. F. , Rider J. G.
Published: June 2010

Poly(vinyl chloride) sheet was oriented by hot stretching at 80°C. Yield stresses in simple tension and compression were measured at 20°C and at a strain rate of 100% min−1 as a function of the angle between the test‐piece axis and the hot‐stretch direction. Simple tensile and compressive yield stresses were also measured in the temperature range −40°C to +80°C, in the hot‐stretch direction at strain rates of 100% min−1 and 1% min−1, and in the unstretched sheet at 100% min−1. The results are discussed in terms of a yield criterion based on that of von Mises but modified to allow for the effects of anisotropy, internal stress and mean normal stress, and are held to justify the inclusion of the internal stress term. By making specified assumptions, the magnitude of the internal stress term is separated from that of the normal stress term and shown to rise slightly with testing temperature and to be only two‐thirds as great at the lower strain rate. A reason is given for thinking that the strain‐rate effect may have been overestimated.
Study of the efficiency of plasticizers in poly(vinyl chloride) by dielectric spectroscopy
Authors: Kisbényi M.
Published: June 2010

Dielectric dispersion and absorption spectra of plasticized polyvinyl chloride systems were investigated in order to obtain information about the efficiency and compatibility of the plasticizer.

Dielectric spectra were measured as a function of temperature at a constant frequency and a constant heating rate within the range of −170 to +150°C.

The glass transition temperature [Tg] is found to be dependent on the quality (structure) and quantity of the plasticizer used. The dipole‐dipole interactions, and thus also the plasticizing effect, are characterized by the dielectric permittivity change [Δet] in the transitions range.

Dielectric spectra of compounds prepared with either commercial or special‐type plasticizers were measured. The effect of the chemical structure on the dielectric spectra was studied on a series of compounds containing phthalate‐type plasticizers having alcoholic side chains of an increasing length. The results of dielectric measurements are compared with those obtained by standard mechanical tests.

From this comparison of results it may be concluded that the investigation of dielectric spectra offers important information regarding the efficiency and compatibility of plasticizers.
Variations of the dielectric and mechanical characteristics of the poly (vinyl chloride) film: Electric discharges in air
Authors: Bagirov M. A. , Abasov S. A. , Malin V. P. , Abbasov T. F.
Published: June 2010

One of the principal reasons of the premature failure of the polyvinyl chloride electrical insulation is the action of the discharges in the air voids of the insulation. Therefore, investigation has been carried out of the changes of the dielectrical permittivity ε and the loss factor tan δ of a polyvinyl chloride (PVC) film, plastified by dibutyl phthalate, under the effect of the electrical discharges in the air. Since by the discharges in the presence of oxygen a vigorous formation of ozone takes place the changes of the above mentioned characteristics after the exposure of samples in the ozone have been investigated separately.

It has been shown that under the effect of the electrical discharges in the air, the temperature dependences of ε and tan δ have changed essentially. ε is subjected to dispersion over the temperature range from 70 to 100°C; tan δ increases over the whole temperature range, the conductivity losses begin at lower temperatures, and the peak of dipole‐segment losses (DSL), which is strongly pronounced in the initial sample, is no more observed. This is due to the fact that under the effect of ozone and owing to the crosslinking of the polymer chains the peak of DSL is shifted to higher temperatures; as a result, both DSL and the conductivity losses are superimposed.

The extension of the sample, leading to an additional orientation of macromolecules, weakens considerably the changes of the dielectrical characteristics due to the discharges.
Boric acid esters as secondary plasticizers for poly (vinyl chloride)
Authors: Potnis S. P. , Khanolkar A. G.
Published: June 2010

In addition to the primary plasticizers which are essential for giving the required ease of processing to and improving desirable mechanical properties of polyvinyl chloride (PVC) compounds, secondary plasticizers also play a significant role in confering specific properties to PVC. It was from this point of view that the boric acid esters were evaluated in PVC compositions. Because of the limited compatibility of boric acid esters with PVC by themselves, their use could be recommended only as secondary plasticizers. In the present paper various boric acid esters prepared in this laboratory [S. P. Potnis and A. G. Khanolkar, Popular Plastics, 15, 20 (1969)] have been evaluated for their performance in PVC compounds, and results obtained indicate that the monomeric and alicyclic esters of boric acid could be used with definite advantage and improve such properties as electrical resistance, heat stability, and in some cases even the mechanical properties.
Long chain branching in poly(vinyl chloride)
Authors: Small K. W. , Yearsley F. , Greaves J. C.
Published: June 2010

The intrinsic viscosity [η]‐weight average molecular weight Mw, relation has been studied for fractions of a range of vinyl chloride homopolymers prepared at 40–80°C in aqueous suspension. In addition to curvature of the log [η]‐log Mw plots for Mw > 2 × 105, at constant Mw a slight but definite trend to lower [η] as polymerization temperature is increased was also observed. Both these effects are ascribed to long chain branching due to an increasing incidence of intermolecular chain transfer as polymerization temperature is increased. Limited examination of poly(vinyl chloride) prepared by emulsion polymerization indicates, by the same criterion, a greater incidence of branching than found in poly(vinyl chloride) prepared at the same temperature by the aqueous suspension process. It is concluded that no single correlation of the Mark‐Houwink type can be expected to apply to vinyl chloride homopolymers prepared over a range of conditions.
Some problems of the thermal degradation of poly(vinyl chloride)
Authors: Kelen T. , Bálint G. , Galambos G. , Tüdös F.
Published: June 2010

The effect of hydrogen chloride on the thermal degradation of poly(vinyl chloride) was studied in dibutyl‐sebacate solution. It was found that hydrogen chloride exerts no catalytic effect at these conditions.

The assumption of hydrogen chloride readdition to the double bonds formed is forwarded as a factor lowering the average length of polyenes. The possible mechanism of stabilizing action of metal soaps is discussed on this basis.
Investigations on the stabilization of poly(vinyl chloride) by metal soaps
Authors: Braun D. , Hepp D.
Published: June 2010

The degradation of mixtures of poly(vinyl chloride) (PVC) and metal soaps was investigated in solution as well as in bulk in an inert atmosphere at 180°C. There are marked differences between stabilized and unstabilized PVC in the dehydrochlorination and in the distribution of the length of the resulting polyene sequences in the polymer. Cadmium octoate retards the dehydrochlorination and causes a shift of the sequence length distribution towards shorter polyene sequences. Thermal dehydrochlorination of stabilized PVC is more strongly retarded in solution than in bulk. Furthermore, there is a more pronounced shift in the sequence length distribution towards shorter polyene sequences when PVC‐stabilizer mixtures are degraded in solution rather than in bulk. The formation of primarily short polyene sequences that absorb in the ultraviolet range is attributed to a direct reaction between stabilizer molecules and PVC in which an acid residue of the stabilizer is exchanged with a “labile” chlorine atom of the polymer chain.
Study of the degradation of poly(vinyl chloride) compounds by dielectric spectroscopy
Authors: Hedvig Peter
Published: June 2010

A continuously recording dielectric spectrometer was constructed to investigate the effects of degradation on the dielectric spectra and ac conductivities of poly(vinyl chloride) (PVC) compounds. Dielectric spectra were found to be affected by the thermal history of the sample. The elimination‐type degradation in hard PVC and in plasticized PVC compounds could be kinetically studied by recording ac conductivity as a function of reaction time. The method was found to be useful for studying the efficiency of stabilizers in a simple way. Changes in the physical structure during the course of degradation could be measured by observing shifts and distortions of the Tg‐dispersion signals.
Peculiar behavior of blood at solid interfaces
Authors: Vroman Leo , Adams Ann L.
Published: June 2010

Adsorption of proteins out of normal and afibrinogenemic blood plasma onto oxidized silicon crystal slices and glass was studied with the recording ellipsometer and by other means. Adsorbed matter was identified by its ability to adsorb specific antibody or to function in blood clotting. Our previous data suggest that fibrinogen as well as factor XII (the protein thought responsible for surface activation of clotting) are adsorbed first. If the plasma was not previously activated, it converts this fibrinogen, and then, in the presence of unactivated factor XII, it removes some. Both conversion and removal are retarded by previous activation of the plasma, or by lowering its concentration or temperature. Blood platelets (the elements that start thrombosis in vivo) adhere most to films on glass that contain unconverted fibrinogen. Present data suggest that plasma from a patient totally lacking plasma fibrinogen, had all properties of normal plasma when fibrinogen was added. Fibrinogen in bulk or pre‐adsorbed state neither helped nor hindered adsorption of factor XII activity. After prolonged contact of normal plasma with an activating interface, adsorbed fibrinogen could be recovered by elution. Readsorption was then followed by reconversion.
Compression mechanics of polymer monolayers
Authors: Yin T. P. , Wu Souheng
Published: June 2010

A theory based on a simple buckling mechanism has been developed to describe the deformation and rupture mechanics of a polymer monolayer. It assumes that the closely packed monomer units are forced to buckle in successive pairs under compression. When the protruding angle of the rupture site reaches 90°, the monolayer collapses. This model is found to accommodate the essential features of compression isotherms of polymer mono‐layers in the condensed region (below the closest packing area at zero surface pressure) up to and beyond the collapse point. The stress‐bearing capacity of the interface is greatly influenced by the ratio of cohesion to adhesion. The compression isotherm may take either a positive or a negative slope beyond the collapse point, depending on whether adhesion is greater or smaller than cohesion.
Air infrared spectroscopy study of the epoxy‐cellulose interface
Authors: O'Brien R. N. , Hartman K.
Published: June 2010

Some aspects of the adhesion of paint to wood were studied by the selection of a well characterized substance to take the place of wood, in this case, cellulose and a well‐known polymer, an epoxy system, which is frequently used as the polymeric constituent of a modern paint. Attenuated total reflectance (ATR) infrared spectra of some wood surfaces from which the correlation with the cellulose ATR spectra can be seen, have been reported [1]. The synthetic spectrum of cured epoxy system and cellulose was prepared by placing a cast and cured epoxy system sheet on one side of a KRS5 internal reflection plate and compressed, reconstituted cellulose on the other side. This spectrum was compared with that of a cast and cured cellulose‐epoxy system mixture. The OH‐stretching band (3350 cm−1) and the C‐O stretching bands (1050‐1000 cm−1) of the cellulose were greatly decreased in intensity, while the epoxy band (915 cm−1) and the band at 1160 cm−1 had virtually disappeared.

A total frequency assignment of both the epoxy system and the cellulose are presented. The adhesion at the cellulose‐epoxy system interface is discussed with respect to the chemical changes inferred from the above‐mentioned spectra.
Oxygen/alkali oxidation of cellulose and model alcohols and the inhibition by iodide
Authors: Minor J. L. , Sanyer N.
Published: June 2010

Certain aspects of cellulose depolymerization by oxygen in alkali were investigated with model compounds. Oxidation of hydroxyl groups was studied using low molecular weight glycols and alcohols. Hydrogen peroxide was identified as the peroxidic intermediate observed during oxygen oxidations of carbohydrates. Oxidation of glucitol by either alkaline hydrogen peroxide or oxygen is autocatalytic with a discrete induction period. When hydrogen peroxide is initially present in the oxygen oxidation, the induction period is considerably reduced. In the presence of potassium iodide, the induction period is lengthened. Potassium iodide inhibits the depolymerization of cellulose by oxygen and alkali and, in the presence of magnesium ions, provides more stabilization than either alone. A mechanism to explain these results is proposed.
Study of cellulose structure and its relation to reactivity
Authors: Nelson Russell , Oliver Don W.
Published: June 2010

Information is presented to show that the total volume of micropores in acetic acid swollen fibers correlates closely with acetylation reactivity. Pore size distribution measurements indicate that the pores with diameters of 25–75 Å may be particularly influential for promoting reactivity since fibers which perform well in acetylation processing have a characteristically high volume of pores in this size range. Internal surface area also correlates with acetylation reactivity if allowances are made for the large fraction of surface area which is associated with pores that are too small for reagent penetration. This lower limit is calculated to be 20–25 Å. Based on estimates of void spaces within and between the cellulose structural building units, acetylation of acetic acid swollen fibers should occur on the external surfaces of the elementary fibrils, the microfibrils and the lamellae as well as on the internal surfaces of the microfibrils and the lamellae. The overall effect of cellulose structure on reactivity seems to be the control of the inward flow of reagents to reaction surfaces but not the outward transport of reaction products. Internal void volume may function to accommodate reaction products as they swell inwardly and thus provide a means for allowing the reaction to go to completion. The relationship between cellulose structure and reactivity can be extended to chemical reactions other than acetylation.
Neutral hydrolysis of alkali lignin to monomeric phenols
Authors: Benigni J. D. , Goldstein I. S.
Published: June 2010

Alkali lignin has been found to undergo neutral hydrolysis to produce simple phenolic materials. Data on the effects of time and temperature on the yields of oil and monomeric phenolic materials produced are presented. Also the use of acidic or basic reaction conditions and other types of lignin are discussed.
Enzymatic degradation of carboxymethylcellulose and other cellulose derivatives
Authors: Bhattacharjee S. S. , Perlin A. S.
Published: June 2010

Several water‐soluble cellulose derivatives have been subjected to degradation with a cellulase preparation from Streptomyces sp. QM B814. Structural analysis of the enzymolysis products is described, particularly in relation to carboxymethylcellulose. For comparison, corresponding derivatives of lichenin, a soluble β‐glucan structurally related to cellulose, have been examined with the use of this enzyme. The results indicate that the distribution of substituents in the cellulose derivatives is not uniform and that accessibility is important in determining the pattern of derivatization. Both carboxymethyl‐and hydro‐xyethylcellulose appear to be attacked by the cellulase in a similar fashion, and the two kinds of substituent groups are equally effective in limiting hydrolysis by this enzyme.
Synthesis and graft copolymerization on some polysaccharides by anionic mechanism
Authors: Simionescu Cristofor I. , Rusan Viorica
Published: June 2010

Some esters like metallated cellulose monoethyl malonate were used as macromolecular initiators for grafting of some vinyl monomers and the obtained products were characterized.
Textile properties of cotton cellulose graft copolymers and terpolymers
Authors: Mares Trinidad , Arthur Jett C.
Published: June 2010

Cotton cellulose graft copolymers and terpolymers were prepared by radiation initiated processes. Monomers copolymerized with irradiated cellulose from solutions of methanol‐water were: methacrylic acid (MAA), methacrylonitrile (MAN), and hexafluoroisopropyl acrylate (6FIPA). Cotton cellulose, immersed in solutions of N‐vinyl carbazole (NVC) in 1,2‐dichloroethane, was irradiated to form a copolymer. Terpolymers prepared were; cellulose‐poly(MAA)‐poly(MAN), cellulose‐poly(MAA)‐poly(6FIPA), and cellulose‐poly(MAN)‐poly(6FIPA). Textile properties of the cotton fabric copolymers and terpolymers determined included: flex and flat abrasion resistance, breaking strength, and water repellency. The properties of the cellulose copolymers and terpolymers were related to chemical structures of the monomers used and the glass transition temperatures of their homopolymers.
Structural changes during deformation of high molecular weight and low molecular weight polyethylene
Authors: Steidl J. , Pelzbauer Z.
Published: June 2010

Structural changes caused by cold drawing low and high molecular weight polyethylene (M = 7 × 104 and 1.5 × 106) were investigated by using wide‐angle x‐ray diffraction, light and electron microscopy. Results obtained from drawn samples subjected to stress and samples at zero stress, revealed important differences in the behavior of these two polymers. In contrast with the low molecular weight polyethylene, the high molecular weight samples were deformed homogeneously without neck formation; the orthorhombic lattice, when subjected to stress, is transformed into a monoclinic one, not only in the initial stage, but over the whole deformation range up to breaking. The spherulitic structure in both polymers changes into the fibrillar one, while the degree of orientation attainable for the low molecular weight polyethylene is higher than that for the high molecular weight sample. During deformation of the low molecular weight polymer, cracks form between fibrils, and the fibrils become separated. Such an effect has not been observed with the high molecular weight material. After the external stress has been removed, a considerable contraction and decrease in orientation characterize the high molecular weight polyethylene. The differences in behavior of the two types of polymers are discussed in terms of different structural models.