bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of vinylpyrrolidone‐methyl methacrylate statistical copolymer in mixed solvents
Authors: Bakauova Z. H. , Bekturov E. A. , Bereza S. V.
Published: June 2010

Intrinsic viscosities of fractions of the statistical copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross‐selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50‐60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark‐Houwink‐Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθand σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
The transport of water through latex films
Authors: Vanderhoff J. W. , Bradford E. B. , Carrington W. K.
Published: June 2010

Upon drying, latexes are transformed from milky, colloidal dispersions to transparent, continuous films in which the contours of individual coalesced particles can still be discerned. Upon ageing at room temperature, however, these latex films undergo a further gradual coalescence in which the particle contours gradually disappear and any imcompatible substances (e.g., emulsifer) are exuded to the surface. With this point of view in mind, the rate of drying at 72°CF and 50% RH was measured for three copolymer latexes: 70:30 vinylidene chloride‐n‐butyl acrylate, 67:33 ethyl acrylate‐methyl methacrylate, 67:33 styrene‐butadiene. The drying process can be divided into three stages: (1) an initial constant rate stage which persists to 60–75 vol% polymer; (2) an intermediate stage in which the rate drops off rapidly to a value 10–20 times smaller; (3) a final stage in which the rate is very much smaller and decreases very slowly with time. These stages can be correlated with the mechanism of film formation: (1) in the first stage, the particles move about with their characteristic Brownian motion, and the water evaporates from the latex at the same rate as for pure water or dilute emulsifier solution; (2) the intermediate stage begins when the particles come into irreversible contact with one another and ends with their coalescence to form a continuous film: during this stage the rate of water evaporation decreases because the water‐air interfacial area is decreasing; (3) in the final stage, the water remaining in the film escapes by diffusion, either through capillary channels between the deformed spheres or through the polymer itself. Measurement of the liquid water and water vapor transmission rates of latex film samples, taken either at the end of the intermediate stage or after sufficient ageing to ensure completion of the further gradual coalescence, showed that the rate of water loss in the final stage is initially representative of diffusion through capillary channels, but slowly and asymptotically approaches a value representative of diffusion through the polymer, presumably reaching it within the time required for completion of the further gradual coalescence (about 14 days for these copolymers). The values obtained for the three copolymers are 6.2 × 10−7, 2.9 × 10−5, and 4.4 × 10−5 g‐mil/min/cm2, respectively, in reasonable agreement with values reported in the literature for similar but not identical polymers. The values for the liquid water and water vapor transmission rates were the same.
General statistics and Markov statistics of binary vinyl copolymers with asymmetric α‐carbon atoms
Authors: Gronski Wolfram , Klesper Ernst , Cantow Hans‐Joachim
Published: June 2010

The statistics of binary copolymers formed by polymerization of asymmetrically substituted α‐olefines is considered. On the basis of the principle of stationarity, the general statistical relations valid for binary systems are extended to these copolymers. Necessary relations between observable probabilities of sequences are given, covering also the case where only one of the two different monomer units may possess an asymmetric center. Moreover, the outlines of second order Markov statistics for copolymers possessing asymmetric centers are formulated.
Synthesis and physical properties of graft copolymers derived from phyllosilicates: I. The chrysotile and vermiculite derivatives
Authors: Zapata L. , van Meerbeek A. , Fripiat J. J. , Faille M. Della , van Russelt M. , Mercier J. P.
Published: June 2010

In this work a new class of composite polymeric materials was described. They were obtained by grafting vinylic polymer chains onto the vinylic derivative of the phyllosilicates. These composite materials are characterized by outstanding mechanical properties, especially by a high modulus of elasticity.
Molecular uniform macromolecules of polyamide 6
Authors: Craubner Hans
Published: June 2010

The molecular weight distribution (MWD) of an autoclave‐polymerized polyamide 6 (PA 6) was determined by solution fractionation to be a mixed distribution, consisting of three regions. The top corresponds to a small fraction of low molecular weight (∠ 1%) and the tail, to a small, weakly crosslinked component of high molecular weight (∠ 1%). Cutting the wings of the distribution by fractionation yields linear PA 6 fractions with an extreme narrow partial distribution accounting for more than 98% by wt. The linear molecular weight averages areMn, lin= 24,800 andMω, lin= 24,810. The nonuniformity isU= 0.3 × 10−3(compared toUPoisson= 4.6 × 10−3). The fractionation efficiency amounts to ϕ = 99%.

A distribution function for the molecular uniform PA 6 is given. Kinetic considerations are discussed. As is shown, the molecular uniformity is then appreciably larger than that of, for example, aPoissondistribution (more than a power of ten), if the rate of the initiation reaction (ki) is appreciably larger than that of the propagation of the chain (kω):r = kω/ki≪ 1.

The extreme narrow linear PA 6 distribution found by solution fractionation is confirmed by fast turbidimetric titration according to dynamic volume pulse technique. Furthermore, the results are supported by the recovery and the evaluated mean properties, such as intrinsic viscosity, melting points and endgroup molecular weight (MW).
Spectroturbidimetric titration of polymer solutions
Authors: Klenin V. J. , Shchyogolev S. Yu.
Published: June 2010

A new modification of the method of turbidimetric titration based on taking the turbidity spectrum in the process of titration (accordingly designated “spectroturbidimetric titration” (STT)) has been proposed. STT permits the mass of the precipitated polymer Mγ to be determined in the process of titration with any change in the degree of dispersity of the precipitated polymer phase. The standardized plotting of the curve of solubility (CS) Mγ/(Mγ)max = f(γ), where γ is the volume ratio of the precipitator, proved to be independent of the nature of possible variation of the relative refractive index of the particles m = m (γ). STT was carried out with the commercial type of polystyrene (PS) (benzenemethanol) and withanionic poly‐α‐methylstyrene(P‐α‐MS) (cyclohexane‐octanol)in the serial turbidimeter FET. The turbidity was measured using five light filters at 4000–6000 Å. The speed of stirring was 64 rpm. Four rates of the precipitator input: W = 0.09, 0.20, 0.41, and 1.03 ml/min were used. Worse reproducibility of the colloid system structure in parallel experiments was found under low W correlated to the best division according to molecular weights. The STT method balanced these two antagonistic principles (like some others, though). Dependence on W of CS has been found. Graphic extrapolation of CS (with fixed Mγ% and W → 0) permitted the equilibrium CS to be determined. In a typical case three characteristic ranges of particles size changing in the process of titration were observed: decreasing (a reduction in gigantic fluctuations), a stable range, and increasing (particles coagulation). The colloid system structure may be regulated by selection of tiration conditions.
Characterization of poly (vinyl chloride) prepared by radiation‐induced bulk poly‐merization at temperatures from −50° TO 90°C
Authors: Carenza M. , Palma G. , Tavan M.
Published: June 2010

Osmotic, viscometric, and light scattering measurements have been carried out on poly (vinyl chloride) samples, obtained by bulk polymerization on exposure to 60Co γ‐rays at dose rates varying over a 100‐fold range and at regularly spaced temperatures from −50 to 90°C. While with the samples prepared at the higher temperatures, solutions could be conveniently made in tetrahydrofuran, cyclohexanone appeared to be a more suitable solvent when polymerization temperatures from 10°C downwards were concerned. Furthermore, with the latter cases, strong heating treatments of the solutions were required. Correlations among the various parameters, deduced from the measurements, were examined and found in agreement with reported relationships for conventional poly (vinyl chloride). The patterns of gradual change of molecular weight with changing polymerization conditions were discussed.
Automated characterization of molecular properties of uncharged polymers
Authors: Keiner J. A.
Published: June 2010

A growing battery of methods has become available in recent years for characterization at a molecular level of natural and synthetic polymers. Several methods are now available with automatic or semi‐automatic operation, suitable for routine or on‐line use and are so used in the polymer industry. The methods for characterization are critically reviewed, emphasizing methods now suitable for routine use in the laboratory or in industry, i.e., infrared spectroscopy, viscometry, osmometry, and gel chromatography.
Transient electric optical rotation for macromolecular characterization
Authors: Jennings B. R. , Baily E. D.
Published: June 2010

In an electric field, the optical rotation of a solution or suspension of helical molecules may be expected to change. Such changes are reported herein for solutions of poly (benzyl‐L‐glutamate) (PBLG) in ethylene dichloride using pulsed electric fields. These measurements enabled the molecular geometry to be evaluated (through the determination of a rotary diffusion constant) simultaneously with the determination of the molecular optical rotation components along the principal molecular axes. Fields were applied parallel to the light beam. Very dilute solutions were studied owing to the use of a stable laser as the light source plus the introduction of a special multiple cell in which the optical path length could be increased while maintaining the field strength. A dilute solution (0.1%) of PBLG gave rotation data in agreement with previously published data. In addition, the helical length and molecular weight were determined from the relaxation effect. Studies on concentrated solutions indicated the presence of aggregation. This highlights the need for caution in improving the observable optical rotation simply by increasing the solution concentration. The apparatus is described in outline and the advantages of this novel transieat method are listed.
Light scattering rayleigh linewidth measurements on some macromolecular solutions
Authors: Sellen D. B.
Published: June 2010

Some light scattering Rayleigh linewidth measurements upon three globular proteins: chymotrypsinogen, bovine plasma albumin, and urease, are described. Measurements were made in 0.2 M NaCl and the diffusion constants calculated showed no concentration dependence. The measurements agreed well with theoretical predictions both as regards angular variation and frequency distribution.
On the mechanism of photoaging of poly‐caproamide
Authors: Pariiskii G. B. , Postnikov L. M. , Ya. Toptygin D. , Ya. Davydov E.
Published: June 2010

The photoaging of polyamides is commonly accepted to be a free‐radical process. It has been assumed1–3 that under action of ultraviolet light the macromolecules may decompose either along the C‐H or the C‐N bonds to macroradicals. The latter may enter a number of secondary processes mutually determining the change of chemical properties of the polymers. Studies of the nature of light‐generated free radicals with the ESR method have been reported earlier,1,3,4 but the interpretation of the results is quite ambiguous, and the ESR signals observed may be due to the secondary radicals being insensitive to the action of light. A possibility of phototransformation of the radicals in a γ‐irradiated polycaproamide has been noted.

The present work is concerned with the study of the effect of the spectral pattern of the light upon the radical nature in pure nylon 6. On the other hand a mechanism is proposed for the phototransformation of radicals established at the photolysis of nylon 6 in the presence of iron chloride additives.
Studies of decomposition of polymer blends by thermogravimetric method
Authors: Mucha M. , Kryszewski M.
Published: June 2010

Studies of thermal degradation in nitrogen atmosphere of homopolymers: polypropylene (PP), polyethylene (PE), poly(vinylidene chloride) (PCVD), and polyacrylonitryle (PAN) as well as of their blends were carried out using the thermogravimetric method. The investigations performed at different heating rates led to thermogravimetric curves which made it possible for the kinetic parameters characterizing thermal degradation, i.e., activation energy E and reaction order n, of the homopolymers and polymer blends in dependence on blend composition to be determined. PP and PE blends show higher thermal stability as compared with pure PP in contrast to the results obtained for PCVD with PAN blends.
Mechanism of catalytic acid hydrolysis of aromatic polyimides and relevant polyamic acids
Authors: Nechaev P. P. , Moiseev Yu. V. , Zaikov G. E. , Vygodskii Ya. S. , Gerashchenko Z. V.
Published: June 2010

The kinetics of catalytic acid hydrolysis of N‐phenylphthalimide, N‐phenylphthalamic acid (model compounds of polyimide and polyamic acids), and of certain soluble polyimides have been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o‐carboxyl group (in case of N‐phenylphthalamic acid). Attack of the nonprotonized amide bond by hydroxonium ions is suggested to be the rate limiting step. A method for determining the cyclization extent of soluble polyimides to within 0.1% is proposed. The effect of structure on the chemical stability of polyimides has been studied.
Laser excited raman spectroscopy of synthetic polymers
Authors: Boerio F. J. , Koenig J. L.
Published: June 2010

Recent advances in instrumentation for Raman spectroscopy are described. The fundamental differences between infrared and Raman spectroscopy are discussed and related to differences in selection rules, sampling techniques, and applications. The use of Raman spectroscopy for polymer characterization is illustrated by the results of recent research. The investigation of crystal structure is demonstrated by results obtained for polyethylene and orthorhombic polyoxymethylene. Detection of conformational changes in crystalline polyvinylidene fluoride and in solutions of polyethylene oxide by Raman spectroscopy is described as is determination of the composition of methyl methacrylate‐glycidyl meth‐acrylate copolymers.
Brillouin spectroscopy of macromolecular solutions
Authors: Nordhaus D. E. , Kinsinger J. B.
Published: June 2010

Brillouin spectroscopy was evaluated as an experimental method for measuring the molecular weights of macromolecules. This evaluation included an examination of instrumental parameters, sample preparation, and spectral analysis. The Brillouin peaks were found to be independant of solute concentration for dilute solutions, in accordance with the assumptions of Miller's approximate theory. This theory was used to calculate molecular weights of five standard polystyrene samples. These values compared well with molecular weights derived from regular photometric light scattering and viscosity measurements.
Formation of supermolecular order in aqueous solutions of poly(vinyl alcohol) in a turbulent flow
Authors: Kolnibolotchuk N. K. , Klenin V. J. , Frenkel S. Ya.
Published: June 2010

The process of formation of the supermolecular order (SMO) in aqueous solutions of poly(vinyl alcohol) (PVA) has been studied by the method of turbidity spectrum in a turbulent flow produced by a blade stirrer rotating at a rate of 1,500 rpm.

The kinetics of SMO formation has been investigated depending upon the polymer molecular weight (Mw) and concentration (C) and temperature (T) of the solution. The rate of formation of SMO was characterized in the first stage of the process by a relative increment in τ at 540 nm per hr. The concentration dependence, K = K(C), is extremal in character having its maximum at C = 0.5–1 g/dl. When T was increased from 20 to 50°CC, K decreased, whereas average equivalent size of supermolecular particles, rλ, remained unchanged. The colloid disperse phase of supermolecular particles (SMP) appears to be in a quasi‐equilibrium with the molecular‐disperse solution, since, after removal of SMP, the process of formation of SMO is resumed at the same rate. To a greater extent the character of SMO formation depends on the chemical structure of PVA (K drops off to zero with increasing content of the acetate groups up to 7.6%) and physical prehistory of the PVA sample (an increase in K after thermal treatment of the polymer in the condensed state). PVA films cast from stirred solutions revealed (by IR spectra) a greater degree of crystallinity then those cast from unstirred solutions. All other conditions being equal, K in a turbulent flow is higher by one to two orders of magnitude than K under static conditions. The data obtained have been explained from the point of view of crystallization of PVA when intensified by the turbulent regime of solution stirring.
Structure changes in glassy hydrophilic polymers under the stress of water sorption
Authors: Spencer H. Garth , Beyerlein Anne , Honeycutt S. C.
Published: June 2010

The sorption of water vapor by poly (vinyl alcohol) films at moderate vapor activities was followed by mass regain and electrical conductance. A slow rearrangement of polymer structure in the swollen state is indicated by the observed sorption overshoot.
Electrooptical investigations on organized structures of spherical polymers in solutions
Authors: Sokerov S. , Vorobeva T. , Stoylov S.
Published: June 2010

Under the action of an electric field at a frequency of 1000 Hz, an interaction occurs between spherical latex particles in aqueous solution. These spheres arrange themselves in linear aggregates along the lines of the force field. The formation of these aggregates is studied by the electric light scattering method. The case is investigated where the aggregates disintegrate after the electric field is switched off. Some preliminary theoretical ideas are presented concerning the electrooptics of the phenomenon. The constant of coagulation and the electric polarizability of the spheres are estimated, their radius being constant and known. The investigations carried out could be the beginning of the development of an electrooptical method for the determination of the electric polarizability of spherical particles in solution. In addition this investigation shows that electrooptical effects by solutions of spherical particles are possible.
Specific solvent interactions in the stereo‐regular polymerization of methacrylic acid
Authors: Lando J. B. , Litt M. , Kumar N. G. , Shimko T. M.
Published: June 2010

A study has been made of the marked effect of solvent on the stereoregularity of poly (methacrylic acid) prepared by the radical polymerization of methacrylic acid initiated by Co60 gamma radiation. The specific interaction of the solvent with the monomer and the growing polymer chains, leading to particular structures at the growing chain end, leads to the observed effect on the stereoregularity of the polymer. It is apparent that solvents of intermediate hydrogen bonding strength and bulkiness lead to highly syndiotactic polymer. Thus poly (methacrylic acid) prepared at −78°CC in a 20% by volume solution of methacrylic acid in 2‐propanol contains 95% syndiotactic triads. The effect of the steric hindrance of the solvent is amply demonstrated by the fact that polymerization in 2‐methylcyclohexanol results in the highest degree of syndiotacticity at 0°CC (82% syndiotactic triads) but yields polymer having only 69% syndiotactic triads at −78°CC. This is in contrast to the usual effect on stereoregularity upon lowering the temperature of radical polymerization. The detailed mechanism of this polymerization and its relation to the polymerization of other monomers capable of hydrogen bonding to solvents will be discussed with specific reference to the particular structures that may give rise to the observed effects.
A model for the structure of ionomers
Authors: Macknight W. J. , Taggart W. P. , Stein R. S.
Published: June 2010

The nature of the distribution of ionic groups in cesium salts of ethylene‐methacrylic acid and ethylene‐acrylic acid copolymers containing 2.1 to 6.3 mol% acid was examined using the small‐angle and wide‐angle x‐ray scattering techniques. The low‐angle data containing a maximum characteristic of these materials were analyzed according to principles of small‐angle scattering theory. The radial distribution functions for a typical salt and unionized copolymer were derived from the combined small‐ and wide‐angle data. The results of these two approaches indicate the presence of ionic clusters of the order of 10–20 Å in size. There is evidence that these clusters are of spherical geometry. The low‐angle maximum is interpreted as an interference resulting from short range ordering of ionic groups around ionic clusters.
Mechanics of elastomeric adhesion
Authors: Andrews E. H. , Kinloch A. J.
Published: June 2010

The mechanics of adhesion have been investigated both theoretically and experimentally, using model adhesive joints consisting of a crosslinked amorphous rubber bonded to a variety of rigid polymeric substrates.

An adhesive failure energy, θ, is defined which is characteristic of the bond but independent of test‐piece geometry. Both theory and experiment show that θ has the form, θ=θ0f(R) where θ0 is the “intrinsic adhesive failure energy” which depends only on the physical and chemical nature of the adhesive‐substrate interface, and f is a function of R, the “reduced” rate of failure propagation obtained from rate and temperature data using the WLF equation.

θ0 is the work of bond fracture across the interface and, for clean interfacial failure, is equal to the thermodynamic work of adhesion wA. Where failure is not purely interfacial, θ0 can be expressed as θ0=iI+r𝒯0+sF where i, r, and s are respectively the area fractions of interfacial, cohesive‐in‐rubber and cohesive‐in‐substrate failure, and I, θ0, and F are the intrinsic failure energies for the interface, rubber, and substrate, respectively.

It is believed that this work is the first to demonstrate explicitly and quantitatively the separate contributions of interfacial properties and bulk rheological behavior to the strength of adhesive joints.
Dielectric relaxation in solutions of poly (ϵ‐caprolactone)
Authors: Jones A. A. , Brehm G. A. , Stockmayer W. H.
Published: June 2010

Dielectric relaxation has been studied for poly (ϵ‐caprolactone) in dioxane solution. As expected from the head‐to‐tail structure [‐(CH2)5COO‐]x, at a given temperature there are two distinct dielectric loss peaks. Radio‐frequency bridge measurements reveal a low‐frequency peak due to a component of the repeat unit dipole parallel to the direction of the chain backbone and amounting to about 0.8 Debye per ester group. The position of this peak on the frequency scale varies with molecular weight as predicted from the longest normal‐mode relaxation time, τ1≅M[η]η0/RT

The second relaxation, which is independent of chain length, is conveniently studied over a wide range of concentrations by the technique of time‐domain reflectometry (TDR). This peak is associated with relaxation by local conformational rearrangement of a component of the dipole moment perpendicular to the chain direction, amounting to about 1.6 Debye per ester group. The extrapolated frequency of maximum loss at infinite dilution is about 3 GHz at 300K, with an apparent activation energy of about 30 kJ mol−1. The dependence of the local relaxation time on concentration can be fitted by a familiar free‐volume equation of the type τ = A exp(B/vf), in which the free volume vf is a linear function of composition.
Epoxy/acrylic simultaneous interpenetrating networks
Authors: Touhsaent R. E. , Thomas D. A. , Sperling L. H.
Published: June 2010

Simultaneous interpenetrating networks were prepared by simultaneously synthesizing crosslinked epoxy and poly (n‐butyl acrylate) polymers. A two‐phase morphology emerged, with the dispersed rubber domains being of the order of 0.1–0.2 m̈ in size. The actual dimensions of the dispersed phase, and the extent of molecular mixing between the two networks, depends on the relative rates of polymerization, or the gelation time. The minimum domain size and greatest molecular mixing occurs when the closest approach to simultaneity is attained. Spherical rather than elongated rubber domains yield the greatest toughening of the epoxy when the domains are smaller than optimum.
Enzymes covalently bound to acrylic gel beads. I. Interaction of hydrophilic anionic gel beads with biomacromolecules
Authors: Krämer D. M. , Lehmann K. , Plainer H. , Reisner W. , Sprössler B. G.
Published: June 2010

Gel beads of excellent mechanical properties are obtained by copolymerization of methacrylic acid anhydride with acrylamide using ethyleneglycoldimethacrylate or N, N′‐methylene‐bis (methacrylamide) as a cross‐linker.

When protein is covalently bound to the anhydride groups of the beads, residual anhydride groups are hydrolyzed to form an anionic matrix (AM). The hydrophilic gel beads are stable to 1M NaOH, mechanical stirring, and dehydration by lyophilization or organic solvents. Proteases, nucleases, and amylases bound to AM are efficient catalysts in breaking down high molecular weight substrates.

As far as the interaction of AM with biomacromolecules at pH 7.5 in 0.05M phosphate buffer is concerned, polyanions like DNA or tRNA are strictly excluded from the gel volume, whereas cationic polymers like basic proteins are strongly absorbed even at an ionic strength of 0.3. Little or no interaction is observed with neutral biopolymers.
Photochemically initiated maleic anhydride addition on polystyrene sensitized by free and bonded sensittzer
Authors: Hrdlovič Pavol , Lukač Ivan
Published: June 2010

Maleic anhydride addition to polystyrene in diluted dioxane solutions initiated by radiation of wavelength longer than 340 nm proceeds only in the presence of sensitizers, such as benzophenone and acetophenone. The degree of addition is, however, about 17 times less than for low‐molecular maleic anhydride addition to cumene under similar conditions. Due to the concentration effect, the efficiency of the bonded sensitizer exceeds that of the freely added one by up to three times in this instance. Quenching experiments showed that maleic anhydride acts as a quencher of poly (vinyl phenyl ketone) photolysis (Ksv = 31.5 1./mole) and copolystyrene/vinyl phenyl ketone (Ksv = 41.5 1./mol), although acting with only one‐half of the efficiency obtained with naphthalene. A comparison of the quenching efficiency of naphthalene with that of maleic anhydride for poly (vinyl phenyl ketone) (1.43) and copolystyrene/vinyl phenyl ketone (1.32) leads to the conclusion that in diluted dioxane solution there is no interaction of maleic anhydride with aromatic nuclei in the copolymer. The sensitized photoaddition is supposed to proceed via an attack by the excited maleic anhydride in the triplet state on the aromatic nucleus and not by the excited state of the charge transfer complex between maleic anhydride and the aromatic nucleus.
Rubber and rubber elasticity: A review
Authors: Gent Alan N.
Published: June 2010

The physical basis of rubber elasticity is reviewed, particular attention being given to the dependence of elastic stresses upon the imposed strains and upon the molecular constitution of the rubber. Applications of this fundamental understanding to a variety of other phenomena, including thixotropic effects shown by rubbers containing particulate fillers, the crystallinity and rigidity of partially crystalline polymers, and the frictional properties of soft solids are also referred to. A brief survey is included of some important but still unsolved problems in rubber elasticity.
The influence of curing systems on the properties of natural rubber
Authors: Chan B. L. , Elliott D. J. , Holley M. , Smith J. F.
Published: June 2010

After a brief historical introduction the influence of curatives on the chemical structure of vulcanizates is discussed. Emphasis is given to physically important features of network structure such as crosslink density, crosslink type, and various main‐chain modifications. The significance of extra‐network materials such as curative residues and zinc soaps is introduced. Nonsulfur systems are briefly considered.

The effects of differences in network structure and in extra‐network materials on aging properties is outlined with special emphasis on the importance of total combined sulfur, conjugated triene groups, and curative residues. The special problem of finding suitable antioxidants and antiozonants for peroxide cured rubber is mentioned. The influence of different curing systems on the crystallization of natural rubber both at low temperatures and at large extensions is described and shown to be a similar function of vulcanizate structure in both cases when compared at constant degrees of crosslinking. Problems in the interpretation of stress‐strain behavior are reviewed.

Changes in the C1 term of the Mooney‐Rivlin relation can only be interpreted as changes in crosslink density or as a filler stiffening effect of insoluble extra‐network material. Changes in the C2 term of this relation also take place as the curing system is changed and are correlated with inelastic behavior. Analysis of stress‐strain relations at high strain using the Martin‐Roth‐Stiehler equation indicates significant differences in the strain‐induced crystallization behavior of vulcanizates based on various curing systems, even when compared at similar crosslink densities.

The inelastic stress‐strain properties of natural rubber vulcanizates are divided into three main regions: (a) the glass transition region; (b) the chemical transition region, and (c) the intermediate region. The effects of network structure and extra‐network materials in each region are considered separately. In particular, the effects of zinc soap structurization on stress relaxation behavior in the intermediate region is described, including the likely mechanisms by which rubber‐soluble zinc soaps reduce the stress relaxation rate.

The influence of curing systems on the strength properties of homogeneous and isotropic natural rubber vulcanizates is described briefly, with particular emphasis on the role of polysulfidic crosslinks and main‐chain modifications.
Theoretical study of the effects of surfactants on seeded polymerization
Authors: Chambers James S. , Smitham James B. , Napper Donald H.
Published: June 2010

A simple analytical theory is developed to explore the effects of surfactants, whether ionic or nonionic, on the rate of polymerization of seeded systems. It is assumed that the average number of free radicals per particle is small (n < 1), that termination is rapid, and that free radicals may exit from the particle.

Some consequences of the variation of the kinetic parameters are explored numerically. It is shown that the radical capture efficiency decreases in the order electrostatic, steric, then electrostatic plus steric for these three different types of stabilization. The radical capture efficiency is shown to be very low (1 free radical captured in 103 – 104) despite the absence of new nucleation. Possible reasons for the low efficiency are discussed.
Mechanism of peroxidation of solid polymers as derived from the kinetics of the induced graft copolymerization
Authors: Chapiro A.
Published: June 2010

Grafting of acrylonitrile onto various radiation peroxidized polymers was used as a technique to investigate the peroxidation mechanism. It was found that in polymers such as polypropylene, poly(vinyl chloride), and polystyrene, a chain hydroperoxidation process only occurs above the glass transition temperature of the polymer. In the vitreous state, the polymer peroxidizes much more slowly via a single step radical‐radical combination process. In polyethylene and cellulose triacetate, a chain hydroperoxidation reaction is also observed at elevated temperatures, but the chain process is stopped at a critical temperature, which is dependent on the radiation intensity. It is shown that this effect can be interpreted, assuming that radical‐radical combination then efficiently competes with chain propagation. A discussion of the results shows that a polymer is likely to suffer more severe oxidation than a mobile liquid of similar chemical structure, owing to the much slower radical‐radical combination process in the viscous medium of the polymer.
Glassy transitions in semicrystalline polymers
Authors: Boyer Raymond F.
Published: June 2010

Considerable confusion exists in the literature concerning the glass temperature, Tg, of many highly crystalline polymers, in particular, linear polyethylene (PE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(oxymethylene) (POM), and poly(ethylene oxide) (PEO). We attempt to resolve some of this confusion first, by defining the nature of the problem; second, by developing criteria for defining the locations along a relative temperature scale (T/Tg or T/TM) of the key relaxations and transitions, Tg, T < Tg, TM, and Tαc for C‐C and CO backbone polymers free from long alkyl side groups; third, by developing a set of typical mechanical relaxation spectra for amorphous, semicrystalline, and single crystal materials of known Tg; fourth, by defining the concept of a double glass transition with values Tg(L) and Tg(U) and the optimum conditions for observing same. Finally, we apply these concepts and criteria to resolving the value of Tg for PVF and PVDF. Criteria employed include ratios of relaxation temperatures such as (T < Tg)/Tg, Tαc/TM, and Tg/TM, typical activation enthalpies for various relaxation processes, thermal expansion and heat capacity data. Two theoretical subjects are explored: the effect of crystallinity on increasing Tg and the effect of crystallinity on the relative strengths of the Tg and T < Tg processes. We also employ a “comparative anatomy” technique of comparing temperatures and related activation enthalpies of the several relaxations and transitions for a series of closely related polymers such as PE, PVF, PVDF, PTFE, Polytrifluorochloroethylene, and poly(vinyl chloride). We suggest that a new scientific discipline of interpreting the relaxation spectra of crystalline polymers may be emerging through integration of a large body of literature, the refinement of old criteria, and the development of new criteria. Even so, we are not yet able to offer a satisfactory interpretation of the relaxation spectra for POM and PEO.
Analysis of polymers by chemical modification
Authors: Schulz Rolf C. , Aydin Oral
Published: June 2010

Part one describes general aspects which must be considered when discussing the chemical analysis of polymers. By means of examples taken from literature, some fundamental procedures are illustrated, for example, color reactions, complex formation, degradation reactions (thermal, oxidative, solvolytic degradation), and polymer‐analogue reactions.

Part two describes our own investigations on analysis of different vinyl acetate copolymers having the general formula . The method is based on the elimination of acetic acid by melting the copolymer with p‐toluene‐sulfonic acid. The acetic acid can be determined by potentiometric titration or gas chromatography. The method may be used for soluble and insoluble copolymers (with R:H; OH; phenyl; C2H5COO) and graft copolymers (i.e., poly(vinyl chloride)) containing 0.2 to 100% vinyl ester. With copolymers from vinyl esters and acrylic esters (R; COOR'), alkaline hydrolysis followed by gas chromatographic determination of the acids and alcohols being formed is more advantageous.
Acrylonitrile copolymerization. VII Solvents effects in styrene copolymerization
Authors: Pichot C. , Zaganiaris E. , Guyot A.
Published: June 2010

The styrene‐acrylonitrile radical copolymerization kinetics have been studied for polymerizations carried out in two different solvents, toluene and dimethylformamide (DMF), in the whole range of monomer mixture compositions and at various dilutions. The copolymer prepared in toluene solutions are poorer in acrylonitrile than those prepared in bulk. The reverse situation is observed in DMF solution, where the polymerization rate is the highest. In the latter case, also for acrylonitrile rich mixtures, the relative polymerization rate of styrene tends to increase with conversion; this effect is attributed to preferential solvation of styrene. Possible explanation of these facts are briefly discussed.
Polymer crosslinking by a bimolecular peroxide decomposition
Authors: Chodák I. , Rado R.
Published: June 2010

The present paper examines the possibility of the utilization of the bimolecular cumyl hydroperoxide redox decomposition, catalyzed by Co11 naphthenate for the polymer crosslinking. The study of the mechanism and the kinetics of this reaction was performed both in a model medium heptane and polymer or polymer solution. In the case of redox initiation, the value of the crosslinking efficiency was found to be about 0.4, and its decrease can be attributed mainly to the formation of ions and, partly, to recombination of peroxy radicals producing dialkyl peroxide. On the basis of data obtained concerning the efficiency and rate of the process, conclusions are made on its applicability, especially for the crosslinking below the melting point of a crystalline polymer, as is the case of the crosslinking of polyethylene films.
Negative C2 values of inhomogeneous polymer networks measured in elongation
Authors: Janáček J. , Vojta V.
Published: June 2010

It was found that negative slopes of the Mooney‐Rivlin plot (negative C2 values) can be expected for polymer networks prepared by means of a crosslinking polymerization of respective monomers in the presence of large concentrations of a diluent, or for such systems having macroscopic porosity. Some examples are given for swollen poly (2‐hydroxyethyl methacrylate) networks prepared in the presence of high concentrations of water (porous systems), and/or ethylene glycol (nonporous systems), and also for a network of partially hydrolyzed polyacrylonitrile prepared in a similar way. Negative C2 parameters are probably connected with inhomogenous deformations of supramolecular domains in the stressed cross section of the systems studied.
Further rapidly reacting ion‐exchange resins
Authors: Bolto B. A. , Siudak R. V.
Published: June 2010

To overcome the very slow reaction rates of weak electrolyte ion‐exchange resins in neutral salt solutions, the resins must be used as microparticles. Ways of handling microparticles are outlined. The present study is aimed at the preparation of large composite particles containing basic and acidic polymers in domains which are clearly segregated so that minimum interaction between the sites of opposite character occurs. Because the domain size is small, rapid reaction rates are achieved. Resins which show this effect have been prepared from basic and acidic monomers by using blocking procedures involving counterions, which significantly reduce the association of the basic and acidic sites. However, although very rapid reaction rates are obtained, the ion‐exchange capacities of the products remain inferior to those of composites made by binding the active microparticles together with an inert binder, showing that substantial self‐neutralization has still taken place. Similar results are obtained with basic and acidic monomers by using precipitation techniques, which are aimed at grafting one monomer onto a precipitated macroradical prepared from the other monomer.
Thermogravimetric studies of polymethylenes and polyethylenes
Authors: Mucha Maria
Published: June 2010

Seven samples of polymethylene prepared during polymerization of diazomethane having different initial molecular weights and five samples of polyethylene (Lupolen type) having a different number of branches were studied by thermogravimetric analysis using Freeman Carrol's and Fuoss's methods to determine the number of CH3 groups per 1000 carbon atoms. The calculated activation energies reflect the effect of both molecular weight and the number of branches on the thermal stability of the polymer. Activation energy values decrease with the lowering of the molecular weight Mv of the polymethylene sample. This decrease of Mv occurred during the initial etching of the sample in fumic nitric acid. The activation energies of the branched polyethylenes decrease with the increase of the number of branches. Thermal stability of branched polyethylenes is lower than that of linear polyethylene.
Thermal oxidative stabilization of radiation‐crosslinked polyethylene‐ethylene propylene rubber blends
Authors: Kammel G. , Wiedenmann R.
Published: June 2010

The influence of co‐ and termonomers on the thermal‐oxidative stability of radiation‐crosslinked stabilized polyethylene‐ethylene propylene rubber (PE/EPR) blends is discussed. For these investigations the selected criteria were the induction period in the oxygen‐uptake test and the resulting mechanical properties after oven‐aging at 135°C.

From the experiments it has been concluded that the addition of only a small portion of EPR containing 5% dicyclopentadiene (DCP) as termonomer greatly reduces the protection against aging as compared to low density polyethylene. The protection against aging for those blends containing the tercomponent 5‐ethylidene‐2‐norbornene (EN) was found to be (up to a ratio of 80% EPDM (EN)) above the values obtained for PE/EPM blends. In this connection the influence of the polymeric antioxidant 2,2,4‐trimethyl‐1,2‐dihydroquinoline on the degree of crosslinking will be considered.
Photochemical decomposition of cyclohexadienone peroxides
Authors: Lind H. , Winkler T. , Loeliger H.
Published: June 2010

Photolysis products of 4‐t‐butyl‐peroxy‐4‐methyl‐2, 6‐di‐t‐butyl cyclohexadienone have been identified and a mechanism of their formation is given.
Some effects of morphology on oxidation and stabilization of polyolefins
Authors: Billingham N. C. , Prentice P. , Walker T. J.
Published: June 2010

Previous work on the effects of crystallinity on the autoxidation of polyolefins is briefly reviewed and shows that polyethylene and polypropylene oxidize exclusively in the amorphous phase. Measurements of the rate of oxidation of poly(4‐methyl pentene‐1) (P4MP) show that the oxidation is first‐order in oxygen pressure over a wide range of film thickness, oxygen pressure, and oxidation temperature. A simple model of diffusion followed by chemical reaction fits the data very well. Values of the diffusion coefficient for oxygen and of its activation energy, calculated from oxidation data, agree well with experiment.

It is shown that increased initial crystallinity increases the oxidation rate of P4MP, while the crystallinity of the polymer decreases markedly during oxidation. These results imply that P4MP oxidizes extensively in the crystal phase.

Ultraviolet microscopy shows that typical stabilizer molecules are rejected from the crystal phase of P4MP; comparison of oxidation induction periods in polypropylene and P4MP, containing antioxidants, supports the view that the effectiveness of stabilizers in P4MP is markedly reduced by rejection from the crystal phase.
Some oxidation characteristics of polypropylene
Authors: Frank H. P.
Published: June 2010

Oxidation and corresponding oxidative degradation of polypropylene was studied under varying conditions. Thermal oxidation in the melt (processing stability) was followed by multiple extrusions, by determining the induction period for oxygen take‐up (165–220°C) and the rate of oxygen take‐up. Various antioxidants of the sterically hindered phenol type were used in these experiments. Long term thermal oxidation (150°C oven aging) was carried out over a period of 400 hr and followed by determining polymer properties ([ζ], density, etc.), antioxidant concentration, and antioxidant decomposition products. Analogous tests were performed after exposing the polymer samples up to 1000 hr to boiling water. In photooxidation (xenon lamp, Spectrotest) the most effective wavelength range in the near UV was found to be at about 312 nm; but even at 378 nm a small photodegradation effect can be observed. The solubility of various additives (antioxidants and UV‐stabilizers) was determined in amorphous polypropylene, but reliable results were obtained for tetrakis [methylene 3‐(3′,5′‐di‐tert‐butyl‐4‐hydroxyphenyl)‐propionate] only (temperature range 100–200°C).
Influence of the arrangement of the crystals and the structure of the noncrystalline regions on the mechanical properties of polyethylene terephthalate
Authors: Biangardi H. J. , Zachmann H. G.
Published: June 2010

Amorphous samples of polyethylene terephthalate were stretched with different rates and stretching ratios at different temperatures. Afterwards they were crystallized. The arrangement of the crystals and the conformations of the chains in the noncrystalline regions were investigated by means of X‐ray wide‐angle scattering, X‐ray small‐angle scattering, birefringence measurements and nuclear magnetic resonance measurements. The influence of the morphological structure on the mechanical strength was determined. The stretching ratio itself generally does not characterize the orientation state. The structure obtained after crystallization depends mainly on the birefringence of the sample after stretching before crystallization. With increasing birefringence one obtains all intermediate structures starting from the well known spherulites composed of twisted lamellae in the unoriented material up to a paracrystalline lattice of lamellae split up into mosaic blocks in the highly oriented state. Also the conformations of the chains in the noncrystalline regions are influenced by the stretching. With increasing orientation the amount of tie molecules with comparatively large end‐to‐end distances becomes larger. The improvement of the mechanical properties with stretching is caused not only by the increasing orientation of the molecules but also by the increasing amount of taut tie molecules.