G. E. Zaikov

Recent Advances in Flame Retardancy of Polymeric Materials

Abstract The Seventh Annual Conference on Flame Retardancy was held in International Plaza Hotel in Stamford, Connecticut, USA on May 20-22, 1996, As before it was organized and sponsored by Business Communications Company (BCC). Scientists from 15 countries (USA, Canada, Germany, Israel, Russia, Belorussia, Italy, UK, China, Taiwan, Japan, France, South Korea, Sweden, Ireland) contributed in the conference. The meeting was aimed to: Create a forum for introducing new technological achievements and development in the field of flame retardancy Review the current state of science and technology in FR Review in applications and markets for FR products Present recent devolopment in local and global standardization and in testing technology Discuss toxicity and environmental issues Provide a unique opportunity for newcomers to FR research technology and marketing to become acquainted with the FR field in all its aspects Discuss halogen-based and non-halogen-based flame retardant chemicals, synergism, intumesce...

The modeling of the simultaneous transport of solvent and low-molecular compounds in swelling polymers

Abstract Mathematical model has been developed in order to predict the behavior of systems consisting of hydrophylic polymer, water, and low-molecular compound. The model has taken into account the processes of swelling of polymers during water sorption. the existence of embedded form of drug in polymer matrix and some others processes. The dependencies of physico-chemical parameters on concentration of water, drug and on mechanical properties of poiymer were justified by corresponding experimental results. Different ratios of these parameters enable to predict the behavior of matrix systems for controlled release of drugs.

Thermal degradation studies of alternating copolymers: I—maleic anhydride-vinyl acetate

Abstract The thermal degradation of the alternating copolymer of maleic anhydride and vinyl acetate has been studied by thermal volatilisation analysis (TVA). An investigation of the decomposition products and a comprehensive analysis of the residues have been made using subambient TVA, IR spectroscopy, 1 H and 13 CNMR spectroscopy, the GC-MS technique and UV spectroscopy. On the basis of this evidence, a mechanism of degradation has been suggested. Under programmed heating at 10°C min −1 , two stages of breakdown, with rate maxima at 260 and 420°C, were observed. The products consisted of acetic acid, carbon dioxide, carbon monoxide, maleic anhydride and water. Acetic acid, carbon dioxide and traces of carbon monoxide were also observed in a detailed isothermal investigation at 205°C. It is suggested that, following the initial loss of acetic acid, structural rearrangements in the polymer chain can occur, with the formation of conjugated double bonds, so accounting for the colour of the partially degraded residues. Some hydroxyl groups are also formed. During degradation, insolubility develops, which has been attributed to reduction in the flexibility of the backbone and some intermolecular dehydration of OH groups. The interaction between the copolymer (or its residue) and water is discussed in relation to potential applications of this material.

The influence of biodegradation on the loss of a plasticiser from poly(vinyl chloride)

The influence of biodegradation by the microscopic fungus Aspergillus niger on the diffusion desorption of a dialkylphthalate plasticiser from PVC was studied. It is shown that the loss of dialkylphthalate accelerates with bio-overgrowth on the PVC. Loss of plasticiser is limited by its diffusion in the material volume in the case of bio-overgrowth, whereas loss from the same polymer in the absence of bio-overgrowth is evaporation limited.

Kinetics and Mechanism of the Oxidation of Stressed Polymer

The fundamental property of chemical reactions in solid polymers is the dependence of reaction kinetics on the structural and molecular-dynamical parameters of a matrix. The latter may differ significantly under stress. Current data concerning the kinetics of oxidation of stressed polymers are reviewed in terms of the relation between stressed polymer structure and molecular motion on the one hand and chain radical reaction kinetics on the other. The influence of stretching stress on different steps in the chain autoxidation process and the relation between oxidation kinetics and polymer durability are discussed for the oxidation of polyolefines.

Phenol antioxidant consumption rate in polypropylene

Abstract The kinetics of the consumption of three sterically hindered phenols in polypropylene (PP) and chlorobenzene at 130°C has been studied. It is shown that under these conditions the rate of consumption of inhibitor is largely controlled by its oxidation by atmospheric oxygen. New inhibitors, including those chemically bonded to polymer macromolecules, are formed in PP in the process of phenol conversion. The observed behavior of these bonded inhibitors suggests that they can be tentatively ascribed to the methylene quinone class.

The initiation of polypropylene oxidation

Abstract The rate of primary initiation of the oxidation of polypropylene (PP) containing catalytic centers from inclusion of transition metals was evaluated. The rate was determined from the retardation period of the oxidation reaction in the fracture spots of stressed PP films with an inhibitor, when the retardation period was close to the value of durability; the number of initiation centers was taken into account. For this purpose, the predicted durability of samples was calculated for the concentration of initiation centers characteristic of the polymer without additives. Inhibited PP films with various complexing agent contents introduced into the polymer to deactivate the catalytic centers were studied. The rate of initiation was shown not to change in the presence of the complexing agent, while the number of centers changed. Comparison of the oxidation kinetics, derived from the oxygen absorption by using data from this study, showed that the macrokinetic parameters were dependent on the number of initiation centers. Thus, the kinetic regularities were shown to be related to the catalytic activity of initiation centers and also to their concentration.

Study of the ozone degradation of polybutadiene, polyisoprene and polychloroprene in solution

Some characteristics of the degradation of polybutadiene, polyisoprene and polychloroprene by ozone in CCl4 solution have been studied. It has been shown that the conditions of O3 mass transfer in the bubbling reactor, upon which the values of the rate constant of the reaction of the elastomer with O3 depend, significantly influence the decrease in the molecular mass observed viscosimetrically. Some differences in the degradation mechanisms of the elastomers were examined using infra-red spectroscopy and functional analysis. The results obtained demonstrate that the efficiency of the degradation processes in terms of O3 consumed increases in the order 1,4-cis-polybutadiene, 1,4-cis-polyisoprene and polychloroprene.

MORPHOLOGICALLY SPECIAL FEATURES OF POLY(3-HYDROXYBUTYRATE)/LOW-DENSITY POLYETHYLENE BLENDS

In an effort to investigate the morphology of biodegradable films, the combination of differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared polarization spectroscopy methods are used. The methods enable one to examine the structural and morphological peculiarities of extruded blend compositions on the base of low-density polyethylene (LDPE) and poly(3-hydroxybutyrate) (PHB) at concentrations of the latter ranges from 0 to 32 wt%. The blend components are thermodynamically incompatible and form the proper morphological elements with good visible interfaces between the disperse phase (PHB) and the continuous matrix LDPE. For film extrusion, blend components affect each other, as is seen by the crystallinity drop for both PHB and LDPE. The dichroism measurements show that the axes of LDPE and PHB molecules are presumably located at right angles, therewith the largest axes of the PHB crystallites are oriented along the extrusion direction. The matrices at all blend ratios, besides 32 wt% composition, are reinforced by alternative bandlike and cylinderlike fibriles of PHB. The architecture of such morphological elements is carefully studied by the SEM method.

Peculiarities of inhibiting the autooxidation of solid polypropylene with 4,4′-bis(2,6-di-tert-butylphenol)

Abstract The kinetics of 4,4′-bis(2,6-di-tert-butylphenol) (BP) consumption in the oxidation of polypropylene (PP) (at 130 °C, in air) has been studied. It is shown that 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ) is the main product of conversion on starting BP. A synergism has been revealed on studying stabilization of PP with the BP-DPQ mixtures. The antioxidative activity of BP was compared with that of some other stabilizers.