The paper presents the results of a study of the dilatometric properties of thermoplastic elastomer nanocomposites based on mixtures of random polypropylene, nitrile butadiene rubber, a compatibilizer - copolymer of polypropylene with maleic anhydride. Nanosized bentonite particles were used as a filler. The concentration of bentonite nanoparticles was varied in the range of 1.0-20 wt %. The values of the free and occupied specific volumes of nanocomposites were determined depending on the temperature and concentration of bentonite. The mechanism and kinetic regularities of the crystallization process of nanocomposites are established.
The work deals with the influence of the technological parameters of injection molding on the basic physicomechanical characteristics of nanocomposites of dynamically vulcanized thermoplastic elastomers based on random polypropylene and nitrile butadiene rubber of various grades. The equipment used was a single-screw molding unit with 4 temperature zones of the material cylinder. Rotational and translational movement of the screw allowed for uniform dispersion of the mixed components of the mixture. To improve the compatibility of the polymer components, a graft copolymer of polypropylene with maleic anhydride at the value of 1-3 wt. % was used as compatibilizer. The influence of the temperature regime of the material cylinder of the injection machine and the molding pressure on the ultimate tensile stress, elongation at break, elastic modulus on bending and volume shrinkage is studied. It is shown that an increase in the indicated technological parameters of molding leads to an increase in strength indicators and a noticeable decrease in the volume shrinkage of dynamically vulcanized thermoplastic elastomer nanocomposites. The influence of mold temperature and holding time under pressure on the ultimate tensile stress and elongation at break of nanocomposites has been considered and optimal conditions for their cooling in the mold established. Besides, the effect of nanocomposites of dynamically vulcanized thermoplastic elastomers with various types of nitrile butadiene rubber on the ultimate tensile stress and elongation at break of nanocomposites analyzed. It revealed that, unlike random polypropylene, dynamically vulcanized nanocomposites are characterized by isotropic properties which make it possible to obtain highquality structural materials of complex configuration.
The literature data on the problems of obtaining and studying polymer composite materials, nanocomposites, dynamically vulcanized elastoplasts are presented. Phase transformations and their infl uence on the structure and properties of multicomponent polymer systems are considered.
The paper presents the results of a study of the thermodefomational characteristics of dynamically vulcanized thermoplastic elastomers based on random polypropylene and nitrile butadiene rubber (SKN). In order to improve the compatibility of polymer mixtures, Exxelor PO1200, a grafted copolymer of polypropylene with maleic anhydride, was used as a compatibilizer. The concentration of maleic anhydride in the composition of the grafted copolymer was 3.0 wt. %. It was shown that as a result of the loading of the compatibilizer, it seemed possible to improve the compatibility of bipolar mixtures, in which there was no separation between the components of the mixture. It was found that with the load of 30 wt. % SKN-18, as well as 40 wt. % SKN-26 or SKN-40 into the composition of random polypropylene, the polymer composition exhibits the properties of thermoplastic elastomers, as a result of which plastic deformation is replaced by a highly elastic characteristic for rubbers. The temperature regions of the solid, highly elastic, and viscous flowing states are determined. In order to give polymer blends greater elasticity, they were vulcanized using crosslinking agents such as dicumyl peroxide and sulfur. It is shown how, in the process of increasing the concentration of dicumyl peroxide from 0.25 to 1.0 wt. %, the thermomechanical properties of dynamically vulcanized thermoplastic elastomers significantly change. It was found that with the introduction of dicumyl peroxide in an amount equal to 1.0 wt. %, the melt flowability of vulcanized materials almost completely lose their ability to flow, and pass from a highly elastic state to a glassy one. With the load of sulfur in an amount of 1.0 to 10 wt. %, the melt flowability of the vulcanized thermoplastic elastomers is preserved.
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