THE INFLUENCE OF ETHYLENE COPOLYMERS WITH VINYL ACETATE ON PROPERTIES OF RUBBER BASED OF BUTADIENE-NITRILE CAOUTCHOUC

Rubber-technical products, which are used in the oil and gas industry, must have high thermal and aggressive strength. Rubbers based on butadiene-nitrile caoutchoucs are usually used for these purposes, since they have good operational properties. However, under the influence of elevated temperatures, the resistance of such rubbers to the action of petroleum products is reduced, as a result of which the physico-mechanical characteristics decrease. To improve the operational properties of rubber-technical products, various technological additives are introduced into the rubber mixtures. Such additives can be copolymers of ethylene with vinyl acetate(EVA), which increase the resistance of rubbers to action of high temperatures and aggressive media. This is due to the fact that these copolymers are well combined with butadiene-nitrile caoutchoucs, forming coordination bonds with rubber molecules, which contributes thereby increasing in the elastic-strength and performance properties of rubber. In this connection, the influence of EVA (sevillenes 11104-030, 11808-340 and MarPol 1802), differing in the content of vinyl acetate units, on the rheometric, physico-mechanical and operational properties of the rubber mixture based on butadiene-nitrile rubber in this paper was investigated. The study was carried out to improve the thermo-resistance of rubber used for the manufacture of oil and petrol resistant rubber-technical products for the oil and gas industry. The rubber mixture was prepared on laboratory rolls and standard samples were vulcanized in an electrically heated press. The study of rheometric properties has shown that EVA affect the characteristics of the vulcanization process of a rubber mixture. For vulcanizates, the influence of the content of EVA in a rubber mixture on the physical and mechanical properties was studied: the conditional tensile strength, elongation at break, tear resistance, rebound elasticity, Shore A hardness, relative compression deformation. The effect of the standard liquid ZHR-1 on the change in these properties, as well as the degree of swelling of the vulcanizates after their daily soaking in the standard liquid SZHR-1 and a mixture of isooctane + toluene, was studied. It has been established that vulcanizate of a rubber mixture containing sevilene 11808-340 is characterized by the best physico-mechanical and operational properties.