The development of optimal conditions for the synthesis of the nitrile-butadiene rubbers with enhanced frost resistance

Currently, there are high requirements for finished rubber products, in particular, for products that are operated in the Far North. The purpose of this work is to determine the optimal conditions for the production of nitrile butadiene rubbers, which provide an increase in the frost resistance of materials based on them while maintaining a high level of physical, mechanical and operational properties. The paper presents polymerization recipes and synthesis conditions. It was found that the fractional addition of acrylic acid nitrile and molecular weight regulator provide optimal conditions for obtaining synthetic rubber with the desired characteristics. The results of testing prototypes for chemical composition and physical and mechanical properties comply with the technical specifications for rubbers of the SKN-SNT brand. Rubbers and vulcanizates SKN 20SNT are the most promising for the creation of frost-oil-resistant products. Physical and mechanical tests have shown that the vulcanizate of the SKN 15SNT sample obtained under optimal synthesis conditions has a tensile strength of 22.7 MPa, an elongation at break of 485%, and a frost resistance coefficient of 0.84. It was also found that the vulcanizate of the SKN 20SNT sample, obtained under optimal synthesis conditions, has a tensile strength of 24.0 MPa, an elongation at break of 478%, and a frost resistance coefficient of 0.61. An increase in the oil and petrol resistance of frost-resistant rubbers and SKN 15SNT vulcanizates can be realized by controlled crosslinking of rubber polymer chains at the polymerization stage. The continuation of this work will be extended tests of prototypes SKN 15SNT and SKN 20SNT in order to determine such indicators as glass transition temperature, average molecular weight, molecular weight distribution, degree of polydispersity, gel content, compositional uniformity, etc.