Properties of Siloxaneurethane Coatings Produced Without the Use of Polyisocyanates

In 2021, the market for polyurethanes, which are widely used in various industries and, in particular, are the film-forming base for a significant share of high-quality industrial paint and varnish materials, was valued at around USD 73 billion. The polyisocyanates used in the production of polyurethanes are toxic substances that have harmful effects on the environment and human health. This prompted the European Union to adopt a regulation proposing to reduce the content of isocyanates in order to prohibit its use in the future. In connection with the above, research is underway to develop ways to produce polyurethanes without the use of isocyanates, the so-called non-isocyanate polyurethanes. The factors restraining the wide application of non-isocyanate polyurethanes as a film-forming base for paint and varnish coatings are insufficiently high reactivity of cyclocarbonate groups with respect to amines. This paper reports an attempt to eliminate the above drawback by using for curing epoxy coatings a mixture comprising the reaction product of trifunctional cyclocarbonate with diethylenetriamine and aminosilane, which, in addition to amine structuring of the epoxy oligomer, is capable of participating in chemical crosslinking by condensation of silanol groups formed by hydrolysis of ≡SiOC2H5 by air moisture. On the basis of different mass ratios of synthesized aminourethane, epoxy resin and aminopropyltriethoxysilane, hybrid-curing coatings were obtained. A comprehensive study of their performance properties showed that the inclusion of a reactive organosilicon component in their composition contributes to the increase in heat resistance and hardness. The latter, together with a decrease in the elasticity of coatings at a certain content of aminosilane, confirms the formation of additional crosslinked siloxane bonds during the formation of coatings.