Non-isocyanate polyurethane (NIPU) from tris-2-hydroxy ethyl isocyanurate modified fatty acid for coating applications

Conventional polyurethanes, in spite of their excellent properties and wide applications possess safety and handling issues related to isocyanate compounds while synthesis. The cyclic carbonate-amine reaction resulting into hydroxyurethane is said to be an isocyanate free polyurethane system and novel route of synthesis as well as good alternative to conventional polyurethanes. In the present work, non-isocyanate polyurethane was synthesized by modification of dehydrated castor oil fatty acid (DCOFA) with tris-2-hydroxy-ethyl isocyanurate (THEIC). The synthesis involved three steps viz esterification of DCOFA with THEIC, epoxidation of the ester formed (TEFA) and subsequent cyclocarbonation of THEIC–ester of fatty acid (CTEFA). The products obtained were confirmed by Fourier Transform Infrared Spectroscopy (FTIR) as well as 1H and 13C Nuclear Magnetic Spectroscopy (NMR). The CTEFA was cured with various amines such as dimethyl diphenyl sulphone (DDS), Isophorone Diamine (IPDA) and hexamethylene diamine (HMDA) to obtain NIPU coatings. The cured coatings were studied for chemical, mechanical, thermal and electrochemical properties. Also, the effect of amine curing agents on the performance of NIPU coatings was investigated. Experimental results showed that incorporation of THEIC into the system significantly improved coating properties.