SUSTAINABLE BENZOXAZINES

Abstract

Rapid advancements in the field of polymers are fast changing the conventional material applications. High performance and wide applicability are key requirements governing the market growth and demand of any particular polymeric resin. In the same vein, polybenzoxazines (PBz) have emerged as a superior class of thermoset resins with superior properties viz. near zero shrinkage, high glass transition temperature, minimal moisture absorption, appreciable mechanical strength and high thermal stability, to name a few. Thus, along with economic viability, PBz resins have gained a strong foothold breaching the traditional domains of epoxies and bismaleimides. The same is evident in the rapid commercialization of PBz resins in the last few decades of their conception. Despite the great promise this class of materials has exhibited, full realisation of their properties has not been achieved yet which may be attributed to certain drawbacks viz. the high temperatures required for ring opening polymerization, low cross link density and brittle nature. Moreover, excessive reliance of PBz industry on petro based feed stock is also a limitation due to rapidly depleting fossil reserves and environmental hazards. This study was conducted to address these research gaps impeding further expansion of PBz resins. newlineOn these lines scalable and cost effective renewable feed stock i.e. naturally occurring phenols viz. cardanol and eugenol have been identified for benzoxazine (Bz) synthesis. The synthetic methodology followed is one pot, atom economised and solvent less with water as the only by- product ensuring a sustainable synthesis. A novel strategy of higher oxazine functionalisation of cardanol Bz was carried out and the efficacy of this strategy was studied in detail by both experimental and kinetic studies. The Bz resins reserve an immense scope of applicability by the virtue of their molecular design which was well utilised in this study to synthesis high loading (gt90%) sulphur copolymers by means of inverse vulcanisation. Thes