Cardanol-based benzoxazine and its potential with ammonium polyphosphate in flame-retardant coatings

Abstract

Polybenzoxazine is a versatile polymer that has high thermal stability, high char yield and inherent flame-retardant properties. Increasing attention is being paid to the synthesis of bio-based benzoxazines using renewable materials. This is attributed to the availability of phenols and primary amines in their precursors and the ability to rival their petroleum-based counterparts. A protocol for cardanol-based benzoxazine synthesis from cardanol and hexamethylenetetramine was optimised for scalability. The cardanol-based benzoxazine was then mixed with ammonium polyphosphate (APP) in different ratios to achieve flame retardancy. The results suggested that increasing the APP/benzoxazine ratio improved its flame retardancy and improved the density and homogeneity of the char layer.