Preparation of thermally curable materials using lignin extracted from sawmill co-product†

Abstract

We have exemplified the chemical reactivity of a new commercially available organosolv-like lignin via reaction with various amines to form benzoxazine groups. The resulting benzoxazine-modified lignin has desirable thermal properties, making it an attractive alternative to non-renewable benzoxazine resins. The thermal properties of the lignin-benzoxazine products can be altered by increasing the number of benzoxazine groups within the lignin. This is achieved by increasing the number of unsubstituted phenol groups in the lignin prior to benzoxazine formation, thereby increasing the number of benzoxazine groups added to the lignin. We were ultimately able to form a curable system from phenolated lignin prepared from lignin extracted from low-value biomass using ultrasonic biorefinery technology via functionalisation with benzoxazine groups. The properties of the new lignin-based benzoxazines are compared to those of Kraft lignin (obtained from pulp) modified by the same chemical reactions.