Synthesis and blend of bio-based benzoxazines from cardanol and diphenolic acid

Abstract

In this study, two benzoxazine monomers, m-alkylphenyl-3,4-dihydro-2H-benzoxazine (CA-Bz) and 4,4-Bis-[6-(3-phenyl-3,4-dihydro-2H-1, 3-benzoxazine)] pentanoic acid (DPA-Bz) were successfully synthesized from fully bio-based phenols (cardanol and diphenolic acid). Their structures were confirmed by FTIR and NMR spectroscopy. CA-Bz/DPA-Bz blend was prepared at weight ratio of 3:1. Polymerization behavior of the blend was investigated by DSC. The ring-opening polymerization temperature of CA-Bz was found to decrease significantly by incorporation of carboxyl groups in DPA-Bz showing thereby the catalytic effect of acid functionality. The modified polybenzoxazine also showed an enhancement of the thermal properties.