Studies on catalyst assisted low-temperature curing of benzoxazines

Abstract

The present study addresses an increasing interest in achieving low-temperature curing of benzoxazines by utilizing chemical substances with acid moieties of varying functionalities as curing catalysts. Specifically, cardanol-furfurylamine (1), card-bisphenol-furfurylamine (2), bisphenol-A-aniline (3) and bisphenol-F-aniline (4) based benzoxazines were chosen for curing studies. The selected catalysts were systematically applied into benzoxazines and its curing behavior was studied with minimum amount of 5 wt%. Catalysts, including those with carboxyl and N,N-dimethyl functionalities, were evaluated based on their performance, with a focus on their substituent effect on curing behavior. The results contribute to the identification of catalysts with optimal potential for achieving the efficient low-temperature curing of benzoxazines with an objective of utilizing them for wide area of applications. Among the catalysts studied, gallic acid was found to be the better catalyst and reduces the curing temperature to 130 °C. The conversion graph for both bisphenol-A-aniline benzoxazine (3) in the absence of catalysts and bisphenol-A-aniline benzoxazine in the presence of catalysts (3 s) have been studied by DSC analysis. The activation energy (Ea) has been calculated using Kissinger-Ozawa method through DSC analysis. Data resulted from different catalysts used for curing of benzoxazines, it was inferred that the pKa values of the catalysts also play a crucial role in the polymerization of benzoxazines. Further, the study aims to meet the growing demand for efficient and economically viable low-temperature curing processes for benzoxazines.