Magnolol-based bio-epoxy resin with acceptable glass transition temperature, processability and flame retardancy

Development of sustainable bio-based epoxy resins having better comprehensive properties than available petroleum-based epoxy resins is of paramount importance for alleviation of energy pressure and enrichment of the potent category of high-performance epoxy resins. In this study, a fully bio-based epoxy resin precursor (DGEM) was synthesized from a naturally occurring magnolol through a highly efficient one step process. The bio-based epoxy resin obtained was then cured with 4, 4′-diaminodiphenyl sulfone (DDS) and compared to the petroleum-based commercial diglycidylether of bisphenol A (DGEBA). After curing with DDS, DGEM/DDS showed higher glass transition temperature than DGEBA/DDS which was 279 °C and 231 °C, respectively. The char yield (in N2), storage modulus and flexural modulus of the former were 1.9-fold, 47.5%, and 41.3% higher than those of the latter, respectively. Interestingly, bio-based epoxy resin of DGEM exhibited excellent processability with extremely low viscosity of 0.155 Pa·s at room temperature and a broader processing window than DGEBA/DDS as well. To exhibit such an excellent processability is very rare for high-performance epoxy resins. In addition, the cured DGEM/DDS also showed outstanding intrinsic flame retardancy, which passed the V-0 rate of UL-94 test. This study offers an opportunity to prepare bio-based epoxy resins with better properties than DGEBA and exhibits great promise in cutting-edge applications.