Comprehensive performance improvement and functional upgrade of Magnolia-based epoxy resins

Abstract

The magnolol- (MEP) and honokiol-epoxy resin (HEP) were prepared from the extract of the natural plant Magnolia officinalis. Those monomers were cured with hardeners, such as 4,4-diamino diphenyl sulfone (DDS) and 4,4′-bis (3-aminophenoxy) diphenyl sulfone (BDS), respectively via solvent-free process to fabricate networks with excellent mechanical properties. The curing procedures occurred in a wide temperature interval (65 °C), which made the concerning vacuum-assisted resin infusion feasible. Notedly, all combinations exhibited increased thermal stability (T_d5, 359.7–381.9 °C) with T_max fluctuating around 450 °C. The phase transition temperature (T_α) screen suggested that except MEP/BDS (T_α, 147.2 °C), other combinations varied from 264.2 °C to 281.2 °C. In addition, DDS allowed the networks with slightly lower thermal expansion coefficients (CTE, 68.1 ppm/ ^oC, <180 °C for HEP/DDS), while the BDS yielded relatively high CTE values (87.1 ppm/ ^oC, <106 °C, for MEP/BDS). The LOI value (33 %) and vertical burning test (UL-94) indicated their outstanding flame retardancy (UL 94 V-0). Furthermore, for MEP/BDS, the unique solvolysis (in DMF or THF) and thermally induced shape memory properties along with the superior flame retardancy demonstrated its overall high performances. As a whole, these performance improvements further facilitate the high-end applications of sustainable resins in cutting-edge areas.