Biobased epoxy resin with ultrahigh glass transition temperature over 400 °C by post-crosslinking strategy

Developing superior heat resistant biobased thermosetting resins is an interesting challenge. Herein, a novel tetra-functional biobased epoxy monomer with phenylpropargyl ether groups (BPBMO) was synthesized, which was then cured with 4,4′-diaminodiphenylmethane (DDM) to produce a biobased resin (BPBMO/DDM), the aggregation structure and integrated properties of BPBMO/DDM were systematically researched and compared with those of commercial petroleum-based DGEBA/DDM. Glass transition temperature (Tg) of BPBMO/DDM is as high as 407 °C, which is not only about 207 °C higher than that of DGEBA/DDM, but also the highest value among all biobased epoxy resins reported. Besides, BPBMO/DDM resin shows higher flame retardance with lower peak heat release rate (pHRR), total heat release (THR) and total smoke production (TSP) than those of DGEBA/DDM. These outstanding performances were beneficial from the unique structure of BPBMO/DDM formed with the ring open reaction between epoxy and amino groups as well as the post-crosslinking of phenylpropargyl ether groups. This work proposes an effective post-crosslinking strategy from the molecular structural design to construct an ultrahigh heat resistant biobased epoxy resin with good flame retardancy.