Plant-derived p-hydroxyphenylacrylic acid-derived epoxy resins exhibit excellent flame retardancy, hydrophobicity, degradability, and low dielectric loss after curing with bio-based fluorinated Schiff bases

Abstract

Epoxy resins are designed to achieve high flame retardancy, hydrophobicity, and dielectric properties. However, the search for sustainable bio-based epoxy resin precursors that do not require additional flame retardants is still underway. Herein, we report a p-hydroxycinnamic acid-derived epoxy resin monomer (HCA-EP) obtained via a simple one-step reaction. HCA-EP can be combined with 4,4′-((2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-dial)bis(azanylylidene))bis(methanylylidene))bis(2,6-dimethoxyphenol) (SA-BTB) and cured to prepare epoxy resins(HCA-EP/SA-BTB). In comparison to HCA-EP cured with a common petroleum-based curing agent(HCA-EP/MeHHPA), such as methylhexahydrophthalic anhydride (MeHHPA), HCA-EP/SA-BTB exhibited a significantly high glass transition temperature (170 °C), excellent hydrophobic properties, and lower dielectric loss. In addition, HCA-EP/SA-BTB passed the V-0 flame rating of the UL-94 test and exhibited an ultimate oxygen index of 43.3%. Notably, it demonstrated a coke yield of 42.3% under N2 conditions, whereas that of HCA-EP/MeHHPA was 18%. Moreover, its flame-retardant index was found to be 19.8, indicating its excellent flame-retardant properties. Further, it could be degraded under acidic conditions. These findings indicate that the proposed method can be used to develop high-performance bio-based thermoset materials.