Fabrication and curing properties of o-cresol formaldehyde epoxy resin with reversible cross-links by dynamic boronic ester bonds

Conventional cured o-Cresol Formaldehyde Epoxy Resin (o-CFER) with permanent crosslink network is relatively stiff, brittle, and unrecyclable. In order to overcome these defects, herein 2,2′-(1,4-phenylene)-bis [4-mercaptan-1,3,2- dioxaborolane] (BDB) is employed as curing agent and a novel type of covalent adaptable network o-CFER is constructed by the reaction between thiols in BDB and epoxy groups in o-CFER. Obtained curing o-CFER vitrimers possess superior thermostability and good mechanical properties. Because of the transesterification of boronic ester bonds, o-CFER network topologies can be altered, contributing a self-healing ability and shape memory to the produced polymer. Besides, it is investigated the effects of the healing time and temperature on self-healing capability and achieved a healing efficiency of above 95% at 160 °C for 12 h. Moreover, through hot press, the pulverized samples of 8%C-o-CFER can be reshaped several times and mechanical properties of the recycled samples are well-restored even higher than those of pristine after being remolded at 200 °C for 60 min.