Reprocessible Epoxy Networks with Tunable Physical Properties: Synthesis, Stress Relaxation and Recyclability

In order to extend the application of epoxy vitrimer, 1,4-cyclohexanedicarboxylic acid (CHDA) was used as a co-curing agent and structure modifier for sebacic acid (SA) cured diglycidyl ether of bisphenol A (DGEBA) epoxy vitrimer to tailor the mechanical properties of epoxy vitrimers with 1,5,7-triazabicylo[4.4.0]dec-5-ene (TBD) as a transesterification catalyst. The glass transition temperature (Tg) of vitrimer increased gradually with the increase in CHDA content. Vitrimers behaved from elastomer to tough and hard plastics were successfully achieved by varying the feed ratio of CHDA to SA. Both the Young’s modulus and storage modulus increased apparently with the increase in CHDA content. Stress relaxation measurement indicated that more prominent stress relaxation occurred at elevated temperatures and the stress relaxation decreased with the increase of CHDA content due to the reduced mobility of the vitrimer backbone. The vitrimers showed excellent recyclability as evidenced by the unchanged gel fraction and mechanical properties after compression molded for several times. With tunable mechanical properties, the epoxy vitrimers may find extensive potential applications.