Shape-memory actuators based on dual-curing thiol-acrylate-epoxy thermosets

In this work, new shape-memory thermosets have been developed using a thiol-acrylate-epoxy dual-curing system. A previously studied system has been successfully modified, introducing different amounts of tri(2,3-epoxypropyl)isocyanurate (ISO) and bisphenol A glycerolate (1 glycero/phenol) diacrylate (BAGA) in order to enhance the thennomechanical properties and the glass transition temperature of the final materials. Preliminary studies on the curing process proved that the curing process is not affected, and the critical ratio remains unchanged. Glass transition temperatures and thermomechanical properties were successfully improved, extending the applicability of these thermosets to the field of soft-actuator. Shape-memory behavior was comprehensively investigated in unconstrained, fully and partially constrained conditions. Unconstrained experiment results showed excellent shape fixation and recovery, coupled with a fast recovery process. On the other hand, fully and partially constrained recovery experiments evidenced optimal performances obtained by the combination of both high crosslinking density and high deformability in the programming stage. Considerably high values of recovery stress (up to 7 MPa) and work output (up to 1300 kJ/m(3)) were found confirming the high potentiality of these dual-cured thermosets in the field of soft-actuation.