Dual-Curing MWCNT nanocomposites for Energy-Efficient electroactive shape memory and In-Situ processing

Abstract

Dual-curing thermosets offer a promising solution to overcome the traditional limitations of epoxy systems, particularly in terms of shape adaptation and post-curing processing. However, there is still limited knowledge on the influence of the thiol-epoxy ratio and the use of reinforcements. In this work, we present a dual-curing thiol-epoxy system with latent anionic homopolymerization, reinforced with 0.175 wt% multi-walled carbon nanotubes (MWCNTs). This combination enables the integration of shape memory, thermoformability, and electrothermal functionality, adding multifunctionality to the system. The system was evaluated across different thiol:epoxy ratios (0.4, 0.6, 0.8, and 1.0). All formulations maintained or improved thermal, mechanical, and electrical properties, with tunable glass transition temperatures and excellent stiffness. Thermomechanical analysis revealed a post-curing processing window exceeding 40 °C, enabling robust shape memory programming. Joule heating experiments confirmed electroactive shape recovery at voltages as low as 55 V, with temperature control up to 175 °C and > 90 % thermal homogeneity. Energy savings through Joule heating for second cure and shape memory of up to 99 % compared to conventional heating were demonstrated. A comprehensive shape-memory analysis was performed, analyzing the influence of the angle restriction fixation (135°, 180°) as well as the heating source (oven or Joule heating), achieving fixations and recoveries > 90 % for some conditions. Furthermore, permanent shape fixation of complex forms was achieved through both convection and Joule-induced second curing. This work demonstrates, for the first time, the integration of electroactivated shape memory, in-situ curing, and energy efficiency in a dual-cure CNT-reinforced epoxy system, supported by both simulations and proof-of-concept validation.