Synthesis and properties of the vapour-grown carbon nanofiber/epoxy shape memory and conductive foams prepared via latex technology

Vapour-grown carbon nanofiber (VGCNF)/epoxy foams were prepared via latex technology. VGCNFs were first dispersed in water-borne epoxy resin by intensive stirring and then mixed with curing agent and blowing agent at room temperature. VGCNF/epoxy foams were obtained from these mixtures via freeze-drying and foaming under a vacuum at 100 °C. The shape memory properties of the epoxy foams were evaluated together with other physical properties. Compression and thermo-mechanical cycle tests were performed to measure the effects of the VGCNFs on the mechanical performance of the foams. Electrical conductivity was measured using a standard four-point method. The experimental results indicated that the VGCNF/epoxy foams had a low glass transition temperature of 48 °C, resulting in a fast recovery rate at 65 °C in 10 s. The epoxy foam had a high shape recovery and fixity ratio of more than 90% after several thermo-mechanical cycles with the addition of 1.0 wt% VGCNFs. The VGCNFs enhanced the strength and electrical conductivity of the epoxy foams. The percolation threshold for conduction was approximately 0.6 wt% of VGCNFs in the composites. Moreover, the electrical conductivity of the improved epoxy foam did not significantly decrease with increasing thermo-mechanical cycles below 80% compression strain.