Effect of Chemistry and Process Parameters on Shape Recovery Behaviour of Shape Memory Epoxies in Flexure

Abstract

Epoxy based Shape Memory Polymers (SMEPs) of varying crosslinking densities were prepared by reacting an aromatic epoxy resin, Diglycidyl Ether of Bisphenol A (DGEBA) with different aliphatic amines varying in chain lengths, triethylenetetramine (TETA), 2,2′ethylenedioxybisethylamine (EDEA) and 4,7,10-Trioxa-1, 13-Tridecanediamine (TTD). Shape memory tests were conducted for all three SMEPs by deforming the samples at temperatures greater than their Tg in flexure (3 point bending). The effect of crosslinking density (CLD), shape fixing temperature (Tfix) and shape recovery temperature (Trec) on shape memory behaviour of SMEPs were studied systematically. In terms of the chemical structure, the results showed that with the increase in CLD, glass transition temperature (Tg) increased with an associated reduction in the shape recovery behaviour. However, superior shape memory behaviour was observed for lower CLD SMEPs. With respect to the process parameters, as the Tfix was lowered below the Tg, % shape fixity increased and the recovery curves shifted towards higher temperature. When Trec was increased above the Tg, recovery rate increased.