Preparation of shape memory epoxy composite materials and investigation of their properties

The main purpose of this study is to prepare shape memory polymer composites using bisphenol A and bisphenol F-based epoxy resin with three different curing agents (methyl-5-norbornene-2,3-dicarboxylic anhydride (MNA), cycloaliphatic polyamine, and citric acid). In this study, polyethylene glycol (PEG) was used as a plasticizer. Furthermore, different amounts of sepiolite and colemanite (1, 3, 5, and 10 wt.%) were used as a sustainable filler. Moreover, the structure and the morphology of the composites were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The mechanical and thermal properties, as well as shape memory behavior of the composites, were investigated by tensile tests, differential scanning calorimetry (DSC) analysis, and bending tests, respectively. According to the results, the tensile strength of the epoxy increased with increasing filler content. The optimum condition of the composites was 10 wt. % PEG and 5 wt.% filler content for MNA and cycloaliphatic polyamine cured epoxies, and 10 wt. % PEG for NPEL 128 and 5 wt. % PEG for NPEF 170 and 3 wt.% filler content for citric acid cured epoxies. The NPEF 170 epoxy resin composites had much lower glass transition temperature than the NPEL 128 composites. The glass transition temperature (Tg) decreased in the presence of PEG and fillers. The epoxy composites exhibited good shape memory performance. The recovery time of all the composites with increasing temperature. The optimum temperature was found to be at 110 oC for MNA and cycloaliphatic polyamine curing agent, and 100 oC for citric acid in the case of the shape memory cycle tests. All composites achieved high recovery values (Rr) of around 99% and 98%. NPEF 170 epoxy composites showed faster shape recovery time. Ten consecutive shape memory cycles have been conducted for the epoxy composites.