Preparation And Performance Study Of Triple Shape Memory Epoxy Composites

Compared with conventional dual-shape memory polymers(DSMPs), notable triple-shape memory polymers(TSMPs) can be better potential applied in aerospace structures, biomedical devices, textiles, and so on.To achieve the triple shape memory effects of epoxy(EP) polymers and simplify the preparation technology of triple shape memory polymers, epoxy polymers with good versatility and dual-shape memory effects were used as the matrix to prepare triple shape memory epoxy composites through technological design. The preparation of triple shape memory epoxy composites can enrich the application of epoxy composites in shape memory field, and provide new methods for the preparation of triple shape memory epoxy composites.First, physically incorporate various amounts of nanosilica particles and polyethylene glycol(PEG) with epoxy, to obtain variational glass transition temperatures of the epoxy composites. The dispersibility of nanoparticles were improved through optimizing technology. Micromorphology, thermal mechanical properties as well as on the dual shape memory effects of the epoxy composites were studied. A novel triple shape memory epoxy nanocomposites with two different glass transition temperatures have been prepared through casting epoxy composites layer by layer, and the triple shape memory effects were studied. The results showed that nanosilica particles were homogenously dispersed in the matrix and well incorporated into the epoxy matrix, and their shape fixity properties were significantly improved by nanosilica particles. The resulting epoxy bilayer composites exhibited TSME.Second, to improve the environmental benefits and biological compatibilities of triple shape memory epoxy composites, triple shape memory poly(ε-caprolactone)(PCL)/epoxy(EP) composites with different polymer architectures were prepared. Miscible PCL/EP blend composites with different PCL contents were investigated as the control samples to compare the triple shape memory effects(TSME) with electrospun PCL microfiber membranes/EP composites. At present, TSME were achieved through blending or blocking copolymers, here electrospun PCL microfiber membranes/EP composites were prepared to explore the TSME of the traditional fiber membranes/matrix composites. The morphologies of the cross-section of PCL/EP composites were studied using a field emission scanning electron microscope(FE-SEM). The thermal mechanical properties were observed by a differential scanning calorimeter(DSC) and a dynamic thermomechanical analysis machine(DMA), and the TSME were also determined through dynamic mechanical analysis. The results show that a huge difference was found in the morphology aspect and the phases of the PCL/EP blend composites were not so continuous. The TSME of the PCL/EP blend composites were poor, and that the TSME of the electrospun PCL fiber membranes/EP composites were clear and fine, but the shape memory fixity ratios need to be improved.Moreover, to further improve the shape memory fixity ratios of electrospun PCL microfiber membranes/EP composites, clay montmorillonite(MMA) modified electrospun PCL microfiber membranes were prepared. The morphologies of electrospun PCL microfiber membranes were studied using FE-SEM and the existence of MMA were confirmed by a transmission electron microscope(TEM). The thermal mechanical properties and the TSME were also observed by DSC and DMA. Results indicate that adding a moderate content of MMA into the electrospun PCL fibers could improve the TSME of the PCL fiber membranes/EP composites. The two rubbery plateaus of the samples with an MMA content of 3 wt% in the PCL fiber membranes were the most obvious, and the enthalpies were the highest. As a result, the TSME of the samples with an MMA content of 3wt% in the PCL fiber membranes were the best and their triple shape memory effects were obviously better than electrospun PCL microfiber membranes/EP composites without MMA.