Effects of PEG and MMT contents on mechanical, thermal, and shape memory properties of MMT/PEG/PLA nanocomposites

Abstract

Shape memory polymer of poly (lactic acid) (PLA) has attracted a significant attention, especially in the field of biomedical application. This is mainly because of its biocompatibility rendering it safe to use in human body. The glass transition temperature (Tg) of PLA is used as a mechanism to activate the shape memory effect. Nonetheless, utilization of PLA in medical application is limited due to its brittleness and relatively high Tg (about 60°C). In this work, poly (ethylene glycol) (PEG) with molecular weight of 4,000 g/mol was used as a plasticizer for PLA. Effect of PEG contents (10, 15, 20, 30, and 40 wt%) on thermal and mechanical properties were investigated by differential scanning calorimetry (DSC) and tensile test, respectively. Furthermore, influence of PEG on shape recovery ratio was investigated at a constant temperature of 65°C. It was found that tensile strength, tensile modulus, and Tg values of the plasticized PLA decreased, while elongation at break increased with the increasing PEG content. The shape recovery of plasticized PLA was slightly decreased as PEG content increased. In order to enhance the shape memory performance of PLA blends, montmorillonite (MMT) nanoparticles were added into the plasticized PLA. Nanocomposites of plasticized PLA with 20 wt% PEG (20PEG/PLA) were prepared with the filler loadings of 1 and 3 phr. The exfoliation of MMT in polymer matrix was confirmed with the observation of a peak position angle of MMT via X-ray diffraction (XRD). The presence of MMT in 20PEG/PLA was found to increase the tensile modulus and shape recovery ratio over those of 20PEG/PLA. In this work, we have illustrated that shape memory performance of PLA can be enhanced by the incorporations of PEG and MMT.