Toward the low actuation temperature of flexible shape memory polymer composites with room temperature deformability via induced plasticizing effect.

Abstract

Semi-crystalline/elastomer blends such as poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) have been well-studied as shape memory polymer (SMP) systems over the last decade. The SMP system is known to be reliable as the activation or transitional temperature (Ttrans) is well defined by its glass transition temperature (Tg). In this study, the possibility of altering SMPs'Ttrans by introducing plasticizer molecules, such as poly(ethylene glycol) (PEG), into the system was investigated. Significant changes in morphologies and thermal behaviours of the composites after the incorporation of plasticizer inferring the possible changes in shape memory behaviours were reported. It was concluded that the SMP performance, in terms of activation temperature, shape fixing (Rf), shape recovery (Rr) ratio, and recovery time, could be improved significantly due to the induced plasticizing effects. With only the incorporation of 5 wt% PEG, the Ttrans of PLA/TPU SMP was successfully decreased from the well-known 75 °C to 50 °C while achieving 85% Rr ratio. An improvement in 37.5% shorter recovery time can be observed with the incorporation of 10 wt% PEG when compared with a pristine PLA/TPU system under 50 °C. The results indicated that plasticizing is an effective method for altering the polymer chain structures and a step closer toward the development of fast response SMPs that can be activated under a low temperature.