Compressive shape memory behavior of spring‐shaped polylactic acid alloy type

ABSTRACT This article presents an experimental study on the shape memory behavior of blends of thermoplastic polyurethane (TPU) and biodegradable polylactic acid (PLA) at the PLA/TPU weight ratios of 70/30 (PT7030) and 50/50 (PT5050). The manufactured springs were studied comprehensively based on their morphological and thermal properties. Scanning electron microscopy micrographs were captured, which verified that TPU was compatible with PLA. The wide‐angle X‐ray diffraction suggested that the crystallinity of PLA was enhanced in the presence of TPU. In order to determine the shape recovery properties [shape recovery ratio (Rr), shape fixing ratio (Rf), and shape recovery force (Fr)], the samples programmed at three different temperatures (Tp) of 70, 80, and 90 ° C and at various recovery temperatures (Tr) over 40 to 90 ° C, were studied. In general, the spring made with PT7030 showed higher Rr, Rf, and Fr values. The highest Rr (99%) was obtained at programmed temperature (Tp) of 70 ° C and recovery temperature (Tr) of 90 ° C. However, the Rr value for this spring programmed at 70 ° C and recovered near body temperature was 50% with Fr of 1.4 N. Furthermore, the highest Fr (15.6 N) was observed in the spring made of PT7030 programmed at 80 ° C and recovered at Tr of 78 ° C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45115.