Shape Recovery and Secondary-Shape Forming in Polyurethane-Shape Memory Polymer
The influence of the strain-holding conditions on shape recovery and secondary-shape forming was investigated. The results obtained are summarized as follows. (1) If strain is held at holding temperature Th = Tg+20K in a short time, irrecoverable strain starts to appear at the holding time th= 0.5h and strain is not recovered at all at th=8h. In the case of Th = Tg+10K, irrecoverable strain appears in a short holding time if holding strain is large and the rate of secondary-shape forming S is 42% at th=8h. (2) If strain of 50% is held at Th = Tg+10K in a long time, strain becomes not to be recovered and S is 93% at th =12h. In the case of Th = Tg, the increasing rate of S increases if th is longer than 40h. If Th is lower than Tg-10K for th= 72h, strain is recovered perfectly by heating and secondary-shape forming does not appear.
N. Ohno and T. Uehara
H. Tobushi et al., "Shape Recovery and Secondary-Shape Forming in Polyurethane-Shape Memory Polymer", Key Engineering Materials, Vols. 340-341, pp. 1217-1222, 2007