Shape Recovery and Secondary-Shape Forming in Polyurethane-Shape Memory Polymer

摘要

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 T_h = T_g+20K in a short time, irrecoverable strain starts to appear at the holding time t_h= 0.5h and strain is not recovered at all at t_h=8h. In the case of T_h = T_g+10K, irrecoverable strain appears in a short holding time if holding strain is large and the rate of secondary-shape forming S is 42 percent at t_h=8h. (2) If strain of 50 percent is held at T_h = T_g+10K in a long time, strain becomes not to be recovered and S is 93 percent at t_h, =12h. In the case of T_h = T_g, the increasing rate of S increases if t_h is longer than 40h. If T_h is lower than T_g-10K for t_h,= 72h, strain is recovered perfectly by heating and secondary-shape forming does not appear.