Driving force for shape memory effect of polymers

In this study, we aim to evaluate the shape memory effect of a Poly (Caprolactone) (PCL) (40%) and a Styrene-Butadiene-Styrene (SBS) (60%) blend. Shape memory cycle tests are performed at different temperatures to detect the best recovery rate. Under appropriate temperature, the blend recovers substantially its original shape. To study the recovery rate evolution, multi cycle tests are realized with controlled temperature. The results indicate that the shape memory effect growths when the number of cycle increases. The stored energy acts as a driving force to bring the polymer to its permanent shape after each loading cycle. Then, an original method is proposed to measure the stress-strain evolution during the recovery. With a variable temperature, no standard test can follow the stress-strain evolution. This test is needed to validate the behavior model.