Modeling of shape memory induction and recovery in heat-shrinkable polymers

A mechanical model was developed to describe qualitatively and quantitatively the stress-strain-time behavior of a prepared shape memory crosslinked polyethylene during hot stretching, stress relaxation under 200% strain at high temperature and strain recovery of the heat shrinkable polymer. The stress-strain, the stress relaxation and the irrecoverable strain behavior of the model were established by driving the constitutive equation, which could qualitatively represent the behavior of the real material. By choosing significant values for the parameters of the proposed model, an excellent fit was obtained between the experimental behavior of the polymer and that predicted by the model. It was also revealed that the main source responsible for the imperfect recovery of the induced strain observed was the stress relaxation occurring during the stretch holding-cooling time step.