Summary: This communication describes a novel kind of PMMA‐PEG semi‐interpenetrating network (semi‐IPN) which shows excellent shape‐memory behavior at two transition temperatures, the Tm of the PEG crystal and the Tg of the semi‐IPN. Based on a reversible order‐disorder transition of the crystals below and above the Tm of PEG, and the large difference in storage modulus below and above the Tg of the semi‐IPN, the polymer has a recovery ratio of 91 and 99%, respectively.
Shape‐memory phenomena of PMMA‐PEG2000 semi‐IPN. 相似文献
Summary: 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.
Stress relaxation of crosslinked polyethylene under 200% strain at 160 °C. 相似文献