THERMALLY STIMULATED SHAPE MEMORY BEHAVIOR OF POLYMERS WITH PHYSICAL CROSSLINKS*

The shape memory effect of polymers was investigated for the purpose of improving the processingconditions of their preparation and broadening the list of polymers for shape memory applications. Emphasiswas put on the possibility of using polymers with physical crosslinks as shape memory materials and theirstructure-function relationships. Segmented block polyurethanes and polyethylene/nylon 6 graft copolymerswere used as examples of polymers with physical crosslinks. It was found that these copolymers can really beused as thermally stimulated shape memory materials with large recoverable strain and high final recoveryrate. The main advantage of using copolymers is their improved processing conditions as compared withpolymers with chemical crosslinks. As only physical crosslinks are introduced, all conventional processingtechniques for thermal plastics can be used, and the materials become easily reusable. The results indicatethat the high crystallinity of these copolymers at room temperature and the formation of stable physicalcrosslinks are the two prerequisites for these polymers to exhibit shape memory effect. The successful use ofblock and graft copolymers imply the possibility of using polymers of various structure and properties asshape memory materials.