THERMALLY STIMULATED DEFORMATION RECOVERY EFFECT OF SEGMENTED POLYURETHANES

The thermally stimulated deformation recovery effect of 4,4'-diphenylm ethane diisocyanate (MDI)- and toluene diisocyanate (TDI)-based segmen ted polyurethanes with polycaprolactone (PCL) soft segments was invest igated. It was found that these segmented polyurethanes may exhibit ty pical shape memory behavior with very large recoverable deformation an d recovery rates. Their critical recovery temperature was around 50-60 degrees C, close to the melting temperature of the PCL crystals of th e specimens. A schematic diagram was given to describe the shape recov ery function of these copolymers. Repeated tests indicate that, after the destruction of some weak crosslinks in the first stretching, the p olyurethane specimens may become dynamically ideal elastic networks, a nd their deformation is almost completely recoverable.