Influences of phase composition and thermomechanical conditions on shape memory properties of segmented polyurethanes with amorphous reversible phase

摘要

We synthesized series of shape memory polyurethanes with amorphous reversible phase (T g-SMPUs) and systematically studied their microphase structure and shape memory properties. The T g-SMPUs having no or less hard phase showed lower shape recovery. When the volume fraction of hard phase was in the range of 20-30%, the T g-SMPUs exhibited the highest shape recovery. As the fraction of hard phase increased further the shape recovery decreased, because more polymer components with higher glass transition temperatures (T gs) would participate in strain storage. For the T g-SMPUs having similar T gs, those polymers having higher volume fraction of hard phase exhibited higher shape fixity, broader shape recovery region, and larger recovery stress. Increasing deformation strain could raise shape fixity and recovery stress but broaden shape recovery region. The highest recovery stress of a material could be achieved when the deformation occurred at its glass transition temperature below which decreasing deformation temperature could not increase recovery stress further.