Shape memory properties of polyurethane/poly(oxyethylene) blends

Shape memory behavior of polymer blends consisting of thermoplastic polyurethane (PU) and crystalline poly(oxyethylene) (POE) have been investigated. PU is in a rubbery state at room temperature and has an ability to recover from a deformed temporary shape to a permanent shape by entropic elasticity, and POE has a role to fix the temporary shape by crystallization and solidification of the system. As a result, excellent shape memory properties can be obtained by blending elastic PU and crystalline POE. With increasing POE content in the blend, the shape fixity ratio below crystallization temperature was increased to almost 100%, but shape recovery above melting temperature occurred more slowly. These experimental results were reasonably described by viscoelasticity and the phase separated morphology of the PU/POE blend. The effect of changing molecular weight of POE on the shape memory behavior was not remarkable. The shape recovery behavior was found to be expressed by using a simple mechanical viscoelastic model.