(589e) Shape Memory Polymers Based On Polyurethane-Polybenzoxazine Blends

Shape memory polyurethanes (SMPUs) have attracted much attention from academic and industrial researchers due to strong potential in biomedical and consumer applications. In this research project, polybenzoxazine (PB-a) is incorporated into a thermoplastic polyurethane (PU) formulation, anticipating that it would play a similar role to hard segment, improve the shape memory properties, and in some cases induce shape memory properties in polyurethanes, which are otherwise not shape memory materials. It is found that benzoxazine monomer forms miscible blend with the prepolymer derived from 4, 4’-methylenebis (phenyl isocyanate) (MDI) and poly (tetramethylene) glycol (PTMG) with average molecular weight of 650 g/mol. In this case, chain extension of prepolymer can be carried out by using 1, 4-butanediol (BD) as in the synthesis of regular polyurethanes. The benzoxazine is later polymerized into polybenzoxazine (PB-a) by thermal curing at 180 °C in 3 hours. The thermal properties, shape memory properties, morphology and structure of PU/PB-a polymers are evaluated as a function of PB-a concentration.
 The results showed that a specimen with 14.8 wt.% benzoxazine offers Young's modulus value of 890 MPa compared to 170 MPa for pristine polyurethane. The addition of benzoxazine is also found to exert significant influence on glass transition temperature (Tg) of the materials. Tg increases from 25 °C to 78 °C after blending 14.8 wt.% PB-a with PU.