Enhancement of Tensile Strength and Shape Recovery Characteristics of Grafted Polyurethane Using Melamine as a Crosslinking Agent

Melamine was grafted to a polyurethane (PU) frame and utilized for cross-linking PU via amino groups. The degree of crosslinking and the solution viscosity increased notably after grafting melamine due to the formation of crosslinks. The thermal transition of the soft segment was not significantly affected, but the glass transition was observed at a slightly higher temperature in case of the grafted melamine. Melamine-mediated crosslinking increased not only the breaking tensile stress but also the shape recovery performance of PU. In addition, crosslinked PU was more flexible at low temperature than unmodified PU. Overall, melamine-mediated crosslinking improved the tensile resistance to stress, the recovery tendency to the initial shape, and the flexibility with minor changes in the thermal transition, tensile strain, and shape retention at a low temperature.