Novel Bismaleimide-Based Shape Memory Polymers: Comparison to Commercial Shape Memory Polymers

Abstract

A series of novel shape memory polymers, synthesized from 4-4-bismaleimidodiphenyl-methane, an extended chain aliphatic diamine, and a bis-isocyanate, have been created and characterized with the aim of providing a family of robust high temperature shape memory polymers with tailorable transition temperatures for use in reconfigurable aerospace structures. In the present study, three of the polymers are chosen for more detailed study of their thermomechanical properties. These materials are compared to commercial resins Veriflex® and Veriflex-E® which are styrene- and epoxy-based proprietary formulations, respectively. The thermal and mechanical properties are determined utilizing thermogravimetric analysis and dynamic mechanical analysis. The temperatures at which 2% weight loss is observed in dry air ranges from 272 to 305 °C for the synthesized polymers, and occurs at 242 and 317 °C for the commercial Veriflex® and Veriflex-E® respectively. The glass transition temperatures, as measured by the peak in the tan(δ) curve, for the synthesized polymers range from 110 to 144 °C which is a higher than the Veriflex® and Veriflex-E® achieve at 84.3 and 100 °C respectively. With operation temperatures of subsonic structural aircraft components often reaching 121 °C (250 °F), the transition temperatures of the bismaleimide-based shape memory polymers are clearly desirable to ensure that shape memory polymers used in aircraft structures will not be prematurely triggered by the existing heat loads. In addition, the shape memory performance of the bismaleimide-based shape memory polymers compares well with the Veriflex® and Veriflex-E® resins.