High transition temperature shape memory polymer composites based on bismaleimide resin

Bismaleimide-allyl phenol polymer system exhibiting shape memory characteristics and possessing transition temperature of up to 220 degrees C (T-trans) was synthesized by coreacting 2,2-bis 4[(4-maleimidophenoxy)phenyl]propane (BMIP) and o,o'-diallylbisphenol A (DABA) with a bismaleimide-end-capped poly(tetramethyleneoxide) (BMI-PTMO). BMI-PTMO that served as shape memory polymer was synthesized and characterized using Fourier-transform infrared (FTIR), nuclear magnetic resonance, chemical analysis and size exclusion chromatography. The cured network containing varying proportions of poly(tetramethyleneoxide) was synthesized by varying the concentration of BMI-PTMO in the ternary blend. Cure characteristics were investigated by FTIR, differential scanning calorimetry and rheometry. Elastic memory composites were processed using carbon fabric from varying blend composition at fixed resin to reinforcement ratio. PTMO enhanced the flexibility of the network. The system as a whole possessing high transition temperature, its storage modulus decreased with increase in PTMO content. The polymer possessed good shape recovery characteristics and the recovery time decreased with increasing concentration of the shape memory component. The system showed shape recovery of 88-98% in about a minute at T-trans. The extent of shape recovery was a direct function of PTMO concentration. The recovery time showed an inverse relationship to the modulus ratio.