Preparation and properties of novel poly(urethane-imide)s via blending of reactive polyimide and epoxy-terminated urethane prepolymers

Polyurethane networks with enhanced thermal stability and electrical insulation properties were prepared from the reaction of epoxy-terminated urethane prepolymers (EPU) and polyimides containing pendant phenol groups (HPI). EPUs were prepared by the reaction of glycidol with NCO-terminated urethane oligomers. The oligomers were prepared from different molecular weight versions of polycaprolactone polyol (CAPA) and hexamethylene diisocyanate. The progress of the reaction was monitored by differential scanning calorimetric analysis in the presence and absence of suitable catalyst. The onset temperature of exothermic reaction of phenolic groups and epoxy rings was chosen as optimum curing temperature and the reaction duration was optimized by gel content measurement. The starting materials and polymers were characterized by conventional spectroscopic methods, and physical, thermal and electrical properties of the crosslinked networks were determined. The novel poly(urethane-imide)s exhibited considerable improvement in thermal and electrical properties in comparison to common polyurethanes.