PSPA is a polymeric anhydride epoxy curing agent which can cure epoxy resins without the use of tertiary amines or other accelerators. In addition to long pot life at elevated temperatures, and low vapor pressure, PSPA approaches the ideal of a one component epoxy system. The unique combination of toughness and thermal resistance allows PSPA cured epoxy systems to pass thermal cycling of 170˚C to -40˚C in the Navy hex-bar test. Even after thermal aging for 10,000 hrs. @ 150˚C, over 95% of the electrical properties are maintained. PSPA can be ground and dispersed in epoxy resin to yield a one component, stable, liquid paste. PSPA also provides the highest degree of thermal stability for toughened epoxies. NASA selected it for use in the Apollo Heat Shields and for the Orion Heat Shield.