CarbonX™ Carbon Fiber Reinforced Ultem® PEI (Polyether Imide) is an amorphous, high-performance polymer that combines excellent thermal properties, exceptional dimensional stability, inherent flame retardancy, and good chemical resistance. Ultem™ resin offers the ability to create parts with excellent properties at elevated temperatures due to a high glass transition temperature (Tg) of 217°C. The addition of high-modulus carbon fiber greatly increases the stiffness / modulus of the material as well as greatly improving dimensional stability.