NASA's Glenn Research Center invites companies to license or establish partnerships to develop its patented high-temperature, low-melt imide resins for fabrication of automotive components. Produced by a solvent-free melt process, these resins exhibit high glass transition temperatures (Tg = 370 to 400 °C), low melt viscosities (10 to 30 poise), long pot-life (1 to 2 hours), and can be easily processed by low-cost RTM and vacuum-assisted resin transfer molding (VARTM). These RTM resins melt at 260 to 280 °C, and can be cured at 340 to 370 °C in 2 hours without releasing any harmful volatile compounds.
This technology was developed to make polyimide resins from novel asymmetric dianhydrides (a-dianhydrides) and kinked diamines to achieve low melt viscosities that are amenable to low-cost RTM and VARTM, while retaining high-temperature finished product performance above 300 °C. The RTM imide resins can be injected into fiber preforms under pressure (200 psi) or vacuum (VARTM). The resins also can be made into powder prepregs with lengthy out-time by melting the resin powders so that they fuse onto fibers.
RTM imide resins display high softening temperatures (370 to 400 °C) and excellent toughness, as evidenced by the RTM370 resins’ open-hole compression strength. The resins also possess significant thermo-oxidative stability by long-term isothermal aging at 288 °C (550 °F) for 1,000 hours. The unique melt process without a solvent provides a manufacturing advantage over the expensive high-boiling solvents previously needed to produce oligomers. This process also eliminates the need for tedious and high-cost solvent removal.