The development of high-temperature polyimides for resin transfer molding

The Resin Transfer Molding (RTM) process offers significant cost savings in the fabrication of polymer matrix composite structures through increased manufacturing efficiency. However, the realization of these cost savings has been limited to low-temperature applications, primarily because the high-temperature resin systems found on the market today do not possess all of the processing characteristics that make them amenable to RTM. A series of addition-cured, polyimide resin systems were developed for high-temperature RTM applications. These "new" high-temperature resin systems were specifically designed to be cost competitive and void of mutagenic or carcinogenic materials. Monomer stoichiometry and oligomer molecular weight were balanced in order to produce RTM polyimides that exhibited low melt-viscosity. Laminates were fabricated with commercial RTM equipment and found to be free of voids and microcracks. All candidate systems that exhibited potential were physically and mechanically tested. An RTM resin was identified that had a dry Tg of 305degreesC and excellent property retention up to 260degreesC. This technology has a high degree of impact on commercial and military aircraft, launch vehicles, and satellites in addition to dual-use applications in the automotive and chemical industry.