A thermosetting polyimide called "DMBZ-15" has been developed for use as a matrix material in relatively inexpensive matrix/fiber composite materials. The glass-transition temperature (Tg) of DMBZ-15 is 414°C. In contrast, the industry standard polyimide for such composites (developed in 1971 at Lewis Research center and known as "PMR-15") has a Tg of 348 °C. Because of its higher Tg, DMBZ-15 is better suited for high-temperature use in automotive and aerospace applications.

The development of DMBZ-15 began as a search for an alternative to the toxic monomer-methylene dianiline (MDA) - used to make PMR-15. The objective of the search was to substitute a more benign diamine for MDA, while maintaining composite-material performance comparable to that of composites made with PMR-15. The search led to the ingredients of DMBZ-15; namely, dimethyl ester of 3,3´,4,4´-benzophenone tetracarboxylic acid (BTDE) and 2,2´-dimethylbenzidine (DMBZ) with nadic ester (NE) as the end cap.

DMBZ-15/Carbon Fiber and PMR-15/Carbon Fiber Composites exhibited similar levels of flexural and compressive strengths.

Experiments were performed on composite material specimens made with PMR-15 and DMBZ-15 matrices, respectively, reinforced with carbon fibers known by the trade name "T650-35." In one set of experiments, flexural strengths were measured at room temperature and at 550 °F (288 °C). In another set of experiments, compressive strengths were measured at various temperatures up to 550°F (288 ° C). In still another set of experiments, measurements of compressive strength were performed after five "hot/wet" cycles; each cycle comprised (1) a soak in water at 200 °F (93 °C) until a weight gain>1 percent was detected, followed by (2) drying at a temperature of 500 °F (260 °C) until the moisture level was reduced to <0.1 percent of the specimen weight. As shown in the figure, specimens of the two composites tested under the same conditions exhibited comparable levels of flexural and compressive strengths.

This work was done by Kathy C. Chuang of Lewis Research Center, Joseph E. Waters of Case Western Reserve University, and DeNise Hardy-Green of the University of Akron. No further documentation is available.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Lewis Research Center
Commercial Technology Office
Attn: Tech Brief Patent Status
Mail Stop 7 - 3
21000 Brookpark Road
Ohio 44135.

Refer to LEW-16560 .