A report describes experiments in which electron paramagnetic resonance imaging (EPRI) was used to determine one-dimensional spatial distributions of free radicals in two plate specimens of PMR-15 polyimide. One specimen had been postcured at a temperature of 315 °C in nitrogen, then thermally cycled 300 times between room temperature and 335 °C in air; the other specimen had been post-cured at 316 °C in air, then further postcured at 371°C in nitrogen, but not thermally cycled. EPRI of the thermally cycled specimen showed a higher concentration of free radicals in the surface layers than in the bulk.
This work was done by Mary Ann B. Meador of Glenn Research Center, Myong K. Ahn of Indiana State University, and Sandra S. Eaton and Gareth R. Eaton of the University of Denver.
Inquiries concerning rights for the commercial use of this invention should be addressed to
NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4 - 8
21000 Brookpark Road
Refer to LEW-16821