Evaluation of Cyanate Ester Prepreg Material Exposed to Uncontrolled Thermal Conditions During Storage

摘要

A contractor realized that freezers used for the storage of multiple lots of YLA's RS3C/M50J polycyanurate prepreg used for the fabrication of space hardware had experienced a malfunction that had not been identified. The freezer had been running at approximately 10-20 degrees F above the specified requirements with some excursions as high as 60 degrees F for extended periods of time. Hydrolysis of the cyanate monomer can form carbamates and thus affect the polymerization mechanism, which may result in a degradation of both mechanical and thermal performance. DMA testing indicated that all composites manufactured from the rolls of affected prepreg yielded acceptable composites. In addition, subsequent thermal post-treatment tests performed in our laboratory indicated that the degree of progressive degradation was negligible for any of the composites manufactured using the affected prepreg. Optical microscopy indicated good consolidation, and subsequent shear testing of parts manufactured from these prepregs also produced acceptable strength values. The prepreg materials have been exonerated by these tests and will be used for the fabrication of hardware.