Development of Pyrrone Structural Foams For Honeycomb Filler.
HUGHES AIRCRAFT CO CULVER CITY CA
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The development of techniques for the preparation of pyrrone structural foams for use as honeycomb filler is described. The feasibility of preparing foams from polymers formed by the condensation of 3,3-diaminobenzidine DAB, or 3,3 ,4,4-tetraaminobenzophenone TABP, with 3,3 ,4,4-benzophenone tetracarboxylic dianhydride BTDA was investigated. Initially, most of the effort was devoted to preparing pyrrone prepolymers with improved and more reproducible foaming properties for making chemically blown foams. When it became apparent that very high curing shrinkages would not allow the use of unfilled pyrrone prepolymers in a foam-in-place process, emphasis was shifted from chemically blown foams to syntactic foams. Syntactic foam formulations containing hollow carbon microspheres were developed. Syntactic foams made from selected formulations were found to have very low coefficients of thermal expansion. A technique was developed for the emplacement of pyrrone syntactic foam formulations in honeycomb core structures.
- Laminates and Composite Materials