ROHACELL~? FOAM FOR SPACE APPLICATIONS

摘要

Rohacell~? foams, closed cell polymethacrylimide (PMI) materials manufactured byrnDegussa, are popular in terrestrial light weight construction such as aircraft seating,rnhelicopter rotor blade core, antenna radome construction and as part of the PHENIXrnmultiplicity detector at Brookhaven National Laboratory. However, the requirements forrntheir use in space-based applications are much more stringent. Our study indicates thatrnstiffness remains reasonably flat over the temperature range of -160℃ to +120℃.rnHowever, the foam swells on the order of 1.8E-3 cm per cm under room temperaturernvacuum and exhibits very slow relaxation in a vacuum at 25℃. While the PMI foamrnevaluated meets NASA outgassing requirements when water is subtracted from the totalrnmass loss, the rate of water diffusion at 23℃ is only 6.3E-11 cm~2/s. At 100℃ this valuernis 1.6E-7 cm~2/s giving activation energy for diffusion of 93.3 kJ/mol; hydrogen bondingrnto nitrogen and adjacent carbonyl groups is a possible explanation for the unusuallyrnstrong bond with water. Thermogravimetric (TGA) and thermal expansion results arernalso presented.