USE OF SEVERAL THERMAL ANALYSIS TECHNIQUES ON A HYPALON PAINT COATING FOR THE SOLID ROCKET BOOSTER (SRB) OF THE SPACE SHUTTLE

摘要

White Hypalon paint is brush-applied as a moisture barrier coating over cork surfaces on each of the two Space Shuttle SRBs. Fine cracks have been observed in the Hypalon coating three times historically on laboratory witness panels, but never on flight hardware. Recent samples of the cracked and standard ("good") Hypalon were removed from cork surfaces and were tested by TGA, TMA and DSC thermal analysis techniques. The TGA data showed that at 700℃, where only paint pigment/extender solids remain, the cracked material had about 9 weight percent more material remaining than the standard material, probably indicating incomplete mixing of the paint before it was brush-applied to produce the cracked material. Use of the TMA film tension method showed that the average static modulus vs. temperature was about 3 to 6 times higher for the cracked material than for the standard material, indicating a much higher stiffness for the cracked Hypalon. The TMA data also showed that an increased coating thickness for the cracked Hypalon was not a factor in the anomaly.