Development of polyurethane-based heat shielding coating for cryo-insulation

Thermal insulation of cryo stages is provided by polyurethane modified Isocyanurate foam (PUIR). To protect PUIR layer from aerodynamic heating, a thermally stable polyurethane based heat shield coating (PUHSC) with better bond integrity to PUIR foam layer was developed. This work briefly describes the preparation of a polyester polyol based polyurethane heat shield coating for cryo insulation. In addition to polyester polyol, PUHSC system contains hydrophobic silica aerogel which improves its thermal stability. The physical, mechanical and thermal properties of the prepared PUHSC were evaluated. PUHSC possess superior properties such as good thermal stability, low thermal conductivity, high specific heat and good bond strength compared to PUIR foam. For evaluating the thermal response of the new system conditions simulating flight, functional level tests such as aerothermal test, wind tunnel test, high altitude thermal simulation (HATS) test and wind tunnel tests were done. The system was successfully implemented in ongoing launch vehicle programmes.