Development of an Improved Coating for Polybenzimidazole Foam

摘要

An improved coating system was developed for Polybenzimidazole (PBI) foam to provide coating stability, ruggedness, moisture resistance, and to satisfy optical property requirements (as/e, < 0.4 and e > 0.8) for the space shuttle. The effort was performed in five tasks:Task 1 to establish material and process specifications for the PBI foam, and material specifications for the coatings, Task 2 to identify and evaluate promising coatings, Task 3 to establish mechanical and thermophysical properties of the tile components, Task 4 to determine by systems analysis the potential weight trade-offs associated with a coated PBI TPS, and Task 5 to establish a preliminary quality assurance programnThe coated PBI tile was, through screening tests, determined to satisfy the design objectives with a reduced system weight over the baseline shuttle silica LRSI TPS. The developed tile provides a thermally stable, extremely rugged, low thermal conductivity insulator with a well characterized optical coating.