An Evaluation of the Liquid Oxygen Mechanical Impact Test

The ambient liquid oxygen (LO 2 ) mechanical impact test (ASTM method D2512-82) has long been used to screen nonmetallic materials for oxygen service. This method is also used to rank batches or lots of particular materials. This study was conducted to evaluate the repeatability of the ambient LO 2 mechanical impact test used by NASA to screen materials for oxygen service (NHB 8060.1B Test 13 Part 1, which is based on the ASTM method). Four materials were tested: Teflon®, Vespel SP-21®, Viton A®, and nylon 6/6. A single batch or lot was used to prepare each polymeric material. Each test material was subjected to several series of tests that were conducted at different impact energy levels. The results show that the variability from series to series in the reaction threshold energy level is within the precision statement of the ASTM method. However, this precision is considerably broader than the reaction threshold implied by the NHB 8060.1B test criteria.