Comparative effects of rocket-grade hydrogen peroxide solution on POM and UHMWPE: aging behaviors and tribological properties

Polymeric materials have a short history of employment as tribological materials in liquid-propellant rocket engines, but they hold promise for the future. Even those polymer materials served already in rocket engines are based on inaccurate or unsubstantiated data. For these reasons, aging tests of polyformaldehyde (POM) and ultra-high molecular weight polyethylene (UHMWPE) in rocket-grade hydrogen peroxide solution were carried out, and then tribological experiments were conducted in this work. The objective is to provide a sound foundation of further selecting or developing polymeric materials for tribological application in rocket-grade hydrogen peroxide environment. The micrographs of polymer specimen with various aging time indicate that POM has poorer aging resistance in hydrogen peroxide solution than UHMWPE. A new absorption peak assigned to hydroxyl group appears on FTIR spectra of POM after aging test due to the oxidation by hydrogen peroxide solution. It is deduced from thermoanalysis that the amorphous regions is the main area influenced by hydrogen peroxide solution. Results of tribological experiments display that the friction coefficients of both POM and UHMWPE decrease with the increase in aging time from 0 to 240 h. However, the wear rates of POM and UHMWPE present different trends with the increase of aging time; the wear rate of POM decreases, whereas the wear rate of UHMWPE increases.