Damage mechanism of polyphenylene sulfide resin in liquid oxygen

A compatible material is defined as one that maintains its original properties in the presence of liquid oxygen. A test for the compatibility of a material with liquid oxygen basically consists of placing the material in liquid oxygen in the presence of a possible ignition source and observing the reaction as a function of the ignition energy. One of the most probable ignition sources is just mechanical impact and in an appropriate test, the disk of a candidate material is submerged in liquid oxygen and impacted with 98 J of impact energy while monitoring a candidate material for flash or sound responses that would correspond to an ignition. The polyphenylene sulfide resin was mechanically impacted in liquid oxygen according to ASTM D-2512 to investigate the compatibility and damage mechanism. The obvious flash was detected for three specimens during the initial series of 20 tests, which demonstrated that the polyphenylene sulfide resin is incompatible with liquid oxygen. The surface microstructure and composition of the specimen before and after mechanical impact were analyzed by SEM and XPS, respectively. The damage mechanism of the polyphenylene sulfide resin in the liquid oxygen was investigated in detail. The high temperature of the local surface resulted in the reaction of polyphenylene sulfide resin with oxygen in forming peroxy radicals of relatively high activity which reacted with hydrogen atoms of polyphenylene sulfide of molecular terminals producing relatively stable sulfur radicals and peroxides. The disappearance of radical of high activity is favorable to inhibit the reaction of the polyphenylene sulfide resin with liquid oxygen.