Effect of Heat Treatment on the Mechanical and Tribological Properties of Polyphenylene Sulfide Fiber Materials

Polyphenylene sulfide (PPS) fiber materials, whose raw fibers had been heat treated previously for 1 to 5 days, were prepared by a hot-pressing method. The tribological properties of PPS resin and fiber materials against an AISI 1045 steel ring were evaluated using a block-on-ring wear tester. The results showed that the sample whose raw fibers had been heated at 240°C for 1 day (S1) exhibited the highest impact strength as well as the lowest friction coefficient and wear rate. The friction coefficient of S1 was 39% lower than that of the PPS resin material, and its wear rate was 1 to 2 orders of magnitude lower than those of the other samples. DSC analysis results indicated that the condensed structure of the samples gradually changed from the crystalline to the amorphous state with the increase of heat-treatment time of the raw fibers. DMA and DSC analysis results proved that severe, oxidative cross-linking reactions occurred when the raw fibers were heated over 3 days. It is concluded that proper heat treatment of the raw fibers is advantageous to improve the degree of crystallinity and appropriate oxidative cross-linking; therefore, the prepared PPS fiber material can exhibit better mechanical and tribological performances.