Polyphenylene sulfide (PPS) is sulfide-containing multifunctional super engineering plastic with excellent mechanical properties, chemical resistance, and economic feasibility. It is a durable, lightweight material suitable for transportation equipment parts however PPS needs harsh processing condition and lacks of research to secure functionality and reliability. In this paper we researched PPS composites gear to reinforce its wear mode. To evaluate strengthened wear resistance and degradation of gears, wear and shape change at real use environment were tested. Life span was predicted through DMA (dynamic mechanical analysis) test including temperature scan, multi-frequency, and creep-release tests. Coefficients of friction for each PPS and PPA (Poly phenylacetylene) composites were measured with pin on disc test and the correlation between temperature changes among the gear drive measured by an infrared thermometer was compared. Wear rate and shape degradation were evaluated every 50 hours with 3D microscopy image profiles. Coefficients of friction of PPS was lower than PPA about 11 percent and the temperature change varies from 5.4℃ (PPA) to 3℃ (PPS) over 120 minutes. Activation energy was calculated using Arrhenius equation with temperature scan and multi-frequency tests and long-term life span by temperature and vibration characteristics was predicted based on the strain when stress is loaded. Compared to PPA, PPS showed less difference in strain when loaded, and it could be seen that PPS based composites possess sustained stability at same stress level. Wear after 233 hours run was 11.62%, 6.18%, and 1.35% for PPA and 4.11%, 3.77%, 0.85% for PPS at drive in, driving, and driven parts. For every tested area, PPS gear was more resistant to wear and its shape degradation was also conspicuously lower than PPA gear. Wear between PPA and PPS composites were tested at harsh operating condition. The wear of PPA composites gear at fail point was 29.39% which was 25.28% higher compared to the PPS composites gear. Long-term life span of the gear was investigated with the change of thermal characteristics using DMA and wear test at 125℃ and PPS composites gear showed more suitable performance at real use conditions. It had more lower coefficients of friction and reliability for heat and vibration for every testing condition and it has shown that PPS/PTFE/GF composites is suitable material for gear.
Mr. Seonku Kang, Researcher, KATECH(Korea Automotive Technology Institute)