Tribological Properties and Gear Performance of Polyoxymethylene Composites

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Abstract
Tribological properties of polyoxymethylene (POM) composites containing a trace amount of silicon carbide (SiC) and/or calcium salt of octacosanoic acid (Ca-OCA) as well as containing polytetrafluoroethylene (PTFE) were investigated by means of a pin-on-disk type wear apparatus. The spherulite size of POM composites was measured using a polarizing microscope. Mechanical properties and gear performance of the composites were also evaluated. It was found that the coefficient of friction was drastically lowered due to the lubricant effect of Ca-OCA added to POM/SiC composites. Further, the wear rate was also decreased by the nucleating effect of SiC and Ca-OCA. Especially, POM/SiC(0.1)/Ca-OCA(1) composite containing SiC 0.1 wt.% and Ca-OCA 1 wt.% showed the coefficient of friction as low as that of POM/PTFE(24) composite containing PTFE 24 wt.%, keeping higher wear resistance. Also, its mechanical properties were found to be the same level as those of unfilled POM, except that its izod impact strength became higher than that of unfilled POM. Furthermore, its gear performance was confirmed to be satisfactory without generating noise under the dry running condition, when the same gears were combined below 13 MPa of bending stress. [S0742-4787(00)00304-0]