Tribological behavior of polypropylene-based composites reinforced with cherry seed powder under lubrication conditions

Abstract

The article presents the effect of cherry seed powder (CSP) addition to the polypropylene (PP) matrix on tribological properties: coefficient of friction (COF) and wear under lubrication conditions using paraffin and silicone oil. The composites differed in the percentage content of the filler (5, 10, 15 wt%) and the size of CSP particles (<400 μm, 400–630 μm, 630–800 μm). 30-minute friction tests were conducted using the “block-on-ring” system, and the wear mechanisms were identified based on SEM analysis supplemented with topographic analysis. To fully interpret the results, mechanical tests of the obtained composites were also performed and a viscosity-temperature analysis of the oils used was performed. In both the case of paraffin and silicone oil, it was observed that adding CSP to the polymer matrix reduces the COF. Paraffin oil tends to reduce the COF by increasing the percentage of filler (regardless of particle size). In contrast, silicone oil has the lowest COF observed in the case of 5 % wt. and the highest granulation. The dominant wear mechanism in the case of paraffin oil lubrication turned out to be micro-abrasion, while in the case of silicone oil, micro-abrasion and micro-adhesion. Moreover, it seems that the lower dynamic viscosity of silicone oil at lower temperatures favored the destructive effect of crushed filler particles on the composite surfaces in the initial parts of the tests.