Friction coefficient and wear resistance of a modified polypropylene impregnated with different oils

P Sędłak,T Stawicki,B Białobrzeska

doi:10.1007/s13726-016-0419-7

Abstract

The aim of the study was to determine the changes in the sliding friction coefficient and wear mechanism of PP impregnated by oils with respect to the unmodified PP under dry sliding conditions. The study showed that the impregnation of the PP clearly influenced the wear rate of PP and its friction coefficient. During the test, the wear behavior of the unmodified and impregnated polypropylenes was investigated using ASTM G77-98 standard wear test equipment in which the specimens were worn by counter sample made by steel 100Cr6. The recording program of the test system enabled the visualization and registration of the following parameters: specimen rotation and load value, linear wear of specimen, friction coefficient, and temperature of specimen and environment. The wear of the specimens was evaluated by weight loss and their wear mechanisms were investigated using scanning electron microscopy. The predominant wear mechanism between a polymer and steel was adhesion. However, at the high sliding velocity, when a higher temperature was generated, the predominant mechanism of wear was thermal wear. Impregnation of PPs moved the thermal wear into the higher sliding velocity values and caused better resistance of the PPs to melting and plastic flow. The most important finding of this investigation was that impregnation of PPs improved their tribological properties at a low value of load represented by the sliding velocity.

Highlights

In the construction and exploitation of machine components, special consideration is given to the application of fundamental knowledge about wear behaviour through lubrication
The lowest value was noted for PP impregnated with rapeseed methyl ester (RME) oil, but for the specimen impregnated with motor oil, the friction coefficient was not much higher
The reduction in value of the maximum friction coefficient was 70 % in the case of PP impregnated with RME and 62 % in the case of PP impregnated with motor oil (Fig. 3) in comparison to unmodified PP

Summary

Introduction

In the construction and exploitation of machine components, special consideration is given to the application of fundamental knowledge about wear behaviour through lubrication This problem has become more significant because one of the consequences of the development of technology is that the values of dynamic and temperature loads transmitted by friction pairs have increased. Bushings of the plain bearings, carrying the heavy loads, are made of special bearing alloys that are characterized by a low friction coefficient and high strength. They require proper and continuous lubrication to reduce wear and to increase durability and reliability. Thereby, a porous structure that can be impregnated by grease agents or nanomaterials

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