ABSTRACTThe environment of Arab countries suffers from the relatively high concentration of dust in air, due to the lack of rain and the vast area of desert, which causes significant increase in wear rate of moving surfaces. To overcome those severe environmental impacts, it is necessary to develop the materials which can resist the abrasion action of sand. The present work aims to develop polyester composites to be used as self lubricated bearing material in different engineering applications. Polyethylene and glass fibres were used to reinforce polyester in order to increase wear resistance of the tested composites. Paraffin, glycerine, almond, olives, cress, sesame and baraka oils were added to polyester during moulding to produce self lubricated composites. The friction coefficient and wear of the tested composites were investigated. The scratch resistance of the proposed composites was tested. The experimental results showed that unfilled polyester composites displayed relatively high friction values as a result of polyester transfer to the steel counterface as well as the increase of the attractive force caused by the electric static charge formed on the two friction surfaces. When polyester matrix was filled by paraffin and glycerine oils significant reduction in friction coefficient and wear was observed. Besides, increasing oil content and polyethylene fibres decreased friction coefficient. Composites containing olive oil displayed higher friction and lower wear than that containing almond oil. This behaviour can confirm the higher wear protection due to the stronger surface interactions between the polar molecules and the sliding surfaces displayed by olive oil. Beside, wear of polyester composites filled by sesame, cress and baraka oils decreased down to minimum then increased with increasing oil content. The minimum wear was displayed by composites filled by 20 wt. % oil content.
El-Aal et al. (2010) studied this question.