A Study on Tribodegradation of Lubricating Oils under Rolling friction and Friction-polymer formation

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Experimental methods and procedures were studied as a first step of the research. The major objectives of the study were to find the experimental method which anable to use only a small amout of test fluids without sever damages during friction tests and to detect the small amout of compounds which were contained in the degraded oils. Rolling-four-ball tribometer was selected as friction apparatus and FT-IR and HPLC-GPC were selected for the analyzes of the degraded oils.The experimental condition of friction experiments were ; axial load : 294N and 98N,rotating speed : 2500rpm, temperature : room temp. Highly purified hydrorefined paraffinic mineral oil was used as the test oil. After the friction experiment under 294N,the oil became greasy and color of the sample oil changed to brownish. Presence of >C=O,-OH,-COO^-, Fe_2O_3 were found in the degraded oil by FT-IR.From the GPC,very large substance was detected in the degraded oil, in spite of the filtration with memblane filter having a pore size of 0.45mum. It was confirmed that such a large size substance was not formed in the static oxydation of the oil. It can be concluded that very fine wear particles on the surface of which oxydation products having >C=O,-COO- groups were adsorbed, were contained in the degraded oil. This made the degraded oil greasy. Under the 98N,the oil did not change to greasy and brownish but some characteristic chemical groups like -COO^- and Fe_2O_3 were also found in the oil.