DEVELOPMENT OF VISCOUS COUPLING OIL (PART 7) STABILITY OF SYNTHETIC HYDROCARBON OIL

In the authors' previous reports, the stabilites of silicons oils, use d as a fluid for viscous couplings, were discussed. This paper deals w ith the stability of high-viscosity synthetic hydrocarbon oils used as a fluid for viscous couplings. An ethylene-alphaolefin copolymer, hav ing viscosity of 106 Pa.s at 25 degrees C, was used as sample of synth etic hydrocarbon oil. Thermal oxidation stabilities of the ethylene-al phaolefin copolymer, which were experimentally confirmed in static hea t tests, were as follows: (i) in an open system at 170 degrees C, cons iderable change in viscosity occurred under a process ofoxidation; (ii ) in a closed system at 200 degrees C, change in viscosity by thermal decomposition was negligible. On the other hand, viscosity of the copo lymer slightly decreased in a viscous coupling test. The copolymer, ho wever, showed significant decrease in viscosity in the ''Accelerated v iscous coupling test,'' which was operated with the oil admired with F exN powder. From these results, it was assumed that the ethylene-alpha olefin copolymer decomposed in the presence of FexN activated by rubbi ng against surfaces of the plates.