Effect of swelling and sand on tribological behaviour of nitrile butadiene rubber/fluorine rubber blends in crude oil

Nitrile butadiene rubber/fluorine rubber blends with different ratios are prepared by a mixing mill and a platen press. In order to get the nitrile butadiene rubber/fluorine rubber blend with proper ratio to meet the requirements of well condition, the effect of swelling and sand on tribological behaviour of the blends in crude oil is studied, and the wear mechanism is also analysed. The results show that structure of nitrile butadiene rubber/fluorine rubber blends gradually transforms from chain-like structure to net-like structure with an increase in the addition of fluorine rubber blends into nitrile butadiene rubber. When the ratio of fluorine rubber blends to nitrile butadiene rubber is set to 2:8, the blend shows regular and dense structure and relatively uniform phase. Swelling of rubber samples in crude oil causes the increase of weight and the decrease of hardness and wear resistance. The sand in the crude oil will scroll or slide between rubber block and the metal wheel. This will increase the plough to the rubber surface and finally increase the friction coefficient and wear loss. The swelling and wear resistances of nitrile butadiene rubber/fluorine rubber blend with the ratio of 2:8 are basically close to that of fluorine rubber blends, which can be expected to be the new formula of stator rubber.