It is inevitable for the soot particles from engine fuel to contaminate the lubricating oil

which may increase the viscosity of lubricating oil

and consequently influence the lubricity and usability of engine. In this paper

the surface properties of biomass fuel soot (BS) and diesel soot (DS) were contrastively investigated by means of Fourier infrared spectrometer

X-ray photoelectron spectroscopy

full-automatic micropore physisorption and chemisorption analyzer

optical contact angle/interface tension meter and Zeta potentiostat in order to study the effect of BS and DS particles on viscosity of liquid paraffin (LP

simulant of base oil for lubricating oil)

and discuss the mechanism of influence of soot surface properties on the viscosity. Results showed that the relative viscosity increased by exponential function with increasing soot content at 40℃. The relative viscosity of oil contaminated by DS was higher than that of BS in case of the same soot contents. The oil contaminated with high concentration soot had the advantage of clearly identified shear thinning behavior

which was more severely in LP contaminated by DS. The main surface elements of BS and DS were carbon and oxygen. The surface oxygen content of DS was less than that of BS. There were some O-containing functional groups on the surfaces of BS and DS. The surface property analysis showed that the specific surface area and the surface energy of DS were higher than those of BS. The lipophilicity of DS was less than that of BS. The DS was apt to agglomerate into larger agglomeration particles in LP

which was the main reason for the fact of DS affecting LP viscosity more severely compared with BS.