A novel boron-nitrogen modified castor oil as an ecofriendly and efficient lubricant additive

Abstract

Borate esters have been emerging as a good candidate in green additives for the increasing needs of environmental protection. A versatile boron–nitrogen-modified castor oil additive (abbreviated as BNC) was prepared. The thermal stability and the oxidation stability of BNC were evaluated. The oil solubility, dispersion stability, lubricity, and biodegradability of BNC in both rapeseed oil and 400SN mineral oil were investigated, respectively. The morphology and tribo-chemical characteristics of the worn surfaces were examined by scanning electron microscope and energy dispersive spectrometer to reveal the possible lubricating mechanisms. The results indicated that the BNC additive had good thermal stability and anti-oxidation ability. The oil solubility and dispersivity of BNC in rapeseed oil is better than that in 400SN mineral oil. The BNC additive could effectively improve the anti-wear and friction-reducing properties of rapeseed oil and 400SN mineral oil. The surface analysis indicated that elemental boron, nitrogen, and oxygen are involved in the lubrication films, and it was deduced that the physical adsorption films, chemical adsorption films, chemical reaction films, and permeable layers work together to reduced friction and wear. Moreover, the BNC could improve the biodegradability of both rapeseed oil and mineral oil, which was attributed to the promoted growth and quantity of microbes by elemental nitrogen involved in BNC. The synthesized BNC additive was demonstrated a potential ecofriendly and effective lubricant additive in industrial applications.