Research On Performances Of N-fatty Acyl Amino Acid-based Lubrication Additive Promoting Biodegradation Of Lubrication Oil

It has been known that environment has been polluted by conventional mineral lubricants because of their low biodegradability and even eco-toxicity. It is hard to change molecular structure of mineral oil, so almost all reports about environmentally friendly lubricants focused on vegetable oil or synthetic ester. But mineral lubricants still dominate the lubricant market because of their excellent tribological performances and low cost. It has in recent years caught the attention of researchers at home and abroad to research and invent additives that can accelerate lubricant biodegradation.For promotion of biodegradability of mineral lubricants in no adverse effects on their performances, N-fatty acyl amino acid as lubricant biodegradation accelerant was prepared, using fatty acid with a degradational long chain hydrocarbon and amino acid which is an organic part as main starting materials. The main functional groups of the additives were preliminarily characterized by infrared spectrum. The solubility in oil and heat stability of the additives were tested by oil-soluble test and thermogravimetric analysis test. The anticorrosion and antirust of N-fatty acyl amino acid were investigated systematically by petroleum products copper strip corrosion test and antirust test. The result shows that N-fatty acyl amino acid as lubricant additives could enhance anticorrosion performance and antirust performance.The biodegradability of mineral lubricant with N-fatty acyl amino acid was examined by the fast evaluating method. The result indicated that a little of N-fatty acyl amino acid could remarkably promote the biodegradation of mineral oil. And the mechanisms of additive promoting biodegradation of lubrication oil were also researched.The tribology performance were investigated systematically by four-ball friction and wear test. The result shows that N-fatty acyl amino acid could enhance remarkably antiwear and friction-reducing abilities of mineral lubricant. The tribology mechanisms of the additives were studied by scanning electron microscopy(SEM) and X-ray photoelectron apectroscopy(XPS). The results demonstrated that tribochemistry reaction was generated on the friction surface. When liquid paraffin including N - fat acyl glutamine was used as lubricant, a complex protecting membrane was formed of -CONH₂, -NH₂ and Fe₂O₃ which were generated by tribochemistry reaction on the friction surface. When liquid paraffin including N - fat acyl cystine was used as lubricant, a complex protecting membrane was formed of -CONH₂, -NH₂, Fe₂O₃, FeS and FeSO₄ which were generated by tribochemistry reaction on the friction surface. Meanwhile, adsorption membrane was generated on the friction surface due to part of polar groups of N-fat acyl amino acids. Adsorption membrane and tribochemistry reaction membrane improved antiwear and friction-reducing abilities of mineral lubricant. Additionally, the composition properties of N-fatty acyl amino acids with ZDDP in Liquid paraffin were investigated. The result indicated that N-fatty acyl amino acids could remarkably enhance friction-reducing abilities, and promote antiwear performance to a certain extent in larger load.