Synthesis Of Dithiocarbamate Derivatives And Their Tribological Properties In Rapeseed Oil

Environmental protection and energy-conservation will be the dominant themes in the 21st century. It is well known that approximately 85% of fluids used as lubricants are mineral oils. Unfortunately, from an environmental point of view, mineral oil based lubricants are not readily biodegradable and contain many kinds of additives; many of which are known to be toxic or otherwise harmful to the environment. The increasing attention on the environmental protection and more restrictive environmental regulations drives the lubricant industry to develop novel potential environmental friendly lubricants and additives.Environmentally friendly rapeseed oil and its derivatives represent alternatives to mineral-based lubricants. Rapeseed oil has high biodegradability, low pollution of the environment, low production costs, low toxicity, high flash points, low volatility, high viscosity indices and compatibility with additives. Howere, it can become good lubricants when appropriate additives are introduced because of the inherent weaknesses of rapeseed oil.According to the relationship between the molecular structure of additive and its tribological properties in base oils,3 series,8 kinds of additives have been designed and synthesized. The molecular structures were identified by means of infrared spectra. Those dithiocarbamate derivatives were:2- hydroxyethyl morpholine-4-dithiocarbamate (HMCT),2-hydroxyethyl dibutylamine-4-dithiocarbamate (HDCT),2-(morpholine-4-dithiocarbamate) butyl acetate (MCTB),2-(morpholine-4-dithiocarbamate) pentyl acetate (MCTP),2-(morpholine-4-dithiocarbamate) hexyl acetate (MCTH),2-(morpholine-4-dithiocarbamate) isooctyl acetate (MCTO-i),di-(dibutylamine-4-dithiocarbamate)(DDCT),di-(dibutylamine-4-dithiocarbamate)-ethyl-n-hexylborate(DDCTB).In this work, the oil solubility, copper corrosion and thermal stability of those dithiocarbamate derivatives in rapeseed oil were studied. The results indicated that the dithiocarbamate derivatives possesed good oil solubility, anti-copper corrosion and thermal stability.The tribological performances in rapeseed oil were evaluated using four ball test machine. The results showed that 8 kinds of additives in rapeseed oil can improve the anti-wear and extreme pressure properties and friction coefficient decrease greatly.In order to explore the lubricating mechanism of the novel additives in rapeseed oil, the morphology of worn steel surfaces were analyzed by SEM and the chemical features of the worn steel surfaces were examined by means of XPS. The results showed that the worn steel surfaces of the test oil systems with additives were smooth, and had light furrows but exfoliation because of corrosion.This is because the additives containing morphine, dithiocarbamate and acid ester or hydroxyl groups reacted with the conterface metal and generated a surface complex protective film consisting of FeS, Fe2O3, FeSO4 and absored compounds contained organic-N or borate in the boundary lubrication conditions, which can improve the tribological properties of rapeseed oil apparently.