Research On Evaluation And Improvement Method Of Lubricant’s Demulsibility Property

Demulsibility property is an important quality indicator of lubricating oil.At present,the demulsibility property of petroleum products is usually measured according to GB/T 7305-2003 evaluation method.However,because the experimental conditions of the national standard do not match the actual operating conditions of the lubricating oil,the measured demulsification performance results are quite different from the demulsification performance of the lubricating oil under the actual operating conditions.Aiming at the shortcomings of the GB/T 7305-2003 experimental method in practical application,this article simulates the actual working condition of lubricating oil,and studies the influence of oil-water ratio and continuous emulsification on the demulsibility property of lubricating oil.According to the experimental results,suggestions for improving the evaluation method of lubricant demulsification performance were put forward.Besides,through adding oil-soluble demulsifier to the lubricating oil,the demulsification performance of A220 lubricating oil was improved at oilwater ratio 6:2.Finally,the stabilization mechanism of lubricating oil emulsion and the action mechanism of demulsifier were studied.The result shows that: Both oil-water ratio and continuous emulsification have a greater impact on the demulsification performance of lubricating oil.With the increase of oil-water ratio,the demulsification performance of lubricating oil becomes worse.As the number of continuous emulsification increases,the demulsification performance of lubricating oil also decrease significantly.Therefore,lubricating oil with qualified demulsification performance measured according to the national standard GB/T 7305-2003 evaluation method may show extremely poor demulsification performance under the actual high oil-water ratio and continuous emulsion condition.Therefore,the influence of high oil-water ratio and continuous emulsification under actual working conditions should be considered when designing the evaluation method of demulsification performance of lubricating oil.Demulsifier DL32-2 has good oil solubility,which can effectively improve the demulsification performance of A220 lubricant when the oil-water ratio is 6:2,and the best use amount is 0.07wt%.Although HK lubricant has higher interfacial modulus,its viscosity is lower and the interfacial tension is higher,so its demulsibility is better.For A100 and MF525 lubricants,although their interfacial tension is less than that of HK,their viscosity and interfacial expansion modulus are relatively small,so their demulsification performance are relatively good.For A220 lubricating oil,although its interface expansion modulus is low,its viscosity is very high,and the oil-water interfacial tension is low,so its demulsification performance is the worst.Demulsifier DL32-2is mainly adsorbed on the oil-water interface film to reduce the strength of the interface film,making it easier for the droplets to coalesce and break the emulsion.