分子模拟探究EO-PO共聚物影响添加剂界面膜的机制

Molecular Simulations Explore the Destabilization Mechanism of EO-PO Copolymers on Additive Interface Membranes

采用全原子分子动力学模拟方法研究破乳剂EO-PO(环氧乙烷-环氧丙烷共聚物)和二苯胺抗氧剂(DPA)、磷酸胺盐极压抗磨剂(PN)、硫化烯烃极压抗磨剂(S4)、金属缓蚀剂(T561)等润滑油添加剂在正辛烷/水体系的微观聚集行为,通过分析界面形态、密度分布、界面厚度、径向分布函数、氢键能等,探究EO-PO分子和各添加剂分子在油水界面的行为。结果表明:各添加剂分子均在油水界面形成对应的界面膜,使得油水混合乳状液相较于单一的油水体系更为稳定,表明各添加剂在作为功能添加剂的同时也起到了一定的乳化作用;EO-PO分子较添加剂分子具有更强的亲水性,可以在界面上顶替添加剂分子与水相互作用,从而达到破坏界面膜的稳定性,使得油相和水相完全分开的效果,因此对于油水乳化液,EO-PO分子具有很明显的破乳作用;在含有不同添加剂的各体系中,EO-PO分子与水有不同程度的相互作用,其中在含有PN和DPA分子的体系中,EO-PO分子对其界面膜破坏较大,破乳效果较佳。

The microscopic aggregation behavior of lubricant additives,especially demulsifier EO-PO(ethylene oxide and propylene oxide copolymer)and diphenylamine antioxidant(DPA),anti-wear and extreme pressure additive sulfurized hydrocarbons(S4),and compound containing phosphate and nitrogen(PN),corrosion inhibitor(T561)in n-octane/water,was studied by the all-atomic molecular dynamics simulation method.The behavior of EO-PO molecules and additive molecules at the oil-water interface was explored by analyzing the interfacial morphology,density distribution,interface thickness,radial distribution function,and hydrogen bond energy.The results show that each additive molecule forms a corresponding interfacial film at the oil-water interface,which makes the oil-water mixed emulsion more stable than the single oil-water system,indicating that each additive also plays a certain role in emulsification while serving as a functional additive.EO-PO molecules have stronger hydrophilicity than additive molecules,which can replace the additive molecules interacted with water on the interface,so as to destroy the stability of the interfacial film and completely separate the oil phase and water phase.Therefore,for oil-water emulsion,EO-PO molecules have an obvious demulsification effect.In each system containing different additives,EO-PO molecules interact with water to varying degrees.In the system containing PN and DPA molecules,EO-PO molecules have greater damage to its interfacial film,showing better demulsification effect.