Interfacial Behaviour Of Hyperbranched Polymer And Mechanism Of Demulsification

Lubricants can be contaminated with water during the application process, which may result in rapid oil degradation and machine failure. The dewatering rate and demulsification performance have been an important technical parameter of lubricants. Currently, the demulsifiers based on linear copolymers are widely applied to destabilize the W/O emulsions. However, these demulsifiers had varying degrees of problems for compatibility and generality.Deferring in the common design of demulsifier based on linear structure, this dissertation synthesized a series of novel demulsifiers based on hyperbranched structure. As potential demulsifier for lubricants, the demulsification behavior, dynamic interfacial tension, and dilational rheological properties of the hyperbranced polymers are investigated. The possible demulsification mechanism and the effects of molecular structure on demulsification efficiency are proposed.In the dissertation, the synthesis process, demulsification behavior and interfacial properties of a series of hyperbranched polymer with polyglycerol as the core and poly(propylene oxide) as hydrophobic arms (HPG-g-PPO) are described. The results show that the demulsification performance of HPG-g-PPO is determined by the HLB value and PPO chain length; The hydrophobic PPO chain has complex effects on interfacial activity of HPG-g-PPO, which lead to faster adsorption at the water/oil interface. The demulsification mechanism of HPG-g-PPO should be related with the Marangoni effects on drop film, molecular substitution at interface, and the floculation between emulsion drops.The demulsification performance and interfacial properties of a series of new fluorinated hyperbranched polyglycerol (HPG-g-PHFBA) are also investigated. The results show that:The hydrophobic and oleophobic properties of fluorinated groups could promote the diffusion rate of polymer, and the amphiphobic fluorinated groups and the hyperbranched structures of the polymer are favorable to improve demulsification efficiency. HPG-g-PHFB A with medium hydrophobic chain length shows the best demulsification performance than that of HPG-g-PPO. The diffusion rate and interfacial viscoelastic properties play an important role in determining the demulsification efficiency of HPG-g-PHFBA. Moverover, the dynamic interfacial tension and dilational properties of the fluorinated polymer at n-decane/water interface are also studied. The results show that:At the earlier stages of adsorption, the transport of the fluoropolymer from the n-decane solution to the interface is governed by pure diffusion-controlled mechanism; At the whole stages of adsorption, the mixed diffusion-reorientation mechanism is more reasonable in describing the adsorption kinetics. The chain length of PHFBA groups is one of the principal factors to control the nature of the interfacial film.