Dynamic interfacial activity and dilational viscoelasticity of polyether demulsifiers at the oil/water interface

A series of polyether demulsifiers with different PO/EO mass ratios and initiators were synthesized. The dynamic interfacial tension curves and dilational interfacial viscoelasticity of these polyethers at different oil/water interfaces were examined using the drop shape analysis method. Dynamic interfacial tension curves indicate weak adsorption of polyether demulsifiers at the diesel/water interface and strong adsorption at the xylene/water interface. Meanwhile, BPF9915 possesses the maximal interfacial activity among these three polyethers at the xylene/water interface, which differs from the diesel/water interface. Therefore, the dynamic interfacial activity of polyethers is related to the oil phase component. The order of dilational modulus of BPF polyethers at the diesel/water interface is BPF9935 > BPF9925 > BPF9915, which is similar to the order of dynamic interfacial activity. However, because of the weak adsorption of BPF polyethers, the values of dilational elasticity of BPF polyethers are small. Although these polyethers reduce the interfacial tension of the xylene/water interface sharply, the values of dilation elasticity of these polyethers at the xylene/water interface are close to those at the diesel/water interface. Therefore, these adsorptive branched polyethers exhibit weak intermolecular interaction. At the crude oil/water interface, the addition of polyethers causes the decrease of dilational interfacial elasticity, indicating the destruction of the dense interfacial adsorption layer by the BPF polyether. In addition, a hydrophobic polyether has a better dynamic interfacial activity in the crude oil, thus replacing the interfacial activity materials more effectively from the crude oil/water interface. Furthermore, the essential influencing factor of dynamic interfacial activity is PO/EO mass ratios rather than initiators. The PO/EO mass ratios will change the hydrophile and lipophilic balance, which is very important for the interfacial adsorption of polyether demulsifiers. (c) 2022 Elsevier B.V. All rights reserved.