Surface. Hawsp / Surfactant Molecular Structure On Interfacial Tension,

How to design and choose high performance polymers and surfactants is a principal question of binary oil-displacing system. The former research result of our research group indicates that the hydrophobic associating water-soluble polymer could increase viscidity effectively and Gemini surfactant has advantages in interfacial activity. It is to say, SP has tremendous potential. But how the molecules structure design and optimization of polymer and surfactant would improve the binary oil-displacing system remains to be seen.The main content of this article is to test the influence of different kinds and the molecular structure of surfactant and Hydrophobically associating water-soluble polymer in term of interfacial tension, and the surface properties of the surfactants, besides, the influence of combination between Gemini surfactants has been studied, same as the affect of combination between FNR & BH-M, SDBS & OP-10 in SP interfacial tension. The research focuses on with the relationship of the chains length on Gemini surfactants and interfacial activity, also the relationship between hydrophobic block length & hydrophobic group content and interfacial tension of SP. The concentration of NaCl sets as 5000mg/L for shielding the NaCl injected during the polymer synthesis and salt effect of surfactants.The interfacial tension of surfactant solution illustrates that, surfactant type has certain influence on interfacial tension, manifesting in the form that nonionic surfactant OP-10 could reduce water-oil interfacial tension slightly better than anionic surfactant SDBS, and nonionic surfactant FNR shows its advantages of decreasing interfacial tension above 1000mg/L, Gemini surfactant BH-2 would decrease the interfacial tension in very narrow concentration range. Three Gemini surfactants——BH-1, BH-2,BH-3 (the chain length increasing) are studied respectively, and we found that the increasing of chain length benefits of reducing water-oil interfacial tension, but BH-3 can not reduce the interfacial tension effectively because of the bad solubility. Mixing three surfactants together, we finally get a combine formula about surfactants that can effectively reduce the oil and water interfacial tension, named as BH-M, i.e. BH-2:BH-3:BH-1= 10:1:1-4:1:1, this mixed surfactant has very good interface properties.Based on the research of the surfactants'surface tension, the critical micelle concentration (CMC) of SDBS is highest (CMC 250mg/L),and BH-M least, only 8 mg/L; the CMCs of three Gemini surfactant——BH-1, BH-2,BH-3 are 70mg/L,51 mg/L,14mg/L respectively, namely, the CMCs reduce while the chain length increasing, and the affect on reducing surface tension of Gemini surfactants is superior to the average of surfactant.The molecular structure of polymer has few influences on dynamic interfacial tension of SP until that the same concentration of surfactant (BH-M) joins, the block length of polymer makes the interfacial tension rise firstly, then the decline of interfacial tension appears on certain degree, it actually depended on the adsorption of surfactant. Furthermore, the interfacial tension of SP is relatively low as the hydrophobic group content of 0.7%. The main reason is that the adsorption of polymer to surfactants diverses. So the block length and hydrophobic group content have an optimal value in order to improve the oil displacement efficiency better.NaCl affects the solubility of Gemini surfactant and the combination between the surfactants obviously, mainly exhibits on the influence of Na+ acting on electrostatic interaction between the ions. Na+ makes the double electric layer thicker and reduces the repulsion between ions, then the adsorption of surfactants in interface easier. It causes the decrease of surface tension and surfactant CMCs on macroscopic, but the advantage of combination between the surfactants also could not be manifested, especially the combination between the BH-M& FNR, because the solubility of BH-M in brine and the concentration of FNR.Through the study of binary system, we know that it was helpful to improve molecules structure design and optimization of the polymer and Gemini surfactant, so as the theoretical basis for further research.