Synthesis of Castor Oil-based Bifunctional Lubricant Additive

Abstract

Poly(castor oil(CO)–styrene(St)) (PCOS) was synthesized in toluene with azodiisobutyronitrile (AIBN) as the initiator using a Schlenk technology. The structure of PCOS was characterized by the Fourier transform infrared spectroscopy (FT-IR), Proton nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC), and the performance of the synthesized copolymer was evaluated as a solidification point depressant and a viscosity index improver. Experimental results show that when the optimum process conditions are m(CO) : m(St) = 1 : 1, and the AIBN mass fraction is 0.4% (based on the total mass of monomers) at 90°C for 6 h, the copolymer yield is 41%, the average relative molecular mass is 3.1  ×  10⁴, and the polydispersity index is 2.9. After addition of the synthesized copolymer, the solidification point of the lubricant fraction (350–395°C) can be decreased by 6–12°C, while the viscosity index can increase by 24–39. Therefore, the synthesized copolymer could be used as a lubricant additive with the double functions of reducing the solidification point and increasing the viscosity index.