Preparation of double-walled polysulfone/graphene oxide microcapsules with high thermal stability and their application in self-lubricating polyamide

Abstract

Double-walled polysulfone/graphene oxide (PSF/GO) microcapsules containing high-temperature-resistant lubricant BIO30 were successfully synthesized. BIO30@PSF microcapsules were first prepared by the solvent evaporation method, and then the surfaces of the PSF microcapsules were activated and modified by polydopamine and GO via in-situ self-assembly to obtain BIO30@PSF/GO microcapsules. GO, which was introduced on the surface of the PSF microcapsules, effectively protected the PSF microcapsules from softening and decomposition. The average particle size and wall thickness of the synthesized PSF/GO microcapsules were about 60 µm and 5.5 µm, respectively, and the encapsulation efficiency was 67.2%. The synthesized microcapsules have high thermal stability. The initial thermal degradation temperature of the microcapsules was higher than 280 °C, and the microcapsules could withstand the molding temperature of polyamide 6 (PA6) composite materials. Self-lubricating PA6 composites were prepared by adding different amounts of PSF/GO microcapsules. Compared with pure PA6, the friction coefficient and wear loss of the self-lubricating PA6 composite with 5 wt% PSF/GO microcapsules under a 50 N load and 300 rpm friction speed decreased by 74.2% and 86.7%, respectively. Further studies confirmed that the boundary lubrication film formed by the release of BIO30 lubricating oil and wear debris in the cavity left by the ruptured microcapsules are the main self-lubricating mechanisms. The synergistic effect between the BIO30 lubricating oil and GO plays an important role in improving the tribological properties of PA6 composites.