Ultra-low friction, ultra-fast response and low-VOC self-lubricating coating based on oil-filled silica microcapsules

Abstract

A complete silica microcapsule filled with PAO6 oil was synthesized by emulsion-templated sol-gel method. The average diameter of microcapsule was about 20 µm, with encapsulation capacity of 70 %. The microcapsules were well-dispersed in aqueous solution and fully compatible with waterborne epoxy emulsion, making it suitable for building VOC-free self-lubricating coatings. With 5 wt% microcapsule, the self-lubricating coating achieved an exceptionally low friction coefficient at about 0.02, approximately 2.6 % of that of the blank coating without microcapsules. The wear volume could barely be measured. The ultra-fast response ability was robust, as confirmed by the negligible running time throughout the continuous start-stop sliding tests. This oil-filled silica microcapsule has great potential for developing high performance and VOC-free self-lubricating coatings.