Self-lubricating coatings via PDMS micro-gel dispersions

In the production of enameled copper wires, coated with the high-performance polymer poly(amide-imide), friction between multiple polymer surfaces as well as between the polymer and the slot substrate are significant issues. Low friction is however of prime importance to increase the achievable packing density of the wires, and therefore the efficiency of the respective products. As state of the art, lubrication is performed by leeching lubricants of low effectivity or the addition of waxy layers, which involves an additional production step. The most potent migrating lubricant for this application is poly(dimethyl siloxane) (PDMS). This polymer however cannot be used in free form due to unfavorable migration behavior at the inherently high temperatures of the process. As a potent solution for this issue, cross-linking of PDMS to non-aqueous micro-gels is investigated. Those micro-gel particles can directly be incorporated into PAI coating systems and show highly favorable migration properties due to formation of stable, uniform layers on top of the PAI coating. Respective friction tests show drastically improved friction behavior in comparison to other self-lubricating systems, and equally high performance as additional wax layers, but within a one-pot coating formulation.