This project aims to develop a non-flammable, and non-aqueous closed-loop degreasing system using basic ionic liquids (ILB) as cleaning agents to remove grease from metal parts, specifically targeting the unique component requirements of Department of Defense (DoD) systems. Key sub-goals include development of ILB that can effectively dissolve various greases typical on DoD systems while having very low vapor pressure and flammability, low corrosivity.  The process must also be able to obtain high recovery efficiency of the IBL to ensure the process is viable.

The project team plans to evaluate the feasibility of using basic ILB, which also include deep eutectic solvents, as sustainable degreasing agents. The closed-loop degreasing system involves the use of ILB that removes grease by 1) selectively forming a non-covalent interaction (electrostatic and hydrophobic) with the polar/nonpolar component of the grease (ΔH_r°), and 2) controlled metathesis reaction of ILB with water to remove grease from the spent-ILB (ΔH_m°>ΔH_r°). The process involves atomization of ILB in a two-compartment chamber (degreasing and flush compartments). The atomized ILB in the degreasing compartment will dissolve the grease and the cleaned part will be flushed with pressurized air in the flush-compartment to remove traces of ILB. The main challenge is to ensure that the ILB mist reach complex shapes, deep holes, and the hard-to-reach/tight areas of metal parts and materials. This will be investigated and addressed by mildly pressurizing ultrasonic mist and modulating mist size and density. The project team will evaluate the use of pressurized air (room temperature and hot) and vacuum drying for the secondary cleaning of the degreased metal parts. The ILB chemistry has the potential to exceed the performance of current halogenated solvents as it provides unique, and effective pathways to clean metal parts and address vapor leakage issue in the traditional vapor degreasing system.

Halogenated solvents are the most effective vapor degreasing solvents as these have low surface tension needed for effective removal of grease from the metal parts while being inherently non-flammable. However, there are concerns regarding obsolescence of currently used vapor degreasing solvents. The novel and innovative concept in this project provides an alternative pathway to degrease metal parts involving the use of ILB as cleaning agents.