Concentrated Polymer Brush in Reciprocating Seal Improves Sealing Performance with Low Friction Even for Rough Surfaces and Immiscible Fluids

To achieve both lowering the fluid leakage and lowering the friction loss in a reciprocating seal, the effect of coating a concentrated polymer brush (CPB) onto the rough surfaces of the reciprocating seal was examined using a homemade apparatus. The apparatus comprised a narrow gap of the reciprocating seal, which consisted of a ring and rod, and measured the leakage rate and friction coefficient. An ionic liquid, an alkane, and air were used; the ionic liquid was a good solvent for the CPB; the others were non-solvents for the CPB and immiscible fluids for the good solvent. The leakage rate measurements show that the swollen CPB by the good solvent prevents the fluid leakage even for the immiscible fluids and the rough surfaces of the reciprocating seal. In addition, the friction coefficient measurements show that the swollen CPB provides low friction under alkane lubrication even when the CPB is coated onto just one-side surface of the reciprocating seal.