Concentrated Polymer Brush as Reciprocating Seal Material for Low Leakage and Low Friction

Abstract

Recently, concentrated polymer brushes (CPBs) have attracted much attention as potential tribomaterials showing an ultralow friction coefficient (e.g., 10−4 in a microtribological analysis). In this study, a homemade apparatus modeling reciprocating seals was developed, which consisted of an inner steel rod and an outer steel ring with a narrow clearance less than several tens of micrometers. A few-micrometer-thick CPB film of poly(methyl methacrylate) well-swollen with an ionic liquid was prepared on each steel surface, and the impact of applying the CPB film to the clearance of reciprocating seals was examined by measuring the leakage rate of a fluid and the friction coefficient in reciprocating motion. The results showed that the CPB film narrowed the clearance between the two steel surfaces, which improved its sealing performance. In addition, the CPB film yielded a quite low friction coefficient (e.g., 10−3), which assured its smooth motion with small energy loss.