Measuring the Static Coefficient of Friction of Non-Fluid Contaminants

Abstract

The purpose of our study was to evaluate whether there are differences between measuring the static coefficient of friction (SCOF) of a non-fluid contaminant when it is directly attached to a tribometer test foot, or “Attached”, versus when it is lying loose on the floor, or “Loose”. The non-fluid materials used in this study included Mylar, Cardboard, Terrycloth Bathmat, and Terrycloth Bathmat with Rubberized Silicon Backing; the floor material was porcelain tile. In addition, 10 participants subjectively rated the “slipperiness” of each material by pushing the materials with one foot across the porcelain tile. The findings of this study revealed that within each technique, Attached and Loose, the measurements were consistent and reliable. Furthermore, both techniques resulted in identical ordering of the materials from lowest to highest SCOF, which was verified by the human subjects’ subjective ratings of slipperiness. However, the Loose technique SCOF values were slightly but consistently greater than the Attached technique SCOF values; the Loose tests of the entire bathmats were found to have greater SCOF values when compared to Loose tests of small samples. These findings suggest that when investigating a specific slip event, a practitioner should measure the SCOF of the non-fluid contaminant using the technique which most closely represents the conditions of the slip event.