The Tribology of Cleaning Processes

The effect of different chemistries on cleaning of hard surfaces has widely been investigated. However, a fundamental understanding of the physical aspects involved in grime removal is yet to be established. A series of surface experiments are presented in this paper to determine the mechanical properties of cleaning processes. Experimental results showed that tribology is a powerful tool to investing the mechanical forces associated with cleaning of soiled surfaces. Analysis of protein-based soil removal from stainless steel suggests that friction coefficient decreases by nearly 28 and 75% for dry and wet samples, respectively, with an increase of 8 times in the normal load. The study also indicates a reduction of the coefficient of friction with an increase in frequency due to the reduced adhesion of counterface pin material on the sample and the possible localized softening of the soil surface. Tests performed using wet samples revealed that friction coefficient significantly decreases as a consequence of the water content. The effect of load on wet samples was mainly observed for short soaking periods (5 minutes). Specimens soaked for 45 minutes showed about 84% lower friction coefficient compared to dry samples but no significant dependency on the applied load. The volume of soil removed was higher for experiments presenting lower friction coefficients. Finally, wet cleaning promoted a higher cleaning efficiency requiring less energy to remove more soil. Overall it was established that purely mechanical forces are not sufficient to complete the cleaning process. Future work investigating the relationship of these tribological aspects with the chemistry of cleaning is to be expected.