Effect of underwater flexibility of a soiled cloth on the detergency of automatic washing machines

To determine the conditions of Terg-O-Tometer (a laboratory-scale test washing machine) that match the cleaning performance in real households, this study compares the detergency performances of a vertical washing machine and a Terg-O-Tometer on cotton and chemical fibers. Consistent with previous studies, the detergency of the Terg-O-Tometer matched that of the vertical washing machine at a rotation speed of 100 rpm for cotton cloth. However, when tested on polyester/cotton blend cloth, the matching rotation speed was 40–80 rpm, depending on the dirt on the fibers. These disparate results are attributed to differences in the frictional force between the cloths generated in the vertical washing machine and Terg-O-Tometer, and to differences in the underwater flexibilities of cotton soiled cloth and polyester/cotton blend cloth.