Preparation and tribological studies of stearic acid-modified biopolymer coating

Adding fatty acids to cellulose derivatives can effectively improve the hydrophobicity and surface energy of materials and decrease the microscale coefficient of friction. In this research, stearic acid (SA) and the hydroxypropyl methylcellulose (HPMC) solution were mixed to prepare HPMC/SA composite films. The SA molecules formed crystals distributed within the HPMC film, thus increasing the surface roughness and surface wettability. The intermolecular interaction between HPMC and SA causes the formation of micelles. SEM images of the wear marks indicate that SA debris generated during wear as a third body. Third-body layer provide load capacity during wear and reduces direct contact between the grinding object and the HPMC coating, reducing friction coefficient and wear effectively. It is considered the dominate wear mechanism of HPMC/SA composite under macroscopic wear.