Abstract
Double network gel (DN gel) has been attracting global attention as new material because of its unique characteristics of higher strength, higher water content and lower friction coefficient than the current polymer gels. Several researches on the tribological properties of DN gel in point contact were found, but there are only few papers on the tribological properties of the gel under plane contact condition. In this study, we investigated the effects of contact pressure and the contact area on the friction coefficients of the DN gel using two kinds of friction testers, a ball-on-disk and a disk-on-disk friction testers. The results obtained by a ball-on-disk apparatus showed that the friction coefficient of DN gel in water was very low, about 0.01-0.02, regardless of the contact pressure and sliding speed. However, the friction coefficients of the gel in plane contact were comparatively higher than those obtained by the ball-on-disk apparatus and depended on the viscosity of lubricant and the sliding speed. The whole experiments showed that the appropriate contact pressure and contact area were necessary to induce the exudation of water from the DN gel inside and then the low friction performance of the DN gel was finally acquired.
