Tribological Performance of Natural Resin Urushi Containing Graphite under Dry and Water Lubricated Conditions

Resin materials are widely used in industrial applications due to their light weight and other desirable characteristics. However, although there are resin materials with self-lubricating functions, there are problems with abrasion and chemical resistance. This study focused on urushi, which has long been used as a coating for armor and other protective layers. Since previous studies have shown that urushi exhibits high wear resistance, this investigation evaluated the tribological performance of urushi mixed with graphite to achieve friction reduction. Friction reduction was observed when graphite was added to the resin. In contrast, accelerated wear was observed compared to that of pure urushi. The SEM-EDS results confirmed that graphite was transferred from one surface to the other as carbon and this carbon was detected in the mating material. This result suggests that friction reduction was achieved by transferring to the counterpart; however, the wear was accelerated by the transfer.