木材

The effects of both solid lubricant coating and polyethylene glycol (PEG) treatment on the behaviour of friction between wood and steeI were studied to obtain the fundamental data on the lubrication of wood without lubricating oil. The powders of graphite. molybdenum disulphide (MoS2) and polytetrafluoroethylene (P. T. F. E.) were used as solid lubricants. Furthermore, PEG of various molecular weights (200 to 4000) was chosen for the PEG treatment of wood. The main results obtained are as follows. (1) There is a discernible difference between both graphite and MoS2, and P. T. F. E. in frictional behaviour during the repetition of sliding. This is considered to be caused by the difference in lubrica ting mechanism of solid lubricants. In this experiment, both graphite and P. T. F. E. show a good lubrication but MoS2 shows poor. Above a certain limit value, the coefficient of friction for both graphite and P. T. F. E. is roughly independent of the surface roughness of steel and the coating weight of solid lubricants. (2) AIthough the hardness of most PEG treated wood is reduced as compared with untreated wood, that of wood treated with PEG 4000 increases only slightly. The PEG treatment of wood gives effectivelubrication for friction between wood and rough steeI. This effectiveness is marked at the higher molecular weight of PEG but is almost independent of the retention of PEG. Therefore, PEG treatment is effectiveas a lubricant even at the lower retention below 10 %.