Friction characteristics between metal tool and wood impregnated with phenol formaldehyde (PF) resin during exposure to high pressure

Friction between metal tools and wood under high pressure (≥1 MPa) necessarily arises during wood deformation processes and is thus an important factor to be taken into account when wood is processed. We focus on the friction characteristics between a metal tool and wood impregnated with phenol formaldehyde (PF) resin, which is widely used to improve the dimensional stability of wood products. To clarify the effects of the metal tool surface temperature, the PF resin concentration of impregnated solution and the lubricants under exposure to high pressure on the friction characteristics, the friction coefficient (μ) was measured while the wood was compressed in the tangential direction at high pressure (6.7 MPa). The results of µ for higher PF resin concentration differed significantly with the temperature of the metal tool surface. When the impregnated specimens slide under softening temperature (≤140 °C), the PF resin squeezing out from the specimen contributed to a decrease of μ because it acts as a lubricant. However, when the impregnated specimens were cured (160 °C), μ increased due to an increase of the sliding resistance on the contact surface. μ was decreased to 0.02 when using a release agent for commodity plastics as a lubricant.