動的摩擦試験法による塗膜の粘性測定および乾燥過程の評価

Abstract

Curing process of acrylic coating on a slide glass is monitored with a microtribometer. The microtribometer equips a hemispherical diamond tip of 16 μm in radius and the tip is reciprocated on the coating surface. The tip is mounted at a free end of a cantilever, whose spring constant is 50 N/m, and the other end is forced to oscillate sinusoidally at 30 Hz with constant amplitude of 50 μm. The viscous force working between the tip and the coating brings about the amplitude-damping and the phase-delay in the motion of the tip. The relative motion of the tip with respect to that of the forced end can be monitored as an induction voltage in the coil. The average AC voltage is proportional to the magnitude of the friction and the integration readily yields the motion of the stylus. In the experiments carried on the acrylic lacquer coating a characteristic viscous behavior was observed, and the friction signal could successfully be simulated by employing proper parameters in the Casson equation for viscosity. It was found that the time evolution of the parameters corresponded to the curing process of wet paint.