PHASE-CHANGE AND VISCOSITY EFFECTS ON A QUARTZ-CRYSTAL MICROBALANCE

The mass-frequency dependence for various materials deposited onto the surface of a resonating quartz crystal was investigated. The relation ship is linear, but the constant of proportionality is different for d ifferent materials deposited. Such frequency changes are commonly desc ribed by the Sauerbrey equation, but in this experiment the equation w as found to be in error by factors of up to 23. This can be accounted for by changes in surface viscosity. Slow temperature changes of a res onating quartz crystal coated with the polymer Antarox CO-880 revealed a significant frequency minimum at the phase-transition points. This is also attributed to a change in the viscosity of the coating at tran sition. The phase-transition temperature for this polymer was verified by differential scanning calorimetry. Quartz crystal techniques mag p rovide a simple, accurate method for the measurements of phase-transit ion temperatures.