Internal friction measurement of organic glass below and near the glass transition temperature

Abstract Internal friction (IF) measurements were made over a wide frequency range, 0.001–10 Hz, for temperatures in the range 11–74 °C. A forced vibration method was adopted using the Vibran apparatus. The specimens used were from the typical organic glass polystyrene, and the measurements were performed on the glassy state from room temperature up to a temperature close to the glass transition. A viscous type relaxation, IF inversely proportional to frequency, was observed at all temperatures. The relaxation time was determined as a function of temperature at various frequencies. The relaxation behavior showed a double relaxation: a combination of two thermal-activation type relaxations. This result was quite similar, especially at lower frequencies, to the result derived from the static viscosity measurement for the same material