Dielectric studies of the effects of thermal history on secondary relaxation in bisphenol‐a‐polycarbonate

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Abstract
The dielectric permittivity and loss of Bisphenol‐A‐polycarbonate (PC) was measured over the frequency range 100 Hz to 200 kHz and temperature range 77–383 K. One sub‐Tg relaxation peak is observed which rapidly broadens with a decrease in temperature. This is attributed to a progressive separation of the γ and β peaks, which at high temperatures are merged to form one peak of high strength. The strength of the sub‐Tg relaxations decreases on physical aging of PC but is increased if the sample is quenched from a temperature above its Tg. Slowly cooled PC has a lower strength of its sub‐Tg relaxation than a quenched specimen. The thermal history of PC affects the magnitude of its sub‐Tg relaxation.