COMPARISON OF DSC HEATING RATE AND HCS FREQUENCY AT THE GLASS-TRANSITION

Heat capacity spectroscopy HCS and differential scanning calorimetry D SC results are compared for eight polymers (especially for polyisobuty lene (PIE) and a random copolymer of n-butyl methacrylate with 8% styr ene) and glycerol. A mean value of the parameter a is obtained as (a) over bar = 4.3 +/- 2, where a = T over dot/delta T omega(max), with T over dot the DSC heating rate, delta T the temperature dispersion from the DSC transformation interval, and omega(max) the frequency of the imaginary part of maximum heat capacity, extrapolated from HCS to DSC temperatures. The results are discussed with regard to the fluctuation dominance of molecular glass transitions, to the fluctuation dissipat ion theorem, and to the Second Law of Thermodynamics. The a value seem s to be universal, not depending on the substance group and fragility. (C) 1997 Elsevier Science B.V.