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DSC was used to study the thermal curve characteristics of four classical polymer glasses: polycarbonate (PC), anionic polystyrene (aPS), polysulfone, and polymethyl methacrylate (PMMA). The onset, peak, and fictive temperatures as well as endotherm characteristics were studied over two decades of heating and cooling rates. Assuming that the fictive temperature is independent of heating rate, the usefulness of Tonsetand ambiguity of Tpeak are demonstrated. The useful [heat/cool] ratio allows use of Tonset to calculate the effective cooling rate of the sample (which is easier to calculate thanTfictive). Comparison with results from annealed samples are shown. The fictive and onset temperatures can be used together to improve the reliability of glass temperature characterization and results are surprisingly constant between the four different types of glasses, leading to a method of providing a single temperature to characterize the thermal history/morphology using a DSC thermal curve. The peak temperature is nearly independent of thermal history, and so provides a characterization parameter that is insensitive to manufacturing and molding procedures.
glass transition, onset temperature, peak temperature, fictive temperature, cooling exotherm, differential scanning calorimetry (DSC), DSC heat/cool ratio, DSC heating rate, DSC cooling rate
Technical director, Solomat Ltd., Heathpark Industrial Estate, Honiton, Devon