Measurement of Polymer Transitions

Many polymers show one or more damping peaks in dynamic mechanical measurement, in addition to the peak associated with the main glass transition temperature (Tg) [1]. These transition temperatures are also normally detected in electrical measurement as well as in nuclear magnetic measurements. In a few cases, secondary transitions have a magnitude great enough to be detected by breaks in volume versus temperature curves or by DTA measurements. These transitions are associated with various stages of polymers, which are discussed here. 

An important transition measurement is that of Tg. The TGA and DTA curves of azopolyamides measured in nitrogen at a heating rate of 5 °C/min are compared by Thayumanaswarmy and Rajindran [2]. 

DTA has been used to determine the Tg of polymers including polystyrene [3], polyimides [4], copolyarylene ethers [5], bis(trichlorophenolate)dipyridine [6], nitroazobenzene substituted polymethacrylates [7] and polycarbonates [8], polydimethyl siloxane modified silica xerogels [9], and linear polydicyclopentadiene [10]. 

Rieger [11] demonstrated that the Tg measured by DTA and dynamic mechanical thermal analysis do not agree unless the frequency of the torsional pendulum is 

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