Temperature correction of dynamic mechanical and thermomechanical analysers during heating, cooling and isothermal experiments

In this work some procedures are outlined to improve the correction of the temperature axis in isochronal and isothermal experiments performed in DMA and TMA apparatus. For the case of experiments on heating, the influence of the position of the metallic standard used during the calibration procedures is found to have great importance, mainly due to the purge gas flux inside the furnace. New calibration routines are proposed, taking into account the mechanical mode used. The isothermal correction can be performed by extrapolating heating results for zero scanning rate or by running experiments at a very low heating rate. A method for correcting the temperature of experiments on cooling with data obtained from heating experiments is also proposed, provided that symmetry between heat fluxes of cooling and heating experiments exists. This method was confirmed by investigating the temperature position of the alpha-relaxation of a thermoset polymer, detected by DMA experiments on heating and cooling. (C) 2000 Elsevier Science B.V. All rights reserved.