Analysis of the thermal environment inside the furnace of a dynamic mechanical analyser

In this work, the thermal environment inside the furnace of a dynamic mechanical analyser was investigated by putting a standard sample in distinct positions inside the furnace. Penetration experiments were carried out in order to compare the measured melting temperature of the sample with the theoretical melting temperature. The thermal gradients were investigated for three distinct modes: compression, three-point bending and extension. In the compression mode a small variation of the measured melting point was found as a function of the radial distance. However, for both extension and three-point bending modes quite important variations were measured along the relevant directions. In the former case the bottom clamp was found to be warmer than the upper one and in the latter mode higher temperatures are found in the extremities of the samples (closer to the furnace wall). Other factors, such as the influence of the heating rate and the purge gas flow rate, were also investigated. In the particular case of the extension mode, it was found that the measured melting temperature decreased with increasing scanning rate. A simple model was used in order to investigate the influence of the temperature gradients on DMA measurements. For temperature gradients along the sample length below 10°C the differences in the viscoelastic parameters (tan d, D∗ and E∗) from the homogeneous case are small when compared with typical experimental errors.  2002 Elsevier Science Ltd. All rights reserved.