moisture may lower the temperatures of these transitions and this is easily
observed by DMA experiments.
As the sample softens through the low temperature transition, the storage
modulus decreases, while the loss modulus and loss tangent show broad peaks.
At the glass transition, E′decreases greatly, while the loss modulus, E′′and
tan(d) show a sharp peak showing the onset of irreversible viscoelastic behavior.
It should be noted that the sensitivity of the DMA technique is considerably
greater than that of TMA or DSC in detecting transitions. The comparable tech-
niques of dielectric thermal analysis (DETA, orDEA) produce similar results
and cover a wider range of frequencies.G3 – Thermomechanical analysis 319