Principle : The DMA is an important technique that allows to measure the mechanical properties and viscoelastic materials such as thermoplastics, thermosets plastics, elastomers, ceramics and metals.
in dma the dynamic stress replaces or is superimposed on the static stress. the analysis in which a dynamic loading is applied to the sample can be used to characterize the phenomena of relaxation associated with transitions of the type glass transition (relaxation primary) or no event (thermal relaxations) side.
depending on the range of temperatures considered, which depends on the viscosity of the polymer, and the dimensions of the sample, various methods of solicitation are used : three-point bending, longitudinal stress, bending, twisting, shear between parallel plates (t > tg), single or double embedding…. the recording of the components of elastic and anélastique, respectively in phase and in quadrature relative to the constraint, as a function of temperature (fixed frequency) or frequency (fixed temperature), gives access to the modules mechanical retention in shear (g’) and elongation (e’), the modules of loss corresponding (g2, e2), as well as the loss angle of tan δ = g2 / g’ (or e2 / e’). the deformations are measured by means of optical systems or lvdt, as for the atm, but the components of elastic and anélastique must be separated.