From a certain strain applied on the polymer, the viscoelastic properties start to change : the modulus of elasticity decreases and a Tan Delta peak is observed as it can be observed in the figure. This level of deformation for which the properties vary is called nonlinear domain. Because the mechanical properties of a material usually need to be preserved during its application time, knowing the limit between the linear and the non linear domain is a key point in the material conception. Isothermal DMA strain sweep is a quick and reliable method to determine the linear domain.
