where E′ 1 is the instantaneous storage modulus at the beginning of E′(T) DMA curve, E′2 is the instantaneous storage modulus immediately after the γ-transition, E′ 3 is the instantaneous storage modulus immediately after the β-transition and E′ 4 represents the instantaneous storage modulus at the beginning of the rubbery plateau (Figure 1), was successfully applied in one of our previous works in an analytical description of changes in the storage modulus of the tested TPU over a wide range of temperatures [13].