Correlation between Mechanical and Dielectric Dynamic Behavior Using Fractional Models: Application to Polylactic Acid

The complementarity between mechanical and dielectric properties is crucial, as it facilitates a comprehensive understanding of material behavior, enabling optimal using. This work mainly focuses on the use of broadband dielectric spectroscopy (BDS) and dynamic mechanical analysis (DMA) to investigate the electrical and mechanical aspects of polymer relaxation phenomena. We have opted to conduct experiments on polylactic acid (PLA) due to its well-known use in various applications, attributed to its notable properties and essential relaxation processes. Differential scanning calorimetry (DSC) was used to identify characteristic temperatures for distinguishing different relaxation processes in the polymer. The obtained experimental results were analyzed using the mechanical fractional model (MFM) and the dielectric fractional model (DFM). The fractional model parameters confirm that higher temperatures correlate with increased molecular mobility within macromolecular chains, especially in relaxation processes associated with the glass transition. Subsequently, a fractional calculus approach is employed to investigate the correlation between the complex modulus and complex permittivity of PLA. This correlation model enables the prediction of the real permittivity ε′(T) curve from the real modulus E′(T) data, providing valuable insights into PLA behavior. These results suggest that the correlation model has the potential to predict the dielectric behavior of a polymer based on its mechanical results and vice versa.