Uma solução computacional para a determinação da massa molar de polímeros lineares por reologia analítica

Abstract

Molecular weight distribution (MWD) determination is crucial in the field of polymer science and engineering. Altough conventional techniques such as GPC have been widely employed, there is potential for the development of alternative methods based on analytical rheology. This work introduces PolyWeight, a Python software with a graphical user interface (GUI) that offers two distinct approaches for determining MWD: an analytical relation-based method (GAR model) and a parametric model-based method (GEX model). By utilizing dynamic moduli, users can calculate the MWD as well as the molecular weight averages such as Mn, Mw and Mz. The functionality of PolyWeight is validated using synthetic data, while the application limits of the software are explored with data extracted from the literature. In this case, some limitations of the GAR model as implemented are highlighted due to the use of a simplified kernel function and the calculation of the relaxation spectrum itself. On the other hand, the GEX model presents excellent agreement. The use of polystyrene rheometry data obtained between 170°C and 230°C allows evaluating the experimental conditions that should be used in the analysis of this polymer. It is observed that the test temperature has a minor influence on the determination of Mn , but directly influences Mw and Mz. It can also be seen that the use of a mastercurve is ideal for this application as long as the reference temperature is less than 200°C, however it is possible to obtain good estimates with the isotherm curves of the dynamic moduli in selected temperatures as well. [resumo fornecido pelo autor]