Determinación de parámetros termodinánicos en la degradación de mezclas de polipropileno y poliestireno a tres tasas de calentamiento

Abstract

The objective of this research project consisted of determining the thermodynamic parameters of the thermal degradation reaction of recycled polypropylene (PP) and polystyrene (PS) blends. The plastics were randomly sampled and then followed by thermogravimetric analysis (TGA) in dynamic tests at three heating speeds 5, 10 and 15 °C min-1 using an inert nitrogen atmosphere from the reference temperature up to 697°C; by means of which, the mass conversion behavior was measured through thermogravimetry, and then the Arrhenius equation was used to adjust the DTG curves. Thus, kinetic parameters were obtained through the application and comparison between isoconversional kinetic methods: Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger- Akahira-Sunose (KAS). It was established through the implementation of different reaction models that the optimal model was the phase boundary-controlled reaction: shrinking area (R2), finding out that the mixture presented a better behavior for this model. From the experimental data, the mass conversion curve was carried out in relation to the elapsed time vs the inverse temperature and the value of the slope representing the activation energy (Ea) and at the point of the ordinate to the origin the pre-exponential factor (A) were obtained. Once the calculations were made and the Objective Error Function (FOE) was implemented for the optimization of the thermogravimetry deviation a difference in the calculated one, the different correlation coefficients were compared, which led to the conclusion that KAS is the method that best suited to the thermal degradation process of polypropylene and polystyrene mixture at three heating rates. It is recommended to establish from the beginning the behavior of the mixture, making it possible to determine the calculations in a better way in the degradation process.