Análisis termodinámico mediante la energía libre de GIBBS del proceso de degradación térmica de mezclas de termoplásticos

Abstract

The present study aims to analyze the Gibbs free energy of thermal degradation of thermoplastic blends; polymers commonly found in municipal solid waste such as PP, PE, PS, PET, PVC using the thermogravimetric analysis method (TGA) which is based on the measurement of the mass loss of the material as a function of temperature applied at three heating rates of 5, 10 and 15 °C.min-1. The data were applied to the free Kissinger_Akahira_Sunose (KAS) model, which was fitted by statistical analysis using linear regression to determine the activation energy (Ea), the pre-exponential factor (A).The model formula based on the Arrhenius equation was used to obtain the graphs of the TGA which measured the sample mass during heating and the DTG which indicated the maximum temperature at which the process reached. The statistical indicator was used to minimize the absolute error (FOE) and select the adjusted data for the kinetic parameters; the activation energy values ranged between (194-215) kJ.mol-1, (168-170) kJ.mol-1, (228-246) kJ.mol-1 for the heating rate of 5, 10 and 15 ºC.min-1 respectively. With the kinetic data obtained, the thermodynamic parameters were determined whose values were positive for enthalpy (ΔH), Gibbs free energy (ΔG) and negative for entropy (ΔS). It is concluded that the total energy of the system has a non-spontaneous process due to its positive values reflecting a greater amount in the rate of 5 ºC.min-1 with a value of 704 kJ.mol-1. It is recommended to select in the DTG graph the data of the steepest curve since it is where the mass variation with the highest degradation was found.