Estudio cinético de la descomposición térmica de plásticos de poliestireno (PS) reciclado

Abstract

The kinetic study of the isothermal degradation of the recycled polystyrene polymer was done by evaluating its behavior during experimentation in a TGA1 STAR system, of samples between 10-15 milligrams subjected to the temperature conditions of 25-900 degrees centigrade, at three different heating rates of 5, 10 and 15 degrees centigrade per minute and in an inert nitrogen environment where the mass variation data was recorded as a function of the conversion, the temperature and conversion variables indicating the maximum degradation point. Through a comparative analysis between the isoconversional mathematical models of Friedman, KAS and Starink the influence of the heating rates and the weight of the sample was studied by determining the kinetic parameters (the activation energy and the pre-exponential factor) and characteristic temperatures as a function of the degree of degradation of the polystyrene. Polystyrene is characterized by having a reaction mechanism that follows a random cleavage route during thermal degradation. The kinetic model that best adjusted to the type of plastic under study is the Friedman model exhibiting the values of 174, 193 and 188 kilojoules per unit mole for the activation energy and 1.34E + 12, 4.78E + 13, 4.31E + 12 per second for values of the pre-exponential factor for 5, 10 and 15 degrees centigrade per minute, respectively. Theoretical explanations of the variation of the thermal and kinetic parameters have been proposed to justify the choice of the appropriate kinetic model.