Thermal degradation kinetic of polylactic acid in multiple extrusions
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Results of a thermal degradation kinetic study of polylactic acid (PLA), raw and reprocessed by extrusion are shown. The reprocessed samples were obtained after each one of five successive extrusions. The samples were tested for glass transition temperature, melt flow index, higher heating value, and dynamic thermogravimetry. Kinetic triplet was determined from the dynamic thermogravimetry data by Flynn-Wall-Ozawa (FWO), Friedman, Gyulai, Kissinger-Akahira-Sunose (KAS), Kissinger, Differential and Integral Arrhenius, Briodo, Chang, Coats-Redfern, Flynn Wall, Horowitz-Metzger, MacCallum-Tanner, Madhusudanan, and Dynamic methods. It was found that activation energy (E) increases with the reprocessing, and that frequency factor (A) increases with the heating rate. It indicates that PLA experiences thermal degradation when is processed by continuous extrusion. It was also found that the average kinetic triplet obtained by isoconversional methods is E=147,14 kJ/mol, ln(A)= 26,94 (with A in min-1), and reaction order n = 0,86, and the triplet averaged from non-isoconversional methods is E=225,30 kJ/ mol, ln(A)= 45,07, and n = 0,91.
Thermal degradation, kinetic triplet, multiple extrusions, PLADegradación térmica, triplete cinético, múltiples extrusiones, PLA
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