Study on thermal degradation kinetics of cellulose-graft-poly(l-lactic acid) by thermogravimetric analysis

The thermal degradation of cellulose-graft-poly(l-lactic acid) at different heating rates in nitrogen was studied by thermogravimetric analysis (TGA) in the temperature range 20-550 °C. Nuclear magnetic resonance (NMR), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC) analyses were utilized to determine the microstructure and glass transition temperature of cellulose-graft-poly(l-lactic acid). The kinetic parameters were determined by using Friedman, Flynn-Wall-Ozawa, and Kissinger methods. Coats-Redfern method was used to investigate the probable degradation mechanism. The results indicated that the trend of activation energy of cellulose-graft-poly(l-lactic acid) increases with increasing the content of the poly(l-lactic acid) and the process of the non-spontaneous degradation stage, goes to a random nucleation with two nuclei on the individual particle mechanism, whose rate-controlling process could be described by conversion rate (α) (integral form 1/(1 − α)).