Kinetics Analysis of Thermal Degradation Reaction of PVA and PVA/Starch Blends

The kinetics of thermal degradation of PVA and PVA/starch (40/60) blends were investigated by thermogravimetry (TGA) and derivative thermogravimetry (DTG). Experiments under non-isothermal conditions were carried out for samples in nitrogen at heating rates of 5, 10, 15 and 20 degrees C/min. The Kissinger, Flynn-Wall-Ozawa, and Coats-Redfern methods were used to calculate the activation energy of degradation and determine the degradation mechanism for PVA and PVA/starch blends. The results showed that these three methods were suitable and effective to describe the thermal degradation of PVA and PVA/starch blends. The thermal stability of PVA/starch blends is higher than that of PVA suggesting that the addition of starch improved the thermal stability of PVA. The thermal degradation of the PVA/starch blends could be separated into three distinct stages. The Coats-Redfern method showed that the degradation mechanism of PVA and PVA/starch blends was a nucleation and growth mechanism in which PVA went to the A(3) mechanism and PVA/starch blends went to the A(4) mechanism.