Thermal degradation and stability of cationic starches and their complexes with iodine

Abstract

Thermal degradation processes of cationic starch (CS) and CS–iodine complex were investigated by thermogravimetry (TG) in air and under nitrogen atmosphere at 10°Cmin−1 heating rate and compared. Moreover, the thermal stability of CS with different degree of substitution (DS) and their complexes with iodine was studied by TG under nitrogen atmosphere at different heating rates. The average Ea values for CS were found to be slightly lower as compared to native starch, suggesting lower thermal stability of modified starches due to cationisation. The main thermodegradation event of native starch–iodine and CS–iodine complexes can be separated in two steps: the release of iodine in the range of 137–196°C, followed by the subsequent iodine induced thermochemical degradation of polysaccharide macromolecules, which appears at lower temperatures than in the absence of iodine. “Blue” inclusion complex showed higher thermal stability than ionic CS–iodine complex.