Effect of lactic/glycolic acid side chains on the thermal degradation kinetics of chitosan derivatives

The thermal degradation properties of chitosan and lactic and/or glycolic a cid grafted chitosan have been studied by differential scanning calorimetry (DSC) and thermogravimetric analyses (TG) in the range of 25-500 degrees C . Both DSC and dynamic TG results show that the samples are thermal degrade d easily after grafting the lactic and/or glycolic acid. From the isotherma l TG experiments, the initial activation energy and the activation energy a t different stages is obtained. The initial activation energy of all grafte d samples is much lower than that of chitosan, especially for the sample GA /CS = 2 and it varies with degree of conversion. The FT-IR spectra of therm ally degraded residues give an indication of the chitosan polyscaccharide r ing degradation after 30 min in 280 degrees C, while sample GA/CS = 2 will degrade only after 15 min. (C) 2000 Elsevier Science Ltd. All rights reserv ed.