Thermal studies on natural and modified gums

Various industrial gums (i.e. gum arabic, gum tragacanth, gum xanthan, sodium alginate, chitosan, carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose) were thermally characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) under nitrogen atmosphere. Major thermal transitions as well as activation energies of the major decomposition stages were determined. Gum tragacanth and hydroxyethyl cellulose exhibited the highest (258 kJ/mol) and the lowest (121 kJ/mol) activation energy of thermal decomposition, respectively. Most of the DSC traces indicated a major intense exothermic transition (around 300 degreesC) followed by weaker exotherm(s). Methylcellulose. however, exceptionally showed an intense endothermic transition. According to the integral procedural decomposition temperature (IPDT) values calculated based on the TGA thermograms, chitosan (IPDT 417 degreesC), carboxymethylcellulose (IPDT 412 degreesC) and methylcellulose (IPDT 386 degreesC) were recognized to be more thermally stable than the other polysaccharides studied. (C) 2003 Elsevier Ltd. All rights reserved.