Kinetics and mechanism of thermal degradation of pentose- and hexose-based carbohydrate polymers.

This work aims at study of thermal degradation kinetics and mechanism of pentose- and hexose-based carbohydrate polymers isolated from Plantago ovata (PO), Salvia aegyptiaca (SA) and Ocimum basilicum (OB). The analysis was performed by isoconversional method. The materials exhibited mainly two-stage degradation. The weight loss at ambient-115°C characterized by low activation energy corresponds to loss of moisture. The kinetic triplets consisting of E, A and g(α) model of the materials were determined. The major degradation stage represents a loss of high boiling volatile components. This stage is exothermic in nature. Above 340°C complete degradation takes place leaving a residue of 10-15%. The master plots of g(α) function clearly differentiated the degradation mechanism of hexose-based OB and SA polymers and pentose-based PO polymer. The pentose-based carbohydrate polymer showed D(4) type and the hexose-based polymers showed A(4) type degradation mechanism.