Characterization of crosslinked cashew gum derivatives

Crosslinked materials from cashew gum (CG) and carboxymethylated CG (CMCG) were synthesized using epichlorohydrin (E) as the crosslinking agent. The products were characterized by 13C nuclear magnetic resonance, IR spectroscopy, swelling degree and thermal analysis. The reaction yield with CG increases with increasing of epichlorohydrin/gum molar ratio (E/G) up to 0.17 (CGgel3 sample) and then decreases. The swelling degree of CGgels decreases with increasing E/G ratio due to the increase of crosslinking density. Carboxymethylation of cashew gum crosslinked gel (CGgel3), denoted as CMCGgel3, increases the swelling degree by 23%. The thermal degradation of cashew gum, carboxymethylated cashew gum and crosslinked derivatives (CMCGgel3 and CGgel3) were evaluated by thermogravimetry and infrared spectroscopy. Activation energies follow the order: CGgel3 > CMCG > CMCGgel3 > CG, and stay in the range of 106–219 kJ mol−1. Infrared analysis performed in residual products after heating at different temperature indicates that the mechanism of thermal degradation includes formation of carbonylic products, double bond and cyclic structures.