Characterization of crosslinked guar by thermal analysis

Guar gum (GG) was crosslinked with increasing amounts of glutaraldehyde (GA ). The resulting crosslinked products were analyzed by differential scannin g calorimetry (DSC), thermal gravimetric analysis (TGA) and wide-angle X-ra y diffraction (WAXD) to determine the influence of crosslinking on the poly saccharide structure. Each crosslinked product thermogram was characterized by two or three sharp endothermic peaks and a wide exothermic peak, with t he latter indicating that a decomposition chain reaction occurred. It was o bserved that: (a) crosslinking altered the structure of GG; (b) the thermal stability of crosslinked GG depended on the amount of GA used with excess amount of the crosslinker reducing the stability of crosslinked GG; (c) the reaction of GG with GA occurred either by inter- or intra-crosslinking, de pending on the amount of GA used; (d) crosslinking of GG with GA resulted i n the formation of new regions in the polysaccharide, characterized by modi fied structures, whose abundance and density were crosslinker concentration dependent. (C) 1999 Elsevier Science Ltd. All rights reserved.