Effect of cross-linking and oxidization on structure and properties of sesbania gum

The effect of cross-linking and oxidization on the structure and properties of sesbania gum (SG) was studied using phosphorus oxychloride as a cross-linking agent, hydrogen peroxide as an oxidant, and ethanol as a solvent. The results showed that the oxidation of SG by hydrogen peroxide was essentially the breaking of long chains without hydroxyl groups being oxidized into carboxyl groups. The breakage of long chains was a key reason of reduction in viscosity. The disruption of SG granules caused by cross-linking was obviously different from the oxidization. The cross-linking had high selectivity, but the oxidization of hydrogen peroxide was random. The crystallinity degree of SG was reduced by cross-linking and oxidization. The cross-linking and oxidization obviously changed the thermal properties of SG, and had obvious influence on the freeze-thaw stability, swelling power and retrogadation of SG. The cross-linking degree was well characterized by the surface hydroxyl numbers. The cross-linking was carried out only on SG granule surface according to evidence of alteration in surface hydroxyl numbers.