Hydroxypropylation of cross-linked sesbania gum, characterization and properties.

Sesbania gum (SG) was successfully modified by combining cross-linking with hydroxypropylation in solvent of ethanol. The hydroxypropylation technology parameters were optimized by the orthogonal test. The results indicated that both cross-linking and hydroxypropylation could improve the freeze-thaw stability, acid and alkali resistance of SG. After the cross-linking and hydroxypropylation of SG, the retrogradation was evidently strengthened. The surfaces of SG derivatives such as cross-linked sesbania gum (CLSG) and hydroxypropyl cross-linked sesbania gum (HCLSG) particles also became very rough, compared with SG. The sequence combination of first cross-linking and then hydroxypropylation was helpful to the follow-up hydroxypropylation of SG. The cross-linking and hydroxypropylation resulted in an obvious reduction in the melting enthalpy of SG, which belonged to a semicrystalline polymer. The cross-linking and hydroxypropylation influenced the thermal properties, and destroyed the crystalline regions of SG. According to SEM, the hydroxypropylation has greater contribution to the destruction than cross-linking. Both cross-linking and hydroxypropylation gave rise to the expansion of SG grains, but the swelling manner was different each other.