A comparative study of carboxylic acids on the cross-linking potential of corn starch films

Starch is among the renewable resources currently highly researched to replace conventional polymers. Cross-linking, which is one of the efficient approaches for modifying starch polymers, is employed in this study. Tartaric, oxalic, and citric acids are used as cross-linking agents, and their cross-linking capability is investigated. DSC, DMA, FTIR, XRD, SEM, and water absorption tests were used to determine the property of the starch film samples. The results demonstrated that citric, tartaric, and oxalic acid could cross-link starch with a potential in their respective orders. This could be because citric acid contains one more carboxyl functional group than tartaric acid and oxalic acid. Tartaric acid was better than Oxalic acid for the two more hydroxyl groups available in it. The number of carbonyl functional groups was found to have a more significant cross-linking influence than the number of hydroxyl functional groups in cross-linking starch. Consequently, Citric acid cross-linked starch (CTPS) outperforms tartaric acid cross-linked starch (TaTPS), oxalic acid cross-linked starch (OTPS), and thermoplastic starch (TPS) in properties such as water resistance, tensile strength, and dimensional stability.