Effect of Corn Starch on the Biodegradability and Absorbency of Superabsorbent Polymer

Abstract

Corn starch, a biodegradable material, was used to modify the properties of a hydrogel, also commonly called superabsorbent polymer, SAP. The starch was used to enhance the gel strength while providing an improved polymer biodegradability. The starch suspension was prepared by agitating the starch in deionized water and was used for treating the SAP particles. The treatment process was done by mixing the starch particle suspension with the SAP allowing the starch to adhere at the SAP surface and the water to diffuse into the inner SAP structure for a volumetric swelling degree of more than 2. The resulting mixture was then heat treated at a temperature of 150^oC until the SAP moisture is less than 5% by weight. The gel strength was determined in terms of the permeability of the gel particles when formed in a layer or bed. The permeability of SAP samples was determined using Gel Layer Permeability (GLP) after the dry SAP particles were allowed to swell at 0.9% sodium chloride solution for one hour. SAP gel strength increased after treatment of starch as shown by the results of GLP tests. To evaluate the biodegradability of the SAP, samples were subjected to high relative humidity environment of 90-95% RH and temperature of 30-35^oC for more than one month where discoloration of the SAP particles were checked regularly. The SAP samples treated with corn starch biodegrades faster as shown by the changes in the color compared with other samples without corn starch treatment.