Biodegradability of blend hydrogels based on carboxymethyl cellulose and carboxymethyl starch

Hiroki, Akihiro; Hong, P. T. T.*; Nagasawa, Naotsugu; Tamada, Masao

Properties such as a degree of swelling (Sw) and biodegradability of blend hydrogels based on carboxymethyl cellulose (CMC) and carboxymethyl starch (CMS) were investigated. The irradiations of 40wt% of CMC/CMS aqueous solution (blend ratio of CMC/CMS: 100/0, 75/25, 50/50, 25/75, 0/100) were carried out using Co -ray source to obtain the blend hydrogels. The gel fraction of CMC/CMS blend hydrogels increased sharply up to 10 kGy and reached a constant value at 30 kGy. Increase in the ratio of CMC increased the gel fraction of blend hydrogel. These hydrogels reached the equilibrium swelling state from initial dried gel in about 2 hours. The blend hydrogels with the maximum Sw of about 800 were obtained at 2 kGy. The Sw decreased significantly with increasing the dose, and leveled off in the range of 20-40 kGy. As a result of the biodegradability test in soil, the discharge of carbon oxide generated by the biodegradation of the blend hydrogels (the Sw of about 100) gradually increased with increasing the ratio of CMS, resulting in the decomposition ratio in the range of 5 to 20% at 30 days. Therefore, the biodegradability of the blend hydrogels was controlled by adjusting the composition of the CMC/CMS and irradiation doses.