Novel biodegradable hydrogel based on natural polymers: Synthesis, characterization, swelling/reswelling and biodegradability

In order to reduce the production costs of hydrogel and decrease the negative impact on the environment, a new low-cost and eco-friendly semi-interpenetrating polymer network (semi-IPN) hydrogels of cassava starch-g-polyacrylic acid/natural rubber/polyvinyl alcohol blends (CSt-g-PAA/NR/PVA) was prepared. The hydrogel was synthesized by aqueous solution polymerization method in the presence of initiator ammonium persulfate (APS) and N,N'-methylene-bis-acrylamide (MBA) as a crosslinker. A reaction mechanism for synthesis of CSt-g-PAA/NR/PVA semi-IPN hydrogels was proposed. Factors affecting the swelling capacity, such as CSt, AA, APS and MBA contents were evaluated and optimized. The sample prepared under optimized conditions had a water absorbency of 794% in distilled water and 244% in 0.9 wt% NaCl solution. It also exhibited an excellent water retention with lower decreasing rate and were highly sensitive to the salt concentration, cation type, pH and reswelling time. The semi-IPN hydrogel demonstrated a good biodegradation with a rate of 0.626 wt%/day. It is believed that the obtained CSt-g-PAA/NR/PVA could have potential applications in agricultural areas because of their good water absorption, excellent retention capacities, high reswelling capability, and cost-effective and ecofriendly preparation.