Synthesis and properties of biodegradable hydrogels based on cross-linked natural rubber and cassava starch

A series of interpenetrating polymer network (IPN) hydrogels based on cross-linked natural rubber (XNR) and cassava starch (CSt) as biodegradable membrane material were synthesized via free radical polymerization in latex state using N,N-methylenebisacrylamide (MBA) and maleic acid as cross-linkers. The IPN XNR/CSt hydrogels were confirmed and characterized by infrared spectroscopy, thermal analysis, and X-ray diffraction. The results showed that with increasing MBA content from 1.0 to 2.5 phr, cross-link density and gel fraction of XNR increased from 0.80 to 0.90 mol M-3 and from 19.7% to 30.5%, respectively. The gel fraction and tensile strength of the IPN XNR/CSt hydrogels also gradually increased as a function of MBA content but the water swelling and elongation at break decreased slightly. The IPN XNR/CSt containing 1.0 phr MBA displayed the highest water swelling of 82%. The weight retentions of IPN XNR/CSt hydrogels after soil degradations for 90 days increased from 48% to 56% with increasing MBA from 1.0 phr to 2.5 phr. The IPN XNR/CSt exhibited not only a good biodegradation but also high mechanical strength and flexibility. Also, the IPN XNR/CSt could be a promising candidate as a biodegradable membrane for longer released fertilizer application.