Apparent Viscosity and Mechanical Properties Studies of Interpenetrating Network Hydrogel from Natural Rubber and Starch

Abstract

Introduction: Viscosity and mechanical properties of interpenetrating network (IPN) hydrogel are important for preparation process, film forming/molding and application. This work aims to the study the effects of different types of starch on apparent viscosity and mechanical properties on IPN hydrogel characteristic. Materials and Method: IPN hydrogel was prepared by the free-radical polymerization and was evaluated apparent viscosity before casting at 25ºC. Crosslink density and mechanical properties were also determined for IPN hydrogel. Results: At temperature 25 ºC, natural rubber provides statistically a lower apparent viscosity than pre-gelatinized rice starch and pre-gelatinized banana starch (22.09 ± 12.86, 2957.67 ± 807.51 and 19253.33 ± 5173.60 cP, respectively, p < 0.05). The viscosity of natural rubber mixture increased after starch into mixture. IPN hydrogel with MBA 2 phr comprising of natural rubber and banana starch provides statistically a higher apparent viscosity than IPN hydrogel from rice starch (9607.33 ± 5965.21 cP and 1667 ± 844.88 cP, respectively p < 0.05). It may be due to banana starch has a higher % amylose content than rice starch which lead to require more energy to move. In addition, a higher MBA amount enhanced higher crosslink density and tensile strength as well as lower elongation at break due to the agglomeration of starch granule that show rigid or stiffer. Conclusion: IPN hydrogel comprising of natural rubber and banana starch is not suitable for this work because discontinuous film was appeared during film forming. Rice starch is applicable to use for IPN hydrogel from natural rubber by this method. IPN hydrogel from natural rubber and rice starch is strong but brittle. Thus, it should be develop the mechanical properties in further study.