Characterization of tapioca starch plasticized by 1-ethyl-3-methylimidazolium acetate

Abstract

Starch is one of natural materials that been used for producing biodegradable materials. The starch-based materials are produced through a process known as gelatinization with the presence of plasticizer and elevated temperature. Properties of starch-based materials are lacking in terms of viscosity, water absorption, thermal and mechanical properties compare with synthetic materials. Researchers are involved in finding ways for improvement of starch-based materials properties and one of that is introducing new plasticizer. 1-ethyl-3-methylimidazolium acetate, [Emim][OAc] is an ionic liquid that used as plasticizer to produce thermoplastic starch. Starch plasticized by [Emim][OAc] were prepared with different total plasticizer contents (50%,70%) and [Emim][OAc]/water ratio (1:6,1:4,2:3 wt%). The thermoplastic starches were characterized in terms of morphology, crystalline structure and thermal degradation. The results showed that 70% of total plasticizer contents were mixed well during gelatinization process. [Emim][OAc] contributed to granule disruption as shown by SEM. Based on the XRD analysis, it was shown that thermoplastic starch at 70% total plasticizer contents and 1:4 wt% ratio of [Emim][OAc]/water, caused disruption of the A-type crystalline structure, generated VH-type crystalline structure and thus increased the mobility of the amorphous starch. The presence of [Emim][OAc] promotes the thermal degradation of starch molecules as described by TGA. Therefore, plasticizer contents and [Emim][OAc]/water ratio are vital parameters that influences the properties of thermoplastic starch.