Effects of relative humidity and ionic liquids on the water content and glass transition of plasticized starch.

The purpose of the present work was to investigate the relationship between the glass transition temperature of the materials produced by the melting method and the water content, as well as the nature and concentration of the plasticizer used. Native starch was successfully treated with ionic liquid to obtain thermoplastic starch (TPS). Ionic liquids have shown a better plasticization, and low absorption of water compared to glycerol, which means a better interaction of starch with ionic liquids. The water binding properties of TPS were studied by commenting the water absorption for the plasticized starch at different % RH and with different ratios of plasticizers. An amount of 22.5 wt% AMIMCl is the maximum that can act as a plasticizer. Above this composition, an increase in the wt% water and wt% AMIMCl induces a phase separation. This value corresponds to a chemical interpretation, which corresponds to a ratio of 1:3 AMIMCl/anhydro-glucose. A schematic representation of the different binding between starch, plasticizer and water has been proposed.