Exploring The Effect Of Humidity On Thermoplastic Starch Films Using The Quartz Crystal Microbalance

The quartz crystal microbalance (QCM) is used as a non-destructive and efficient characterization tool for thin thermoplastic starch (TPS) films. Thin TPS films (1-2 ?m) were prepared with 30% (w/w starch) plasticizers using either glycerol or an ionic liquid, 1-ethyl-3-methylimidiazolium acetate ([emim+][Ac? ]), as the plasticizer. The differences in the mechanical properties and environmental effects on the plasticized TPS films were explored. The modulus of starch-glycerol films was higher than starch-[emim+][Ac? ], consistent with literature data and bulk AFM measurements, likely due to superior plasticization by the ionic liquid. The starch-[emim+] [Ac-] films were shown to have relative stable properties at low humidity that may be due to some antiplasticization effects at low water content despite absorbing more water than starch-glycerol films at higher humidity.