Exploring the effect of humidity on thermoplastic starch films using the quartz crystal microbalance

Abstract 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  μ 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.