Effect of plasticizers on the mechanical and thermomechanical properties of cellulose-based biocomposite films

Biocomposites based on natural cellulose fibers (CF) and hydroxyethyl cellulose (HEC), were produced in the form of green packaging films. The effect of the different single-component plasticizers (glycerol, propylene carbonate and ethylene carbonate) on the mechanical and dynamic thermomechanical properties of the films were studied. Moreover, the softening effect of the two-component plasticizer based on deep eutectic solvents (DESs) was addressed. Of the single-component plasticizers, glycerol was found to be the most efficient by increasing the elongation at break of the composite by 53%. A similar, or even better, increase in elongation at break (up to 81%) was obtained with DESs based on choline chloride and glycerol, glucose or urea. Based on the dynamic mechanical analysis at varying humidity, the performance of plasticizers was strongly attributed to the humidity. The DES based on tetrabutylammonium bromide and propylene carbonate was most efficient at providing thermoformability to the composite by lowering the thermal softening temperature. Based on the obtained results, DESs are a highly promising plasticizers for the cellulose-based biocomposites with similar or even better plasticizing effect compared to conventional plasticizer. In addition, DESs can be used to improve the thermoformability of biocomposites, by lowering the thermal softening temperature.