New strategies in the preparation of exfoliated thermoplastic starch–montmorillonite nanocomposites

A simple method based on the combination of the intercalation from solution and melt-processing preparation methods was used to prepare highly exfoliated and compatible thermoplastic starch (TPS) and montmorillonite clay (MMT) nanocomposites. The effects of the MMT content on the thermal, structural, and mechanical properties of the nanocomposites were investigated. XRD diffraction was used to investigate the MMT exfoliation/intercalation degrees in the TPS matrix. Data from thermogravimetric analysis and differential scanning calorimetry revealed that the addition of MMT increased the thermal stabilities of TPS nanocomposites. Young's modulus and tensile strength increased from 8.0 to 23.8 MPa and 1.5 to 2.8 MPa with an increasing MMT content from 0 to 5 wt% without diminishing their flexibility. The improvement in such properties can be attributed to the good dispersion/exfoliation of MMT in the TPS matrix. Combining both methods, it was possible to obtain homogenous and transparent nanocomposites with excellent thermal and mechanical properties for application as packaging materials.

Graphical abstractThe diffraction peaks of the nanocomposites with 3% and 5% MMT shifted to lower 2θ or larger d001 spacing in relation to the diffraction peak of the MMT. The peak shift indicates that the gallery has expanded, and it is usually assumed that polymer chains have entered or have been intercalated in the gallery.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We investigated a simple method to prepare highly exfoliated nanocomposites. ► Nanocomposites are composed by thermoplastic starch and MMT clay materials. ► A good intercalation and exfoliation of the clay platelets in matrix were observed. ► Tm increased from 134.9 to 157.4 °C when the MMT content increased from 0 to 5 wt%. ► The same increase in MMT provoked a significant increase in the mechanical properties.