MECHANICAL BEHAVIOUR OF THERMOPLASTIC STARCH/MONTMORILLONITE/ALUMINA TRIHYDRATE NANOCOMPOSITES

Thermoplastic starch (TPS) is a biodegradable biopolymer that has exhibited great prospects to replace conventional synthetic polymers in commercial applications. However, one of the most critical limitations of TPS is the lack of crucial mechanical properties. This study proposes the novel combination of cassava starch, montmorillonite nanoclay (MMT) and alumina trihydrate (ATH) in the form of a nanocomposite which is expected to demonstrate improved mechanical properties. The nanocomposites were processed through melt-extrusion in twin-screw extruder where loadings of MMT and ATH were varied between 1 to 6 wt% and 26 to 37 wt%, respectively. The mechanical properties were evaluated through tensile testing according to ASTM D882. The fractured surfaces of the specimens were evaluated using scanning electron microscopy (SEM) to further validate the mechanical properties of the nanocomposites. The melt viscosity and processability of the nanocomposites were also evaluated through melt flow index (MFI) testing according to ASTM D1238. Presence of MMT and ATH in TPS demonstrated increase in Young’s modulus, maximum tensile stress and decrease in elongation at break up to 57.6 MPa, 5.1 MPa and 39.2%, respectively. In the presence of ATH, increase in loading of MMT continued to improve Young’s modulus and maximum tensile stress while declining elongation at break. Without ATH, MMT was only capable of improving mechanical strength up to a loading of 3 wt% where adverse effects were observed when the loading was further increased to 6 wt%. Increase in loadings of both MMT and ATH, simultaneously were found to depreciate the MFI and thus, the processability of the nanocomposites