Abstract

Expanded polystyrene foams are lightweight and cheap, but they have excellent strength and insulation properties. However, their inability to biodegrade in traditional landfill situations makes their disposal problematic. Starch, a polysaccharide, has the potential to replace synthetic thermoplastics for some applications but starch-based foams are hydrophilic, which limits their applications. In this work, polylactide (PLA), a sustainably derived and industrially compostable polymer, was added to starch/cellulose composite foams to enhance their water barrier properties. PLA powder at various weight % was mixed with moistened starch and cellulose mixture, and composite foams were prepared by compression moulding at 220 °C. The thermomechanical and viscoelastic properties of the produced foam materials were analysed by thermogravimetric analysis, dynamic mechanical thermal analysis, mechanical testing, and also by the 3-point compressive mechanical quasi-static testing. It was found that the tensile strength of the composite foams increased with an increase in the PLA loading, which increased from 2.50 MPa for 0% PLA to 3.27 MPa for 9.72% PLA loading. The flexural strength also increased from 345.91 kPa for the 0% PLA to 378.53 kPa for the composite foam containing 4.86% PLA; beyond which the flexural strength started decreasing with an increase in PLA loading. Similarly, the stiffness of the starch/cellulose composite also increased with an increase in PLA loading up to 4.86%, and further increase in PLA loading decreased the stiffness. The flexural modulus of the composite foams increased from 522 MPa for 0% PLA loading to 542.85 MPa for the 4.86% PLA loading. The thermal stability of the starch/cellulose composite foams also increased and the water absorbency decreased with the increased PLA loading.