Starch, sugarcane bagasse fibre, and polyvinyl alcohol effects on extruded foam properties: A mixture design approach

Biodegradable foams made from cassava starch, sugarcane bagasse fibres, and polyvinyl alcohol (PVA) were obtained by extrusion. The effects of varying proportions of these three components on foam properties were studied, as well the relationship between their properties and foam microstructure. The addition of PVA in high proportions (40%) increased the expansion index and led to a significant reduction in water adsorption of starch foams, generally improving foam properties. Fibre addition at low levels improved the water resistance, but at high levels, resulted in denser and more coloured foams, with a yellowish aspect. The mechanical properties of the foams were affected by both relative humidity (RH) of storage and foam formulation. In general, as the RH increased, the foam strength decreased. At high RH (90%), fibre addition at high proportions resulted in a reinforcing effect on starch foams, improving their strength.