Mechanical Properties of Starch and Poly(lactic acid) Biodegradable Sheets Added of Carboxylic Acids

Thermoplastic starch and poly(lactic acid) (PLA) blends have been studied as potential materials for the production of biodegradable packaging. However due to the hydrophilic characteristic of starch and hydrophobic nature of PLA, these polymers are incompatible at microscopic level and this fact interfere significantly in the mechanical properties of the obtained materials. Several compatibilizer have been investigated to improve the compatibility between these polymers, including carboxylic acids. Thus, this study evaluated the mechanical properties of thermoplastic starch and PLA sheets added of citric and adipic acids produced by flat extrusion (calendaring-extrusion) and stored at different relative humidity. The sheets containing citric acid were thinner, more resistant and showed higher values of elongation at break. The relative humidity of storage interfered significantly in the mechanical properties, possibly due to the plasticizing effect of water. Citric acid was an additive which improved the mechanical properties of the starch and PLA sheets produced by flat extrusion. Furthermore, it is important to control the relative humidity of storage to not alter the mechanical properties of the starch based blends. DOI: 10.14685/rebrapa.v5i2.164