Modified Starches on the Properties of Extruded Biodegradable Materials of Starch and Polyvinyl Alcohol

This work aimed to study the effect of modified cassava starches, and PVA grade on the properties of biodegradables sheets produce with starch/PVA blends by an extrusion-calendering process; using native starch, distarch phosphate, acetylated distarch phosphate, acetylated distarch adipate or oxidized starch; PVA with 88% and 98% hydrolysis degrees (HD), and glycerol as a plasticizer. The sheets had tensile strength, Young's modulus, and elongation that ranged from 1.0 to 6.8 MPa; 3.2 to 16.2 MPa and 130 to 443%, respectively. Sheets produced with higher HD PVA had better mechanical properties, independent of starch type. Materials produced with all starch types presented similar response for the same PVA, except those with oxidized starch, that had the poorer mechanical properties. All the sheets were visually homogeneous and had good processability. Sheets produced with higher HD PVA (98%) had better mechanical properties and higher crystallinity than those produced with lower HD PVA (88%) because the higher the HD, the higher the number of hydroxyl groups, which leads to a better interaction with the starch. The biodegradable sheets can be produced on an industrial scale because they have adequate mechanical properties and use well-known industrial techniques.