Biodegradable Sheets of Starch/Polyvinyl Alcohol (PVA): Effects of PVA Molecular Weight and Hydrolysis Degree

Biodegradable blends of polyvinyl alcohol (PVA) and starch has potential to replace non-biodegradable plastic materials. PVA/starch sheets were produced by extrusion-calendering using five PVA grades with different molecular weights (MW) and hydrolysis degrees (HD). The blends were composed by 40:25:35 wt% of native cassava starch, PVA and glycerol as plasticizer respectively, and sheets were produced in a twin-screw extruder coupled in a 3-roll water-cooled calender. The sheets were characterized by mechanical properties, water vapor permeability, opacity, X-ray diffraction, crystallinity index, FT-IR spectra, and microstructure (SEM). The biodegradable sheets presented satisfactory processability, handleability, and mechanical properties, with a uniform appearance. The materials produced with high HD PVA were more rigid, and those produced with high MW PVA were more resistance, and all PVA grades had good compatibility with starch in the extrusion-calendering process. Therefore the PVA/starch blends are adequate for industrial scale production of biodegradable materials.