Mixture design to develop biodegradable sheets with high levels of starch and polyvinyl alcohol

摘要

A mixture design was used to analyse the effects of polyvinyl alcohol (PVA) on glycerol-plasticised cassava starch sheets obtained by flat extrusion from a twin-screw extruder. PVA was the main component that improved the properties of the sheets, and glycerol presented the opposite effect. The properties ranging: tensile strength (0.22-1.5 MPa), Young's modulus (0.45-7.29 MPa), elongation at break (59-111%), puncture resistance (10-107 N/mm), puncture elongation (5.64-10.13mm), crystallinity index (17-21%) and water vapour permeability (3.39-7.40 x 10(-5) gm(-1) day(-1) kPa(-1)) for the sheets. Scanning electron microscopy showed good compatibility between the components of the blend because the resultant materials were continuous and cohesive and did not exhibit phase separation. The sheets were not significantly different from others, based on XRD and FTIR analyses, consistent with the literature. PVA was able to improve the mechanical and barrier properties of starch-based sheets.