Biopolymer-clay nanocomposites: cassava starch and synthetic clay cast films

摘要

Polymer-clay nanocomposites (PCN) based on cassava starch, synthetic hectorite clay and inverted sugar cane syrup (plasticizer) were prepared by solvent-assisted (casting) process producing transparent and homogeneous films. Small amounts of clay (5-15 wt.%) resulted mainly in exfoliated nanocomposites while large amounts (30 wt.%) promote the intercalated nanocomposites formation. FT-Raman bands sensitive to hydrogen bonding in starch granules are progressively shifted to lower wavenumbers as the clay content is raised. Nanocomposites show a similar thermal behavior up to 320 oC while the biomolecule decomposition at about 500 oC is dependent on the clay content. CO2 release at about 300 oC (non-oxidative decomposition of polymeric chains) decreases if compared to the gas delivery at ca. 500 oC, as the clay content is increased. Films with clay content higher than 10 wt.% show no substantial benefit for either elongation or resistance properties.