Biopolymer-Clay Nanocomposites: Cassava Starch and Synthetic Clay Cast Films

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 degrees C while the biomolecule decomposition at about 500 degrees C is dependent on the clay content. CO2 release at about 300 degrees C (non-oxidative decomposition of polymeric chains) decreases if compared to the gas delivery at ca. 500 degrees C, as the clay content is increased. Films with clay content higher than 10 wt.% show no substantial benefit for either elongation or resistance properties.