Thermal and microstructural characterization of biodegradable films prepared by extrusion–calendering process

Native starch (corn, potato and waxy corn) and phosphorylated corn starch blended with bagasse fiber and glycerol were used for the preparation of biodegradable films. The processing extrusion variables were: feed moisture FM (18.25–20.5%), fiber content FC (0–10%) and type of starch TS (native or phosphorylated). The analysis of infrared spectroscopy showed OH and C–O bands at 2750–3250 and 550–1000 cm−1, related to plasticizer–starch interactions. Films processed without fiber revealed peaks of low intensity associated to the plastizicing of starch. Differential scanning calorimeter displayed some changes in calorific capacity that could be attributed to molecular excitations and the mobility of polymeric chains (Tg) in a range of temperature between 40 and 80 °C. The dynamic mechanical analyses presented a decrease in the loss modulus at a temperature lower than 100 °C associated to a more structural mobility of bonds indicating a film with more flexibility. The thermal and microstructural characterization of films showed appropriate functional properties in the development of packing materials or flexible containers type bag.