Mechanical, thermal and structural properties of rice starch films reinforced with rice starch nanocrystals

A rice starch based film, reinforced with starch nanocrystals (prepared by submitting native granules of rice starch to acid hydrolysis at 40 °C) was prepared by casting film-solution on leveled trays. The influence of the content of starch nanocrystals (5 to 30%) on the mechanical, thermal and structural properties of rice starch films was investigated. The rice starch films showed an increase in tensile strength but decreasing elongation at break and water barrier properties with the addition of rice starch nanocrystals. The addition of starch nanocrystals increased the crystalline peak structure of rice starch film. However, too high starch nanocrystals content resulted in a decreased crystallinity of the resulting film. The behavior of the thermal properties of rice starch films reinforced with starch nanocrystals was investigated by means of dynamic mechanical thermal analysis, differential scanning calorimeter and thermogravimetric analysis. No endothermic peaks were observed in the glass transition temperature (Tg) of the rice starch film. However, increasing endothermic heat flow was observed when addition and increasing of starch nanocrystals in rice starch films. This can restrict the mobility of the starch chain due to the establishment of strong interactions between rice starch and starch nanocrystals. In addition, a lower content of starch nanocrystals showed smoother than high starch nanocrystals in a rice starch film matrix,