Starch films reinforced with mineral clay

Abstract

A mineral clay was used as filler in order to improve the mechanical properties of glycerol-plasticized Cará starch films. These were characterized by mechanical and dynamic mechanical analysis, X-ray diffraction (XRD), thermogravimetry, infrared spectroscopy, and scanning electron microscopy. Dynamic mechanical analyses showed that the composite films give rise to three relaxation processes, attributable to a transition of the glassy state of the glycerol-rich phase, to water loss including the interlayer water from the clay structure, and to the starch-rich phase. A film obtained with 30% in w/w of clay showed an increase of more than 70% in the Young modulus compared to non-reinforced plasticized starch. Both XRD and infrared spectroscopy showed that glycerol can be intercalated into the clay galleries and that there is a possible conformational change of starch in the plasticized starch/clay composite films. Clay exfoliation occurred in unplasticized starch/clay mixtures.