Developing composite films from carboxymethyl starch, polyvinyl alcohol, and kaolin for sustainable packaging applications

Health and environmental problems are rising by the day due to an increasing use of synthetic plastics. However, biobased packaging from starch, with its numerous advantages, or its derivatives offers a promising solution to this problem. In this study, we aimed to explore a sustainable approach to developing a bioplastic film from carboxymethyl starch, polyvinyl alcohol, and kaolin to serve as a substitute for synthetic packaging. The study objects included carboxymethyl starch, polyvinyl alcohol, glycerol, and kaolin. All the materials were heated in water to form viscous solutions. The solution was then cast into films using a mold and the water was evaporated through oven-drying. The cast films were characterized via scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. They were analyzed for their tensile mechanical, barrier, sorption, and biodegradability properties. We also investigated the effects of polyvinyl alcohol and kaolin on the morphology and functional properties of the films. The micro-surface morphology of the carboxymethyl starch/polyvinyl alcohol blend revealed a smooth and homogenous structure, while the film reinforced with kaolin had a more compact structure with zones of particle aggregations. The highest thermal stability was observed in the composite films containing carboxymethyl starch, polyvinyl alcohol, and kaolin. Higher contents of polyvinyl alcohol and kaolin significantly improved the films’ thermal, tensile mechanical, barrier, and sorption properties. The films also demonstrated a substantial rate of biodegradability. The best properties were observed in the films containing 40% of carboxymethyl starch, 60% of polyvinyl alcohol, and 4.5 per hundred resin (phr) of kaolin. The composite films made from carboxymethyl starch, polyvinyl alcohol, and kaolin had good biodegradability, renewability, and improved functional material properties. Therefore, they can be considered a sustainable alternative to the traditional synthetic plastics in packaging applications.