Effect of alkaline treatment on mechanical, thermal, and biodegradation properties of bamboo filler-reinforced corn starch films

Abstract

Although starch-based bioplastics are becoming more popular as environmentally friendly substitutes for petroleum-based plastics, their limited mechanical strength and thermal stability restrict their usefulness. To examine the effects of bamboo filler loading and chemical treatment on mechanical, thermal, and biodegradation properties, corn starch films reinforced with untreated and alkaline-treated bamboo filler were prepared by solution casting. To improve bamboo filler-corn starch matrix adhesion and eliminate surface impurities, bamboo filler was treated with 5 wt% sodium hydroxide. Tensile testing (ASTM D882), thermogravimetric analysis (TGA), and biodegradability tests in freshwater and saltwater environments were used to characterize composite films with 2–10 wt% bamboo filler. The findings demonstrated that, while retaining a degree of flexibility, NaOH-treated bamboo filler increased tensile strength, with a maximum increase of approximately 52.8% when compared to untreated bamboo filler composites. All films had similar degradation onset temperatures (~300°C), according to thermal analysis; treated bamboo filler composites showed a shallower DTG peak, indicating better thermal uniformity. In freshwater, the immersion tests showed increased visible microbial colonization, whereas no discernible microbial growth was observed in simulated seawater. Overall, alkaline treatment successfully improved the mechanical and thermal performance of starch-based composites without sacrificing biodegradability, underscoring their potential as eco-friendly packaging materials.