Effect of thanaka powder (TK) content on the structural and functional properties of polylactic acid/TK composites for sustainable packaging

Abstract

Growing global concern about plastic packaging waste has led to the development of eco-friendly polymer composites. Each year, hundreds of millions of metric tons of plastic are discarded, highlighting the need for green packaging solutions. In this study, composites based on PLA and TK were prepared at different compositions using a twin-screw extruder and hot compression molding. Traditionally used for sun protection and skincare, TK contains bioactive compounds with anti-inflammatory, antioxidant, and antibacterial effects. A higher TK content in the composite led to a reduction in tensile strength (approximately 21.3% at 10% TK content) and impact strength (around 15.1% at 10% TK content) compared to the composite without TK, and also resulted in a rougher surface morphology. DSC data indicated that the addition of TK increased the PLA matrix's degree of crystallinity and glass transition temperature. The color of PLA/TK composites became yellower and darker with increased TK content and demonstrated UV protection properties. Moreover, the antibacterial activity of the TK powder was determined against S. aureus and E. coli (Gram-positive and Gram-negative, respectively). TK powder demonstrated more potent antibacterial activity inhibiting S. aureus than E. coli bacteria. In contrast, antibacterial tests showed no activity in the composite material, including PLA and PLA with TK composites at various concentrations. Despite this, the findings suggest that PLA/TK composites hold promise for packaging applications, offering biodegradability, enhanced tensile modulus, and UV protective properties.