Color Stability Enhancement of Curcumin Bioplastic Films Using Natural Hybrid Fillers of Montmorillonite and Revalorized Cellulose

This work aligns with the United NationsSustainable DevelopmentGoals 9 and 12 by promoting the use of revalorized biomass and theelimination of hazardous chemicals through an adaptable all green,safe, and sustainable by design fabrication process for naturallycolored bioplastic films with improved color stability. Naturally colored packaging systems with improved colorstabilityare essential as alternatives to mainstay synthetic colored conventionalplastics, which typically present high toxicity and environmentalpollution challenges. Herein, we report a versatile all green fabricationprocess for colored bioplastic films. Curcumin (CUR), a model plant-basedcolorant, was incorporated with newly developed natural hybrid fillersof montmorillonite (MMT) and biomass waste-recovered cellulose (CEL)for improved color stability performance. The CUR-based hybrid fillerswere compounded with polylactic acid (PLA) to fabricate sustainable,colored composite films via hot-melt extrusion. Fourier transforminfrared (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis(TGA) results indicated good compatibility between the filler counterparts.Macro- and microstructure analysis of the colored films confirmedthe good dispersion of the natural hybrid fillers within the PLA matrix.No change was observed in the thermal properties of the colored films,while dynamic mechanical analysis (DMA) results demonstrated a moderateincrease in the films' elastic modulus, from 870 to 970 MPa.The color entrapment efficiency of the hybrid filler-based films wasevaluated through a study of CUR release in ethanol. A sustained CURrelease profile reaching around 50% after 48 h was observed in thehybrid filler-based films in contrast to 80% in the PLA-CURfilm. This was correlated with the significantly improved color stabilityof the PLA films containing the hybrid fillers under weathering conditionsof UV irradiation, high temperature, and humidity. Over a period of10 days, the CUR-CEL-MMT-based films had relatively consistent colorstability, showing a color shift value (& UDelta;E*)of only 1.1 in comparison to 5.1 for the PLA film containing onlyCUR.