Effects of date palm and green tea polyphenol extracts on the thermal stability and mechanical properties of poly lactic acid

Poly (lactic acid) (PLA) is a biodegradable polymer whose thermal and mechanical performance can be enhanced through natural additives such as polyphenols. In this study, polyphenols extracted from green tea (Camellia sinensis L.) and date palm (Phoenix dactylifera L., Arecaceae) were incorporated into PLA at concentrations of 1, 5, and 10 wt.% using an internal mixer. The oxidative thermal stability of the blends was examined by thermogravimetric analysis and differential scanning calorimetry, while their morphology and mechanical properties were also characterized. Both polyphenols improved the thermal stability of PLA, with green tea polyphenols showing a greater effect, likely due to their broader range of active compounds. However, increasing polyphenol content reduced the glass transition temperature, tensile strength, and Young’s modulus, while enhancing elongation at break and ductility. These findings indicate that plant-derived polyphenols act as both thermal stabilizers and plasticizers within the PLA matrix.