Synergistic effects of thermoplastic starch and nanofibrillated cellulose on the mechanical, thermal, and micromorphological properties of polylactic acid composites

Abstract Filling and reinforcing highly brittle and costly polylactic acid (PLA) with nanocellulose and starch has been found to be a promising approach for practical applications. However, the strong tendency of nanocellulose to agglomerate significantly affects the overall performance of the resulting composites. This study employed ball‐milling method to incorporate nanofibrillated cellulose (NFC) into starch, innovatively producing reinforced thermoplastic starch (TPS), which is then used to enhance the mechanical properties and reduce costs of PLA without compromising biodegradability. The effects of the ratio of PLA to TPS and the amount of NFC added were thoroughly investigated. Notably, the inclusion of NFC and TPS not only enhanced tensile strength but also improved toughness. At a PLA:TPS ratio of 70:30 with 4 wt% NFC, the composites achieved maximum toughness of 10.73 kJ/m 3 , a 973% increase over pure PLA. Furthermore, adding 7 wt% NFC significantly boosted tensile strength and elastic modulus, increasing by 14.7% and 29% respectively compared with NFC‐free composites, reaching 37.11 and 710.94 MPa. Additionally, NFC and TPS addition enhanced PLA crystallization and thermal stability. Thermal decomposition of PLA typically occurred at approximately 250°C. However, blending raised the initial thermal decomposition temperature of PLA/TPS/NFC composites to 290°C, indicating enhanced thermal stability. These findings enhance the application potential of PLA‐based composites, extending to environmentally friendly packaging and furniture industrial applications. Highlights NFC dispersion in TPS composites was enhanced through ball milling treatment. Composites with 4 wt% NFC showed a 973% toughness increase over pure PLA. The developed composites achieved maximum tensile strength (37.11 MPa). TPS imparted toughness to PLA, which reduced its brittleness. The thermal decomposition temperature of the composites rose to 290°C.