Enhancing polylactic acid composite film performance via chemically modified micro- and nanofibrillated cellulose for sustainable food packaging

Abstract

Polylactic acid (PLA) is a sustainable food packaging polymer, but its limited mechanical and barrier properties restrict its use for light- and moisture-sensitive products. PLA films containing 1–5 % chemically modified microfibrillated (MMFC) and nanofibrillated cellulose (MNFC) were prepared via solvent casting and characterized. FTIR confirmed successful chemical modification with maleic anhydride, while the main PLA peaks remained unchanged. XRD showed a slight increase in matrix crystallinity for MMFC/MNFC films compared to control PLA; however, no apparent trend was observed across the different fiber loadings. FE-SEM observations suggested relatively smooth surfaces at lower filler concentrations, whereas some degree of aggregation appeared to occur at 5 % loading. DSC results suggested a slight increase in glass transition temperature and a decrease in cold crystallization temperature, which may indicate reduced chain mobility and a potential influence on crystallization behavior. Incorporating 1–3 % MMFC increased tensile strength to 42.41 MPa while maintaining flexibility, whereas 5 % loading reduced performance due to fiber aggregation. Thermal adhesion strength improved at low filler contents, with MNFC showing better heat-seal performance. WVTR decreased from 4.44 to 3.93 g/m ² ·24 h with 1–3 % fillers. UV-C transmittance decreased from 78.3 % in neat PLA to 56.7 % and 66.0 % for 5 % MMFC and MNFC films. These results demonstrate that low loadings of chemically modified MFC and NFC enhance physical, mechanical, barrier, and photoprotective properties of PLA films for sustainable food packaging.