Poly(lactic acid) (PLA), a bio-based polymer with poor water and moderate oxygen barrier performance, has become a material of interest in the packaging industry due to its sustainability. Cellulose nanocrystals (CNCs) are added into PLA film to enhance its barrier performance without affecting its transparency. Beside these attributes, heat sealing and mechanical properties are also important features for films intended for packaging applications and need to be investigated. This study assessed the influence of CNC addition (0.5 to 2 wt%) on the surface texture, heat sealing, mechanical and barrier properties of PLA cast films manufactured through a continuous extrusion melt-process. Irrespective of CNC content, the addition of CNC increased the surface roughness of PLA due to the presence of CNC agglomerates indicating a poor dispersion. The sealing performance, i.e., the hot tack strength and seal strength of PLA films as well as the burst pressure of PLA pouches, significantly improved by adding up to 1% CNC into PLA matrix, probably attributed to the increased stress transfer efficiency at the interface. Significant improvements in both the tensile strength and modulus were achieved by adding CNC into PLA matrix, insensitive to CNC content. Nevertheless, these occurred at the expense of ductility since both the elongation at break and the energy to break decreased, results supported by the dart impact strength showing that PLA/CNC composite films were more brittle than neat PLA films. Both water vapor and oxygen permeabilities decreased significantly with the increased CNC content because of the tortuosity effect. The overall performance of the studied PLA/CNC films indicated that they had great potential to be used in packaging applications.
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