Improved water resistance and air barrier performances of paper coated with polylactic acid/organoclay nanocomposites

Abstract Paper packaging coated with synthetic materials raises major environmental and health concerns. As a response, new promising approaches consist of using sustainable coatings based on nano‐biocomposites. In this work, polylactic acid (PLA)/organoclays (OC) aqueous dispersions thickened by xanthan gum were applied on paper using the bar coating technique. Morphological and topographical analyses using scanning electron microscopy and laser confocal microscopy showed a smooth polymeric layer completely covering the fibrous and porous surface of the paper, resulting in a substantial improvement in the barrier properties. Water vapor transmission rates and water absorptivity had undergone a major decrease when coatings containing 3 and 5 wt% OC were used, while no significant difference was observed between the 1 wt% OC formulation and pure PLA. Moreover, coated paper showed no air porosity with 0 mL/min values recorded for all samples, thus confirming the morphology observations of the surfaces and cross‐sections. Additionally, the contact angle measurements indicated a slight decrease in the hydrophobicity of the base paper when coated with PLA and 1 wt% OC. However, this reduction was reversed with the addition of 3 and 5 wt% OC, restoring the hydrophobicity. Highlights Polylactic acid (PLA)/organoclay (OC) coatings sealed and covered completely the paper's surface. Water resistance of the base paper had a major improvement due to the coatings. The porous surface of the paper was successfully sealed, leading to no air porosity. Adding 3 and 5 wt% OC resulted in excellent barrier performances. PLA/OC coatings have the potential to replace synthetic paper coatings.