Nanocellulose-reinforced, multilayered poly(vinyl alcohol)-based hydrophobic composites as an alternative sealing film

A flexible, hydrophobic, and multilayered poly(vinyl alcohol) (PVA) film evolved to replace a commercially available nonbiodegradable easy seal-paper (ES-PAPER) sealing film. First, environmentally friendly fillers, such as cellulose nanocrystals (CNCs) or cellulose nanofibers (CNFs), were added to produce PVA + CNC/CNF composites via blade coating and solution casting to strengthen the mechanical properties of PVA. Subsequently, biodegradable and hydrophobic materials, such as poly(ethylene glycol)–poly(lactic acid) (PEG–PLA) and neat PLA, were added to prepare multilayered PEG–PLA and PLA hydrophobic composites using double-sided solution casting. The hydrophobicity of PVA was enhanced through heat treatment. Finally, the mechanical properties of the as-prepared PVA film were compared with those of a commercially available ES-PAPER sealing film. PVA + CNC/CNF composites exhibit excellent transparency and mechanical properties, whereas PVA + CNCs 3.0 wt% have the highest Young's modulus and tensile strength, which are, respectively, 3% and 96% higher than the Young's modulus and tensile strength of an ES-PAPER sealing film. With regard to strain at break, the prepared PVA film also exhibited a value many times larger than that of the ES-PAPER sealing film because of good filler dispersibility, which significantly enhanced the durability of the sealing film.