Improving the water resistance of nanocellulose-based films with polyhydroxyalkanoates processed by the electrospinning coating technique

Polyhydroxyalkanoates (PHAs) comprise a family of biodegradable aliphatic polyesters with enhanced sustainable profile and high water vapor barrier. As environmentally friendly materials, nanostructured cellulose-based films, also called nanopapers, such as films made of cellulose nanofibrils (CNFs) and lignocellulose nanofibrils (LCNFs), are also of growing interest due to their high mechanical strength and outstanding oxygen barrier properties at dry conditions. Unfortunately, nanopapers are highly hydrophilic, lacking of sufficient moisture resistance for uses in, for instance, food packaging. The present study reports, for the first time, on the effect of electrospun poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) double side coatings on the morphology, water contact angle, mechanical properties, and barrier performance of CNF and LCNF films. The resultant multilayer structures showed significantly improved water contact resistance, more balanced mechanical properties, and higher barrier performance against water vapor in comparison to the neat nanopapers. Although the PHA-coated nanopapers presented slightly lower aroma barrier due to the intrinsic affinity of PHA for limonene uptake, these sustainable multilayer films further improved the oxygen performance of the nanopapers, showing significant potential as barrier materials even at high humidity conditions. As a result, the here-developed novel films, based on nanopapers double side coated with electrospun PHB and PHBV layers, appear as a very promising fully bio-based material concept for food packaging applications due to their outstanding water vapor and oxygen barrier performance.