Barrier biopaper multilayers obtained by impregnation of electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with protein and polysaccharide hydrocolloids

Multilayer biopapers composed of two electrospun layers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were impregnated, at the inner side of one of the layers, with cellulose nanocrystals (CNCs) and their composites with hydrocolloids, to develop high-barrier fully biobased structures. The study aimed for the first time at comparing the impregnation of electrospun fibers with several biopolymer solutions. Thus, neat CNCs, and CNCs mixed as a minor fraction, that is, 2 wt%, with gelatin (GE), agar (AG), xanthan gum (XG), and gum arabic (GA) were assessed in their potential to improve the barrier properties of PHBV. Glycerol plasticizer was added to the composite formulations. The impregnated electrospun multilayer mats were subsequently annealed, below the PHBV melting point, to yield continuous films by an interfiber coalescence process, so-called biopapers, and thereafter characterized to evaluate their potential for high barrier food packaging applications. The morphological characterization revealed good interlayer adhesion, more noticeably for those containing CNCs and their nanocomposites with AG and XG. From their mechanical response, it was inferred that the material behavior was governed mainly by the rigidity of the PHBV substrates, and this could not be significantly improved by impregnation with any of the various hydrocolloids. Whereas the water vapor barrier was not seen to improve in any of the samples, the barrier to the organic vapor limonene, used as a standard for aroma barrier, was however improved in the samples impregnated with AG and XG composites. Interestingly, the oxygen barrier properties were significantly improved but only by impregnation with pure CNCs. This study reports for the first time a scalable impregnation technology approach to produce fully biobased barrier multilayers.