Nanostructured interlayers of zein to improve the barrier properties of high barrier polyhydroxyalkanoates and other polyesters

• The effect of a zein interlayer on PHA with different valerate content was analyzed.
• PLA and PET multilayer systems were also prepared and used as reference materials.
• Zein nanofibers improved oxygen permeability of the multilayer structures.
• PHA’s-zein multilayers can be postulated as potential substitutes of PET.

This paper compares the effect of incorporating high barrier self-adhesive nanostructured interlayers of zein between layers of other polyhydroxyalkanoate materials (a PHB homopolymer and a PHBV5 copolymer with 5% valerate content). Furthermore, similar reference multilayer structures based on both a polylactide (PLA) and a polyethylene terephthalate (PET) were also prepared, retaining high levels of transparency. The results indicate significant differences of the effect of the interlayer between different materials. Thus, while the oxygen and limonene barrier properties were significantly improved by the presence of a zein nanostructured interlayer, the water vapour permeability of these multilayer systems were seem to vary among materials since the zein interlayer was only efficient as a barrier element in the PHA materials as compared to PLA. Flexibility of PHB and PHBV multilayer structures were also greatly improved by the addition of zein interlayers whereas minor changes were observed in PLA and PET multilayer systems. These results provide complementary insight into the use of electrospun nanostructured zein to generate fully renewable solutions in multilayer form to enhance the barrier performance of polyhydroxyalcanoates.