Melt processing and characterization of polyvinyl alcohol and polyhydroxyalkanoate multilayer films

Multilayer films for food packaging applications composed of polyvinyl alcohol (PVOH) as the core layer and polyhydroxyalkanoate (PHA) as the outer skin layers were produced by the co-extrusion process. Rheological properties of PVOH and PHA were performed and analyzed before co-extruding into a cast film. Analysis of the rheological data indicated the processing temperatures and grades of the PVOH and PHA polymers that would produce similar viscosity and melt flow properties. To improve adhesion of the layers, PHA was grafted with maleic anhydride using a dicumyl peroxide initiator to provide a tie layer material, which improved the peel strength of the PHA and PVOH layers by over 2x. Oxygen transmission rate (OTR) testing showed that the multilayer sample provided an OTR of 27 cc/m(2)-day at 0% relative humidity (RH) and rates of 41 and 52 cc/m(2)-day at relative humidity values of 60% and 90% RH, respectively. This indicates significant barrier performance enhancement over monolayer PVOH that provided an OTR of 60 cc/m(2)-day at 0% RH and 999 cc/m(2)-day at 60% RH. Biodegradation testing of the films in the marine environment showed that both the unmodified and maleated PHA polymers displayed high levels of mineralization, whereas the PVOH material did not. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013