The increasing demand for sustainable paper-based packaging is driving research towards developing renewable coating materials with high barrier properties against gas, water vapour and odours. Poly(vinyl alcohol) (PVOH), a petroleum-derived but biodegradable polymer, is a real option for sustainable packaging. It is water soluble with excellent oxygen and aroma barrier properties, with a high resistance to oil, grease and solvents. Our current work focuses on improving the water vapour barrier property of PVOH-clay- plasticiser based films and coatings by controlling the polymer network density.

Figure 1. Degree of swelling in water at 22C and 90C for crosslinked PVOH films prepared with different crosslinking times and in comparison with respective WVTR values.

Chemical cross-linking, annealing and freeze-thaw cycles are involved. This more tightly cross-linked polymer network will reduce swelling and reduce the number of pathways for water to navigate. This project is closely related to the EU funded, Marie Curie International Training Network 'NEWGENPAK', which focuses on environmentally-friendly and economical paper products used in packaging.