Evaporated barrier layers on biodegradable polymers

Products from biodegradable materials, preferably produced from renewable resources are often regarded as solutions both for resource problems - due to their renewable source - as well as for overflowing landfill sites due to their convertability into the useful products compost and biogas. The problem in general is that the product properties attainable by those materials are relatively poor. Especially in packaging, barrier properties against water vapour and gases are far from those obtainable with even the very basic polymers. As a technical solution for this problem, vacuum coating with barrier layers from oxides of magnesium, aluminium and silicon by microwave-plasma assisted electron beam evaporation is presented in this paper. For different biodegradable films from synthetical sources (aliphatic polyesters, polycaprolactone), bacterial polymers (PHB/V) and natural polymers/derivatives (cellulose, cellulose acetate, starch and their blends), the influence of substrate properties , coating conditions and coating materials on the resulting barrier properties and the biodegradability is shown.