EVOH is a copolymer of ethylene and vinyl alcohol, is colourless, clear and has very good barrier properties. In dry conditions or with a moisture condition of RH 60%, its moisture penetration rate is very low and its gas transmission rate is almost as low as aluminium foil. In some flexible packaging applications when considering the process mechanical performance requirements, the use of EVOH barrier film can increase the barrier properties by 10 -20 times which can efficiently stop oxygen and moisture penetration and effectively prevent product flavour, moisture or liquid escape and avoid the internal liquid or gas of theproduct dissolve into the tie layer.
EVOH used as a barrier layer in multi-layers structure films is suitable for packing food, beverages and easily oxidized products to extend product shelf lives. EVOH resists grease and organic solvent and preserves fragrances to keep the original flavour and also protect from unpleasant gas inward penetration. It is easy to recycle. When burning, no harmful vapour is produced. It is therefore regarded as a green material and more and more countries are interested in it. It shows a strong growth trend. However, EVOH is a copolymer and contains alcohol so it is sensitive to moisture and water. Therefore to use as middle layer, it is normally combined with polyolefins to enhance moisture barrier.
