EVOH films

EVOH (ethyl vinyl alcohol copolymer) has outstanding barrier properties to gases such as oxygen, nitrogen, carbon doixide and helium.

With a very low permeability to oxygen, EVOH films prevent goods, mainly foods and pharmateucical products, to be deteriorated by contact with O2.

EVOH : a high barrier to oxygen

Due to their excellent barrier qualities, EVOH films are widely used with controlled atmosphere packaging, modified atmosphere packaging and vacuum packing.
The chart on the right shows the efficiency of EVOH barrier to gases compare to other materials such as PET or PVDC.
Regarding moisture, EVOH keeps its barrier properties till 80% of moisture contained in resins. The same observation can be done concerning package of products containing high rate of moisture. EVOH is still performing better till 80% of relative humidity.

EVOH : better barrier results with blown extrusion

However, with blown extrusion process, Evoh is always coextruded, mainly with polyolefines (polypropylene or polyethylene). PP and PE have poor gas barrier properties but they are good barrier to moisture. When coextruded with EVOH, the polyolefines protect Evoh against moisture and the film keeps its barrier properties to gases.

Through orientation and heat treatment, the gas barrier properties of Evoh can be increased. These characteristics allows to obtain better results with blown extrusion than with cast extrusion.

EVOH : excellent barrier to preserve aroma and flavor

Evoh is a very good barrier against flavor and aroma permeation. Keeping aroma and flavor inside the package avoid any losses of flavor and aroma but also deterioration by contact with aroma and/or flavor which are outside the package.

Due to a very low permeation of aroma and flavor, Evoh films allows to obtain longer shelf lifes.

Evoh has also a very low permeation to fuel vapor.