EVOH Films

Properties

Ethylene-vinyl alcohol copolymer or EVOH is a flexible, crystal clear, and glossy thermoplastic copolymer with excellent flex-crack resistance, and very high resistance to hydrocarbons, oils and organic solvents. It also has some of the best barrier properties to gases such as oxygen, nitrogen, and carbon dioxide making it especially suited for packaging of food, drugs, cosmetics, and other perishable or delicate products to extend shelf life. In comparison with many other common films, EVOH has superior barrier properties. However, EVOH loses its good gas barrier properties when exposed to moisture. For this reason and to optimize both cost and performance, it is frequently used in multilayer, co-extruded films like HDPE, PP, and PET, which have superior moisture barrier properties.

EVOH films are usually not or only slowly biodegradable. However, blending with other compounds or copolymerization with other monomers can greatly increase the decomposition rate. One example is a blend of EVOH and polyvinyl alcohol (PVOH).

EVOH films are also difficult to recycle because the EVOH oxygen barrier layer sandwiched between two or more PE layers has a tendency to gum up when reprocessed, resulting in holes in the recycled PE film. On the upside, EVOH waste does not produce toxic or harmful by-products when properly incinerated.

Due to the low odor, high chemical resistance, and inertness, many EVOH grades are suitable for food, medical, and pharmaceutical packaging applications under FDA regulations.

Applications

EVOH is extensively used for atmosphere packaging where a certain atmosphere is needed inside the package to improve the shelf life of food products. In other words, EVOH film is frequently used for fresh produce when minimal permeability is needed. EVOH layers offer very high resistance to hydrocarbon fuels, mineral oils and many organic solvents. This makes this material ideal for applications involving chemicals, such as plastic fuel tanks, chemical packaging and protective clothing. Other applications include pipes, hydrogen fuel cells, medical and pharmaceutical packaging, and agricultural films.