Ethylene vinyl alcohol (EVOH) is a formal copolymer of ethylene and vinyl alcohol. Because the latter monomer mainly exists as its tautomeracetaldehyde, the copolymer is prepared by polymerization of ethylene and vinyl acetate to give the ethylene vinyl acetate (EVA) copolymer followed by hydrolysis. EVOH copolymer is defined by the mole % ethylene content: lower ethylene content grades have higher barrier properties; higher ethylene content grades have lower temperatures for extrusion.

Properties

EVOH is best characterized as a random copolymer of ethylene and vinyl alcohol and grades are identified by the mol% of ethylene content. EVOH was developed as a derivative of PVOH with ethylene as modifier mol% ethylene was established as an index for the modification level. The mol% ethylene influences the balance of gas barrier and formability/orientability among other properties. The lower the EVOH mol% ethylene is, the higher the gas barrier properties, density, and melting point temperature, and the higher the EVOH mol% is, the greater the flexibility and ease of processing among other properties. 

Applications:

EVOH is very versatile, making it one of the dominant barrier materials for a broad range of applications, not only in food applications, but in non-food applications as well. In addition to providing excellent oxygen barrier for food packaging, EVOH is capable of meeting other demanding requirements, such as oxygen barrier in medical packaging, flavor preservation in coffee, and barrier to fragrances and solvents in cosmetics packaging. For example, EVAL 27 mol% (L type) is used for very high barrier in flexible food packaging applications.