EVOH

is a semicrystalline plastic copolymer made from ethylene and vinyl alcohol monomers. The ratio of these two components directly controls its properties: lower ethylene content means better gas barrier performance but reduced moisture resistance, while higher ethylene content improves flexibility and processability.

Its defining characteristic is an exceptionally low permeability to oxygen, carbon dioxide, and other gases and aromas. This barrier performance surpasses most other packaging polymers by orders of magnitude under dry conditions, making EVOH one of the most effective barrier materials available.

However, its barrier properties degrade significantly when exposed to moisture, which is why EVOH is almost always sandwiched between moisture-resistant polymers like polyethylene or polypropylene in multilayer structures rather than used alone.

Packaging is by far the dominant application. EVOH-based multilayer films and rigid containers are used extensively in food packaging — vacuum-packed meats, dairy products, sauces, condiments, and retort pouches — to extend shelf life by blocking oxygen that causes spoilage and rancidity. It is also used in pharmaceutical blister packs and medical device packaging for the same reasons.

Beyond food, EVOH serves as a fuel barrier layer in multilayer plastic fuel tanks and fuel lines in automotive applications, preventing hydrocarbon permeation that would otherwise contribute to evaporative emissions. This use is tightly regulated in many markets.

Additional applications include agricultural films, where EVOH blocks agrochemical vapors, and hot water pipes, where it prevents oxygen diffusion into underfloor heating systems that would otherwise corrode metalwork.

EVOH is generally considered safe for food contact and is approved by major regulatory bodies worldwide.