Details
Material hierarchy: Polymer - Thermoplastic - Polyolefin
Ethylene-vinyl alcohol is abbreviated EVOH. Copolymers of ethylene and vinyl alcohol provide excellent barriers to the permeation of oxygen and other gases, odors, and flavors. EVOH resins generally are used within packaging structures because of their strong tendency to absorb moisture, which leads to deterioration of the barrier properties.
Multilayer structures that contain EVOH are produced by coating, laminating, coextrusion, or coinjection molding. In such structures, the EVOH is encapsulated by other polymers, often polyolefins, which keep moisture out. In most cases, adhesive tie layers are required to bond the hydrophilic EVOH to hydrophobic polymers. A notable exception is with nylon, where bonding is achieved without adhesives.
Common Applications
- Barrier packaging for food products - The major use of EVOH barrier packaging is for food products although there are applications involving solvents and other chemicals. The most common combination is with polypropylene. Blow-molded bottles for kethcup, barbecue sauces, and salad dressings and thermoformed containers for jellies, sauces, and prepared foods all are sold commercially.