Etyleenivinyylialcool

Etyleenivinyylialcool, commonly known as ethylene vinyl alcohol copolymer (EVOH), is a thermoplastic polymer composed of ethylene and vinyl alcohol units. It is typically produced by hydrolysis of polyvinyl acetate or by post-polymerization conversion of poly(ethylene-co-vinyl acetate) to poly(ethylene-co-vinyl alcohol). The resulting material is a copolymer whose composition can vary, with the molar content of vinyl alcohol and ethylene adjusted to tailor properties.

A key feature of etyleenivinyylialcool is its exceptional barrier performance against gases. EVOH exhibits very low permeability to oxygen and carbon dioxide, making it highly effective as a barrier layer in packaging. Its barrier performance is strongly influenced by humidity: high moisture can plasticize the polymer and reduce gas barrier effectiveness, so EVOH is commonly used in multilayer structures where moisture is controlled or managed.

The mechanical properties and processability of EVOH depend on its composition and degree of hydrolysis. Grades are formulated for extrusion and coextrusion into films and laminates, often as an intermediate barrier layer between other polymers such as polyamides, PET, or polyolefins. EVOH is valued for clarity, stiffness, and compatibility with food-contact packaging, but its performance is moisture-sensitive, and it is usually employed as part of a multilayer system rather than as a sole material.

Regulatory and safety aspects vary by region, but EVOH and EVOH-containing packaging are widely approved for food contact in many jurisdictions. Environmental considerations focus on recyclability and the integration of EVOH within multi-material packaging streams.