Ethylene-vinyl alcohol copolymer or EVOH is a flexible, crystal clear, and glossy thermoplastic copolymer produced through alcoholysis of poly(vinyl acetate). In commercial EVOH resins, the vinyl alcohol content typically various between about 55 and 75 mole percent. Both the melting point and glass transition temperature increases with decreasing ethylene content whereas the oxygen gas transmission rate decreases. In other words, grades with low ethylene content provide the best gas barrier whereas those with the highest ethylene content offer the greatest flexibility and easiest processing.
for evoh to be produced, using solution polymerization with a heat exchanger. The method entails simultaneously passing the solvent solution of vinyl acetate and discharged ethylene through a heat exchanger provided with a cooling means, thus, causing the solution of vinyl acetate to absorb and solubilize ethylene before the solution returns to the polymerization vessel. In the vessel, the vinyl acetate with solubilized ethylene is mixed with the polymerization solution.
EVOH Resin is frequently used in multilayer, co-extruded films like HDPE, PP, and PET which have superior moisture barrier properties. Besides packaging, EVOH resins find uses in several other industries such as construction, automotive, cosmetic and agriculture. Important applications include under-floor heating pipes, plastic fuel tanks, agrochemical containers, soil fumigating films, and vacuum insulation panels.