Ethylene vinyl acetate or EVA is a copolymer of ethylene and vinyl acetate. It is an extremely elastic and tough thermoplastic of excellent clarity and gloss with little odor. It has excellent adhesion to many substrates, is inert, has good flex crack and puncture resistance, and good adhesion and heat-sealing properties.
Typically, this thermoplastic resin is copolymerized with other resins like LDPE and LLDPE or it is part of a multilayer film. In blends and copolymers, the percentage of EVA ranges from 2% to 25%. It enhances clarity and sealability of olefins (LDPE/LLDPE) whereas a higher percentage of EVA is often used to reduce the melting point. It also improves the low temperature performance. In general, the mechanical properties will depend on the vinyl acetate content; the higher its percentage is, the lower is the barrier to gas and moisture and the better the clarity.
EVA is only an average barrier to gases and moisture, which makes it not a good choice for food packaging applications and, therefore, has been replaced by metallocene PE in many of these applications. mPE also offers faster hot tack, and has better down-gauging properties, which allows for thinner films and packaging. Nevertheless, EVA remains an important packaging material and demand will remain strong particularly for non-food applications.
EVA is used in several film applications. Usually, this resin is not used alone but is combined with other film resins. Important applications include sealants in meat and dairy packaging structures, footwear, wire and cable insulation, photovoltaic encapsulation, and lamination of glass to improve impact resistance.