EVA

A flexible copolymer used in shoe foams and hot-melt adhesive binders.

Also known as
ethylene vinyl acetate, EVA copolymer

In everyday products

Structure and behaviour

–CH₂–CH₂– and –CH₂–CH(O–C(=O)–CH₃)–

Ethene-derived and vinyl-acetate-derived segments occur in grade-dependent proportions. Both use their C=C bonds for chain growth; the ester groups remain pendant, so EVA is not a backbone polyester.

  • Acetate-bearing segments interrupt polyethylene-like packing; increasing vinyl acetate content generally increases flexibility and lowers softening temperature.
  • The copolymer’s composition changes the chain itself, unlike adding a separate plasticiser to PVC.
  • Foamed EVA gets much of its cushioning from gas cells, with formulation and crosslinking affecting recovery.
  • In a hot-melt adhesive, EVA provides a cohesive polymer binder while tackifiers and waxes adjust wetting and flow.
  • A cooled thermoplastic adhesive can soften again; a crosslinked shoe foam cannot simply be melted into the same flowing material.

Preparation routes

Ethene and vinyl acetate route

Addition copolymerisation. Both monomers add through their carbon–carbon double bonds to form a chain containing ethene-derived and vinyl-acetate-derived units. Both double bonds participate, while acetate groups stay attached to the vinyl-acetate-derived segments. Changing their proportion changes flexibility without a separate PVC-style plasticiser.

Industrial initiators and reaction controls support chain growth. Foaming agents, adhesive waxes and tackifiers are added in later product-formulation steps. Neither the foam gas nor an adhesive tackifier belongs in the required monomer pair.

  1. EVA product general extrusion guideCelanese
  2. Ateva ethylene vinyl acetate copolymersCelanese

From ethene and ethanoic acid to vinyl acetate

  1. Ethene + Ethanoic acid + Oxygen → Vinyl acetate

    Ethene, ethanoic acid and oxygen react in a catalytic gas-phase process to make vinyl acetate. Unreacted ethene and acid are recovered, and the monomer is refined. The product retains a polymerisable vinyl group alongside its ester group. It is chemically distinct from ethyl ethanoate, which has a saturated ethyl group.

  1. Vinyl acetate monomer: reaction, feedstock recovery and refiningLOTTE INEOS Chemical
  2. Vinyl acetate monomerCelanese

Material limits

Shoe foam and glue-stick grades serve different jobs. Compression history, cell structure, ageing and attached outsole or textile layers complicate shoe recovery. Crosslinking also changes reprocessing options. Vinyl acetate percentage is more informative than density alone when comparing the polymer resins; neither predicts a finished shoe’s performance.

Sources

  1. Ateva ethylene vinyl acetate copolymersCelanese
  2. EVA product general extrusion guideCelanese
  3. Sustainable plastics: the role of chemistryRoyal Society of Chemistry