EVA, short for ethylene-vinyl acetate copolymer, is a thermoplastic polymer formed by the copolymerization of ethylene and vinyl acetate monomers. It typically appears as transparent or translucent granules, is odorless and non-toxic, and is classified as an environmentally friendly material.

Its core properties are determined by the vinyl acetate (VA) content: the lower the VA content, the closer the material is to the rigidity of polyethylene; the higher the content, the better the elasticity, flexibility, and transparency, and the greater the tackiness. Typically, when the VA content is between 10% and 22%, EVA combines light weight with high elasticity, making it an ideal choice for footwear materials and cushioning pads.

The introduction of polar vinyl acetate monomers into the EVA molecular chain disrupts the regular crystalline structure of polyethylene, endowing it with advantages such as light weight, high elasticity, water resistance, and corrosion resistance. It has a low density of only 0.91–0.93 g/cm³, a closed-cell structure that does not absorb water, and resistance to acid and alkali corrosion. It also offers good insulation and processability, allowing it to be formed into various products through processes such as injection molding and foaming.