They are made of ethylene-vinyl acetate copolymer foam, or EVA, a durable plastic foam that is an alternative to materials such as rubber and vinyl often used because of its ability to remain strong at low temperatures and its resistance to UV rays and cracking.
EVA (Ethylene-vinyl acetate) foam is made from blended copolymers of ethylene and vinyl acetate. In one sheet of EVA foam, The weight percentage of vinyl acetate usually ranges from 10 to 40%. Polyethylene material is another important element for EVA foaming production.
EVA foam, or ethylene-vinyl acetate, is a closed-cell foam made from blended copolymers of ethylene and vinyl acetate. It has a high level of chemical cross-linking, which results in a semi-rigid product with a fine uniform cell structure.