The material of EVA sole is ethylene/vinyl acetate copolymer (also known as ethylene-vinyl acetate copolymer), which is made by copolymerization of ethylene (E) and vinyl acetate (VA). It is called Ethylene Vinyl Acetate in English. Abbreviated as EVA, the content ranges from 5% to 40%.
Compared with polyethylene, EVA has been widely used in the fields of foamed shoes, functional greenhouse film, packaging film, hot melt adhesive, wire and cable, toys and so on, because of the introduction of vinyl acetate monomer in the molecular chain, which reduces the high crystallinity, improves flexibility, impact resistance, filler compatibility and thermal sealing performance.
Characteristics of EVA sole:
EVA sole is characterized by good softness, rubber-like elasticity, good flexibility, transparency and surface gloss under 0 C, good chemical stability, good anti-aging and ozone resistance, non-toxicity. It has good mixing property with filler, good dyeing and processing property.
It has a great relationship with the content of ethylene acetate, molecular weight and melt index. When the melting index (MI) is constant and the content of vinyl acetate (VA) increases, its elasticity, softness, compatibility and transparency also increase. When the content of VA decreases, the properties are close to polyethylene, the rigidity is increased, the wear resistance and electrical insulation are improved.
When the content of VA is constant, the melt index increases, the softening point decreases, the processability and surface gloss improve, but the strength decreases. Otherwise, with the decrease of the molecular weight of MI, the impact and anti-environmental stress cracking properties increase. The polarity of acetate increases elasticity and viscosity, decreases crystallinity and electrical properties, and dissolves in hydrocarbon solvents and oils.