Deciphering molecular codes: The birth and core advantages of EVA

Since its inception in the 1960s, ethylene-vinyl acetate copolymers (EVA) have created composites with both plastic and rubber properties thanks to their unique molecular structure-the random copolymerization of ethylene units (-CH₂-CH₂-) and vinyl acetate units (-CH₂-CO-O-). This structure gives EVA three core competencies:

Temperature adaptability: the glass transition temperature (Tg) is between -70℃ and 100℃, which makes it able to withstand extremely cold environment and can be applied to high temperature mold forming;

Processing flexibility: By adjusting the vinyl acetate content (VA content of 5%-30%), to achieve continuous control from soft foam to hard sheet;

Interface affinity: Polar ester groups enhance the bonding performance with other materials, becoming a "golden partner" in the field of adhesives.

Second, the innovation of the manufacturing process

Modern EVA production presents two technical routes:

High pressure bulk method: Under 150-300MPa high pressure, molecular chains can be orderly arranged through free radical polymerization, and the density of the produced material can be as low as 0.91g/cm³, which is used for aerospace lightweight parts.

Solution copolymerization method: using toluene as solvent to prepare ultra-high molecular weight EVA (Mw>200kg/mol), its tensile strength can reach 45MPa, used in high-end wire and cable insulation layer.

In 2021, the "Green EVA" process developed by BASF, a German company, uses bio-based ethylene raw materials and ionic catalytic polymerization technology to reduce carbon emissions by 60%, marking a key step towards sustainable manufacturing in the industry.