Chemical English name: ethylene-vinyl acetate copolymer
Chemical Chinese name: Ethylene-vinyl acetate copolymer
Molecular formula: (C2H4)x.(C4H6O2)y
Molecular weight: 2000 (average)
Ethylene and vinyl acetate copolymer is the most important product of ethylene copolymer, which is generally referred to as EVA abroad. However, in my country, people divide ethylene and vinyl acetate copolymers into EVA resin, EVA rubber and VAE emulsion according to the difference in vinyl acetate content. The specific division is as follows:
(1) The product with vinyl acetate content less than 40% is EVA resin;
(2) Products with vinyl acetate content of 40% to 70% are very flexible and elastic. EVA resin in this content range is sometimes called EVA rubber;
(3) The vinyl acetate content is usually in the emulsion state in the range of 70% to 95%, which is called VAE emulsion. The appearance of VAE emulsion is milky white or slightly yellow.
EVA resin is an ethylene-vinyl acetate copolymer, and the general vinyl acetate (VA) content is 5% to 40%. Compared with polyethylene, EVA is widely used in foam shoes due to the introduction of vinyl acetate monomer into the molecular chain, which reduces high crystallinity and improves flexibility, impact resistance, filler compatibility and heat sealing performance. materials, functional shed film, packaging film, hot melt adhesive, wire and cable and toys and other fields. Generally speaking, the performance of EVA resin mainly depends on the content of vinyl acetate on the molecular chain. With the development of my country's footwear industry and the increase in the amount of functional shed film, my country's demand for EVA resin has increased year by year, and its main uses include:
(1) Foam shoe material
Shoe material is the most important application field of EVA resin in my country. In the EVA resin used in shoe materials, the vinyl acetate content is generally 15% to 22%. Because EVA resin blended foam products have the properties of softness, good elasticity and chemical corrosion resistance, they are widely used in the soles and interior materials of middle and high-end travel shoes, hiking shoes, slippers and sandals. In addition, this material is used in the fields of sound insulation boards, gymnastics mats and sealing materials. Shunde and Zhongshan in Guangdong, Jinjiang and Quanzhou in Fujian and Wenzhou in Zhejiang are the main production bases of my country's shoe industry, which consume a lot of EVA resin products every year.
The main use of EVA film is to produce functional shed film. Functional shed film has high weather resistance, anti-fog droplet and thermal insulation properties. Since polyethylene is not polar, even if a certain amount of anti-fog droplet agent is added, its anti-fog droplet performance can only be maintained for about 2 months; The shed film made of adding a certain amount of EVA resin not only has a high light transmittance, but also has a great improvement in the anti-fog droplet performance, which generally lasts for more than 4 months. In addition, EVA can also be used to produce packaging films, medical films, lamination films, casting films, etc.
(3) Wire and cable
With the continuous development of computer and network engineering, people use more and more halogen-free flame retardant cables and silane cross-linked cables for the safety of computer rooms. Because EVA resin has good filler inclusion and cross-linkability, it is widely used in halogen-free flame retardant cables, semiconductor shielded cables and two-step silane cross-linked cables. In addition, EVA resin is also used to make some special cable jackets. EVA resin used in wire and cable, the vinyl acetate content is generally 12% to 24%.
EVA resin also has many applications in toys, such as children's wheels, seat cushions, etc. In recent years, my country's toy processing industry has developed rapidly. Most of the production is concentrated in coastal Dongguan, Shenzhen, Shantou and other places, mainly for export and external processing, and the brand and shoe materials used are basically the same.
(5) Hot melt adhesive
The hot melt adhesive with EVA resin as the main component, because it does not contain solvent, does not pollute the environment and has high safety, it is very suitable for automated assembly line production, so it is widely used in book binding, furniture edge banding, automobiles and household appliances. assembly, footwear, carpet coating and anti-corrosion coating of metal. Hot melt adhesives mainly use varieties with a vinyl acetate content of 25% to 40%.
EVA resin is also widely used in the fields of ink, luggage, wine bottle cover and so on.