EVA is an ethylene-vinyl acetate (vinyl acetate) copolymer. It is made by copolymerizing ethylene (E) and vinyl acetate (VA). The English name is Ethylene Vinyl Acetate, referred to as EVA, or E / VAC. Generally vinyl acetate (VA) content is 5% to 40%. Compared with polyethylene, EVA introduces vinyl acetate monomer in the molecular chain, which reduces crystallinity, improves flexibility, impact resistance, compatibility of fillers and heat sealing performance. Generally speaking, the properties of EVA resin mainly depend on the content of vinyl acetate in the molecular chain. Because the proportion of constituent components is adjustable to meet different application needs, the higher the content of vinyl acetate (VA content), the higher its transparency, softness and toughness.
The polymerization method uses high-pressure bulk polymerization (for plastics), solution polymerization (PVC processing aid), emulsion polymerization (adhesive), and suspension polymerization. Emulsion polymerization is used for vinyl acetate (VA) content higher than 30%, and high-pressure bulk polymerization is used for low vinyl acetate content.
Water resistance: closed cell structure, no water absorption, moisture resistance, good water resistance.
EVA resin is an ethylene-vinyl acetate copolymer. Generally, the vinyl acetate (VA) content is 5% to 40%. Compared with polyethylene, EVA is widely used in foamed shoes due to the introduction of vinyl acetate monomer in the molecular chain, which reduces high crystallinity, improves flexibility, impact resistance, compatibility of fillers and heat sealing performance. Materials, functional shed film, packaging film, hot melt adhesive, wire and cable and toys. Generally speaking, the performance of EVA resin mainly depends on the content of vinyl acetate in the molecular chain.
Shoe material is the main application field of EVA resin in China. In the EVA resin used in shoe materials, the vinyl acetate content is generally 15% to 22%. Because EVA resin blended foam products have softness, good elasticity, chemical resistance and other properties, they are widely used in the soles and interior materials of high-end travel shoes, hiking shoes, slippers, sandals. In addition, this material is also used in the field of sound insulation boards, gymnastic mats and sealing materials.
The main purpose of EVA film is to produce functional greenhouse film. The functional shed film has high weather resistance, anti-fog and heat preservation performance. Because polyethylene is not polar, even if a certain amount of anti-fog is added, its anti-fog performance can only be maintained for about 2 months; and The shed film made by adding a certain amount of EVA resin not only has a high light transmittance, but also has a great improvement in anti-fog performance, which can generally exceed 4 months. In addition, EVA can also be used to produce packaging films, medical films, laminated films, cast films, etc.
Wire and Cable
With the continuous development of computer and network engineering, for the sake of the safety of the computer room, people are increasingly using halogen-free flame-retardant cables and silane-crosslinked cables. Because EVA resin has good filler inclusion and crosslinkability, it is used more in halogen-free flame-retardant cables, semiconductor shielded cables, and two-step silane crosslinked cables. In addition, EVA resin is also used to make some special cable jackets. The EVA resin used in wire and cable generally has a vinyl acetate content of 12% to 24%.
EVA resin is also widely used in toys, such as baby wheels and seat cushions.
Hot melt adhesive
Hot melt adhesive with EVA resin as the main component, because it does not contain solvents, does not pollute the environment and has high safety. It is very suitable for automated assembly line production. Assembly, shoemaking, carpet coatings and metal anticorrosive coatings. Manufacture refrigerator ducts, gas pipes, civil plates, containers and daily necessities, etc., can also make packaging films, gaskets, medical equipment, can also be used as hot-melt adhesives, cable insulation, etc.
EVA emulsion is the abbreviation of vinyl acetate-ethylene copolymerization emulsion. It is a polymer emulsion that uses vinyl acetate and ethylene monomers as basic raw materials and copolymerizes with other auxiliary materials through emulsion polymerization.
EVA emulsion is mainly used in adhesives, coatings, cement modifiers and paper processing, and has many excellent properties.
EVA emulsion has permanent flexibility. EVA emulsion can be regarded as an internal plasticized product of polyvinyl acetate emulsion. Because it introduces ethylene molecular chains in polyvinyl acetate molecules, it creates discontinuities in acetyl groups, increases the degree of freedom of rotation of polymer chains, and hinders space. Small, the polymer main chain becomes soft, and plasticizer migration does not occur, ensuring that the product is permanently soft.
EVA emulsion has better acid and alkali resistance. EVA emulsion can maintain stable performance in the presence of weak acid and weak base, so it will not break milk regardless of mixing with weak acid or weak base, and the product has a wide range of applications.
EVA emulsion is resistant to UV aging. Because the EVA emulsion uses ethylene as an internal plasticizer of the copolymer, the EVA polymer has internal plasticity, and the plasticizer will not migrate, thereby avoiding polymer performance aging. Therefore, not only the EVA emulsion has good stability to ultraviolet light, but also the EVA emulsion can maintain this characteristic after film formation.
EVA foam shoe material
EVA emulsion has good compatibility. EVA emulsion can be mixed with most additives, such as dispersant, wetting agent, antifreeze, defoamer, preservative, flame retardant, etc., so it can meet various needs; EVA emulsion can be mixed with many pigments and fillers. No coagulation will occur; EVA emulsion can be directly mixed with many low-molecular and high-molecular water-soluble polymers, such as polyvinyl alcohol aqueous solution, polyethylene glycol aqueous solution, starch or modified starch gelatinized solution, sodium polyacrylate aqueous solution, Polymaleic acid aqueous solution, polyoxyethylene aqueous solution, urea-formaldehyde, phenol-formaldehyde aqueous solution, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose aqueous solution, etc .; EVA emulsion can be directly mixed with many other polymer polymer emulsions, such as polymer Vinyl acetate emulsion, polyacrylate emulsion; EVA emulsion can be directly mixed with aldehydes, esters, ketones, organic acids, polyols, higher alcohols, halogenated hydrocarbons, aromatic hydrocarbons, such as formaldehyde, glyoxal, and phthalic acid Butyl ester, dioctyl phthalate, acetic acid, carbon tetrachloride, chloroform, benzene, toluene, xylene, octanol, ethylene glycol, glycerol, ethyl acetate, butyl acetate, and the like.
EVA emulsion has good film-forming properties. Emulsion adhesives can only form transparent films at a certain temperature. This temperature is called the minimum film-forming temperature. The minimum film forming temperature of EVA is generally lower than 5 ° C, so it can form a film well, and the film has good barrier properties to water droplets.
EVA emulsion has good adhesion. It has a good adhesion to fiber, wood, paper, plastic film, aluminum foil, cement, ceramics and other products.
According to the waterproofing of EVA emulsion polymer, it can be divided into two types: general purpose and waterproof. General-purpose EVA polymer grades have good rigidity and high tack strength, but poor water resistance; waterproof product grade EVA polymers have good flexibility and water resistance, but low bonding strength. According to EVA application performance, copolymer composition and copolymerized third monomer type, EVA emulsion can be divided into two categories: viscose and textile.
Sticky-type EVA is mostly used as a general-purpose adhesive, and textile-type adhesive is mostly used as an adhesive for textile fibers, but there is no absolute limit between the two.
Because EVA emulsion has many excellent properties, it has a very wide range of uses in practical applications.
EVA emulsion is widely used as a binder for adhesives. EVA emulsion has good mechanical properties, the average particle size of the emulsion particles is small, there is a good balance between creep resistance and heat sealability, it has good wet viscosity and fast curing speed. EVA emulsion has a wide range of bonding properties. In addition to bonding wood, leather, fabrics, paper, cement, concrete, aluminum foil, galvanized steel and other materials, it can also be used as pressure-sensitive adhesives and heat sealants. Materials such as polyethylene, polypropylene, polyvinyl chloride, polyester and other films have unique adhesive properties.
EVA emulsion can be used as a binder for coatings. Polyvinyl acetate emulsions, acrylic emulsions, EVA emulsions, styrene-butadiene emulsions, styrene-styrene emulsions, acetic acid-benzene emulsions, and other coatings are collectively referred to as latex paints. EVA latex paints can be used as interior and exterior wall coatings, roofing waterproof coatings, and fireproof coatings Anti-rust paint. EVA latex paint film has good foaming resistance, aging resistance and is not easy to crack, has good adhesion to a variety of substrates, is safe, non-toxic, and easy to use. EVA latex paint can be applied not only on wood, masonry and concrete, but also on metal, glass, paper, and fabric surfaces. It has a good affinity for paint and can be painted on each other.
EVA emulsion can be used in paper processing. With the development of synthetic polymer technology, many polymer materials play a great role in paper processing, especially some synthetic polymer emulsions are more superior in paper processing. EVA emulsion is one of them. EVA emulsion is mainly used for paper impregnation, paper coating and pulp addition in paper processing. Its characteristics are that it can glaze a variety of papers, increase wet and dry strength, toughness, gloss, improve color stability, and reduce ink printing. Consumption, improve paper quality. As a pulp additive, various non-asbestos gaskets can be made. EVA emulsion can also be used for special paper processing, such as making disposable napkins, face towels, diapers, sanitary napkins, etc. by dry-expanded papermaking.
EVA emulsion can be used as a cement modifier. Cement is one of the most widely used materials in construction engineering. However, the simple cement products have the disadvantages of easy cracking, poor water resistance, impact resistance, and poor acid resistance, which affect the practical effect of cement to a certain extent. Since the 1920s, people have been working on the modification of cement. With the continuous deepening of research, it has been found that many synthetic latexes have better effects on cement modification, such as polyvinyl acetate emulsions, acrylic emulsions, styrene-butadiene and toluene emulsions, and EVA emulsions. Among them, EVA emulsion has good water resistance, acid and alkali resistance and weather resistance, and the price is cheaper than similar products. Therefore, it is being widely used as a new material in civil engineering. In recent years, due to environmental protection considerations, EVA redispersible powders have gradually appeared on the market, and gradually replaced the position of EVA emulsions in cement modifiers, becoming the main products of major cement modifiers.
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