EVA (ethylene-vinyl acetate copolymer) can be divided into three categories based on its VA (vinyl acetate) content: EVA resins with a VA content of 5% to 40% are primarily used for polyethylene modification and the manufacture of wire and cable materials, films, and other molded products or blends; EVA elastomers with a VA content of 40% to 70% are primarily used as rubber elastomers and PVC modifiers; and VAE emulsions with a VA content of 70% to 95% are typically formulated into emulsions and are primarily used as adhesives, coatings, and paints. Generally speaking, EVA with a vinyl acetate content below 5% is primarily used in films, wire and cable, LDPE modifiers, and adhesives. EVA with a vinyl acetate content of 5%-10% is used in elastic films. EVA with a vinyl acetate content of 20%-28% is primarily used in hot-melt adhesives and coatings. EVA with a vinyl acetate content of 5%-45% is primarily used in films (including agricultural films) and sheets, injection molding, molded products, foam products, and hot-melt adhesives.
EVA resin has a wide range of applications. The VA content of EVA resin used in films is less than 20%. EVA film offers advantages such as high transparency, excellent impact toughness, and thermal stability. It is physiologically harmless, breathable, and has low low-temperature shrinkage. As a functional agricultural greenhouse film, it offers high light transmittance, excellent thermal insulation, aging resistance, and anti-fog properties, making it an ideal base material for agricultural films. EVA can also be used as packaging film, medical film, laminating film, and casting film.
EVA resin is characterized by excellent softness and rubber-like elasticity, maintaining good flexibility even at -50°C, excellent transparency and surface gloss, good chemical stability, excellent aging and ozone resistance, and non-toxicity. It also blends well with fillers and offers excellent coloring and molding properties.
EVA resin has a wide range of applications. Generally, EVA with a vinyl acetate content below 5% is primarily used in films, wire and cable, LDPE modifiers, and adhesives. EVA with a vinyl acetate content of 5% to 10% is used in elastic films. EVA with a vinyl acetate content of 20% to 28% is primarily used in hot-melt adhesives and coatings. EVA with a vinyl acetate content of 5% to 45% is primarily used in films (including agricultural films) and sheets, injection molded and molded products, foamed products, and hot-melt adhesives. For example:
(1) Films, sheets and laminated products: They have sealing, adhesive, softness, toughness and compactness, and are suitable for elastic packaging films, heat shrinkable films, agricultural films, food packaging films, laminated films, and can be used as the middle layer of polyolefin laminated films.
(2) General supplies: They have flexibility, resistance to environmental stress cracking, and good weather resistance. They are suitable for industrial use, such as power wire insulation bags, household appliance accessories, window sealing materials, etc.
(3) Daily necessities include sports equipment, toys, cushions, straps, sealed container lids, EVA rubber footballs, etc.
(4) Automotive accessories include shock absorbers, fenders, and interior and exterior decorative accessories.
(5) Foam products: Pressurized foaming includes foam plastic slippers, sandals, building materials, etc. Injection foaming includes various industrial parts, women's shoe soles, hot melt adhesives, etc.
Molding Processing of Ethylene-Vinyl Acetate Copolymers
EVA can be molded through various processes, including injection molding, extrusion, blow molding, calendering, rotational vacuum thermoforming, foaming, coating, heat sealing, and welding. Ethylene-Vinyl Acetate Copolymer (EVA) EVA resin is an ethylene-vinyl acetate copolymer, typically containing 5% to 40% vinyl acetate (VA). Compared to polyethylene, EVA incorporates vinyl acetate monomer into its molecular chain, resulting in lower crystallinity and improved flexibility, impact resistance, filler compatibility, and heat sealing properties. It is widely used in foamed shoe materials, functional greenhouse films, packaging films, hot-melt adhesives, wire and cable, and toys.
Applications of EVA Resin
EVA resin is an ethylene-vinyl acetate copolymer, typically containing 5% to 40% vinyl acetate (VA). Compared with polyethylene, EVA has a lower crystallinity and higher flexibility, impact resistance, filler compatibility and heat sealing performance due to the introduction of vinyl acetate monomer into the molecular chain. It is widely used in foamed shoe materials, functional greenhouse films, packaging films, hot melt adhesives, wires and cables, and toys. Generally speaking, the performance of EVA resin mainly depends on the content of vinyl acetate in the molecular chain. In 2001, the market consumption of EVA resin in my country was about 290 kt. With the development of my country's shoemaking industry and the increase in the use of functional greenhouse films, my country's demand for EVA resin will continue to increase year by year. (1) Foamed shoe materials Shoe materials are 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 between 15% and 22%. Since 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 mid-to-high-end tourist shoes, hiking shoes, slippers and sandals. In addition, this material is also 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 footwear industry, consuming a large amount of EVA resin products every year. In 1999, my country consumed about 150 kt of EVA resin in the fields of foamed shoe materials and shock absorption. (2) Film The main use of EVA film is to produce functional greenhouse film. Functional greenhouse film has high weather resistance, anti-fog and heat preservation properties. Since polyethylene is not polar, even if a certain amount of anti-fog agent is added, its anti-fog performance can only last for about 2 months; while greenhouse film made by adding a certain amount of EVA resin not only has a higher light transmittance, but also has a greatly improved anti-fog performance, which can generally exceed 4 months. In addition, EVA can also be used to produce packaging film, medical film, laminated film, casting film, etc. In 1999, there were more than 50 companies in my country that used EVA resin to process films. In 1999, my country produced a total of 800 kt of greenhouse film, of which 220 kt was functional greenhouse film, and consumed about 30 kt of EVA resin. Together with packaging film, medical film and other fields, my country consumed a total of 37 kt of EVA resin in the film field. (3) Wires and cables With the continuous development of computer and network engineering, people are increasingly using halogen-free flame-retardant cables and silane cross-linked cables for the sake of computer room safety. Because EVA resin has good filler tolerance and cross-linking properties, 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 the sheath of some special cables. The vinyl acetate content of EVA resin used in wires and cables is generally between 12% and 24%. In 1999, the wire and cable industry consumed a total of about 6,000 t of EVA. (4) Toys EVA resin is also widely used in toys, such as children's wheels and seat cushions. In recent years, my country's toy processing industry has developed rapidly, with production concentrated in coastal areas such as Dongguan, Shenzhen, and Shantou, mainly focusing on export and external processing. According to analysis, these manufacturers consume about 5,000 tons of EVA resin each year, using brands that are basically the same as those used for shoe materials. (5) Hot melt adhesive Hot melt adhesive with EVA resin as the main component does not contain solvents, does not pollute the environment, and is highly safe. It is very suitable for automated assembly line production, so it is widely used in book binding, furniture edge banding, automobile and household appliance assembly, shoemaking, carpet coating, and metal anti-corrosion coating. Hot melt adhesive mainly uses varieties with a vinyl acetate content of 25% to 40%. Although there are products of this brand in China, they have not been produced for a long time, so all of them are occupied by imported materials. In 1999, my country's hot melt adhesive industry consumed an estimated 17 kt of EVA resin; 1-3% of the enclosed curing agent W-8035/W-8235 is added to the hot melt adhesive production process. It can significantly improve comprehensive properties such as water resistance, wear resistance, and bonding strength.
(6) Others
EVA resin is also widely used in inks, bags, wine bottle caps, and other fields. It is estimated that these areas consume no less than 15 kt of EVA resin.
