Common Features
When the vinyl acetate content of EVA is less than 20%, then it can be used as plastic. EVA has good low temperature resistance, its thermal decomposition temperature is low, about 230 °C, with the increase of molecular weight, the softening point of EVA rises, the machinability and the surface gloss of plastic parts decreases, but the strength increases, the impact toughness and environmental stress cracking resistance improves, EVA chemical resistance, oil resistance compared with PE (polyethylene), PVC (polyvinyl chloride) slightly worse, and with the increase of vinyl acetate content, the change is more obvious.
The performance of EVA compared with PE is improved mainly in the aspects of elasticity, flexibility, gloss and air permeability, etc. In addition, its environmental stress cracking resistance has been improved, and its tolerance to fillers has been increased. More reinforcement fillers can be added to avoid or reduce the decline of EVA mechanical properties compared with PE. EVA can also be modified to get new applications. Its modification can be mainly considered from two aspects: first, EVA is used as the main graft trunk of other monomers; The second is partial alcoholysis of EVA.
Characteristic of danger
Powder and air can form an explosive mixture, when it reaches a certain concentration, it will explode when it meets Mars. Decomposition by heating produces flammable gases.
Main Use
EVA resin is ethylene – vinyl acetate copolymer, general vinyl acetate (VA) content in 5% ~ 40%. Compared with polyethylene, EVA, due to the introduction of vinyl acetate monomer in the molecular chain, reduces the high crystallinity, improves the flexibility, impact resistance, filler phase solubility and thermal sealing performance, and is widely used in foam shoe material, functional shed film, packaging film, hot melt adhesive, wire and cable and toys and other fields. Generally speaking, the performance of EVA resin is mainly determined by the content of vinyl acetate on the molecular chain.
Foamed shoe material
Shoe material is the main application field of EVA resin in our country. In the EVA resin used for shoe materials, the content of vinyl acetate is generally 15% ~ 22%. Because EVA resin blend foam products have soft, elastic, chemical corrosion resistance and other properties, so it is widely used in middle and high grade travel shoes, hiking shoes, slippers, sandals soles and interior materials. In addition, this material is also used in the field of soundproof panels, gymnastics MATS and seals.
Thin film
The main use of EVA film is the production of functional shed film. Functional shed film has high weather resistance, anti-fogging and heat preservation performance. Because polyethylene does not have polarity, even if a certain amount of anti-fogging agent is added, its anti-fogging performance can only be maintained for about 2 months. The shed film made by adding a certain amount of EVA resin not only has a higher light transmittibility, but also greatly improves the anti-fog droplet performance, generally lasting more than 4 months. In addition, EVA can also be used in the production of packaging film, medical film, laminated film, casting film and so on.
Wire and cable
With the development of computer and network engineering, more and more people use halogen-free flame-retardant cable and silane cross-linked cable for the safety of computer room. EVA resin is widely used in halogen-free flame retardant cables, semiconductor shielded cables and two-step silane cross-linked cables due to its good packing tolerance and crosslinking. In addition, EVA resin is also used to make some special cable jacket. EVA resin used in wire and cable, vinyl acetate content is generally 12% ~ 24%.
toy
EVA resin also has many applications in toys, such as children’s wheels, seat cushions and so on.
Hot melt adhesive
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 wireless bookbinding, furniture edge sealing, automobile and household appliances assembly, shoe making, carpet coating and metal anticorrosive coating.
Production of refrigerator conduit, gas pipe, civil plates, containers and daily necessities, packaging film, gasket, medical equipment, can also be used as hot melt adhesive, cable insulation, etc.
EVA emulsion
EVA emulsion is short for ethylene acetate – ethylene copolymer emulsion, which is made of vinyl acetate and ethylene monomer as the basic raw materials and other auxiliary materials through emulsion polymerization method.
EVA emulsion is mainly used in adhesives, coatings, cement modifiers and paper processing, has many excellent properties.
EVA emulsion has permanent flexibility. EVA emulsion can be regarded as the internal plasticizer product of polyvinyl acetate emulsion. Because it introduces ethylene molecular chain into polyvinyl acetate molecule, the acetyl group produces discontinuity and increases the rotational freedom of polymer chain. The spatial obstruction is small, the polymer main chain becomes soft, and the plasticizer migration does not occur, ensuring the permanent softness of the product.
EVA emulsion has good acid and alkaline resistance. EVA emulsion in the presence of weak acid and weak base conditions can maintain stable performance, so it will not be mixed with weak acid or weak base demulsification phenomenon, a wide range of product applications.
EVA emulsion is resistant to UV aging. EVA emulsion is made of ethylene as a copolymer of internal plasticizer, so that EVA polymer has internal plasticizer, plasticizer will not migrate, so as to avoid polymer performance aging. Therefore, not only EVA emulsion has a good stability to UV, but also EVA emulsion film can maintain this characteristic.
EVA emulsion has good miscibility. EVA emulsion can be mixed with most additives, such as dispersant, wetting agent, antifreeze, defoaming agent, preservative, flame retardant and so on, so it can meet a variety of different needs; EVA emulsion can be mixed with many pigments and fillers without condensation; 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 gelatinization solution, sodium polyacrylate aqueous solution, polymaleic acid aqueous solution, polyoxyethylene aqueous solution, urea aldehyde, phenolic aqueous solution, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose aqueous solution, etc.; EVA emulsion can be directly mixed with many other polymer emulsion, such as polyvinyl acetate emulsion, polyacrylate emulsion; EVA emulsion can be directly mixed with aldehydes, esters, ketones, organic acids, polyols, advanced alcohols, halogenated hydrocarbons, aromatic hydrocarbons, such as formaldehyde, glyoxal, dibutyl phthalate, dioctyl phthalate, acetic acid, carbon tetrachloride, trichloromethane, benzene, toluene, xylene, octanol, ethylene glycol, glycerol, ethyl acetate, butyl acetate, etc.
EVA emulsion has good film forming properties. The emulsion adhesive can only form a transparent film at a certain temperature, which is called the minimum film forming temperature. The lowest film forming temperature of EVA is generally lower than 5 °C, so it can be very good film forming, and the skin film has good barrier to water droplets.
EVA emulsion has good adhesion. It has a good bonding effect on fiber, wood, paper, plastic film, aluminum foil, cement, ceramics and other products.
According to the waterproof division of EVA emulsion polymer, it can be divided into general and waterproof two categories. General brand EVA polymer has good rigidity and high bonding strength, but poor water resistance; Waterproof product brand EVA polymer has good flexibility, good water resistance, but low bonding strength. According to the application performance of EVA, copolymer composition and copolymerization of the third monomer type, EVA emulsion can be divided into two categories: adhesive and spinning. Viscose EVA is mostly used as a general adhesive, and the spinning adhesive is mostly used as a textile fiber adhesive, but there is no absolute boundary between the two.
EVA emulsion has many excellent properties, so it has a very wide range of uses in practical applications.
EVA emulsion is widely used as a base material for adhesives. EVA emulsion has good mechanical properties, the average particle size of the emulsion is small, there is a good balance between creep resistance and heat sealing, has a good wet viscosity and fast curing speed. EVA emulsion has a wide range of bonding properties, in addition to wood, leather, fabric, paper, cement, concrete, aluminum foil, galvanized steel and other materials, can also be used as pressure sensitive adhesive and heat sealing adhesive, and for some difficult to bond materials such as polyethylene, polypropylene, polyvinyl chloride, polyester and other films is unique adhesion.
EVA emulsion can be used as a base material for paints. The coatings made of polyvinyl acetate emulsion, acrylic emulsion, EVA emulsion, styrene-butadiene emulsion, styrene-propylbenzene emulsion and styrene-acetate emulsion are collectively referred to as latex paint. EVA latex paint can be used as interior and exterior paint, roof waterproof paint, fireproof paint, rust proof paint. EVA latex paint coating film blistering resistance is good, aging resistance is not easy to crack, and a variety of substrates have good adhesion, safe and non-toxic, easy to use. EVA latex paint can not only be coated on wood, masonry and concrete, but also on the surface of metal, glass, paper and fabric. It has a good affinity with paint, and can be brushed on the surface of each other.
EVA emulsion can be used in paper processing. With the development of synthetic polymer technology, many polymer substances play a great role in paper processing, especially some synthetic polymer emulsion has more advantages 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 give a variety of paper gloss, increase the dry and wet strength of paper, toughness, gloss, improve color stability, reduce ink printing consumption, improve the grade of paper. As a pulp additive, all kinds of non – asbestos gaskets can be made. EVA emulsion can also be used for special paper processing, such as using dry extruded paper to make disposable napkins, face towels, diapers, sanitary napkins and so on.
EVA emulsion can be used as modifier of cement, cement is one of the most widely used materials in construction engineering. But simple cement products are easy to crack and water resistance, impact resistance, acid resistance is poor, to a certain extent affect the practical effect of cement. Since the 1920s, people have been committed to the study of cement modification. With the deepening of research, people found that many synthetic latex has a good effect on cement modification, such as polyvinyl acetate emulsion, acrylic emulsion, butadiene and toluene emulsion, EVA emulsion and so on. EVA emulsion has good water resistance, acid and alkali resistance and weather resistance, and its price is cheaper than similar products. Therefore, as a new material, Eva emulsion is widely used in civil engineering. In recent years, for the consideration of environmental protection, EVA redispersible latex powder has gradually appeared in the market, and has gradually replaced EVA emulsion in the position of cement modifier, and become the main product of cement modifier.