Epoxy adhesive: types, properties and characteristics

For gluing parts made of various materials, adhesives based on binders are used. Casein, starch, rubber, dextrin, polyurethane, resin, silicate and other natural and synthetic compounds can act as the main component. Each glue has its own characteristics and scope. An adhesive mixture based on epoxy resin is considered a universal high-tech composition.

The main component in epoxy adhesive is epoxy resin. It is a synthetic oligomer that is not suitable for use on its own. Synthetic resin is widely used in the production of paints and varnishes and finishing materials. Depending on the manufacturer and brand, the resin can be a liquid honey-colored consistency or a dark solid mass.

The epoxy package contains two components. There is a significant difference between them. In order for the epoxy resin to acquire adhesive properties, hardeners are added to it. Polyethylene polyamine, triethylenetetramine and anhydrite are used as the hardening component. Epoxy resin hardener is capable of forming a strong polymer structure.

The popularity of epoxy is determined by its positive qualities.

The epoxy adhesive mixture exhibits the following properties:

• forms a non-shrinkable seam without cracks;
• high adhesion to various materials;
• resistance to chemical solvents, alkalis and oils;
• heat resistance up to +250 gadus;
• frost resistance up to -20 degrees;
• resistance to mechanical stress;
• elasticity allows you to drill and grind the seam without chips;
• hardened glue lends itself to staining and varnishing;
• does not conduct electric current;
• the cure rate does not depend on the thickness of the adhesive layer;
• the ability to add additional components to the composition;
• moisture resistance;
• weather resistance;
• wear resistance.

The addition of asbestos increases heat resistance and hardness. Titanium dioxide imparts a white color to the entire solution. Iron oxide will help to achieve red color and fire resistance. Iron powder will increase the coefficient of thermal conductivity and heat resistance. Reduces the viscosity and hardens the epoxy mixture with silicon dioxide. The soot will give the glue a black color. Will increase the strength and dielectric properties of aluminum oxide. Glass fibers and sawdust will add significant volume when filling large voids.

The downside when using epoxy adhesive is the setting speed. In a short period of time, you need to apply and fix the glue line, remove excess glue and clean the work area and hands. After the adhesive has hardened, removal is carried out only with strong mechanical stress. The quicker you start cleaning up sticky epoxy, the easier it is to clean up the dirt with minimal effort.

Do not glue objects that come into contact with food with epoxy. Nickel, tin, Teflon, chromium, zinc, polyethylene, silicone are not sticky. Soft materials break on contact with the resin-based composition.

Due to the large number of unique properties, the adhesive epoxy mixture has been widely used in various sectors of the national economy. Epoxy grout is used in various fields.

• In the construction industry. The adhesive is used to fill cracks in concrete, cement screeds, reinforced concrete beams and slabs, further strengthening the entire structure. They are used to connect iron and concrete elements in bridge construction. Sections of building panels are glued with epoxy. It gives waterproofing properties to the insulation and chipboard, reduces heat losses, creating tightness in the sandwich panel. During finishing work with tiles and mosaics, an epoxy mixture is used as an adhesive solution, which quickly hardens and has moisture-repellent properties.
• In the automotive industry. In production, brake pads are attached with epoxy glue, plastic and metal surfaces are bonded, used in automotive repair work for metal and plastic. It helps to repair defects in the body and the gas tank, to restore the trim.

• In the manufacture of ships and aircraft. In the construction of watercraft, the hull is treated with epoxy to impart water-repellent properties to the material, used to join parts of fiberglass, fasten technological units. When assembling aircraft, heat-shielding elements are attached with epoxy glue. They use epoxy to manufacture and fix solar panels.
• At home. With the help of epoxy glue, you can repair furniture, shoes, repair plastic, metal and wooden parts of decor and technology. You can repair a crack in the aquarium and collect shards of a glass vase or shade. The epoxy will glue the chipped porcelain stoneware and seal the gap in the ceramic tile, securely fix the hooks and holders on the wall. The epoxy compound is suitable for sealing sewer and water pipes, heating elements. Epoxy is widely used in needlework to create handicrafts and souvenirs. It is used to attach decorative elements in the manufacture of jewelry and hair accessories. Sequins, half beads, satin ribbons, lace, polymer clay and other materials are glued.

Epoxy adhesive mixture is a synthetic mass in which an irreversible chemical reaction takes place to form a durable material. The resin-based adhesive can include a modifier, hardener, solvent, fillers, plasticizers.

The main component in the adhesive is epoxy resin. It also consists of epichlorohydrin with phenol or bisphenol. The resin can be modified. An epoxy resin modified with rubber improves the toughness characteristics. Organophoric modifiers reduce the flammability of the product. The addition of the Laproxiv modifier increases the elasticity.

Compounds of aminoamides, polyamines, organic acid anhydrides can act as a hardener. Mixing epoxy with a hardener will initiate a thermosetting reaction. The proportion of hardeners is 5-15% of the resin.

Solvents can be xylene, alcohols, acetone. The solvent does not exceed 3% of the total solution volume. Plasticizers are added to improve the reliability of the fastened parts. For this, ester compounds of phthalic and phosphoric acid are used.

Fillers are used to impart bulk and additional physical characteristics to the finished product. Dust of various metals, mineral powders, fibers, cement, sawdust, micropolymers are used as fillers.The amount of additional fillers can vary from 1 to 300% of the total weight of the epoxy resin.

Operating temperature range - from -20 to +120 degrees. The extra strong adhesive can withstand temperatures up to +250 degrees.

Epoxy adhesive has a hazard class 3 according to the classification of GOST 12.1.007-76 and is a low-hazard irritant substance, but it can cause an allergic reaction on the skin. For the environment, it is environmentally hazardous and toxic if released into water bodies.

The pot life of the prepared mixture ranges from 5 minutes to two hours, depending on different manufacturers. The different composition of the glue shows strength from 100 to 400 kgf per 1 cm2. The average density per m3 is 1.37 tons. Elasticity upon impact and displacement of the seam - within 1000-2000 MPa. The cured epoxy layer shows resistance to gasoline, alkalis, acids, salts, oils, kerosene. Degradable in toluene and acetone.

Epoxies vary in volume and weight. Components of 6 and 25 ml are poured into syringes. Twin syringes are convenient to use at home for gluing small surfaces. Universal epoxy adhesive mixtures are characterized by a long pot life of up to two hours and are produced in containers of 140, 280 and 1000 g. Fast-curing epoxy approaches the speed of curing to cold welding, it is produced in tubes of 45 and 70 ml and in buckets and bottles of 250 and 500 g. ... For industrial use, epoxy components are supplied in drums of 15, 19 kg.

Epoxy adhesive mixtures are divided into groups according to three characteristics: by the number of components, by the density of the mass, by the method of polymerization. The composition of the glue can be one-component and two-component.

One-component glue contains one package, it does not need preliminary preparation. One-component mixtures can cure at room temperature or with increasing heat. The strength characteristics of such compositions are lower than in a two-component solution. Products in two separate packages are more in demand on the market. The two components are mixed before gluing. Universal epoxy two-component adhesive forms a flexible monolithic layer of high strength.

The viscosity of liquid solutions depends on the consistency of the epoxy resin. To increase the fluidity of the resin, it must be heated. Liquid glue is easy to apply and fills all the pores of the material. When hardened, it forms an elastic moisture-resistant seam.

The clay-like composition is similar in structure to plasticine. It is produced in the form of bars of different sizes. For work, the mixture is kneaded by hand and carefully distributed on the surface to be glued. The plastic mass is often dark metallic in color because it is used for cold welding. It is applied to seal holes and irregularities in metal.

The polymerization method depends on the hardener used. Liquid mixtures with anhydrite and polyamine hardeners begin to cure under normal conditions. In order for the finished seam to be waterproof with increased protective qualities from solvents, acids and oils, it is necessary to perform high-temperature heating. Enough exposure to a temperature of + 70-120 degrees. A super-strong layer is formed when heated at + 150-300 degrees. When hot curing, a heat-resistant layer with electrical protective properties is obtained.

Adhesive consumption depends on the thickness of the applied layer. For 1 m2, on average, 1.1 kg of epoxy is consumed with a layer thickness of 1 mm. When gluing porous surfaces such as concrete, the consumption of the mixture increases. It also increases the cost of applying glue to wood-based panels and wood. To fill the cracks, 1.1 g is consumed per 1 cm3 of void.

According to their quality characteristics, four brands of epoxy glue stand out: Cold Welding glue, EDP brand, Contact plastic mass, Moment brand liquid components.

Epoxy adhesive "Cold welding" designed for quick repair of metal products. It can be produced in the form of plasticine and liquid ingredients. It is characterized by a high speed of hardening and special strength. It is a liquid or plastic epoxy mass capable of hardening within 5-20 minutes.

Many manufacturers make this brand of glue. Foreign company Akapol produces epoxy adhesive Poxipol two consistencies. It hardens 10 minutes after mixing. Russian manufacturer "Astatine" produces glue "Epoxy Metal" in liquid form, curing occurs in 5 minutes. Under the brand "Anles" production is produced "Uniplast", "Epoxy titanium" for metals. Under the brand name Runway sell glue "Epoxy steel".

The universal epoxy composition of EDP is suitable for many types of materials - wood, metal, plastic, earthenware, ceramics, rubber, fabric, glass, plaster, leather, concrete, stone, etc. Domestic manufacturer LLC "NPK" Astat " produces glue of the EDP brand - epoxy-diane with polyethylene polyamine. The mixed composition can be used for up to two hours at work. Within 24 hours, the finished glue line reaches its declared strength. LLC GK "Himalyans" produces EDP brand glue with a pot life of up to one and a half hours. JSC "Anles" manufactures an analogue of the brand EDP ​​glue "Epox-universal". LLC "Ecoclass" produces a universal epoxy under the brand "Class"... Under the brand name "Khimkontakt" sell universal epoxy adhesive "Khimkontakt-Epoxy".

Epoxy mixes brands "Contact" represent a plastic, rapidly hardening mass. It is characterized by an increased temperature limit from -40 to +140 degrees. The composition is capable of sticking to a damp surface.

Convenient for household use epoxy mortar "Moment"... Popular brand Henkel's Moment... He manufactures two lines of epoxies - two-component liquid adhesive "Super Epoxy" in tubes and syringes of different sizes and "Epoxylin", packaged in 30, 48, 100 and 240 grams. Epoxy equal component glue has positive reviews "Super-grip" production CJSC "Petrokhim"... Consumers note the ease of use when mixing components.

It is best to work in a well-ventilated area so as not to irritate the respiratory system with epoxy fumes. Wear protective gloves and clothing that you don't mind getting dirty. The place of work can be covered with newspaper or cloth so as not to contaminate the surface. Prepare the application tool and mixing container in advance. You can use disposable tableware.

The processing of the product is carried out before mixing the adhesive, since the solution must be applied immediately after manufacture.

Before you start preparing an epoxy mixture with your own hands, you need to study the manufacturer's instructions attached to the package. It contains the proportions of the resin and hardener components. The ratios of substances differ from manufacturer to manufacturer.In general purpose liquid adhesives, you usually need to mix 1 part hardener and 10 parts epoxy.

If the epoxy is viscous, it will be difficult to mix the components. To easily dilute the resin, it must be heated in a water bath or heating radiator to 50-60 degrees. Using a syringe without a needle, measure a small amount of resin and pour it into a container. Then take the required portion of the hardener and dissolve in the resin, stirring vigorously, to obtain a homogeneous mass.

After mixing the components, the surfaces are glued. On one side, you need to apply the ready-made glue and press both halves with effort, fixing for 10 minutes without displacement. If a small amount of solution is squeezed out of the seam, it must be immediately removed with a napkin. Until the epoxy is completely cured, do not use the product or subject it to stress.

Sawdust and other fillers can be added to the prepared epoxy mortar, which add additional volume, improve the quality of the finished joint and give the desired color. If you add sawdust to the epoxy, then you need to fill the mold with the finished mixture. You can use a spacer to make a product item. The hardened part can be sanded, painted and drilled.

To close up a defect in the metal products of the car body, fiberglass and thick gauze are impregnated with epoxy glue. Then the part is closed with a processed piece, additionally processing the edges with epoxy mortar. In this way, you can restore a product in need of repair.

The drying time of the adhesive solution depends on the air temperature and the proportions of the main components in the mixture. The addition of a larger proportion of the hardener to the epoxy will help speed up the hardening of the finished mixture. The setting rate is increased by heating the glue line after the composition has set. The higher the temperature, the faster the epoxy cures.

The full cure time determines the type of epoxy adhesive. Cold weld hardens within 5-20 minutes. Liquid mixtures of EDP thicken in an hour, set in two hours, completely polymerize in a day.

It is not recommended to work with epoxy in cold weather. In this case, it is difficult to dry the glue line, since crystallization of the components occurs. It is necessary to use epoxy at temperatures from +10 to +30 degrees. Resistance to viscosity in heat allows for better work.

In the instructions on the packaging, the manufacturer indicates that the components of the epoxy glue should be stored in their original packaging at a room temperature of 20-25 degrees. The package should be placed in a dry place in an upright position so as not to damage its integrity. Damage to the container and contact with air leads to a deterioration in the quality of the material. Do not store the glue in an open, sunny place so that children can access it. Epoxy packaging is placed separately from food and utensils.

The fresher the epoxy resin and the hardener, the better the polymerization process goes, the adhesion improves, the adhesive seam is better. It is impossible to store the prepared composition; it must be immediately used for its intended purpose. Remains of the finished epoxy mixture cannot be stored, they must be disposed of.

When working with epoxy, protective agents should be used to avoid contact of the mixture on the skin. If it was not possible to prevent contamination, then the uncured mixture is thoroughly washed off with soapy water. When it was not possible to completely wash off the remnants of the components, you will have to use acetone, wiping the stubborn stain.

There are several ways to remove cured epoxy from various materials.

• Freezing the stain. Since the epoxy mixture is able to withstand temperatures down to -20 degrees, freezing in the freezer does not seem to be effective. A special aerosol refrigerant is used for freezing. The epoxy becomes brittle when sprayed with refrigerant. Now you can clean the resin with a spatula or blunt knife. Care must be taken so that sharp shards do not cut the skin.
• Heating pollution. High temperatures will soften the epoxy mixture. For heating, you can use a household hairdryer or iron. A hairdryer at the maximum temperature level is used to heat solid heat-resistant surfaces. You can direct a stream of hot air to the dirt for a few minutes. The softened area is removed with a spatula. Heating is carried out until the surface is completely cleaned. If the epoxy glue gets on the fabric, then heating is carried out with an iron, placing a cotton rag on the front side.
• Scraping. Power tool cleaning is suitable for scratch-resistant hard surfaces. The scraping can be done with any sharp metal instrument.
• Use of chemical solvents. This method is suitable for wear-resistant materials that will not degrade with thinners. Acetone, ethyl alcohol, toluene, butyl acetate, aniline are used as dissolving agents. The contaminated area is moistened with any solvent, allowed to act, then proceed to mechanical cleaning.

Epoxy can be washed off glass or mirrors with solvents or acetic acid. The method of heating the surface and the contaminated area will also be effective. A spatula and a soft cloth will help to remove the remnants of glue.

You can use a solvent-soaked cloth to wipe off the epoxy from the glue application tool. Cleaning should be started immediately after completion of work, without allowing the composition to harden. The sooner you start wiping off the contaminated area, the easier the glue will be washed off. The following methods of disposal of epoxy mixture on various surfaces will help clean up the dirt and preserve the appearance of the product.

How to properly prepare epoxy glue, see the video below.