Despite the fact that a large number of adhesives have been created to date, epoxy two-component adhesive is one of the most popular and frequently used compounds both in production and in the household.
Its secret is the high strength characteristics of the bonded surfaces, excellent interaction with most materials. In this article, we will understand what epoxy glue is, how to properly prepare and apply it.
What is this
Epoxy resin, which is the main ingredient of glue, was first made in 1938, and since 1940, the production of glue begins on a large scale. The first commercial name for the adhesive was Araldit-1. It was a brand new general purpose adhesive for industrial and general domestic use.
Over the past few decades, the building materials industry has made strides in developing unique bonding compositions and techniques. Numerous types of epoxy formulations have been devised that can operate over a wide range oftemperatures, while giving high-strength joints with a long service life.
Universal epoxy adhesive will bond all materials except these:
- elastic poreless;
- plexiglass;
- polystyrene;
- PTFE;
- kapron;
- polyethylene.
Also, curved surfaces, such as shoe soles, are not subject to this glue. But what sticks together with particular strength is the metal parts. It is worth mentioning that the glue has waterproof properties.
Operation principle
Epoxy two-component adhesive is obtained by mixing two ingredients - hardener and epoxy. According to their chemical structure, both active components are polymers with a small molecular weight, as a result of which, when they are mixed, polymerization occurs - the process of combining simple molecules.
This process occurs simultaneously throughout the entire volume of the adhesive, so after hardening the adhesive is one large polymer molecule. Epoxy resin in this case is the mass-forming component, and the hardener is the component that starts the polymerization process.
It is important to follow this rule: both components of the epoxy adhesive should not come into contact and mix with each other until the preparation of the composition, only immediately before gluing. This is because the curing process of the resin is irreversible.
The polymerization process can be accelerated by increasing the temperature. This can also be achievedincrease in hardener volume. The slow can be obtained by reverse actions.
Where applicable
The use of epoxy adhesive is due to the combination of its universal properties.
Used:
- In the mechanical engineering industries - in the production of abrasive tools, fastening of brake pads, in the manufacture of technological equipment or plastic parts to metal surfaces, during the repair of a car body or gas tank, trim, gearbox and other things.
- In construction - when connecting reinforced concrete structures of bridges, when soldering three-layer panels, for filling cracks in concrete, when gluing ceramic tiles, in the process of gluing concrete to metal.
- In everyday life, the epoxy composition is indispensable for repairing shoes, reconstructing small parts of furniture, sealing pipe joints, creating gift compositions (for example, Moment epoxy glue).
- In shipbuilding - in the assembly of fiberglass ships, the installation of high-load attachment points, the creation of watertight barriers, the processing of hulls of boats and yachts with fiberglass reinforcement.
- In aircraft design - when creating glue-welded joints in the process of assembling aircraft, in the manufacture of solar panels, fixing external and internal thermal protection.
Composition
Universal Epoxy Adhesive (EPA) is a thermosetting synthetic product formulated as a combination of an epoxy resin base and additional ingredients.
Additional elements of the composition are:
- Hardeners. These are: Lewis complexes with esters and amines, anhydrides of organic acids, polymer hardeners-modifiers (polyamides on fatty acids), di- and polyamines (organosilicon and pheno-formaldehyde resins, rubbers), aminoamides (dicyandiamide).
- Solvents - alcohols, xelol, acetone, other organic compounds. The mass of solvent should not exceed three to five percent of the volume of dry resin. Alcohols speed up the curing process of the universal epoxy adhesive.
- Fillers - synthetic or glass fiber fabrics, carbon and glass fibers, powdered substances (aluminum and nickel powder, silica, beryllium, zinc, vanadium or aluminum oxide, carbon black). The content of fillers as a percentage of the resin weight largely depends on the additive and can vary from 50 to 300%. Metal oxides act as stabilizers and hardeners for thermal oxidative degradation.
- Plasticizers. These are phthalic and phosphoric acids (their esters). More preferred is the use of oligomeric and polymeric plasticizers, oligoamides and oligosulfides. They regulate the physical and mechanical characteristics of the adhesive and increase the reliability of gluing parts.
Properties
As a result of combining the ingredients into one composition, an epoxy adhesive is obtained with the following characteristics:
- heat resistance - depending on the filler, the parameter can reach +250 °С;
- frost resistance - adhesivethe connection is able to withstand up to -20 ° C;
- good oil/petrol, weather tolerance;
- excellent resistance to degradation by chemicals and detergents;
- elasticity - after hardening, with slight shifts in the elements of the seam, there is no rupture;
- resistance to cracks and shrinkage;
- waterproof - the gluing point has waterproofing qualities;
- high adhesion to most materials, including cement, drywall and wood.
The disadvantages of two part epoxy adhesive are:
- quick curing composition - no time to correct mistakes;
- does not bond silicone, polyethylene, Teflon and some other materials;
- precautions required for operation.
Classification by composition and consistency
Adhesive on epoxy resin is divided into types according to the following criteria: composition, consistency, method of curing.
The composition of the adhesive is divided into:
- Two-component - Supplied as a set of two containers: one for paste resin, the other for powder or liquid hardener. The components are mixed with a special spatula immediately before use. Useable within two minutes.
- One-component - transparent epoxy adhesive containing an organic solvent with resin or one liquid resin. Sold ready to use. It is applied forconnecting small parts, sealing pipe joints and gaps.
There are two types of glue according to the consistency:
- Liquid - resembles a gel, convenient because it is well applied to the surfaces to be glued, does not need preparation.
- Plastic composition - similar to ordinary plasticine. Sold in cylindrical containers. Before use, it is required to cut off part of the mass, knead it and dilute it with water until a paste-like mixture is obtained.
Classification by curing method
According to the method of curing, epoxy adhesive (EDP) is subdivided depending on the hardener used:
- Requiring heat treatment - compositions containing liquid epoxy resin, fillers, plasticizers and aliphatic polyam harden within one to four days without heating at a temperature of about +20 ° C. But structural changes in such adhesives take a long time. To speed up the process and increase the strength of the connection, it is recommended to heat this composition.
- Unheated Epoxy Adhesive - These joints, cured without exposure to temperature, are resistant to chemical attack by acids and alkalis, but after a long stay in water (about three months), the strength of the joint decreases.
- Modified compositions - have a curing temperature ranging from +60 to 120 °C. Are applied to connection of nonmetallic details and metals. The compositions have a viscous structure, resistant to the effects of fuels and lubricants and solvents.
- Glueshot curing - especially strong compositions with a curing temperature of plus 140 to 300 ° C. They have improved electrical insulation qualities and heat resistance.
For home use
Modern industry produces several brands of glue for home use.
The most popular formulations are:
- Epoxy adhesive "Moment" - sold in all construction stores, has an affordable price for the general consumer. The glue is packaged in small tubes containing a plastic mass weighing 50 grams, or large packages designed for reusable use. The terms of use of the glue after opening are several months if stored at temperatures up to +25 ° С.
- Glue-plasticine "Contact" - used for gluing surfaces in contact with moisture - pipe joints, shelves in the bathroom. The glue hardening time is one to two minutes.
- Glue "Cold welding" - designed for instant connection of metal products. Does not damage the edges of metal parts, glues alloys that cannot be welded.
- EDP epoxy adhesive is designed to bond different surfaces - from metal to glass and porcelain. According to consumer reviews, it is considered optimal in terms of price-quality combination. It is used for repairing car parts, repairing cracks in plumbing and other purposes.
Epoxy glue: instructions for use
The whole process of using the adhesive composition can be described in three main stages: cleaning the surfaces to be glued, preparing the glue and directlybonding.
Processing of surfaces to be glued is carried out in the first place, since the strength of the connection depends on its quality. In addition, the glue after preparation must be applied quickly, there will be no time to bother with cleaning.
First, the surfaces are cleaned with fine sandpaper, then treated with a degreaser with any available agent, and then dried.
In manufacturing plants, parts are processed using shot, sand or ultrasound. The surfaces to be bonded are then etched in an acid bath and degreased with solvents.
The quality of the adhesive joint and its curing speed largely depend on how to dilute the epoxy adhesive.
Steps of preparing the adhesive composition:
- The epoxy is squeezed out of the tube into the mixing container.
- A few grams of hardener is added to it. The standard proportion is as follows: epoxy resin - 10 parts, hardener - 1 part. An overdose of hardener in the ratio (5:1) is allowed.
- Ingredients are carefully mixed by hand.
- The resulting solution is carefully applied to the surface of one part.
- The second part to be glued is firmly pressed against the first one at the place where the glue is applied and fixed for ten minutes.
- Then the product is left alone for several hours, during which the glue line will acquire the necessary strength.
Reviews
Most of those who have used glue say that they were satisfied with the result. Compoundit is durable and dries quickly.
Customer reviews urge to observe the proportions of epoxy glue indicated on the package when diluting. Otherwise, there is a risk that it will take longer than the calculated time to set.
Also, those who used such glue are advised to use rubber gloves - the glue is hard to wash off the skin of the hands, and then it remains very dry.
All consumers note that epoxy resin glue is indispensable in the household for repairing small parts, chips, and sealing seams. When applied correctly, the result is excellent.
Precautions
When using epoxy formulations, it is important to follow the precautions on the label exactly to avoid adverse effects.
They can be:
- Dust and harmful fumes - for protection, wear a protective charcoal mask and work in a well-ventilated area.
- Before diluting the epoxy, be sure to wear rubber gloves to protect your hands.
- Do not use utensils used for cooking as a container.
- Children must be kept out of work area.
- If product gets into eyes, seek medical attention immediately.
- If glue gets on the skin, wipe it with acetone and wash with soap.
Although epoxy resin adhesive is harmless once cured, it should not be used for gluing dinnerwarefood.
Before starting work, the place must be covered with a protective layer - paper or film, otherwise it will be difficult to clean off a drop of glue that accidentally got on the surface.
Helpful tips
If the glue or resin does not extrude well from the tube, it must be heated by placing it on a battery or placing it in hot water.
To extend the shelf life of the adhesive mass, the air is pumped out of the package and the tube is placed in a cold place, such as a refrigerator.
When adding dyes to the adhesive composition, it must be borne in mind that the strength of the product will be less. If oil paint is added, then the glue becomes plastic and not so hard.
Water must not get into the solution during the preparation of the glue.
If after two days the mass has not hardened, there are several reasons that need to be corrected:
- glue expired;
- it's too cold in the room;
- little hardener added.
You can check the quality characteristics of the prepared glue as follows: take a small amount into a metal spoon and heat it over a fire, avoiding boiling. If the glue has hardened after cooling, the proportions are chosen correctly, if not, you should add more hardener.
If all the necessary proportions and rules of application are observed, glue will be a good helper in the household.
