ADHESIVES, GLUES AND SEALANTS


Epoxy adhesives and glue - definition and properties of epoxy

What is an epoxy adhesive?

Did you know that the helicopter blades are bonded by epoxy adhesives?, Thanks to the high strength and performance offered by these kind of adhesives, probably many objects around you are bonded with epoxy glue.

Epoxy adhesives are those glues whose base polymer is formed by the chemical group known as epoxy, epoxy glues are also known as rigid adhesives or rigid glues, due they possess a high strength or load resistance, about 30 MPa to shear stresses, and very little elongation, over 10% before fracture, these properties are due to the structure of thermoset polymers which adopt the adhesive once it is cured.

Epoxy adhesives are classified into 2 groups:

2 component epoxy adhesives.

Note - All information described about 2-component epoxy adhesives makes reference to the basic principles. For each adhesive the valid information is contained in the technical data sheet do it by the manufacturers, due that the formulation of the adhesive changes its properties.

Basic components of adhesives epoxy 2C and polyreaction.

Resin - diepoxide or polyepoxide - Component A

Hardener - Polyamines or mercaptans - Component B

The type of curing or polyreaction that takes place in the 2-component epoxy adhesive is polyaddition.

Considerations of epoxy 2 components

Curing time varies from few hours to several days, curing can be accelerated by the addition or increasing temperature, producing an effect of increasing the degree of crosslinking takes place an increase of the resistance to stress or loads.

Keep in mind the pot-life, due that it is a 2-component adhesive, after mixing , it begins to occur curing chemical reactions, the pot-life varies with the temperature of use, an increase in temperature acts as an accelerator of chemical crosslinking reaction by reducing the pot life of the adhesive.

It is very sensitive to the mixing errors; it usually that this kind of adhesive or glue, comes in a cartridge with the two components, which are mixed in proper proportion in order to avoid mistakes.

Typical properties of epoxy 2 components.

Mechanical properties:

Chemical properties:

1 component epoxy adhesives.

Note - All information described on 1-component epoxy adhesives are referenced to the basic principles. For each adhesive the valid information is contained in the technical data sheet do it by the manufacturers, due that the formulation of the adhesive changes its properties.

Basic components of adhesives epoxy 1C and polyreaction.

Resin - diepoxide or polyepoxide.

Hardener - Polyamines, mercaptans, phenolic resins...

The type of curing or polyreaction that takes place in the 1 component epoxy adhesive is polyaddition.

Considerations of epoxy 1 component

1 component epoxy adhesive requires heat input in order to activate the hardener, starting the process of crosslinking and curing.

As this type of glue is 1 component, it has not pot life, the adhesive is applied on the substrate and then the temperature is applied to unlock and activate the hardener to react with the resin in order to produce the polymer.

Some epoxy adhesives 1 component has the ability to absorb oils, not being needed cleaning pretreatment of oils.

Typical properties of epoxy adhesives 1 component

Mechanical properties

Chemical properties

Applications and examples of the epoxy adhesive

Epoxy adhesives 2 component and 1 component are used in all the joints that require high strength or load resistance due to its high resistance to fracture presented by these kind of adhesives.

The main advantage of the 1 component epoxy adhesive with respect to the 2 component epoxy adhesive is the fast rate of cure and its superior resistance against the loads or efforts, because the heat input energy source that we need to apply, create a highly crosslinked structure in a short space of time.

epoxy adhesive applications

Epoxy adhesives are used in a wide branch of industry sectors, from manufacturing of structures in the aviation industry to the manufacture of hangers, sleeves for tools, fiber reinforced plastics, binding of the blades of wind turbines, etc ...

Depending on the fillers that contains, epoxy adhesive is also used as electrical conductors applied in microelectronics, as well as the thermal conductors.

Finally and for you calm whenever "get on a helicopter," I will say that the average resistance of epoxy adhesives are 30MPa, ie a drop of only 1cm x 1cm of epoxy adhesive is capable of lifting 300 kg of steel.


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