ADHESIVES, GLUES AND SEALANTS


Silicones, adhesives and sealants based silicones.

Do you know that the aquarium, hob, shower screen and even the light bulbs in your house are connected and / or sealed by silicone adhesives?. Thanks to the silicones adhesives we can bond differents materials that require a high temperature resistance and high resistance to microbiological agents.

It was in the 1940s when the chemist Frederick Kipping achieved to synthesize in the laboratory the first silicone compounds, baptizing them with the name of silicones, so F.Kipping is considered the father of silicones.

Silicones are considered as hybrid adhesives, due that the polymer backbone is inorganic and also has an organic secondary structure, that is why their mechanical and chemical properties are halfway between inorganic and organic adhesives, resulting an elastomeric material with a high temperature resistance and high elongation capacity (elasticity).

On the other hand we can classify the wide range of silicone based adhesives depending on the type of polyreaction that occurs during their curing process:

The formation of the adhesive (polymer) is produced by chemical polycondensation with ambient moisture, due it cure by polycondensation that type of reaction emitted volatiles compounds during it curing process, which it depends on the reactant monomers that contain the adhesive, so we can find :

Due this type of adhesive its one component we must take into account about skin formation time, this time varies slightly depending on the internal composition of the adhesive, so we find silicones having a skin formation time of about 5 minutes or 30 minutes. It is important to check that value by product data sheets.

Silicones adhesives 2-component (polycondensation)

This type of adhesives are supplied in 2 separate cartridges which have to be homogeneously mixed in order to activate and accelerate the curing process, these adhesives emit alcoholsduring the curing process due to the polycondensation reaction that occurs internally.

Like all 2-component adhesives we need to mix the components with the proper ratio recommended by the manufacturer, as well as consider the pot-life. This kind of adhesive is used when bonded joints require thicknesses greater than 6 mm, allowing fast and homogeneous curing throughout the thickness of the bead of silicone.

Silicones adhesive temperature curing 1 component (polyaddition)

These silicones require energy input in the form of heat in order to activate and produce the curing, unlike the moisture-curing silicones which are formed by polycondensation, these silicones cured by polyaddition process not emitting any kind of volatile compound to the environment.

Due the need of temperature the substrates bonded using these adhesives must be able to withstand the temperature of activation and curing within a range between 100 and 150 ° C, so these types of adhesives are restricted to the use of joints plastics, wood, painted surfaces...

One of the main features of these silicones is their short cure time, obtaining cured between 10 seconds to 1 hour, depending on the thickness applied, on the other hand should be noted that the adhesion comprises a lower range compared with other silicones based adhesives.

Silicone adhesive 2 components (polyaddition)

2 components silicones are whose curing is produced by polyaddition chemical reactions, preventing the emission of volatile compounds into the environment. Like all 2-component adhesives we need to mix the components with the proper ratio recommended by the manufacturer, as well as consider the pot-life or pot life.

Silicones based adhesives properties

Applications of silicones

As a consequence of the properties described above, silicones are used in bonded joints where it requirehigh temperature resistance as sealing of lighting, stoves, insulation of electrical and electronic materials that reach high temperatures, barbecues ...

Due to its high chemical stability against external agents such as oxygen, UV light and ozone silicones are used for joints and sealed glass in windows, doors, solar panels ...

Silicones are incompatible with microbiological growth, so they are very often used as sealing materials in showers, toilets, kitchens, etc ...

Now that you know what are silicones, did you know that currently the research centers are working with silicone materials that enable the transmission of information at breakneck speeds?, In short, thanks to the silicones internet surfing will be instant.


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