How to understand silicone sealants: professional advice

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Along with polyurethane foam, silicone sealants serve as a “magic wand” for insulating seams. Installation of windows, renovation of a bathroom – nowhere without sealing. We will tell you about the different types of silicone sealants and help you make the right choice..

How to understand silicone sealants

A story with chemistry: how a sealant works

Silicone sealants were invented in the 60s of the last century and since then have become an almost irreplaceable insulating material..

The production recipe is constantly being improved, new, highly specialized types of sealants appear, but the advantages remain unchanged:

  • excellent adhesion to most materials – including smooth surfaces: glass, ceramics, plastic;
  • stable water resistance;
  • elasticity – the dried composition can be stretched 4 times without breaking;
  • thermal and frost resistance (average temperature indicators – from -50 to +180 ° С);
  • resistance to aggressive environments and ultraviolet light (does not require additional processing like polyurethane foam, does not crumble or crack under the influence of the sun);
  • durability and reliability – does not deteriorate even with prolonged aggressive exposure.

How to understand silicone sealants

Silicone sealant is a mastic (viscous substance) that hardens when exposed to humid air or certain chemicals.

As the name implies, the main constituent of the sealant is silicone rubber – a compound derived from silicon-containing compounds.

Pure silicone is a very stable material that retains its properties for an unlimited period of time, even with large temperature differences. The adhesion of silicone rubber is rather low, therefore, special additives are used in the production of sealants:

  • enhancers of strength and adhesion to surfaces
  • vulcanizers that convert a viscous mass into a rubbery
  • fillers – organic and mechanical
  • plasticizers that increase elasticity
  • coloring pigments

How to understand silicone sealants

The use of various components depends on the intended use of the sealants.

Classification of silicone sealants

Just like polyurethane foam, silicone sealants can be one- and two-component:

Sealant One-component Two-component (silicone compound)
View Ready to use Mixing of components
Solidification method On contact with air Base reaction with catalyst – solidifies when two components are mixed
Curing diameter 2 to 15 mm In any volume
Applications Private and mass construction and renovation Industrial use

Two-component sealants are not found on hardware store shelves as they require a high level of craftsmanship. Their rare use has led to the fact that the term “silicone sealant” now means only one-component formulations.

The chemical formula of the sealant, or rather the solvent included in its composition, determines the features and possibilities of using the waterproofer:

Type of sealant Features: Applications disadvantages
Acidic (acetate) Pronounced vinegar smell (acetic acid is formed on contact with moisture), low cost. Indicated by the letter A on the packaging Non-oxidizable metals (stainless steel), glass, ceramics, wood Incompatible with alkaline materials, corrosive to metals
Neutral (alcoholic and oxime) Virtually no smell (there may be a faint smell of alcohol), indicated by the letter N on the package. Is universal Suitable for almost all materials without additional use of a primer About one and a half times more expensive than acid
Sanitary The presence of an antifungal organic component – fungicide, resistance to detergents Used in high humidity – bathrooms, swimming pools Reduced UV resistance (due to the addition of fungicide)

The ideal sealant is almost 100% silicone. But to reduce the cost of the final product, manufacturers have adapted to using various fillers – mechanical and organic, which significantly affects the elasticity and shrinkage. Determining the percentage of filler is quite simple – you need to weigh the tube with the sealant. A standard 310ml cartridge should weigh no more than 340g – provided it contains pure silicone. Fillers are usually much heavier – the weight of the cartridge can be up to 500 g.

Another trick is the addition of organic solvents. It will not be possible to determine their impurity by weight – the specific gravity is approximately equal to the mass of silicone. You can reveal the content of such a “addition” by applying a sealant to a plastic wrap. Pure silicone does not react with polyethylene, and organic solvent will immediately cause swelling and bubbles on the film.

How to understand silicone sealants

The most popular colors for silicone sealants are white and transparent. Keep in mind that it will not work to paint the general construction sealant – the paint will crack and crumble. Therefore, if it is necessary to seal colored surfaces, try to select the appropriate tone from the pigmented sealants.

Narrow profile sealants

The areas of application of general construction silicone sealants are practically unlimited, however, there are designs that require a special approach. For use in harsh conditions and on difficult surfaces, highly specialized sealants are used.

Name Purpose and features Applications
Aquarium Sealing small glass structures. Safe for fish and reptiles after hardening Assembly and repair of aquariums and terrariums
Window Sealing window and door openings. Mold and water resistant Treatment of external and internal seams on complex materials: PVC, plaster, polycarbonate
For fireplaces Fire resistant, smoke and gas tight sealing Installation and repair of stoves, fireplaces, grills, chimneys
For marble Sealing and joining of parts made of natural porous stone. Does not affect surface color Cladding of facades with marble and granite, finishing of kitchens and bathrooms
For acrylic baths Neutral sealant for use in high humidity areas. Excellent adhesion and resistance Sealing of sewerage systems, bathtubs, shower cabins, sinks

How to understand silicone sealants

They contain additional additives that are responsible for enhancing the necessary qualities. As a rule, the name can be used to determine the main scope of application of the sealant:

Brands and remarks: which manufacturer to trust

When choosing and buying silicone sealant, you should adhere to the rule: a high-quality product cannot be cheap. As mentioned above, unscrupulous manufacturers are cunning, offering a low price due to the same low quality. Of course, proven brands also have defective batches, but their share is extremely small.

Basically, low quality is provided initially – a large percentage of impurities proportionally worsens the quality of silicone: elasticity and strength decrease, resistance to aggressive influences decreases, color changes, curing is impaired.

How to understand silicone sealants

When choosing a quality product, you need to pay attention to the following factors:

  1. Manufacturer – there are quite a few proven brands: Macroflex, Soudal, Moment, Econ, Quadro.
  2. Original branded packaging with all information (quality indicators and composition).
  3. The seller has certified copies of certificates.

It is worthwhile to be wary of the product:

  1. With a large weight (over 340 grams with a volume of 310 ml).
  2. With the words “100% silicone” – no manufacturer uses pure silicone, without additives and plasticizers.
  3. With a very low price (the production technology is such that the cost of one tube of sealant costs about 70-90 rubles. Add to this amount the average trade margins of 20-50% – and you will see the real price of a quality product).
  4. With a shabby and even more so a paper label.

In the following articles, we will tell you about the closest brothers of the silicone family – acrylic and bituminous sealants, help you choose a high-quality sealant gun and teach you the wisdom of using it.

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