How to understand silicone sealants: professional advice

Recommendation points

• A story with chemistry: how a sealant works
• Classification of silicone sealants
• Narrow profile sealants
• Brands and remarks: which manufacturer to trust

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..

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.

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

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.

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

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.

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.