Silicone Sealants

The main useful properties that determine the use in construction and repair:

• Excellent water resistance
• Elasticity ( Elasticity )
• Good adhesion to most materials
• High heat and cold resistance (from −60 to +300 ° C) ^[1]
• Resistance to solar ultraviolet
• Resistance to aggressive environments
• Durability

First appeared in the 1960s.

There are two main groups of silicone sealants.

Single component formulations

These are customary store-type sealants in tubes, they are also found in “foil packs” (film tubes ) and in larger packaging. Cured by moisture in the air. The most common (according to the claims of builders, this is the largest field of application of silicones in the world ), but can only be completely hardened within a reasonable time in a thin layer from 2 mm to 10-12 mm. (some manufacturers give a strand diameter up to 15 mm).

As a rule, the term "silicone sealant" means exactly one-component compositions.

One-component silicone sealants are divided into 2 groups according to their chemical composition:

1. Acidic (from a chemical point of view - " acetoxy "). Smell of vinegar pretty much. Visibly cheaper than neutral. May cause corrosion (metals, cement-containing materials, etc.). The mechanism of polycondensation: the interaction of terminal hydroxyl groups of polydimethylsiloxane with a crosslinking vulcanizing agent (for example, methyltriacetoxysilane) in the presence of water, with the formation of a network structure and cleavage of acetic acid.
2. Neutral (Chemically, this is mainly " methoxy " or " alkoxy "). Smell weak. More expensive than acid.

By appointment silicone sealants are divided into construction , special and automotive , but this division is fuzzy and very conditional.

Most often on the packaging is written the main purpose of the sealant:

• "Automotive". “Automotive black”, “Automotive red” are the established Loctite types.
• "Sanitary". For bathrooms, showers, toilets. Most often contains a biocide that prevents the development of mold and fungi.
• "Aquarium" - especially for aquariums, terrariums, etc.
• "Universal"
• "Insulating" - for electrical engineering.
• "High-temperature" or "Heat-resistant" are NOT silicone, as the main component is sodium silicate (liquid glass)
• "Low modulus" - for interpanel seams. Maintains high deformation .
• and etc.

Bicomponent Formulations

The so-called "silicone compounds" such as TF-1, Vixint, Pentelast, Elastosil. The “base” solidifies by reacting with the “catalyst” when mixed. Can harden in any volume. Distributed significantly less one-component sealants, as they are mainly used for industrial solutions.

Exterior Works

• sealing during minor roofing work;
• sealing of drainpipes;
• sealing glass structures and structural elements in winter gardens;
• sticking of detached stone tiles;
• sealing during minor roofing work around the chimney;
• sealing of vinyl liner joints;
• sealing window frames and boxes.

Works inside the house

• making seams around stone window sills;
• sealing joints of gypsum boards to the ceiling;
• sealing elements heated to a high temperature.

Works in high humidity rooms

• sealing the junction of showers and walls;
• sealing of connections in sewer and water networks;
• gluing mirrors;
• sealing joints of washbasins to walls;
• sealing joining of sanitary equipment.

There are a lot of low-quality silicone sealants on the market. Of course, all manufacturers of high-quality silicone sealants may have defective batches, but in the total quantity produced their share is small. In most cases, poor quality is inherent in the sealant initially - as a rule, this is a consequence of the cheapening of the composition by diluting it with some cheap organic matter (oil, kerosene, etc.). The phrase "100% silicone" may well appear on the packaging. With dilution and reduction in the proportion of silicone rubber, the sealant loses the intrinsic properties of silicone. Elasticity ( elasticity ) and mechanical strength decrease, resistance to high and low temperatures, ultraviolet, water deteriorates, shrinkage, changes in shape and color (turns yellow, darkens), durability decreases.

There is a lack of curing, when, after any period of time, the sealant is “smeared”. This is the norm for glass sealants, since glass inevitably “walks” in the frame or in the car, but is unacceptable for other applications.

It may seem that silicone sealants are a universal remedy with unlimited possibilities. However, they have certain disadvantages:

• Most sealants should not be applied on wet surfaces.
• High-quality (not diluted with a large number of organics) silicone sealants can not be painted with conventional dyes.
• A bottleneck for silicone sealants are plastics ( polyethylene , polypropylene , PVC , polycarbonate , fluoroplastic ), to which adhesion is not enough. Often, the problem is solved by choosing an expensive professional silicone sealant or using special “ undercoats ” (“primers”) that enhance adhesion before applying sealant.