Rubber-based sealants: types and applications / Articles

Rubber-based sealants are a class of elastic sealing materials whose polymer base consists of natural or synthetic rubbers. These materials are designed to fill joints, seams and connections to ensure their impermeability to gases, liquids and vapours, as well as to protect structures from environmental exposure. Sealants are widely used in construction, mechanical engineering, automotive, aviation, electrical engineering and shipbuilding.

Classification of Rubber-Based Sealants

By curing mechanism, rubber sealants are divided into two main groups: curing (vulcanising) and non-curing.

Non-curing sealants are thermoplastic materials that remain in a plastic or plastoelastic state during operation. They soften when heated and return to their original state when cooled. Such sealants are used for sealing detachable joints and joints subject to periodic dismantling. For their manufacture, high-molecular-weight rubbers with low unsaturation or fully saturated ones are used — polyisobutylene, butyl rubber, ethylene-propylene. These rubbers in the unvulcanised state are characterised by high resistance to oxygen, ozone, acids, alkalis and oxidising agents, as well as high dielectric properties and gas impermeability.

Curing sealants are materials that, after application to the sealing surface, undergo chemical changes, forming a strong elastic layer. Curing can occur under the action of atmospheric moisture, catalysts or heating. This group includes sealants based on silicone, polyurethane, polysulfide and fluorine-containing rubbers.

Main Types of Rubbers for Sealants

Butyl rubber sealants. Butyl rubber is a copolymer of isobutylene (98%) and isoprene (2%). Sealants based on it possess low vapour permeability, low gas permeability and thermal conductivity, good elasticity and resistance to UV radiation. They are actively used in the production of insulating glass, for sealing gaps, seams and joints in metal, wooden and glass structures.

Silicone sealants. The base is a low-molecular-weight polyorganosiloxane rubber with terminal hydroxyl groups. Silicone sealants possess high heat and frost resistance (from -60 to +300 °C), resistance to UV radiation and atmospheric precipitation. By type of vulcanisation, they are divided into acidic and neutral. They are used for sealing joints in ceramic materials, glass and some metals.

Polyurethane sealants. One-component polyurethane sealants are elastic sealing materials based on polyester resins. The curing process occurs through interaction with atmospheric moisture. The material operates in the temperature range from -40 to +80 °C, possesses water resistance, good adhesion and corrosion resistance. They are used for sealing inter-panel joints of building structures with surfaces of concrete, metal, wood or PVC, as well as for fixing thermal insulation panels.

Polysulfide (thiokol) sealants. The base is liquid polysulfide rubbers. These sealants possess high resistance to solvents, oils and fuels, as well as good adhesion to metals and concrete. They are used in aviation, shipbuilding and construction. The brittle point of polysulfide sealants is about -42 °C, tensile strength — 1.5–4.0 MPa.

Fluorine-containing sealants. They possess the highest chemical and heat resistance among rubber sealants. Tensile strength is 7.0–14.0 MPa. They are used in critical components of aviation and chemical industries.

Properties of Rubber-Based Sealants

Rubber sealants are characterised by a complex of valuable properties:

Elasticity — the ability to deform without failure under tension and compression. Elongation at break for various types ranges from 150% to 700%.
Adhesion — the ability to firmly bond to various materials: concrete, metal, glass, wood, PVC.
Temperature range — operating temperatures depend on the type of rubber and range from -60 to +100 °C for most grades.
Weather resistance — resistance to UV radiation, moisture, ozone and temperature fluctuations.
Chemical resistance — resistance to weak solutions of salts, acids and alkalis (up to 10%).
Gas impermeability — low permeability to gases and vapours, especially for butyl rubber sealants.

Regulatory Framework

In Russia and CIS countries, requirements for rubber sealants are regulated by the following standards:

GOST 14791-79 — non-curing construction sealing mastic. The standard applies to non-curing sealing mastic made on the basis of polyisobutylene, ethylene-propylene, isoprene and butyl rubbers, fillers and plasticisers.
ASTM C920 — international standard for elastomeric joint sealants. Classifies sealants by type (S — single-component, M — multicomponent), by grade (P — self-levelling, NS — non-sag), by class of movement (100/50, 50, 35, 25, 12.5) and by use (T — traffic, NT — non-traffic, I — interior, M — masonry, G — glazing, A — asphalt, O — other).

Applications

Construction. Sealants are used for sealing inter-panel joints, joints of prefabricated building structures, waterproofing of internal and external surfaces of concrete and reinforced concrete structures, and corrosion protection. Butyl rubber sealants are widely used in the production of insulating glass and for sealing gaps in metal, wooden and glass structures.

Automotive industry. Rubber-based sealants are used for sealing welded seams, joints of parts, as well as for bonding glass and sealing joints between body parts. Polyurethane sealants are used for fixing thermal insulation panels and in components requiring high strength and elasticity.

Aviation and shipbuilding. Polysulfide and fluorine-containing sealants are used for sealing fuel tanks, cabins and other critical components where high chemical and heat resistance is required.

Electrical engineering and instrumentation. Rubber sealants are used for sealing electronic components, cable entries and connectors due to their high dielectric properties.

Global Market

The global butyl rubber sealants market was valued at USD 8.54 billion in 2024. It is projected to grow to USD 9.02 billion in 2025 and to USD 12.59 billion by 2031 at a CAGR of 5.8%.

The broader elastomeric sealants market was valued at USD 5.32 billion in 2024, with a projected growth to USD 9.53 billion by 2033 (CAGR 6.8%).

Key market growth drivers are the expansion of the construction industry, growth in automotive production and increasing demand for energy-efficient buildings. The main challenges are related to feedstock price volatility (isobutylene and isoprene) and tightening environmental regulation of volatile organic compound emissions.

The largest manufacturers of rubber sealants are 3M, ExxonMobil, Henkel, Sika, as well as Russian enterprises producing butyl rubber sealants according to GOST 14791-79.

Conclusion

Rubber-based sealants represent an important class of elastic sealing materials combining high elasticity, adhesion, weather resistance and chemical resistance. Butyl rubber, silicone, polyurethane, polysulfide and fluorine-containing sealants find application in construction, automotive, aviation, shipbuilding and electrical engineering. The development of the regulatory framework and the growth of the elastomeric sealants market determine sustainable prospects for this industry in the long term.