Classification of sealants, complete types of industrial sealants

There are many varieties and types of sealants. In order to meet the same usage requirements, several sealants with different base materials can be used; and the same base material can produce sealants with different properties and different uses. There are many ways to classify sealants from the perspective of both the manufacturer and the user of the sealant. Generally, it can be classified according to the following four methods.

1. Classification by sealant base material

1. Rubber type

This type of sealant is rubber-based. Commonly used rubbers include polysulfide rubber, silicone rubber, polyurethane rubber, neoprene rubber and butyl rubber.

2. Resin type

This type of sealant is resin-based. Commonly used resins include epoxy resin, unsaturated polyester resin, phenolic resin, polyacrylic resin, polyvinyl chloride resin, etc.

3. Oil-based type

This type of sealant is oil-based. Commonly used oils include various vegetable oils such as linseed oil, castor oil and tung oil, as well as animal oils (such as fish oil).

2. Classification according to sealant vulcanization method

1. This type of sealant series uses moisture in the air to vulcanize. It mainly includes single-component polyurethane, silicone rubber and polysulfide rubber. The polymer base material contains active genes, which can react with water in the air to form cross-linking bonds and vulcanize the sealant into a network structure. Moisture in the atmosphere acts as a catalyst in the vulcanization reaction.

2. Chemical vulcanization sealant

Two-component polyurethane, silicone rubber, polysulfide rubber, neoprene rubber and epoxy resin sealants all fall into this category and are generally vulcanized at room temperature. Some single-component chlorosulfonated polyethylene and neoprene rubber sealants and polyvinyl chloride sol paste sealants (such as spot welding glue for automobiles) must be vulcanized through chemical reaction under added conditions.

3. Thermal transformation sealant

Sealants using plasticizer-dispersed polyvinyl chloride resin and asphalt-containing rubber are two different types of thermal transition systems. Vinyl resin plasticizer is a liquid suspension at room temperature and is converted into a solid by heating and hardened; while the rubber-asphalt combined sealant is hot-melt.

4. Oxidation hardening sealant

Surface-dry caulking or glazing sealants are of this type, mainly based on dry and semi-drying vegetable oils. Medium oils can be refined polymerized, blown or chemically modified. Use cobalt naphthenate as a drier to accelerate surface drying without hardening the interior; lead naphthenate can harden both the surface and the interior; and manganese naphthenate can make the interior hardening more effective.

5. Solvent evaporation solidifying sealant

This is a sealant based on a non-sticky polymer after the solvent evaporates. This type of sealant mainly includes butyl rubber, high molecular weight polyisobutylene, acrylates with a certain degree of polymerization, chlorosulfonated polyethylene and neoprene rubber.

6. Non-drying and permanent plastic sealant

Such sealants usually include polybutylene, medium molecular weight polyisobutylene, high viscosity non-oxidizing adhesives such as styrene-based oils, non-drying vegetable oils, blown semi-drying oils or butyl rubber as base materials of sealant.

3. Classification by sealant form

1. Paste sealant

This type of sealant is a low-level sealant and usually uses three main materials: oil and resin; polybutylene; and asphalt. Fixed glass often used to seal small windows. The maximum joint movement deformation is +5% or -5%, and the validity period is generally 2 years.

2. Liquid elastomer sealant

This type of sealant consists of a liquid polymer that cures to an elastic state. They have the ability to withstand repeated joint deformation. The service life of liquid elastomer sealants is generally 15 to 20 years. This type of sealant has high adhesion and shear strength and good flexibility at room temperature. Its disadvantages are high price, usually requiring primer, inconvenient on-site mixing of two-component sealants, and sensitivity to temperature and humidity during vulcanization.

3. Hot melt sealant

Hot melt sealant, also known as hot construction sealant, refers to a sealant based on a blend of elastomer and thermoplastic resin. Hot melt sealant can be formulated to have properties close to those of liquid elastomer sealants, but its advantage over liquid elastomer sealants is that it does not require the addition of vulcanizing agents.

4. Liquid sealant

This type of sealant is mainly used for sealing mechanical joint surfaces to replace solid sealing materials (paper, asbestos, cork and vulcanized rubber) to prevent the internal fluid of the machine from leaking from the joint surfaces, so liquid sealants are also called liquid gaskets.

4. Classification according to the performance of sealants after construction

1. Curing sealant

This type of sealant can be divided into two categories: rigid and flexible. Rigid sealants are solids formed after vulcanization or solidification and are rarely elastic; flexible sealants are elastic and soft after vulcanization. Rigid sealants are characterized by their inability to bend and usually the joints are not removable. Flexible sealants remain soft after curing.

2. Non-curing sealant

This type of sealant is a soft solidifying sealant that remains non-drying (tackifier continues to migrate to the surface) after application. This glue is usually in paste form and can be applied to the joints with a scraper or brush. It can be used with sealants of different viscosities and properties.

3. Types of commonly used sealants

Various methods were listed in the previous classification of sealants, the most widely used of which is to divide sealants into two categories: vulcanized and non-vulcanized. Among the vulcanized sealants, the most widely used is the room temperature vulcanization type, while the heating vulcanization type is used less frequently. Non-vulcanized sealants include liquid sealant and putty. In addition, commonly used anaerobic adhesives are added.

4. Selection and construction technology of liquid sealant

The selection of sealant should be comprehensively considered based on the conditions of use, the material and sealing surface condition of the seal, the type and characteristics of the sealing medium, and the coating process. Under normal circumstances, when the force is large, and when it is subjected to impact force and alternating force, a sealant with higher strength should be selected; when the temperature difference is large, a sealant with good toughness should be selected.

5. Construction method of liquid sealant

The construction method of liquid sealant can be selected according to the state of the glue. The paste seal can be applied with a scraper or injected with an injection gun; the liquid sealant can be applied with a brush or sprayed; and the film sealant can be applied by paving.

5. Domestic sealant

1. Room temperature vulcanized polysulfide rubber sealant is a multi-component material that is vulcanized into elastomer at room temperature. It is a dry adhesive sealant. The commonly used ones are HBC series sealants.

2. Room temperature vulcanized silicone rubber sealant

Silicone rubber sealant has a variety of special properties, such as high temperature resistance, low temperature resistance, and good electrical insulation properties.

3. Anaerobic adhesive

4. Other vulcanized sealants

5. Non-vulcanized sealant

Most of the non-vulcanized sealants are non-drying and semi-drying, among which the putty-like ones are also called non-vulcanized putty. This type of glue has low temperature sensitivity. The sealant does not deform, crack, or skin within the operating temperature range. It has good long-term storage properties, but has low mechanical properties. It is suitable for sealing of detachable parts or fastened joint surfaces. Groove sealing and filling of large structural gaps play an important role in liquid gaskets and are widely used in sealing removable parts.