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Classification of sealants
by：Kastar
2021-03-23
There are many varieties and types of sealants. Generally can be classified according to the following four methods.
One, according to the sealant base material classification.
1. Rubber type
This type of sealant is based on rubber. Commonly used rubbers are polysulfide rubber, silicone rubber, polyurethane rubber, neoprene rubber, and butyl rubber.
2. Resin type
This type of sealant is based on resin. Commonly used resins are epoxy resin, unsaturated polyester resin, phenolic resin, polyacrylic resin, polyvinyl chloride resin, etc.
3. Oil-based
This type of sealant is based on oil. Commonly used oils include various vegetable oils such as linseed oil, castor oil, tung oil, and animal oils (such as fish oil).
Second, according to the classification of sealant vulcanization methods.
1. This type of sealant series uses moisture in the air for vulcanization. It mainly includes one-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-linked bonds and vulcanize the sealant into a network structure. The moisture in the atmosphere acts as a catalyst in the sulfidation reaction.
2. Chemical vulcanized sealant
Two-component polyurethane, silicone rubber, polysulfide rubber, chloroprene rubber, and epoxy resin sealants all fall into this category and are generally cured at room temperature. Specific one-component chlorosulfonated polyethylene and neoprene rubber sealants and polyvinyl chloride sol paste sealants (such as spot welding glue for automobiles) must be vulcanized by chemical reaction under additional conditions.
3. Thermal transition type sealant
The plasticizer-dispersed polyvinyl chloride resin and the asphalt-containing rubber used together are two different thermal conversion systems. The vinyl resin plasticizer is a liquid suspension at room temperature, converted into a solid by heating to hardening, while the rubber-asphalt combined sealant is hot-melt.
4. Oxidation hardening sealant
Sealant for caulking or installing glass with dry surface belongs to this type, mainly based on dry and semi-dry vegetable oil. The intermediate oils can be refined, polymerized, blown, or chemically modified. Cobalt naphthenate is used as a drier to accelerate the surface drying without hardening the inside; lead naphthenate can harden both the surface and the interior, and manganese naphthenate makes the internal hardening more effective.
5. Solvent evaporating solidified sealant
This is a sealant based on non-sticky polymers after the solvent evaporates. This type of glue mainly includes butyl rubber, high molecular weight polyisobutylene, acrylate with a certain degree of polymerization, chlorosulfonated polyethylene, and neoprene.
6. Non-drying, permanent plastic sealant
This type of sealant usually includes polybutene, medium molecular weight polyisobutylene, high-viscosity non-oxidizing adhesives such as styrene-based oil, non-drying vegetable oil, blown semi-drying oil, or butyl rubber as the base material Sealant.
Three, according to the form of sealant classification.
1. Paste sealant
This type of sealant is a low-grade sealant, usually using three primary materials: oil and resin, polybutene, asphalt. The fixed glass commonly used to seal small windows has a maximum seam deformation of +5% or -5%, and the validity period is generally two years.
2. Liquid elastomer sealant
This type of sealant includes liquid polymers that can be vulcanized to form an elastic state. They can withstand repeated seam deformations. The service life of liquid elastomer sealant is generally 15 to 20 years. This type of bond has high adhesion and shear strength and has good flexibility at room temperature. Its disadvantage is the high price; under normal circumstances, a primer is needed. The two-component sealant is inconvenient to mix on-site, and it is sensitive to temperature and humidity during vulcanization.
3. Hot melt sealant
Hot melt sealant, also known as hot construction sealant, refers to a bond based on a blend of elastomer and thermoplastic resin. Hot melt sealant can be formulated into performance close to the liquid elastic sealant. Still, it is superior to liquid elastomer sealant in that it does not need to add a vulcanizing agent.
4. Liquid sealant
This type of sealant is mainly used to seal the mechanical joint surface to replace solid sealing materials (paper, asbestos, cork, and vulcanized rubber) to prevent the machine's internal fluid from leaking from the collective body, so liquid sealants are also called liquid gaskets.
Fourth, according to the performance classification of the sealant after construction.
1. Curing sealant
This type of sealant can be divided into rigid and flexible categories. The solid formed after vulcanization or solidification of tough adhesive rarely has elasticity; flexible sealant has elasticity and softness after vulcanization. The characteristic of rigid glue is that it cannot be bent, and the seam is usually immovable. The flexible sealant remains soft after vulcanization.
2. Non-curing sealant
This type of sealant is a soft coagulation sealant, and it remains non-drying (the tackifier continuously migrates to the surface) after construction. This glue is usually in the form of a paste and can be applied to the joints with a spatula or brush. It can be used with sealants of different viscosities and different properties.
3. Types of commonly used sealants
There are many methods listed in the previous classification of sealants. Among them, the most widely used is to divide sealants into two categories: vulcanized and non-vulcanized. The most commonly used vulcanized adhesive is the room temperature vulcanization type, and the heated vulcanization type is rarely used. The non-vulcanized bond includes liquid sealant and putty. Also, the commonly used anaerobic glue is added.
4. Selection and construction technology of liquid sealant
The selection of glue should be comprehensively considered according to the conditions of use, the seal's material and the state of the sealing surface, the type and characteristics of the sealing medium, and the coating process. When the force is large and subjected to impact and alternating points under normal circumstances, a sealant with higher strength should be selected; when the temperature difference is significant, a bond with good toughness should be chosen.
5. Construction method of liquid sealant
The construction method of liquid sealant can be selected according to the state of the glue. Paste seal can be applied by scraping or injection gun; liquid adhesive can be applied by brushing or spraying; film sealant can be used by paving method.
Five, domestic sealant
1. Room temperature vulcanized polysulfide rubber sealant is a multi-component material vulcanized into an elastomer at room temperature. It is a dry adhesive sealant, and HBC series sealants are commonly used.
2. Room temperature vulcanized silicone rubber sealant
Silicone rubber sealant has various unique properties, such as high-temperature resistance, low-temperature resistance, and good electrical insulation properties.
3. Anaerobic glue
4. Other vulcanized sealants
5. Non-vulcanized sealant
Most non-vulcanized sealants are non-drying and semi-drying, and the putty-like ones are also called non-vulcanized putty. This type of glue is not sensitive to temperature, and the bond will not deform, crack, or crust within the use temperature range, and has good long-term storage, but it has low mechanical properties. It is suitable for sealing detachable parts or fastening joints. Groove seals and fills up large structural gaps. It occupies a significant position in liquid gaskets and is widely used in the sealing of detachable parts.
One, according to the sealant base material classification.
1. Rubber type
This type of sealant is based on rubber. Commonly used rubbers are polysulfide rubber, silicone rubber, polyurethane rubber, neoprene rubber, and butyl rubber.
2. Resin type
This type of sealant is based on resin. Commonly used resins are epoxy resin, unsaturated polyester resin, phenolic resin, polyacrylic resin, polyvinyl chloride resin, etc.
3. Oil-based
This type of sealant is based on oil. Commonly used oils include various vegetable oils such as linseed oil, castor oil, tung oil, and animal oils (such as fish oil).
Second, according to the classification of sealant vulcanization methods.
1. This type of sealant series uses moisture in the air for vulcanization. It mainly includes one-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-linked bonds and vulcanize the sealant into a network structure. The moisture in the atmosphere acts as a catalyst in the sulfidation reaction.
2. Chemical vulcanized sealant
Two-component polyurethane, silicone rubber, polysulfide rubber, chloroprene rubber, and epoxy resin sealants all fall into this category and are generally cured at room temperature. Specific one-component chlorosulfonated polyethylene and neoprene rubber sealants and polyvinyl chloride sol paste sealants (such as spot welding glue for automobiles) must be vulcanized by chemical reaction under additional conditions.
3. Thermal transition type sealant
The plasticizer-dispersed polyvinyl chloride resin and the asphalt-containing rubber used together are two different thermal conversion systems. The vinyl resin plasticizer is a liquid suspension at room temperature, converted into a solid by heating to hardening, while the rubber-asphalt combined sealant is hot-melt.
4. Oxidation hardening sealant
Sealant for caulking or installing glass with dry surface belongs to this type, mainly based on dry and semi-dry vegetable oil. The intermediate oils can be refined, polymerized, blown, or chemically modified. Cobalt naphthenate is used as a drier to accelerate the surface drying without hardening the inside; lead naphthenate can harden both the surface and the interior, and manganese naphthenate makes the internal hardening more effective.
5. Solvent evaporating solidified sealant
This is a sealant based on non-sticky polymers after the solvent evaporates. This type of glue mainly includes butyl rubber, high molecular weight polyisobutylene, acrylate with a certain degree of polymerization, chlorosulfonated polyethylene, and neoprene.
6. Non-drying, permanent plastic sealant
This type of sealant usually includes polybutene, medium molecular weight polyisobutylene, high-viscosity non-oxidizing adhesives such as styrene-based oil, non-drying vegetable oil, blown semi-drying oil, or butyl rubber as the base material Sealant.
Three, according to the form of sealant classification.
1. Paste sealant
This type of sealant is a low-grade sealant, usually using three primary materials: oil and resin, polybutene, asphalt. The fixed glass commonly used to seal small windows has a maximum seam deformation of +5% or -5%, and the validity period is generally two years.
2. Liquid elastomer sealant
This type of sealant includes liquid polymers that can be vulcanized to form an elastic state. They can withstand repeated seam deformations. The service life of liquid elastomer sealant is generally 15 to 20 years. This type of bond has high adhesion and shear strength and has good flexibility at room temperature. Its disadvantage is the high price; under normal circumstances, a primer is needed. The two-component sealant is inconvenient to mix on-site, and it is sensitive to temperature and humidity during vulcanization.
3. Hot melt sealant
Hot melt sealant, also known as hot construction sealant, refers to a bond based on a blend of elastomer and thermoplastic resin. Hot melt sealant can be formulated into performance close to the liquid elastic sealant. Still, it is superior to liquid elastomer sealant in that it does not need to add a vulcanizing agent.
4. Liquid sealant
This type of sealant is mainly used to seal the mechanical joint surface to replace solid sealing materials (paper, asbestos, cork, and vulcanized rubber) to prevent the machine's internal fluid from leaking from the collective body, so liquid sealants are also called liquid gaskets.
Fourth, according to the performance classification of the sealant after construction.
1. Curing sealant
This type of sealant can be divided into rigid and flexible categories. The solid formed after vulcanization or solidification of tough adhesive rarely has elasticity; flexible sealant has elasticity and softness after vulcanization. The characteristic of rigid glue is that it cannot be bent, and the seam is usually immovable. The flexible sealant remains soft after vulcanization.
2. Non-curing sealant
This type of sealant is a soft coagulation sealant, and it remains non-drying (the tackifier continuously migrates to the surface) after construction. This glue is usually in the form of a paste and can be applied to the joints with a spatula or brush. It can be used with sealants of different viscosities and different properties.
3. Types of commonly used sealants
There are many methods listed in the previous classification of sealants. Among them, the most widely used is to divide sealants into two categories: vulcanized and non-vulcanized. The most commonly used vulcanized adhesive is the room temperature vulcanization type, and the heated vulcanization type is rarely used. The non-vulcanized bond includes liquid sealant and putty. Also, the commonly used anaerobic glue is added.
4. Selection and construction technology of liquid sealant
The selection of glue should be comprehensively considered according to the conditions of use, the seal's material and the state of the sealing surface, the type and characteristics of the sealing medium, and the coating process. When the force is large and subjected to impact and alternating points under normal circumstances, a sealant with higher strength should be selected; when the temperature difference is significant, a bond with good toughness should be chosen.
5. Construction method of liquid sealant
The construction method of liquid sealant can be selected according to the state of the glue. Paste seal can be applied by scraping or injection gun; liquid adhesive can be applied by brushing or spraying; film sealant can be used by paving method.
Five, domestic sealant
1. Room temperature vulcanized polysulfide rubber sealant is a multi-component material vulcanized into an elastomer at room temperature. It is a dry adhesive sealant, and HBC series sealants are commonly used.
2. Room temperature vulcanized silicone rubber sealant
Silicone rubber sealant has various unique properties, such as high-temperature resistance, low-temperature resistance, and good electrical insulation properties.
3. Anaerobic glue
4. Other vulcanized sealants
5. Non-vulcanized sealant
Most non-vulcanized sealants are non-drying and semi-drying, and the putty-like ones are also called non-vulcanized putty. This type of glue is not sensitive to temperature, and the bond will not deform, crack, or crust within the use temperature range, and has good long-term storage, but it has low mechanical properties. It is suitable for sealing detachable parts or fastening joints. Groove seals and fills up large structural gaps. It occupies a significant position in liquid gaskets and is widely used in the sealing of detachable parts.
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