What is sealant?
Sealant refers to a sealing material that deforms with the shape of the sealing surface, is not easy to flow, and has a certain adhesiveness. It is an adhesive used to fill configuration gaps for sealing. It has the functions of anti-leakage, waterproof, anti-vibration, sound insulation and heat insulation.
Classification of sealants
One. Classification by sealant base material
Rubber type: This type of sealant is based on rubber, and commonly used rubbers include polysulfide rubber, silicone rubber, polyurethane rubber, neoprene rubber and butyl rubber.
Resin type: This type of sealant is based on resin, and commonly used resins include epoxy resin, phenolic resin, polyacrylic resin, unsaturated polyester resin, polyvinyl chloride resin, etc.
Oil-based type: This type of sealant is based on oil, and the commonly used oils are various vegetable oils (such as linseed oil, castor oil, and tung oil, and animal oil, etc.).
Two. Classification by sealant vulcanization method
Wet air vulcanized sealant: This type of sealant is vulcanized with moisture in the air, and it mainly includes one-component polyurethane, silicone rubber and polysulfide rubber. The polymer base material contains active groups, which can react with water in the air to form cross-linking bonds, so that the sealant is vulcanized into a network structure.
Chemical vulcanization sealants: Two-component polyurethane, silicone rubber, polysulfide rubber, neoprene and epoxy resin sealants belong to this category, and are generally cured at room temperature; some one-component chlorosulfone Polyethylene and neoprene sealants and polyvinyl chloride sol paste sealants must be vulcanized by chemical reaction under heating conditions.
Heat transfer sealant: PVC resin dispersed with plasticizer, and sealant with bitumen-containing rubber are two different types of heat transfer systems. Vinyl plasticizers are liquid suspensions at room temperature and harden by heating to solidify, while rubber-asphalt sealants are hot-melt.
Oxidation-hardening sealant: Surface-drying sealant for inlaying or mounting glass, based on dry or semi-dry vegetable or animal oils, which may be refined polymerized, blown or chemically modified.
Solvent volatilization coagulation type sealant: sealant based on non-viscous polymer after solvent volatilization. This type of sealant mainly includes butyl rubber, high molecular weight polyisobutylene, acrylate with a certain degree of polymerization, chlorosulfonated polyethylene And sealants such as neoprene.
Three. According to the performance of sealant after construction
Curing sealant: It can be divided into two types: rigid sealant and flexible sealant;
a) Rigid sealants form hard solids after vulcanization or solidification, and rarely have elasticity; some varieties of such sealants play both sealing and bonding functions, and their representative sealants are epoxy resin, polyester resin Resin-based sealants such as polyacrylates, polyamides and polyvinyl acetate.
b) Flexible sealants remain soft after vulcanization, and they are generally based on rubber elastomers; the flexibility varies greatly, and the hardness is in the range of 10 to 80. Some varieties of this type of sealant are pure rubber, and most of them have good adhesive properties.
Non-curing sealant: This type of sealant is a soft setting sealant that remains non-drying after construction. Usually a paste, it can be applied to the joint with a scraper or a brush, and many sealants of different viscosities and different properties can be formulated.
Four. Classification by sealant form
Paste sealant: This type of sealant is basically used in static joints, and the service life is generally 2 years or more. Three main materials are usually used: oil and resin, polybutene, and asphalt.
Liquid Elastomeric Sealants: Includes liquid polymers that vulcanize to a true elastic state, which have the ability to withstand repeated seam deformation. The polymer elastomers used in elastomer sealants include liquid polysulfide rubber, mercapto-terminated polypropylene ether, liquid polyurethane, room temperature vulcanized silicone rubber, low molecular weight butyl rubber, etc.
Hot melt sealant: Hot melt sealant, also known as thermal construction sealant, refers to a sealant based on a blend of elastomer and thermoplastic resin. This type of sealant is usually extruded directly into the seam through a certain mouth model under heating (150 ~ 200 ℃); thermal construction can improve the wetting ability of the sealant to the bonded base material, so it is suitable for most bonded bases. The material has good adhesion. Once in place, it cools to form or form a film into a strong elastomer with little shrinkage. The main materials of thermal construction sealants are mainly isobutylene polymers, EPDM rubber and thermoplastic styrene block copolymers.
Liquid sealant: This type of sealant is mainly used for the sealing of mechanical joint surfaces to replace solid sealing materials, namely solid gaskets, to prevent the leakage of mechanical internal fluids from joint surfaces. This type of sealant is usually made of polymer materials such as rubber, resin, etc. as the main material, together with fillers and other components. Liquid sealants are usually divided into four categories: non-drying adhesive type, semi-drying viscoelasticity, dry adhesion type and dry peelable type.