Polyurethane sealant (polyurethanesealant) is a sealant with polyurethane rubber and polyurethane prepolymer as the main component. This kind of sealant has high tensile strength, excellent elasticity, abrasion resistance, oil resistance and cold resistance, but water resistance, especially alkali resistance water resistance. It can be divided into three kinds: heating vulcanization type, room temperature vulcanization type and hot-melt type. The room temperature vulcanization type has a single component and a two component component. It is widely used in buildings, squares, roads as caulking sealing materials, sealing and automobile manufacturing, installation of glass, electronic filling, submarines and the rockets.
Polyurethane sealant has the following characteristics: excellent wear resistance; soft performance; adjustable wide range; high mechanical strength; good adhesion; good elasticity, excellent resilience, can be suitable for the dynamic joint; good weather resistance, service life can reach 15~20 years; excellent oil resistance; resistance to biological aging; moderate price.
Polyurethane sealants also have some shortcomings. For example, it can not be heat-resistant for a long time. Light color formulations are susceptible to ultraviolet aging. The storage stability of mono component is greatly influenced by packaging and external environment, usually cured slowly, and bubbles and cracks may occur in high temperature and hot environment. At the same time, the water resistance of the polyurethane sealant is also poor, especially the alkali water resistance is not good.
The main uses of the polyurethane sealant are the civil construction industry, the transportation industry and so on. For example, in Japan, about 75~80% of polyurethane sealants are used for construction, 15% for automotive, mechanical manufacturing, and 5% for civil and other aspects.
The specific application in the aspects of Architecture: connection and construction joints of precast concrete and other building materials filling sealing, sealing caulking between wood frame and wall around the doors and windows of concrete buildings, lightweight structures (such as curtain wall) paste glue, balcony, swimming pool, bathroom waterproof sealing facilities, air conditioning and sealing other system joints, insulation double-layer glass, heat insulation window seal.
The application of polyurethane sealant in automobile includes the assembly and sealing of the window (mainly windshield glass), the assembly of the body and other parts.
In civil engineering, polyurethane sealant used in high-grade roads, bridges and runways flexible joints and caulking sealing concrete, ceramic and PVC materials such as sewers and underground gas pipes, wire circuit conduit connection sealing, subway tunnels and other underground tunnel sealing joints etc..
Polyurethane sealant can also be used for flexible joints of cables (such as underground cables) and electronic components for dust proof and aseismic. It can be used for sealing systems such as refrigerated trucks, cold storage insulation and cryogenic vessels.