Sealant is a polyurethane rubber and polyurethane prepolymer as the main component of the sealant. Polyurethane sealant has high tensile strength, excellent flexibility, abrasion resistance, oil resistance and cold resistance, but water resistance, especially poor alkali resistance. Can be divided into heating vulcanization, room temperature vulcanization and hot melt type three. Which room temperature vulcanization and a single component and two components of the points.