Polyurethane sealant, also known as PU sealant, is usually composed of polyols and diisocyanates of oligomers such as polyacetylates, polyethers, and polydialkenes, with diols or diamines as chain extenders, and gradually polymerized. Sealing adhesive can usually be prepared using pre polymer method and one-step process. The characteristics of polyurethane sealing materials are low hardness, moderate strength, good elasticity, water resistance, mold resistance, shock resistance, transparency, excellent electrical insulation and flame retardancy, no corrosion to electrical components, and good adhesion to metals such as steel, aluminum, copper, tin, as well as rubber, plastic, wood and other materials. Encapsulation materials can protect installed and debugged electronic components and circuits from the effects of vibration, corrosion, moisture, and dust.