Weld sealant is a paste sealant composed of PVC paste resin polymerized by emulsion method or micro-suspension method, phthalate plasticizer, diluent, tackifier, thixotropic agent, inorganic filler and pigment, which has good thixotropy. After heating and plasticizing, it becomes an elastomer with certain bonding strength, which has excellent wear resistance, bending flexibility and chemical medium resistance, and has good binding force with electrophoretic primer and epoxy polyamide primer, and is widely used for sealing internal and external welds of automobile bodies. PVC-type weld sealant has become an ideal material for automobile body weld sealing because of its low cost, odorless and non-toxic, good construction technology and excellent sealing effect, and it is the most widely used and studied weld sealant.

PVC welding sealant has three main functions on the car body:

(1) Weld sealing The cab of the car body is a whole made of many parts welded together, and there is a weld at the weld. By applying sealant at the weld, the cab is sealed and isolated from the outside world;

② Anti-corrosion function The weld on the car body is located in the corner and hidden part of the car body, which is the weak point of car body painting and is corroded first. After applying a layer of sealant, it is equivalent to adding a protective layer outside the car paint coating, which improves the corrosion resistance of the car paint coating;

(3) Applying plastic sealant on the weld can also achieve the purpose of leveling the car body and shaping.