PVC hard board is made of polyvinyl chloride as the main raw material and is made by special foaming process. It is one of the new chemical building materials of typical building materials of plastic wood. It is an ideal green building decoration material. Widely used in automobile and ship manufacturing, furniture, kitchen and bathroom materials, decoration and other industries, the market demand is large. The key to the production process of PVC hard board is the decomposition and nucleation of the foaming agent. The process of growth and fixation of the bubble is compatible with the plasticizing and forming process of the PVC melt.
First, in the production process, it is necessary to strictly control the screw speed, extrusion temperature, pressure, etc., and it is also closely related to the structure of the machine head, die, and die. The production practice shows that the screw speed and the extrusion output of the plate In proportion, it is inversely proportional to the density of the board.
The higher the screw speed, the faster the extrusion speed, the faster the temperature rise of the melt increases the difficulty of process control, but the degree of foaming is uniform, and the surface quality of the product is good; on the contrary, when the screw speed is too low, the extrusion speed is slow, the melt is made. Poor plasticization reduces production efficiency, while foaming near the lip of the mold makes the surface of the sheet rough.
The quality of the second PVC hard plate is also affected by the residence time of the material in the extruder barrel and the die. The residence time is too short, the foaming agent is not decomposed sufficiently, the plate density is too large, the residence time is too long, and the excessive foaming is easy. The mechanical properties are reduced, so the screw speed should be determined according to different process methods of crust foaming. It is necessary to comprehensively consider the use requirements of the equipment and the cooling sawing time of the plate. The screw speed and extrusion speed are different according to the thickness setting of the plate, generally not exceeding 4m/min.
Third, the production process varies with the changes of materials, extruders, and molds. The materials are different, the specifications of the extruder are different from the screw structure, and the specifications and shapes of the extruded profiles are different. The process adjustment methods adopted are quite different. The complexity of the rigid PVC extrusion process itself determines the difficulty of achieving foaming of the crust.