The appearance of leucorrhea on the surface of the PVC foam board, that is, the white straight lines that occur in the same direction as the sheet extrusion, is a sign of the direct contact and friction between the slab and the shaped plate surface of the corresponding part of the die and the leucorrhea. The difference between the leucorrhea and the dark band is two There is a difference in the degree of contact between the person and the stereotyped template and the degree of compression. The gray color is a sign that the leucorrhea retentate begins to degrade; the bright band is a sign that the slab is directly in contact with the shape and rubbed.
1. The gap between the corresponding cross-section of the die and the vaginal discharge is too small, resulting in a small flow rate, and the thickness of the melt is slightly reduced when it is extruded from the die. 2. The material contains unclean impurities and stays in the die, which causes the flow of the melt to decrease when extruding from a certain part of the die, and leucorrhea appears, especially when the unclean regenerated materials are added or the components are complicated and the stabilizer is lacking. If the material is too much, the melt will be retained when it is extruded from a certain part of the die. If the leucorrhea problem is not dealt with in time, with time, the leucorrhea will gradually change into a light gray zone and a black zone. 3. The temperature of the extruder is improperly controlled, and the screw temperature control device is not used. When the material is extruded in the extruder, confluence core, or die, the cross-sectional temperature is not balanced, local micro-degradation, sticky material occurs, and the melt is extruded from the die. When there is less leucorrhea in the flow velocity at a certain part of the die. A lot of practice has verified that the treatment of leucorrhea has certain timeliness. If the treatment is not timely or the leucorrhea evolves from the leucorrhea to the gray zone, the treatment opportunity will be lost. During the treatment, the extruder screw wear and equipment conditions and recent process setting changes should be well understood, so that the treatment can be dealt with in a targeted manner.
The appearance of pores on the surface of the PVC foam board is a sign that the local density of the melt is too low. Generally, there are two types of pores and round pores. The influencing factors include resin, foaming agent, regulator, calcium carbonate, stabilizer, and other raw material factors, which are also related to mold and process. If a large area of cells appears on the surface of the foamed product, the PVC foam board manufacturer can appropriately adjust the foaming regulator treatment; if individual cells occasionally appear on the surface of the foamed board, likely, the mixing process, temperature, and temperature have not been followed. The feeding procedure is related to the uneven mixing, and the material should be replaced; if circular cells appear continuously, the dosage of the yellow and white foaming agent should be adjusted appropriately; if the surface of the foamed board sometimes has long cells, it belongs to the local low density of the board. The reason for the characterization of pores is more complicated and should be based on the time, location, and probability of the occurrence of pores.