In the PVC foam board extrusion process, the problems encountered can be basically classified into four categories.
1. Stability problem: insufficient stability will affect the entire board surface, the board surface will be yellow, and the foamed sheet will be brittle.
2. Melt strength problem: Insufficient melt strength results in a large foam cell and a long longitudinal bubble.
3. Lubrication problem: Lubricant is divided into external lubricant and internal lubricant. External slip is beneficial to demoulding, which is good for the smoothness of the surface of the sheet. The outer slip is too small, the temperature in zone 5 of the extruder is difficult to control, and it is easy to heat up. This will lead to high temperature of the combined core, large bubbles, string bubbles, yellowing and other problems in the middle of the sheet, the surface of the sheet is not smooth; the outer slip is more, the precipitation will become serious, and the structure inside the mold and the surface of the sheet slip. Precipitation will also manifest as some individual phenomena moving back and forth irregularly on the board. The internal slip is beneficial to the plasticization and the fluidity of the melt. The inner slip is not enough to control the thickness of the plate surface. The thickness of the plate is thin on both sides; the inner slip is more, and the temperature of the combined core is high.
4. Dispersion problem: Poor dispersion will bring the surface of the foam board to be not smooth.