pvc foam plate affect the quality of the factors Process temperature control

common problem

PVC foam in the process of extrusion, the basic problems can be classified as four categories, one stability problem; Second, the melt strength problem; Third, lubrication problems; Fourth, the problem of dispersion. These four types of problems, especially the first three types of problems will be mutual constraints, cross-effects, from the surface phenomenon is sometimes difficult to immediately clear, to observe the analysis, find the root causes of the problem can be solved.

1. The lack of stability, will affect the entire board, the board yellow, foam sheet brittle

2. Insufficient melt strength will cause the foam cells to be large, and the longitudinal section is so long.

 To determine whether the melt strength is insufficient, the most direct way is to press the back of the three rollers behind the package in the roll on the sheet, the melt strength can feel flexible when pressed. If it is difficult to bounce after pressing, indicating poor melt strength. Because the screw structure and cooling methods vary widely, it is difficult to determine whether the temperature is reasonable, in general, in the extruder to allow the load, 3-5 area temperature is low as well. In the foam pipe in order to obtain foam uniform products, but also need to ensure that PVC material has a good melt strength. The company developed the foam auxiliaries is to solve the problem of foam products developed, and can effectively improve the quality of foam pipe.

3. Lubricants

Lubricants are divided into external lubricants and internal lubricants, the outer slip is conducive to stripping, the smoothness of the surface of the board is good, too much outside the slide, the extruder 5 area temperature is not easy to control, easy to heat up, which will lead to confluence High temperature, the middle of the plate out of the big bubble, string bubble, yellow and other issues, the surface of the plate is not smooth; outside the slide, the precipitation will become serious, the performance of the mold and the surface of the sheet outside the slippery, For some individual phenomenon in the board from time to time to move back and forth. The slippage is conducive to the plasticity and melt flow, the slippage is difficult to control the thickness of the board, the performance of the middle plate thickness on both sides of the thin; within the slide more prone to high core temperature phenomenon. 4. Poor dispersion will bring the surface of the board is not smooth

 Process temperature control problem: the four issues mentioned above are fundamental issues, is the basis of deep-seated problems. Compared to the above four issues, the process temperature control will be much more intuitive, is the surface problem, but the temperature control is not good, will lead to the emergence of fundamental problems. Improve the processing temperature, material stability time will be reduced, the stability of the problem; the original lubrication balance will be broken, the general performance of the external lubrication is insufficient, especially after the late lubrication, need to increase the amount of external lubrication; The melt strength decreases, the foam sheet increases, the number of cells decreases, the sheet is brittle and easy to break; the temperature increase reduces the melt strength and reduces the melt viscosity, the viscosity reduces the shear dispersing ability, Ability is not strong in terms of screws, sometimes there are scattered uneven.