PVC foaming regulator is actually an acrylate
Processing Aid. It has all the basic characteristics of PVC processing aids. The only difference from PVC general processing aids is the molecular weight. The molecular weight of PVC foaming regulators is much higher than General purpose processing aids.
In the process of PVC foam sheet extrusion, the problems encountered can basically be classified into 4 categories, one is stability problem; the other is melt strength problem; third is lubrication problem; fourth is dispersion problem. These four types of problems, especially the first three types of problems, will restrict each other and have cross-effects. From the surface, it is sometimes difficult to distinguish them immediately. It is necessary to observe and analyze them to find the root of the problem to solve the problem.
Insufficient stability will affect the entire board surface, the board surface will turn yellow, and the foam sheet will be brittle.
Insufficient melt strength will cause the foamed sheet to have large cells and long vertical sections. The most direct way to judge whether the melt strength is insufficient is to press the sheet wrapped on the middle roll with your fingers behind the three rolls. When the melt strength is good, you can feel elasticity when pressed. If it is difficult to bounce up after pressing, it indicates that the melt strength is poor. Because the screw structure and cooling method are quite different, it is difficult to judge whether the temperature is reasonable or not. Generally speaking, within the allowable load of the extruder, the temperature in zone 3 to 5 is better.
In order to obtain uniform foam products in the foamed pipe, it is also necessary to ensure that the PVC material has good melt strength. The foaming additives developed by the company are developed to solve this problem of foamed products and can effectively improve the quality of foamed pipes.
Poor dispersion will cause the surface of the board to be uneven.
Process temperature control issues: The four issues mentioned above are fundamental issues, foundations, and deep-seated issues. Compared with the above four problems, the process temperature control is much more intuitive. It is a superficial problem, but poor temperature control can induce fundamental problems. Increasing the processing temperature will reduce the material stabilization time and cause stability problems; the original lubrication balance will be broken, which is generally manifested as insufficient external lubrication, especially in the later external lubrication, the amount of external lubrication needs to be increased; increased temperature will also cause The melt strength decreases, the foamed sheet cells increase, the number of cells decreases, and the sheet becomes brittle and easy to break; the increase in temperature reduces the melt strength and also reduces the melt viscosity, and the viscosity decreases. For a screw with a weak capacity, uneven dispersion sometimes occurs.
