What are the extrusion problems of PVC foam board?What are the extrusion problems of PVC foam board?
What are the extrusion problems of PVC foam board? This is the related question we are going to talk about in this issue. The answer to this question is in the following elaboration:
1. If the stability is not enough, the whole board surface will be affected. The board surface will turn yellow and the foam sheet will be brittle.
2. Lack of melt strength will result in large bubble holes and long longitudinal cut surface bubbles.
The most direct way to judge whether the melt strength is insufficient is to press the plate wrapped on the middle roll with fingers behind the three rolls. When the melt strength is good, the elasticity can be felt. If it is difficult to spring up after pressing, the melt strength is poor. It is difficult to judge whether the temperature is reasonable because of the large difference between screw structure and cooling mode. Generally speaking, in the allowable load of extruder, the temperature of zone 3-5 is better than that of zone 3-5. In order to obtain even foam products, it is also necessary to ensure that PVC materials have good melt strength. Therefore, the quality and model of foaming regulator is very important, of course, the yellow and white hair foaming agent should also be well matched.
3. Lubricants are divided into external lubricants and internal lubricants. External sliding is conducive to demoulding and is beneficial to the surface finish of the plate. There is too little external sliding. The temperature in zone 5 of the extruder is not easy to control and it is easy to heat up. This will lead to high temperature of the confluence core, blisters, blisters and yellowing in the middle of the plate, and the surface of the plate is not smooth The precipitation will become serious due to the excessive external sliding, which is manifested in the structure in the mold and the precipitation on the surface of the plate, as well as the irregular back and forth movement of some individual phenomena on the surface of the plate. Internal sliding is beneficial to plasticization and melt fluidity. If the internal sliding is insufficient, it is difficult to control the thickness of the plate surface, which shows that the thickness in the middle of the plate is thin on both sides; if there is more internal sliding, it is easy to have high temperature of the confluence core.
The main content of this issue is these, I hope you have a better understanding of PVC foam board.