PVC FOAM BOARD is a kind of PVC product that has risen rapidly in recent years. The product has quickly won the favor of customers with the advantages of environmental protection, beauty, moisture resistance and convenient installation. In the process of extrusion of pvc foam board, the common abnormal states mainly include: the board is uneven, the surface is not smooth, the density is not exact, the wave lines, the toughness is not good, etc. How should we solve these problems?

Surface is uneven

Generally, the local unevenness of the wallboard mainly occurs in the vacuum forming section of the forming mold. If the degree of vacuum is not enough, or the cooling water of the setting mold is not enough, the adjustment method is to increase the amount of cooling water in this part, and increase the degree of vacuum through water sealing to speed up the cooling rate of wallboard products. If the local water is open to the maximum and is still not level, then remove the setting die to clean up its vacuum path.

Surface is not smooth

The reason is that the overall temperature of the mold is too high or the vacuum pump of the extruder is not working properly. Adjustment: lower the temperature of the mold by a few degrees as a whole or clean the vacuum pump of the extruder.

Cracked pvc foam board

Check to see if the pvc foam board is damaged and flooded. Or the content of lubricants in the formula is too high, especially the amount of external lubrication is too high. Or use a relatively inferior stabilizer, the amount of internal and external lubrication is too much, and the stabilizing component is too small.

Surface wave lines

The main reason is the uneven discharge. The reasons for the uneven discharge are: excessive plasticization and too soft melt; uneven material flow; mismatch between traction and extrusion; excessive melt strength and rebound, etc.;

We can solve this from the following aspects:

一、Process：

1）Reduce the production speed, such as screw speed, feeding speed, etc., and appropriately increase the traction speed; in production, sometimes the wave pattern disappears by adjusting this way.

2 ) Reduce the extrusion temperature. Many companies that currently produce pvc foam board use small pipe materials, plastic steel materials or foamed sheet materials for production. These materials are secondary processing materials, and plasticization is extremely fast. Appropriate reduction of plasticization has certain benefits for production and product stability.

二、Equipment：

1. Increase the clearance of the screw, appropriately reduce the shear, and slow down the plasticization;

2. Clean the die head and polish it, especially the ends of the die, so that the molten material flows smoothly.

3. Check whether there is a problem with the mold, such as forgetting to install the positioning pin, or whether there is a problem with the screw, such as non-concentricity, etc., which will cause the material flow to be biased, generally only on the side with more material, and it is difficult to eliminate it by adjusting the formula.

三、Formula：

1、Appropriately increase the amount of external lubrication and reduce the amount of internal lubrication, but do not adjust too much.

2、On the premise of not affecting the foaming, the foaming regulator can be appropriately reduced or a foaming regulator with a smaller melt strength can be selected. This situation is limited to the case where the melt strength is too large to prevent the material at the outlet from being melted. The body strength is too large and rebounds, forming a wave pattern.

Poor toughness

The first is to use too many secondary materials. Secondly, consider whether the amount of external lubrication is too high, especially if cheap stabilizers are used. In order not to paste, the amount will increase, which will lead to too much external lubrication in the overall formula. Consider again whether the plasticization of the PVC material is in place. Poor plasticization or over-plasticization will make the product brittle. Finally, if these problems are ruled out or the toughness is not enough, the toughening modifier CPE-135A can be appropriately added.

In the production process of pvc foam boards, attention should be paid to the state of the equipment, surrounding hygiene and discipline. The equipment status should be paid attention to (1) whether the current of the main engine and the pressure of the machine head are suitable (2) whether the temperature on the temperature control table and each ammeter can work normally (3) whether the temperature of the main motor and the gear box is too high (4) Whether the vacuum pump is normal (5) Whether the thermocouple of the mold can be inserted to the end (6) Whether the water and electricity are normal.