Today we will discuss the common quality problems in the production process of PVC foam board and the causes.
The foamed sheet can be divided into high and low foaming according to the difference of foaming multiplier. According to the different degree of soft and hard foam texture, PVC foam sheet can be divided into hard foam, semi-hard foam and soft foam. We commonly used PVC foam board is a rigid low foam sheet.
For PVC foam board, the size and uniformity of the bubble holes are the key factors affecting its quality. If the bubble holes are small and uniform, the toughness of the foam is good, the strength is high, and the surface quality is guaranteed. If you want to reduce the density of PVC foam board, only small and uniform bubble holes to further reduce the possibility of its density, the bubble holes scattered and large is difficult to reduce the density of PVC foam board
Problems that easily occur during the production of PVC foam board
Yellowing of the PVC foam board surface
Cause: Extrusion temperature is too high or stability is not enough.
Solution: Reduce the processing temperature, if it can’t be solved, adjust the formula to increase the stability and increase the dosage of stabilizer and lubricant appropriately.
Middle yellowing of PVC foam board
Cause: related to the core temperature of the barrel mold temperature is too high, the amount of lubricant is not reasonable, and the amount of white foaming agent also has a certain relationship.
Solution: Properly reduce the temperature of the mold, the screw temperature should also be adjusted; add the right amount of white heat-absorbing foaming agent to absorb the excess heat released during the decomposition of the foaming agent AC.
Surface bending of PVC foam board
Cause: uneven flow of raw materials or PVC foam board surface cooling is not sufficient
Solution: The factors that cause uneven flow rate of raw materials generally include large traction fluctuations or unbalanced ratio of the amount of internal and external lubricants in the formula. If it is the cause of the machine is easy to exclude. The formula adjustment is generally to reduce the amount of external lubricant, and then adjust the amount of internal lubricant, and at the same time to ensure that the PVC foam board is fully cooled.
Cross-sectional bubble holes or bubble layering
Reason: It can be attributed to one point, that is, the melt strength is not enough, the reasons for insufficient melt strength are: (1) the use of excessive foaming agent or foam regulator is not enough or the ratio of the two is not coordinated, or the quality of the foam regulator. (2) Poor plasticization, low processing temperature or excessive lubrication.
Solution: First, appropriately reduce the amount of foaming agent, observe the effect, if it does not work, you can add the right amount of regulator or change to a strong regulator of the melt; second, if it is the cause of poor plasticization, you can appropriately increase the processing temperature or appropriately reduce the amount of lubricant.