PVC foam board is widely used in passenger cars, train car ceilings, box core layers, interior decorative panels, building exterior wall panels, display panels, signs, interior decorative panels, office, residential, public building partitions, screen printing, computer lettering, commercial It can be said that people's daily life is closely related to decorative frames, dust chamber panels, ceiling panels, and other places. In the production process, the birth of PVC foam panels has to go through a series of tests, and they will appear a lot. The question is, how are these problems created, and how can they be solved?
(1) The board surface turns yellow
Reason: Extrusion temperature is too high or stability is insufficient
Solution: reduce the processing temperature, if it does not improve, you can adjust the formula to increase the stability, and appropriately increase the stabilizer and lubricant, so that it is easy to quickly find out the problem and solve the problem as quickly as possible.
(2) Yellowing in the middle of the plate
Reasons: The core temperature of the first barrel is related to the high temperature of the mold, and the amount of the second lubricant is unreasonable, which is again related to the white foaming agent.
Solution: Appropriately reduce the mold temperature and adjust the screw temperature; appropriately increase the internal lubrication; add an appropriate amount of white endothermic foaming agent to absorb the excess heat released by the decomposition process of the foaming agent AC.
(3) The layout is curved
Reason: uneven material flow or insufficient cooling
Solution: The factors that cause uneven material flow are generally large traction fluctuations or unbalanced internal and external lubrication in the formula. The factors of the machine are easy to eliminate. The formula adjustment generally adjusts the internal lubrication under the premise that the external lubrication is as little as possible (without the occurrence of paste). There will be good results, while ensuring that the cooling is even and in place.
(4) There are bubbles or bubble layers on the cross-section
Reason: It can be attributed to one point, that is, the melt strength is not enough, and the reasons for the insufficient melt strength are: 1) Excessive foaming agent or insufficient foaming regulator or the ratio of the two is inconsistent, or the quality of the foaming regulator; 2 ) poor plasticization, low processing temperature or excessive lubrication.
Solution: First, appropriately reduce the amount of foaming agent to see how the effect is. If the effect is not large, add an appropriate amount of regulator or use a powerful melt regulator; second, if the plasticization is poor, the processing can be appropriately improved temperature or appropriately reduce the amount of lubricant.
(5) The thickness of the board surface is uneven
Reason: uneven discharge
Solution: The opening of the die lip can be adjusted, and if the flow rate is too large, the choke rod can be adjusted; if the formula is adjusted, if the middle is thick and the two sides are thin, it means that the melt fluidity is relatively poor, and the internal lubrication can be appropriately increased, especially the amount of 316 types, or appropriately reduce the external lubrication; on the contrary, if the two sides are thick and the middle is thin, the adjustment direction will also be opposite.
(6) Lubrication problem: Lubricant atmosphere is an external lubricant and an internal lubricant. External sliding is conducive to demolding, which is good for the smoothness of the surface of the sheet. If the external sliding is too small, the temperature of the 5th zone of the extruder is not easy to control, and it is easy to heat up. This will lead to high temperature of the confluent core, large bubbles, clusters of bubbles, yellowing and other problems in the middle of the plate, and the surface of the plate is not smooth; if the outside slips more, the precipitation will become serious. High-quality pe wax is generally used for internal and external lubrication of foamed boards.