Common Problems and Treatment of PVC Profiles in Dongguan

The production process of PVC is not complicated. The common production line is generally composed of rolling press, printing press, back coating machine and cutting machine. It mainly produces thin films with thickness of only 0.3MM to 0.7MM by direct stirring of rolling press, roller rotation and high temperature rolling. At the same time, the film is printed on the front of the film through the back of the printing machine. The coating machine attaches a layer of back coating to the back of the film.

Do not underestimate this coating. It is an important guarantee for the quality of the PVC film. The backing coating is made up of special materials. It is a high energy affinity agent. Because of the coating on the back, the PVC film can be tightly integrated with the middle density board or other boards, and it can not be opened for ten or fifteen years. The problem of decidua abscission.

Because the whole production process is carried out at high temperature (the temperature in the rolling machine reaches 220 degrees), this makes the PVC film have high light resistance and fire resistance, and ensures the high quality of the PVC film. Of course, the requirements for the production machinery are very high. Usually, the cost of the production equipment of a production line is about 39 million marks, equivalent to about 160 million yuan, but the other one is about 100 million yuan. Aspect,

The production process of PVC film is quite simple, and the machine output is also very large, so in a comprehensive view, PVC is actually a product with low input and high output.

Variation of PVC Profile

The existence of internal stress in profiles not only causes bending deformation or cracking, but also affects the mechanical properties and apparent quality of profiles.

Causes of internal stress in profiles:

1. After extrusion and stretching during the forming process, macromolecule orientation has high elastic deformation which is not relaxed, mainly concentrated in the surface layer, which results in large orientation stress and uneven orientation, resulting in uneven internal stress.

2. During the cooling stage of profiles, when the temperature is higher than the glass transition temperature, the plastic is viscoelastic fluid, accompanied by stress relaxation. When the temperature is lower than the glass transition temperature, the plastic becomes solid. It is difficult to fully adapt the curing time to the chain relaxation speed. The profiles will freeze more or less after forming. Internal stress.

3. In the cooling setting stage, the uneven cooling shrinkage will inevitably lead to the difference of volume temperature inside and outside the profile, up and down, left and right.

4. Profiles may be deformed and cracked when they are stored for a long time, when the temperature is changed and when the stress is changed.

5. The uneven wall thickness of hollow profiles easily results in uneven cooling, slow cooling at the thick wall and fast cooling at the thin wall, which results in internal stress due to the difference of cooling rate. Solution: the wall thickness of profiles is as equal as possible and uniform as possible. If there must be unequal wall thickness, the joint should gradually transition to avoid sudden change of section. The cooling at the thick wall must be properly strengthened in the die.

6. The whole production line of PVC profiles should be adjusted on a central line. If not on a central line, when the profiles pass through the dry setting die and enter the water tank for final cooling, the profiles will be artificially bent or distorted. Therefore, every change of the die should be made to the extruder, the die, the setting die, the concentricity and the level of the tractor. Correct the line accurately.

7. Because of the asymmetry of profile section, when the tracked track of tractor is pressed on the profile surface, the force on all sides of the profile will be uneven and deformation will occur, especially on the thin-walled profile. Therefore, the tractor crawler clamping force should be adjusted appropriately and the traction force should be kept constant.

8. When profiles are stored, they should be placed straight, above 1M from the heat source, and stacking height should not exceed 1M, in order to avoid plastic deformation of profiles, storage temperature should not be too high, not exceeding 40 C.

9. The uneven discharge of die and the uneven speed are one of the main factors causing bending. If the flow of die is uneven, the uniform discharge around the die can be adjusted by blocking and inserting blocks. If the temperature difference of each side of the die is large, the temperature around the die should be adjusted to be uniform.