3 secrets of PVC film suppliers want to hide
We focus on keeping improving our quality, material and parameters.
As one of the expert of PVC film suppliers, we'd love the share the common quality issues with our customers, to show them the difference between us and other suppliers, which are the most secret things they don't want you know.
1. Large Shrink ratio
If the stretching of the pvc film is performed under the condition of higher than the Vicat softening temperature, and then cooling, the orientation of the molecular segments will be frozen; when reheating, due to the movement of the molecular segments, the PVC film will resume stretching The trend of pre-stretch size, this is the so-called "elastic memory".
The size of the biaxial stretching should be as stable as possible, so that the PVC film shrinks uniformly, and at the same time, the temperature during stretching is maintained for a period of time and then slowly cooled to room temperature.
Therefore, if the suppliers can't do it well while calendering, the PVC film will have a big shrink ratio.
2. Uneven thickness
There are two reasons cause the uneven thickness of PVC film, one comes from the calender itself, the second one comes from the stretching process.
3. Irregular winding
There are 4 reasons may cause this:
Is the PVC film roll speed stable?
Does the PVC film stick to the roller?
Is the tension roller adjusted properly?
Is the PVC film flat, and is its thickness uniform?