Key Word: Taili Plastic Machinery; Taili Plastic Machinery-Capacity Improving Expert; Efficient; Stable; PVC Products
Recently, I received a phone call from a friend, who said that he was very distressed. In the process of production, he has turned the material temperature very low, but the PVC products still got yellow.
In fact, there are several reasons for the yellowing of PVC products. He also investigated several reasons one by one. He had replaced the barrel, changed PVC material and lowered the injection melting temperature to be only 180 degrees. Theoretically, under this kind of temperature, produce yellowing phenomenon can’t appear. However, there is still obvious yellowing phenomenon in the material during the air shooting test.

1. Replace the barrel
When facing the yellowing of PVC product, the barrel and screw should be inspected at the first. Because PVC raw material can make a big damage to the screw. If the storage material is not clean, yellow problem is easy to appear. However, the customer said that he had replaced the new barrel and this problem still exist, so we'll consider it from another angle.
2. Inspect the raw material
In general, we must pay more attention to the raw material facing yellowing problems. If some other impurities get mixed in the raw materials, the yellowing problem will easily appear.
3. Inspect the process
In the process of inspecting the process, we must not only pay attention to the melting temperature, injection and other processes, but also check the back pressure of the injection molding machine. PVC is a kind of non-Newtonian liquid. Most of its heat comes from the internal stress caused by intermolecular friction, rather than the heating of the barrel surface, so the back pressure of the injection molding machine has a great influence on the yellowing of the product.
After checking, our friend said that some time ago, an intern mold technician came and adjusted the back pressure, about which he didn't know earlier. No wonder he couldn’t find the reason. He relaxed the back pressure a little bit and the problem was solved at once.
Taili Plastic Machinery always keeps in mind that what a good injection molding machine factory should do is to help improving the capacity and boosting the profits, rather than offer the similar products the customers need. This is also what Taili Plastic Machinery keeps doing.
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