Avoid black spots on TPU tape

TPU has the characteristics of high tension, high tensile strength, toughness and aging resistance. It is a mature eco-friendly material, which is friendly to both environment and human health. In recent years, it has became the main material of many products. However, due to various reasons in actual production, black spots become a common problem in TPU product process, no exception of TPU elastic tape. What are the reasons for the black spots on TPU tape during processing?

The reason can be analyzed from the following aspects:

1. The machine is not clear enough

It refers to the feature of TPU. TPU itself is easy to absorb moisture in the air. And it owns elasticity and extension originally as well. Therefore, TPU material will be sticky when melted in the high temperature extrusion machine. During the production process, some residual TPU will be wrapped on the screw for a long time and not brought out. Over time, these residual TPU will be decomposed. Firstly, it will turn yellow. And then completely decompose into the black carbide, which will be brought to the surface of the product to appear as black spots or black blocks.

In addition, if the machine needs to be shut down, the TPU in the screw nozzle is hard to  completely emptied unless be cleaned specially. That the long-term alternate risen and fallen temperature with no replenishing of new materials makes the residual TPU material decompose and carbonize to become black spots.

2. The TPU raw material is not clean enough

There are also several reasons will lead to contamination of raw material. The first reason is that the material be polluted during process of prilling. Secondly, impurities may be mixed in during packaging, transportation, and storage. Its obvious feature is that you can see impurities on the surface of the material particles when open package and see carefully.

Besides, any substance can become impurity. For example, dust in the air, material-like suspended matter, shavings or granules of other materials, powdery masterbatch and dyeing agent. In order to prevent impurities from becoming black spots, management must be strengthened to control each part of purchasing TPU material.

For TPU black spots, it is recommended to focus on prevention. The main way to prevent black spots on TPU is cleaning machine. If the machine is not shut down for a long time, please clean regularly the carbides that may be produced or have just been produced in time. If the machine is shut down, choose to use TPU shutdown maintenance material, which means that use it to completely replace the TPU before shutting down machine to avoid carbonization of residual TPU. After starting up machine, replace this cleaning material with TPU. Generally, it supposed to use professional TPU screw cleaning material to clean machine regularly, in order to prevent black spots in the production process.