Injection Mold of Tungsten Disulfide

As tungsten disulfide has good lubricating performance and excellent high temperature resistance, it can be coated on injection mold to improve its lubricating performance and prolong its service life. In addition, the coating thickness of tungsten disulfide is very small.

Injection mold is a tool to produce plastic products. The structure and size of the products can be optimized with the aid of injection mold. Injection molding is a process to produce complex parts in enormous quantities. The heated and melted plastic is injected into the mold cavity by high pressure. Then it is cooled and solidified and the molded product is obtained. The injection mold consists of two parts: the dynamic mold and the static mold. The dynamic mold is installed on the moving mold of the injection molding machine, and the static mold is installed on the fixed mold of the injection molding machine.

Demoulding is usually difficult during the injection molding process. Two main causes are as follow:

1. Excessive injection pressure and small forming shrinkage make the demoulding difficult. Under this condition, the friction between plastic and mold should be reduced.

2. The part is stuck on the static mold because of the large friction. In this case, the static mold resistance should be reduced.

It can be seen that the friction reduction is the key to solve the problem of difficult demoulding.

As a new type of solid lubricating material, tungsten disulfide can be coated on injection mold to reduce the friction effectively. It has the following performance.

1. Low friction coefficient (0.03), which is one tenth of that between metals without coating.

2. High temperature and extreme pressure resistance. Tungsten disulfide can be used under the load of 10000psi. And the working temperature range is between -460°F and 1200°F.

3. Small coating thickness(0.5μm). Tungsten disulfide with small coating thickness can be tightly attached to the substrate.

4. Good chemical stability. Tungsten disulfide is non-toxic and non corrosive.

With theses excellent properties, tungsten disulfide can be used in injection molding to deal with the demoulding difficulties.

Moreover, the addition of tungsten disulfide can effectively improve the fluidity of the resin. Thus working procedures such as the spraying of stripping agent, the cleaning of the mold and so on can be saved, which greatly improves the yield of the products.

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