Kaisu hollow blow molding machine uses PP raw material

PP is a typical crystalline polymer, and to improve its transparency, the following 7 aspects can be considered:

1、 The matrix resin itself

The transparency of the matrix resin itself has a significant impact on the transparency of PP products. To improve the transparency of PP, a small amount of polyacrylate resin with good transparency and compatibility can be added.

2、 Nucleating agent

Nucleating agent: can significantly increase the crystallization rate, increase the crystallization rate, and increase the crystallinity ratio.

Inorganic nucleating agents are mainly composed of ultrafine talc powder and SiO2, as well as calcium carbonate, mica powder, inorganic pigments, and fillers. They are inexpensive and have abundant sources, but they have a certain impact on the gloss and transparency of products.

Organic nucleating agents are low relative molecular weight organic compounds with nucleating effects, represented by sorbitol and its derivatives. They have good compatibility with matrix resins and can significantly improve the transparency and surface gloss of products.

As for the amount of nucleating agent, when the amount of nucleating agent exceeds 0.3%, the transparency improvement effect is not significant and may even decrease; But when the dosage is less than 0.2%, the nucleation quantity is insufficient and the transparency increase is not enough. It can be inferred that the optimal amount of nucleating agent is between 0.2% and 0.3%. So, an appropriate amount of nucleating agent can better improve the transparency of PP.

3、 Extrusion temperature

If the temperature is too high, the low molecular weight substances in the nucleating agent will decompose and evaporate, reducing the effective components in the nucleating agent and the improvement effect of transparency. Moreover, if the temperature is too high, it will destroy the original crystal nucleus in PP, reduce the heterogeneous nucleation center, and reduce the modification effect; If the temperature is too low, the dispersibility of the nucleating agent is poor, and the transparency effect is poor. Therefore, choosing an appropriate extrusion temperature is particularly important for improving transparency.

4、 Toughening agent

Toughening agents, due to their immiscibility with PP and different refractive indices, can refract at the interface, thereby affecting the transparency of the object. As the toughening content increases, the area of the mutual interface also becomes stronger, and the transparency of the product becomes worse.

5、 Process parameters

The ideal processing temperature, cooling temperature, injection pressure, and other process parameters also greatly contribute to the transparency of PP.

Processing temperature: When the processing conditions are met, the lower the processing temperature, the smaller the crystal size, and the better the transparency;

Cooling temperature: The lower the cooling temperature, the lower the crystallinity and the better the transparency.

Injection pressure, injection time, and holding time can affect the orientation of molecules. And orientation can affect the crystallization of molecules, so shortening the injection and holding time and reducing pressure can improve its transparency to a certain extent without affecting the performance and appearance of the product.

6、 Forming and processing technology

Compared with the injection, pull, and blow molding processes, it was found that the injection and blow molding processes are most beneficial for increasing transparency in products.

7、 Mold

The higher the smoothness of the mold, the better the transparency of the product.

Zhangjiagang Kaisu Machinery Strategic Development