transparent PP injection
transparent PP injection
The transparency of the matrix resin itself has a great influence on the transparency of PP products. In order to improve the transparency of PP, a small amount of polyacrylate resin with good compatibility and excellent transparency can be added.
2. Nucleating agent
It can significantly improve the crystallization rate, crystallization rate and crystallization fineness ratio.
(1) Inorganic nucleating agent inorganic nucleating agent mainly consists of ultra-fine talc powder and SiO2, as well as calcium carbonate, mica powder, inorganic pigments and fillers. It has low price and rich sources, but it has a certain impact on the luster and transparency of products.
(2) Organic nucleating agent organic nucleating agent is a low relative molecular weight organic matter with nucleation. Represented by sorbitol and its derivatives, it has good compatibility with matrix resin and can significantly improve the transparency and surface gloss of products.
(3) For sorbitol, when the amount of nucleating agent exceeds 0.3%, the transparency improvement effect is not obvious, or even decreases; However, when the dosage is less than 0.2%, the nucleation quantity is insufficient and the transparency is not increased enough. It can be seen that the dosage of nucleating agent is preferably between 0.2-0.3%. Therefore, the appropriate content of nucleating agent can better improve the transparency of PP.
3. Forming temperature
If the temperature is too high, the substances with low molecular weight in the nucleating agent will decompose and volatilize, reducing the effective components in the nucleating agent and reducing the improvement effect of transparency. Moreover, if the temperature is too high, the original crystal nucleus in PP will be destroyed and the heterogeneous nucleation center will be reduced, resulting in the reduction of modification effect; When the temperature is too low, the dispersion of nucleating agent is not good, and the transparency effect is poor. Therefore, choosing an appropriate molding temperature is particularly important to improve transparency.
4. Toughening agent
Toughening agent because the toughening agent and PP are not mutually soluble and the refractive index is also different, it will refract at the mutual interface, thus affecting the light transmittance of the article. With the increase of toughening content, the area of mutual interface is stronger, and the light transmittance of products is worse.
5. Process parameters
Process parameters ideal processing temperature, cooling temperature, injection pressure and other process parameters are also very helpful to the transparency of PP.
Processing temperature: under the processing conditions, 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 better the transparency.
Injection pressure, injection time and holding time will affect the orientation of molecules. The orientation will affect the crystallization of molecules, so shortening the injection and pressure holding time and reducing the pressure can improve its transparency to a certain extent without affecting the performance and appearance of products.
6. Forming process
The molding process compares the products obtained by injection, drawing and blowing process. It is found that injection and blowing process is the most beneficial to increase transparency.
7. Mould
The higher the finish of the mold, the better the transparency of the product.
