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How To Improve PP Product Transparency? Seven Points Is All There Is To It
Oct 05, 2018

1. The matrix resin itself
The transparency of the matrix resin itself has a great impact on the transparency of PP products. In order to improve PP transparency, a small amount of polyacrylate resin with good transparency and compatibility can be added.
2. Nucleating agent
The rate of crystallization and the proportion of crystallization can be increased.
(1) the inorganic nucleating agent mainly consists of ultra-fine talc powder and SiO2, and also includes calcium carbonate, mica powder, inorganic pigments and fillers, etc., which is cheap in price and rich in source, but has certain influence on the gloss and transparency of the products.
(2) organic nucleating agent organic nucleating agent is a kind of organics with low relative molecular weight, represented by sorbitol and its derivatives. It has good compatibility with matrix resin and can significantly improve product transparency and surface gloss.
(3) in the case of sorbitol, when the amount of nucleating agent exceeds 0.3%, the effect of transparency improvement is not obvious, and 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 amount of nucleating agent should be between 0.2-0.3%. Therefore, suitable nucleating agent content can better improve the transparency of PP.

3. Molding temperature
If the temperature is too high, substances with low molecular weight in the nucleating agent will decompose and volatilize, reducing the active ingredients in the nucleating agent and reducing the improvement effect of transparency. Moreover, higher temperature will damage the original crystal nucleus in PP and reduce the heterogeneous nucleating center, resulting in lower modification effect. However, if the temperature is too low, the dispersibility of nucleating agent is not good, and the transparency effect is poor. Therefore, choosing a suitable molding temperature is particularly important for improving transparency.
4. Toughening agent
The toughening agent is not mutually soluble with PP, and the refractive index is different. The refraction will occur at the mutual interface, thus affecting the light transmittance of articles. With the increase of toughening content, the area of mutual interface is more intense, and the product's light transmittance is worse.

5. Process parameters
The process parameters, such as ideal processing temperature, cooling temperature and injection pressure, are also of great help to PP transparency.
Processing temperature: the lower the processing temperature, the smaller the crystallization 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 pressure maintaining time affect the orientation of molecules. The orientation will affect the crystallization of molecules, so the transparency can be improved to some extent by shortening injection and pressure maintaining time and reducing pressure without affecting the product performance and appearance.
6. Molding processing technology
Compared the products of injection, drawing and blowing process, it is found that injection and blowing process is most beneficial to increase transparency.
7, mould
The higher the finish of the mold, the more transparent the products will be.