The injection molded polypropylene (PP) sample is easy to yellow and opaque. How can I get PDouble Screw Extruder Machinep products with higher transparency?

Date:2022-7-19 Author:Sam

PP is very sensitive to oxygen, and yellowing may be oxidized degradation during processing. PP is a semi -crystalline polymer. The level of crystallization and the size of the crystalline size are very large to the mechanical properties of the product and the optical properties. Due to the different refractive indexes of the crystal area and the amorphous area, the interface will be refracted or reflected. When the crystallization of the polymer increases, the mechanical properties will be significantly improved, but the transparency will decrease. Therefore, the reduction of size is an increase in increased Pelletizing line The transparency of the polymer is very effective. The melting point of the PP is 170-172 ° C, the decomposition temperature is above 300 ° C, and the contact temperature of the oxygen starts to turn yellow at 260 ° C. Therefore, the suitable processing temperature is between 180-225 ° C.



Therefore, if you want to obtain PP products with higher transparency, you can use the following methods:


1. \u0026 nbsp; reduce processing processing Temperature, best between 180-200 ° C. When the processing temperature is low, there are many original crystal nuclei remaining in polypropylene melting. When cooling, it plays the role of crystal nucleus, which accelerates the crystallization speed, inhibits the size of the crystal, and improves the transparency of PP. Essence


2. \u0026 nbsp; reduce the modular temperature, set between 30-60 ° C. When the sudden cold can be generated in the PP, the increase of the quasi -crystal can increase the number of polypropylene and crystal speed, thereby increasing transparency.


3. \u0026 nbsp; add a transparent nuclear agent. A large number of active points increase the number of crystal nuclei, and significantly speed up the crystallization rate, increase the number of crystals, hinders the growth of the crystal, and reduces the size of the ball crystal. The product obtained by this method is high, and the mechanical properties have improved to a certain extent.