Goodtech is a leading plastic injection molding manufacturer in China. Many types of plastics are used in the plastic injection molding process. Now I will introduce the injection molding process of PC plastics.
PC plastic has the characteristics of high mechanical strength, wide operating temperature range, good electrical insulation performance, good dimensional stability, and transparency.
1. Plastic processing
PC has a high water absorption rate. It must be preheated and dried before processing. Pure PC is dried at 120°C, and modified PC is generally dried at 110°C for more than 4 hours. The drying time cannot exceed 10 hours. Generally, the air extrusion method can be used to judge whether the drying is sufficient.
The use ratio of recycled materials can reach 20%. In some cases, 100% recycled materials can be used, and the actual amount depends on the quality requirements of the product. Imported plastic agent company's recycled materials cannot mix different masterbatches at the same time, otherwise it will seriously damage the nature of the finished product.
2. Selection of injection molding machine
Due to cost and other reasons, current PC products often use modified materials, Chi Mei 757, especially electrical products, but also need to increase fire resistance. When flame-retardant PC and other plastic alloy products are molded, the plasticizing system of the injection molding machine The requirement is good mixing and corrosion resistance. Conventional plasticizing screw is difficult to achieve. When choosing to purchase, it must be stated in advance.
3. Mould and gate design
The common mold temperature is 80-100℃, and the glass fiber is 100-130℃. Small products can use needle gates. The gate depth should be 70% of the thickest part. Other gates have rings and rectangles.
The larger the gate, the better, to reduce defects caused by excessive shearing of the plastic. The depth of the exhaust hole should be less than 0.03-0.06mm, and the runner should be as short and round as possible. The draft angle is generally about 30'-1.
4. Melting temperature
The air injection method can be used to determine the processing temperature. Plastic import agents can not only help us use plastic products scientifically, but also facilitate the classification and recycling of plastics, and effectively control and reduce "white pollution". General PC processing temperature is 270-320℃, some modified or low molecular weight PC is 230-270℃.
5. Injection speed
It is more common to use faster injection speed for molding, such as electrical switch parts. Common is slow → rapid prototyping.
6. Back pressure
The back pressure of about 10bar can be appropriately reduced without air lines and color mixing.
7. Detention time
If the residence time is too long at high temperature, the material will degrade, release CO2, and turn yellow. Do not use LDPE, POM, ABS or PA to clean the barrel. Apply PS cleanup.
8. Matters needing attention
Some modified PCs are easy to produce dark brown liquid bubbles due to too many recycling times or uneven mixing of various components.
Publish Date: January 13, 2021 5:57 AM