PC plastic is generally called polycarbonate, because of its excellent mechanical properties, commonly known as bulletproof adhesive. PC plastic has high mechanical strength, wide range of temperature, good electrical insulation (but no change in arc resistance, good dimensional stability, etc.). This machine vertical injection molding machine is committed to provide customers with the best vertical injection molding machine process solutions. To provide customers with the most appropriate technology and scheme, To meet the needs of high quality products.
There are many modified products which are widely used in electrical products, electric instrument shells and electronic products structure parts. They are usually filled with fiberglass, mineral fillers, chemical flame retardants, other plastics and other plastics. The fluidity and processing temperature of PC plastics are poor, and the processing temperature is relatively high. Therefore, the processing of many kinds of modified materials requires special plasticizing injection structure.
1. Treatment of plastics
PC must be preheated and dried before processing. When pure PC is dried at 120 ℃, modified PC is usually dried at 110 ℃ for more than 4 hours. Drying time can not exceed 10 hours.
The proportion of recycled materials can reach 20%. In some cases, 100% of recycled materials can be used, depending on the quality requirements of the products. The recycled materials can not mix different color masterbatch at the same time, otherwise the properties of finished products will be seriously damaged.
2. Selection of injection Molding Machine: due to cost and other reasons, many kinds of modified materials, especially electrical products, need to be improved in fire resistance when forming flame-retardant PC and other plastic alloy products. The requirement of plasticizing system of injection molding machine is to mix well, resist corrosion, the conventional plasticizing screw is difficult to achieve, must be explained in advance when selecting and purchasing. Huameda company has special PC screw for customers to choose.
3. Mold and gate design: common mold temperature 80-100 ℃, glass fiber 100-130 ℃, small products can be needle gate, the depth of the gate should be the thickest part of 70, other gates have ring and rectangle.
The bigger the gate, the better, so as to reduce the defects caused by excessive shear of plastic. The depth of vent hole should be less than 0.03-0.06mm, the flow channel should be as short and round as possible.
4. Melting temperature: the processing temperature can be determined by air injection. The processing temperature of PC is 270-320 ℃, and that of some modified or low molecular weight PC is 230-270 ℃.
5. Injection speed: the injection rate is usually formed with a high injection rate, such as a switch for an electric device. It is commonly used as a slow speed. →Rapid prototyping.
6. The back pressure of about 10 bar can be reduced properly without air stripe and color mixing.
Retention time: stay at high temperature for too long, the material will degrade, release CO2, become yellow. Do not use LDPE POM ABS or PA cleaning machine barrel. Apply PS cleaning.
Note: some modified PCs are easy to produce dark brown liquid bubbles due to too many times of recovery (reduction of molecular weight) or uneven mixing of various components.