PC-polycarbonate plastic injection molding processing technology
Chinese call PC-polycarbonate material is known as polycarbonate, because of its excellent mechanical properties, commonly known as bulletproof glue. PC material has high mechanical strength, a wide range of temperature, electric insulation performance is good, but the arc performance unchanged), good dimensional stability and transparency, etc. In the casing electrician products, all structures, electronic products are widely used. PC modified product is more, there are usually added glass fiber (GF), mineral filler (M), chemical flame retardants, and other plastic, etc. PC’s liquidity is poorer, the processing temperature is higher, so the many levels of modified materials processing need special plasticizing injection structure.
Characteristics of PC plastics
1, must be preheated before processing dry
The processing of plastic PC-polycarbonate bibulous rate is larger, must be preheated before processing dry, pure PC 120 ℃ drying, modified PC generally with 110 ℃ drying temperature more than 4 hours. The drying time can’t more than 10 hours. Generally available to the vacant extrusion method to determine whether a dry enough. The use of a reworked material ratio can reach 20%. In some cases, may use reworked material, 100% of the actual quantity depends on product quality requirements. Reworked material cannot mix different masterbatch, otherwise, it will seriously damage the nature of the finished product.
2，Choose materials according to the purpose
Selection of injection molding machine now PC products due to cost and other reasons, the use of modified materials, especially the electric products, still must increase the fireproof performance, in the flame retardant PC and other plastic molding, alloy products is mix well to the requirement of plastic injection machine plasticizing system, corrosion resistance, the conventional plasticizing screw hard, when the choose and buy, be sure to explain in advance.
3, Mold and gate design Common mold temperature is 80-100 ℃, and glass fiber is 100-130 ℃, small products available needle gate, the gate depth should be the thickest part of 70%, other gates are circular and rectangular. Gate the bigger the better, in order to reduce the plastic shear caused by excessive defects. The depth of the vent should be less than 0.03 0.06 mm, port as far as possible short and round. The draft is generally about 30 ‘- 1 °.
4，General PC-polycarbonate processing temperature is 270-270 ℃
Melt temperature can be used for empty injections to determine processing temperature. General PC processing temperature is 270-270 ℃, some modification or low molecular weight PC for 230-230 ℃.
5，back pressure around 10 bar back pressure
See more with the fast injection speed rate of injection molding, such as electrical switch parts. Common for slow and rapid prototyping. Backpressure around 10 bar back pressure, without gas lines and color mixture, can be appropriately reduced.
6, residence time
At high temperatures for a long time, material qualitative, cut out CO2, become yellow. Don’t use LDPE, POM, ABS or PA cleaning barrel. Application of PS. 8, matters needing attention Some modified PC material, due to too many times (lower molecular weight) or ingredients mixing unevenly, easy generation dark brown liquid.