LCP material injection molding process and applications
The molding temperature of LCP plastic raw materials is high, and the melting temperature is in the range of 300 to 425 ° C due to different varieties. LCP has low melt viscosity and good fluidity, similar to olefin plastics. LCP has a very small coefficient of linear expansion and good dimensional stability. The molding processing conditions are as follows: molding temperature 300~390°C; mold temperature 100~260°C; molding pressure 7~100MPa, compression ratio 2.5~4, molding shrinkage 0.1~0.6.
Generally, the barrel temperature, nozzle temperature, and material melting temperature are shown in the table.
If the life of the screw is taken into account, the temperature difference between the rear part, the middle part and the front part can be reduced. In order to prevent the nozzle from flowing, the nozzle temperature can be 10 ° C lower than the temperature shown in the table. If the fluidity is to be increased, the temperature can be set to 20 ° C higher than the temperature shown in the table, but the following must be noted.
When the temperature of the cylinder is lowered: the residence time is too long, the pellets will not be aged in the cylinder, and corrosive gas will not be generated, so the long residence time generally does not cause any major problems. However, if the molding is interrupted for a long time, lower the temperature of the barrel. When molding again, it is better to throw away the mold.
2. Mold temperature
The mold temperature of LCP plastic material can be molded between 30 °C and 150 °C. However, we generally set the mold temperature to around 70 °C - 110 °C. In order to shorten the molding cycle, prevent flash and deformation, choose a low mold temperature; if the product size is required to be stable (especially for products under high temperature conditions), reduce the occurrence of weld seams and solve the problem of insufficient filling, etc. Choose a high mold temperature.
The speed of the screw is typically 100 rpm. In the case of glass-containing or carbon-containing glass (eg A130, A230, etc.), in order to prevent the glass fiber from being broken, we must choose a lower speed. In addition, the back pressure is as low as possible. When the barrel temperature is set to 300 ° C, the residence time of the material in the barrel has an effect on the mechanical properties and color of the plastic.
4. Injection pressure and injection speed
The most suitable injection pressure must depend on the material, the shape of the product, the mold design (especially the sprue, runner, gate) and other molding conditions. However, LCP has no grade and its melt viscosity is very low, so the injection pressure is lower than that of ordinary thermoplastic resins. It is a good method to use low pressure at the beginning of the molding and then slowly increase the pressure. The molded article can be molded under the injection pressure of 15 MPa to 45 MPa. In addition, the curing time of the LCP is relatively fast, so a fast injection speed is easy to obtain good results.
5. Molding cycle
The molding cycle depends on the size, shape, thickness, mold structure and molding conditions of the molded article. As mentioned above, LCP has good fluidity, so its filling time is short and the curing speed is faster, so we can get a shorter molding cycle. A representative molding cycle is from 10 seconds to 30 seconds.
The main applications:
1) LCP plastic materials are excellent in high strength, high rigidity, high temperature resistance, electrical insulation, etc., and are used in electronics, electrical, optical fiber, automotive and aerospace.
2) Fiber made of LCP material can be used as fish net, bulletproof clothing, sporting goods, brake pads, optical fiber display materials, etc., and can also be made into film for soft printing lines, food packaging and so on.
3) LCP plastic materials have been used in microwave ovens to withstand high and low temperatures. LCP can also be used for printed circuit boards, satellite electronic components, jet engine parts; for electrical and electronic machinery parts or components; and for medical applications.
4) LCP plastic raw materials can be added with high filler as integrated circuit packaging material, instead of epoxy resin as the encapsulation material of coil bobbin; for fiber optic cable joint sheath and high strength components; instead of ceramic as filling material in chemical separation tower Wait.
5) LCP plastic raw materials can also be blended with polysulfone, PBT, polyamide and other plastics to form alloys. After molding, the mechanical strength is high, which can replace plastics such as glass fiber reinforced polysulfone, which can improve mechanical strength. It can also increase the strength of use and chemical stability.
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