1、 Barrel temperature
Generally, barrel temperature, nozzle temperature and material melting temperature are shown in Table 1.
If the service life of the screw is taken into account, the temperature difference in the rear, middle and front can be reduced. In order to prevent the nozzle from salivating, the nozzle temperature can be 10 ℃ lower than the temperature shown in the table. If the fluidity is to be improved, the set temperature can be 20 ℃ higher than the temperature shown in the table, but the following conditions must be noted.
When lowering the barrel temperature: if the retention time is too long, it will not lead to the aging of granular materials in the barrel, and no corrosive gas will be produced. Therefore, the long residence time will not cause any major problems. However, if the molding is interrupted for a long time, please lower the barrel temperature and throw away several molds when molding again.
Barrel temperature (℃) during molding of each grade
2、 Mold temperature
The mold temperature of LCP molding is between 30 ℃ and 150 ℃. But we usually set the mold temperature at 70 ℃ - 110 ℃. In order to shorten the molding cycle, prevent flash and deformation, low mold temperature should be selected; if the product size is required to be stable (especially for products under high temperature conditions), the generation of fusion joint and the problem of insufficient filling should be reduced, then the high mold temperature should be selected.
Barrel temperature: 300 ℃
Retention time 0 min refers to the molding under normal cycle
Figure 1 Relationship between the retention time in the barrel and the retention rate of tensile strength
Residence time in barrel (min)
Barrel temperature: 300 ℃
Retention time 0 min refers to the molding under normal cycle
Figure 2 Relationship between the retention time in the barrel and the retention rate of tensile rate
Residence time in barrel (min)
Barrel temperature: 300 ℃
Retention time 0 min refers to the molding under normal cycle
Figure 3 residence time and discoloration (△ E) in the barrel
Temperature (℃) Fig. 4 thermal decomposition curve
When the barrel temperature is set at 300 ℃, the influence of the material residence time in the barrel on the mechanical properties and color is shown in Fig. 1-fig. 2. The mechanical properties of the non filling stage will decrease slightly when it is retained in the barrel for 15 minutes. However, the mechanical properties of GF remain unchanged when it is retained in the barrel for 60 minutes.
Either one has a slight change in color (△ E).
The weight loss obtained by thermobalance is shown in Fig. 4. The temperature at which the decomposition begins gradually is about 460 ℃, much higher than the usual molding temperature.
3、 Plasticizing
The screw speed is generally 100 rpm. If it is a material containing glass fiber or carbon glass fiber (such as a130, A230, etc.), in order to prevent the glass fiber from being broken, we must choose a relatively low speed. In addition, the back pressure should be kept as low as possible
4、 Pressure and speed
The most suitable pressure must depend on the material, product shape, mold design (especially straight gate, runner, gate) and other molding conditions. However, LCP has no grade and its melt viscosity is very low, so the pressure is lower than that of general thermoplastic resin.
At the beginning of molding, use low pressure, then slowly increase the pressure, which is a better method. Most of the molded products can be molded under the pressure of 15mpa-45mpa. In addition, the curing time of LCP is relatively fast, so it is easy to get good results if the curing speed is fast.
5、 Molding cycle
The molding cycle depends on the size, shape, thickness, mold structure and molding conditions of the product. As mentioned above, LCP has good fluidity, so its filling time is relatively short, and the curing speed is relatively fast, so we can get a shorter molding cycle. The typical molding cycle is 10 seconds - 30 seconds
