PPS material: injection molding process of PPS plastic

Although the moisture absorption of PPS plastics is weak, in order to improve the appearance of the products and prevent salivation, pre drying at 140 ℃ for 3 hours or 120 ℃ for 5 hours is still needed.

In order to prevent bridging during drying, it is recommended to pre dry at 105 ℃ for 5 hours according to the specific conditions of the grade.

Due to the strong hygroscopicity of carbon fibers, pre drying is especially necessary for carbon fiber reinforcement grades (2130a1, 7140a4, etc.).

As far as natural color is concerned, in order to obtain more stable color phase, the drying conditions should be kept uniform.

Precautions for setting molding conditions

(1) Barrel temperature

When the barrel temperature under the hopper is excessively reduced, the friction between the barrel and the screw tends to increase.

If there is no liquidity problem, a small cooling will help to reduce retention discoloration. In particular, it is set at 300-320 ℃ for the molding of non black molding products.

(2) Mold temperature

The mold temperature has a great influence on the characteristics.

From the appearance, dimensional stability, heat resistance and creep resistance, the mold temperature is higher than 130 ℃ but not lower than 120 ℃.

(3) Injection pressure

The injection pressure of 30-100mpa is usually used. In order to reduce the flash, it is recommended to carry out low pressure forming.

(4) Injection speed

In order to obtain a good appearance, high-speed injection should be carried out. However, high-speed injection can easily lead to warping and scorching of the molding products, so as long as the appearance is good, there is no need to overuse high-speed injection. Zhenghao special engineering plastics is specialized in the production and sales of PPS plastic raw materials with complete models and preferential prices. Welcome to call us for negotiation. Fortune hotline: 13656263509, contact person: Mr. Yan.

(5) Back pressure

In order to keep the measurement stable, it is suggested to set the back pressure at 2 ~ 5MPa. When the measurement is unstable, the back pressure can be increased to 8-10 MPa.

(6) Screw speed

Generally, 40-100 rpm is suitable. Do not exceed 200rpm, otherwise the glass fiber will be cut off and the resin will be heated.

(7) Retention in cylinder

Even if PPS plastic remains in the barrel for a long time, its viscosity will not increase significantly. It can be seen that the use of hot runner is effective.

Cleaning after molding

It is suggested that under normal conditions, under the condition of maintaining the barrel temperature of PPS plastic molding, first use polycarbonate containing glass fiber, then use polyethylene to clean, and then use the two to repeatedly clean alternately. The efficiency will be higher if the cleaning material in the cylinder is completely discharged and then loaded with the next cleaning material. Polycarbonate containing glass fiber can also be replaced by commercially available acrylic cleaning materials.

The following describes the stop and start of molding machine and material switching method.

(1) When forming stops

It is recommended to clean durafide at the same barrel temperature as durafide, and then use resins with good thermal stability (HDPE, commercial acrylic cleaning materials, etc.) at the same molding temperature as durafid. If durafide molding is to be continued, only durafid can be used for cleaning.

(2) At the beginning of molding

If the resin in the barrel is stable within the molding temperature range of PPS plastic, it can be heated to the molding temperature of PPS plastic intact, and then cleaned with PPS plastic.

If the molding temperature range of the resin is different from that of the PPS plastic, it is recommended to adjust the barrel temperature to the molding temperature of the residual resin in the barrel, and then use the resin (high-density polyethylene, polycarbonate, as the case may be) that can be used at both the molding temperature of the PPS plastic and the residual resin, and then set the molding temperature of the PPS plastic and clean it 。

If the resin in the barrel is PPS plastic, it can be heated to the molding temperature of PPS plastic intact and cleaned.

(3) Resin switching

If it is a resin that can be switched with PPS plastic intact, it can be cleaned intact while keeping the barrel temperature according to the above molding stop and start method. Zhenghao special engineering plastics is specialized in the production and sales of PPS plastic raw materials with complete models and preferential prices. Welcome to call us for negotiation. Fortune hotline: 13656263509, contact person: Mr. Yan.

If it is a resin that cannot be switched with PPS plastic intact, it is recommended to clean the resin with good thermal stability (HDPE, etc.) at the molding temperature of both PPS plastic and the resin to be switched, and then set the molding temperature.

(4) Others

If it is kept in the cylinder for a long time, the natural color of PPS plastic will sometimes change color, so it should be cleaned thoroughly.