Key points of injection molding for PC plastic raw materials

PC plastic raw materials require high transparency, resulting in surface defects such as silver, black stripes, black spots, bubbles, and color differences. Therefore, special attention should be paid to the design of raw materials, machinery and equipment, molds, injection molding processes, and even the initial products.

1. PC plastic raw materials must be sealed, stored, transported, and produced to ensure that the raw materials do not contain any impurities and have a dust-free and pollution-free production environment. PC plastic raw materials contain moisture, and heating them without drying will cause material degradation due to moisture content. Therefore, it is necessary to dry them thoroughly.

2. Mold design and mold temperature

The design of the wall thickness of PC products should not be too thin, not less than 1 millimeter, and should be uniform. The draft should also be large enough; The transition section should be smooth and gradually transitioned, without any gaps during the condensation process; Set the gate position, make the gate and runner as wide and thick as possible, and if necessary, add a cold material well; The exhaust holes and slots must be considered sufficient.

The temperature of PC molds is generally controlled at 80-100 degrees Celsius. For other products with complex shapes, thin walls, or high requirements, it can be increased to 100-120 degrees Celsius, but cannot exceed the thermal distortion temperature of the mold.

3. Processing temperature

The processing temperature of PC plastic raw materials must consider the shape, size, mold structure, performance, and application of the product. The processing temperature is generally controlled between 270-320 degrees Celsius. The temperature of the material should not exceed 340 degrees Celsius. If it exceeds 340 degrees Celsius, the decomposition of PC will cause the product color to turn black, with defects such as dark stripes, black spots, bubbles, etc., significantly reducing various properties at the same time.

4. Injection pressure

The internal pressure injection pressure has a significant impact on the mechanical properties, molding shrinkage rate, appearance, and release performance of PC products to a certain extent. The surface of the product should be smooth to obtain a complete, and the general injection pressure should be controlled between 80 and 120 MPa. For products with thin walls, long processes, complex shapes, and small gates, a high injection pressure of 120 to 175 MPa is generally chosen.

5. Maintain pressure and duration

The pressure and holding time of PC product packaging have a greater impact on internal stress. If the holding pressure is too small, it will result in insufficient shrinkage effect, which can easily lead to vacuum bubbles or surface subsidence; Excessive holding pressure can easily generate internal stress near the entrance. So in the actual processing and production process, we use high temperature and low pressure solutions for the materials we use. The selection of holding time is consistent with the thickness, size, and mold temperature of the product. Generally, small and thin products do not require a long time, while thicker products have longer holding time. The pressure for long and short residence times can be determined by the gate sealing time.

6. Screw speed and back pressure

Due to the high viscosity of PC plastic raw materials, in order to prevent excessive screw load, we generally control the screw speed at 30 70r/min, and the back pressure is 1/10 of the injection pressure.