How To Optimize Injection Technology And Improve PC/ABS Electroplating Performance?

Electroplated PC/ABS plastic products are widely used in automobiles, home appliances and IT fields for their bright metal appearance. Material formula design and electroplating process are generally considered to be the key factors affecting the electroplating performance of PC/ABS, but few people pay attention to the impact of injection molding process on electroplating performance.

 

Injection molding temperature

Under the condition of ensuring that the material is not easy to crack, a higher injection molding temperature can achieve better electroplating performance.

 

At a lower injection molding temperature, the fluidity of PC/ABS material is poor, and the molded product has a large internal stress. The stress is released during the passivation process, resulting in uneven ion implantation on the surface of the product, resulting in poor appearance of the electroplated product and poor electroplating adhesion.

 

And a higher injection molding temperature can reduce the injection residual internal stress of the product, thereby improving the electroplating performance of the material. Relevant research shows that compared with the product with an injection temperature of 230℃, when the temperature is increased to 260℃-270℃, the coating adhesion is improved by about 50%, and the surface appearance defect rate is also greatly reduced.

However, the injection temperature should not be too high. If it exceeds the cracking temperature of the material, it may cause the surface appearance of the injection molded product to be poor, thereby affecting its electroplating performance.

 

Injection molding speed and working pressure

Lower injection molding working pressure and appropriate injection molding speed are beneficial to improving the electroplating performance of PC/ABS.

 

Excessive injection molding pressure will cause excessive extrusion of the internal molecular structure of the product, resulting in higher product internal stress, resulting in uneven product passivation and weak electroplating adhesion;

 

Appropriately increasing the injection molding speed can increase the cutting of the glue inlet, resulting in an increase in the liquid temperature, thereby increasing the fluidity of the entire material, which is beneficial to the filling of the product and reducing the internal stress of the product; but cutting too much will cause the cracking of the material, resulting in problems such as gas marks, peeling, and burrs.

 

Packaging pressure and packing transition point

Too high packing pressure and late packing transition point can easily lead to overfilling of the product, stress at the inlet, and high residual stress inside the product. Therefore, the packing pressure and packing transition point should be set according to the actual product filling situation.

 

Mold temperature

High mold temperature is beneficial to improving the electroplating performance of the material.

 

Under low mold temperature, the material has poor fluidity. During the filling process, the product is squeezed and stretched between molecules, resulting in a serious tendency of molecular chains of the material after cooling. The product has large internal stress and poor electroplating performance. On the contrary, under high mold temperature, the material has good fluidity, which is conducive to filling. The molecular chain is in a natural curling state, the product has low internal stress, and the electroplating performance is greatly improved.

 

The specific mold temperature setting must be set in combination with the mold water channel, heating method and molding cycle requirements. The mold temperature should be increased as much as possible without affecting other properties. While controlling the mold temperature, the mold temperature distribution should be kept uniform. Uneven mold temperature distribution will cause uneven shrinkage stress and affect the electroplating performance.

 

Extruder screw speed ratio

A lower extruder screw speed ratio is beneficial to improving the electroplating performance of the material.

 

The setting of the extruder screw speed ratio controls the metering time of the plastic, that is, the time when the plastic enters the material pipe, is mixed by the extruder screw, and is transported to the nozzle.

 

The extruder screw speed also affects the uniformity of melting. Too fast an extruder screw speed will aggravate the shearing of the material in the extruder screw, and the melt temperature will rise sharply. The faster the extruder screw speed, the worse the mixing effect of the plastic, resulting in greater melt temperature differences, which will also cause differences in filling fluidity and cooling, which is one of the main reasons for the generation of internal stress in the product.

 

Therefore, generally speaking, under the premise of ensuring the melting of the material, the extruder screw speed can be set to make the metering time shorter than the cooling time.