Electroplated PC / ABS modified plastic parts are widely used in automobiles, home appliances and IT industries due to their beautiful metallic appearance. Material formulation design and plating process are generally considered to be the main factors affecting the plating performance of PC / ABS modified plastics. However, few people have paid attention to the impact of modified plastic injection molding process on the plating performance.

Injection temperature

Under the condition that the material will not be cracked, higher injection temperature can get better plating performance.

At lower injection temperature, the fluidity of PC / ABS modified plastic material is poor, and the injection molded product has a large internal stress. During the roughening process, the stress is released, resulting in uneven etching on the surface of the product, which in turn causes electroplating. The appearance of the product is poor, and the plating adhesion is poor.

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

However, the injection molding temperature should not be too high. If the cracking temperature of the material is exceeded, the appearance of the surface of the injection molded product will be poor, which will affect its plating performance.

Injection speed and pressure

Lower injection pressure and appropriate injection speed are beneficial to improve the plating performance of PC / ABS modified plastics.

Excessive injection pressure will cause excessive extrusion of molecules inside the product, resulting in higher product internal stress, which will lead to uneven product roughening and poor plating adhesion;

Properly increasing the injection speed can increase the shear at the gate position, leading to an increase in the temperature of the fluid, which will increase the fluidity of the entire material, which is conducive to the filling of the product and reduces the internal stress of the product; but too much shear will cause the material Cracking, producing air marks, peeling, burrs and other problems.

Holding pressure and holding pressure switching point

An excessively high holding pressure and a later holding pressure switching position may easily lead to overfilling of the product, stress concentration at the gate position, and high residual stress inside the product. Therefore, it is necessary to set the holding pressure and the holding pressure switching point in combination with the actual product filling state.

Mold temperature

High mold temperature is beneficial to improve the plating performance of the material.

In the low mold temperature state, the material has poor fluidity. During the filling process of the product, due to the squeeze and stretching between molecules, the molecular chain of the material is severely oriented after the product is cooled down, the internal stress of the product is large, and the plating performance is poor. On the contrary, under high mold temperature conditions, the material has good fluidity, which is conducive to filling, the molecular chain is in a natural curled state, the internal stress of the product is small, and the plating performance is greatly improved.

The actual mold temperature setting needs to be set in combination with the requirements of the mold waterway, heating method and molding cycle. The mold temperature should be increased as much as possible without affecting other performance; while controlling the mold temperature, it is also necessary to maintain a uniform temperature distribution of the mold , Uneven mold temperature distribution will cause uneven shrinkage internal stress and then affect plating performance.

Screw speed

A lower screw speed is beneficial to improve the plating performance of the material.

The setting of the screw speed is to control the measuring time of the plastic, that is, the time for the plastic to enter the material tube to be mixed by the screw and transported to the nozzle.

The rotation speed of the screw also affects the uniformity of plasticization. A too fast rotation speed of the screw will increase the shear of the material in the screw, the melt temperature will rise sharply, and the faster the rotation speed of the screw, the worse the mixing effect of the plastic will form a melt glue. The increase in temperature difference causes the difference in filling flow and cooling, which is one of the main reasons for the formation of internal stress in the product.

Therefore, generally speaking, on the premise of ensuring the melting of the material, the screw speed can be set to make the measurement time slightly shorter than the cooling time.

to sum up:

In the injection molding process, the injection temperature, injection speed and pressure, mold temperature, holding pressure, and screw speed will all affect the plating performance of PC / ABS modified plastics.

The most direct adverse effect is too high internal stress of the product. Excessive internal stress will affect the uniformity of the etching in the roughening stage of the electroplating, and then affect the electroplating binding force of the final product.

In short, it is necessary to combine the product structure, the state of the mold, and the state of the molding machine, and set the appropriate modified plastic injection molding process to reduce the internal stress of the material, which can significantly improve the plating performance of PC / ABS modified plastic materials.