Plastic electroplating products not only have the advantages of lightweight and excellent mechanical properties of plastics, but also have a good metal appearance. They are widely used in the fields of automotive interior and exterior decoration and toiletries. Among them, the coating adhesion performance is an important index to evaluate the quality and function of plastic electroplating products. The effect of pre-treatment of plastic electroplating plays a key role in the adhesion between the coating and the substrate of plastic electroplating products.

Analysis of existing pretreatment technology

Principle and method

Coarsening includes mechanical coarsening and chemical coarsening. The purpose is to roughen the plastic surface to increase the bonding force between the substrate surface and the coating. The adhesion of the coating obtained by mechanical roughening is relatively limited, and the surface will lose luster, which is very unfavorable for decorative electroplating and can only be used for matte products. Chemical roughening can obtain a coating adhesion about 10 times higher than mechanical roughening, and a uniform surface can be obtained. It is through the reaction of some substances in the plastic with the roughening liquid, thus forming a depression on the surface of the part with a diameter of 0.2μm to 1μm, increasing the contact area between the electroplating surface and the plastic surface, improving the hydrophilicity and roughness of the plastic surface, so as to ensure a good adhesion between the coating and the substrate.

Weakness analysis

The chemical roughening effect is affected by many factors, including substrate type, roughening degree and substrate surface structure. Among them, the surface structure of the substrate will be greatly affected by the shear stress on the surface of the substrate. Especially for plastics with complex structure, for two-color injection molded parts, due to the fixed thickness of the parts, after the two-layer two-color injection molding process is changed, the thickness of the single layer becomes thinner, so that the flow resistance of the molten material in the mold becomes larger, so that the surface shear stress becomes larger, which greatly affects the surface structure of the substrate, and the surface with excessive stress also makes it difficult for the coarsening solution to invade the substrate, resulting in a serious decrease in the bonding force between the coating and the substrate after electroplating, and even the situation that the plating cannot be carried out occurs.

In practical work, if the coarsening effect is not good, it is necessary to add a pre-coarsening process before the first process of the pretreatment process. However, the pre-coarsening process is generally used in the whole process, which is often used in organic solvents such as acetone. There are huge hidden dangers such as fire safety and occupational diseases, as well as environmental protection pressure. For plastic electroplating production enterprises, the whole surface process will be avoided as much as possible, but the improvement of other influencing factors is limited. In order to meet the minimum coating adhesion performance requirements for product use, it is necessary to optimize the coarsening process of electroplating pretreatment.

Application Analysis of Plasma Treatment Technology in Pretreatment of Plastic Electroplating

Engineering philosophy

Plasma is an ionized gaseous substance formed by the detachment of some or all electrons from atoms or molecules. Its main components include positively charged ions, negatively charged electrons and neutral particles. In this state, whether the gas is partially ionized or completely ionized, the total number of positive and negative charges in it remains equal, so it is called plasma. Plasma, also known as plasma, is considered to be the fourth state of matter in addition to solid, liquid and gaseous states.

Plasma surface treatment technology can directly clean and etch the surface of the material without introducing impurities while grafting functional groups to improve the hydrophilicity of the material. The treatment of the material only affects tens of nanometers below the surface without destroying the internal structure. The process is simple, safe, non-toxic and environmentally friendly, and can be used for plastic coarsening. By plasma etching plastic surface, the surface roughness can be improved, thereby improving the adhesion between the coating and the substrate.

Advantage analysis

The application of low temperature plasma surface treatment technology to the pretreatment of plastic plating can replace the three steps of oil removal, coarsening and neutralization on the surface of plastic in the traditional process, so that the reaction can be carried out efficiently and quickly. The reaction conditions are mild, the process is simple and safe, and it is non-toxic and environmentally friendly. It will not affect the structure and properties of plastics, and the coarsening effect is better. While coarsening, it can also improve the hydrophilicity of plastic substrate and provide sufficient anchoring points for metal particles. Moreover, the plasma treatment process is low in cost, simple in operation, and suitable for large-scale production. At the same time, it also solves the problem of poor coating adhesion of complex structural injection molded parts, especially two-color injection molded parts, improves product quality and brings huge economic benefits.