Due to the special structure of plastic surface, although the surface of plastic parts is modified through surface pretreatment, the weak interface layer is removed, the surface of plastic parts is activated, and the adhesion of coating film is increased, the selection of coating, coating process and coating environment management in the manufacturing of mechanical plastic shell will also affect the coating quality.

Therefore, the selection of mechanical plastic shell coating should follow the "similar phase solubility principle", in order to ensure the good miscibility of ABS and coating resin and solvent, make the coating film and plastic surface form a very thin mutually soluble layer, enhance the adhesion, not only have a good decorative effect, but also meet the physical and chemical performance requirements of the paint film.

At present, mechanical plastic shell coating mostly use manual air spraying process, labor intensity, poor working environment, coating efficiency is only about 20% ~ 30%, paint loss, high cost, man-made quality instability factors directly affect the quality of products.

With the development of science and technology, mechanical plastic shell manufacturing industry in the mold coating in the plastic processing development is very fast, that is, the use of electrostatic coating coating in the mold wall, in the plastic molding, at the same time to complete the surface coating of plastic parts. Due to the plastic molding temperature is higher, is conducive to the coating curing, the mold itself roughness is very low, therefore, the coating surface is very clean, high gloss.

After the mechanical plastic shell is moulded, the mold is slightly lifted, injected into IMC at high pressure, the mold is closed at high pressure to make IMC fully expanded, and after hardening, the plastic surface is very smooth, it can get high quality decorative products at a low cost, and the moulded parts can be immediately packaged or sent for assembly, very convenient.

The mechanical plastic shell of these two coating technology coatings are solvent-free, no organic solvents in the process of operation, so there is no environmental pollution, paint utilization rate is very high, to avoid heavy painting, no special coating equipment, when the injection is completed painting.