What is the cause of poor luster of injection molded products, and how can plastic manufacturers eliminate it?

(1) Defect characteristics

The main manifestation of poor luster of injection molding products is: the surface of plastic parts is dull or uneven luster.

(2) Causes of defects and elimination methods

The main reason for poor luster is that injection molds, injection molding processes, plastic raw materials, etc., the specific analysis is as follows.

1) Injection mold

A. If the mold factory for the injection mold cavity processing is poor, such as scars, microholes, wear, rough and other insufficient, it will react to the plastic parts, so that the surface of the plastic parts poor luster, in this regard, to carefully process the injection mold, so that the cavity surface has A small roughness, if necessary can be polished chrome plating.

B. If there is oil, water stains on the surface of the injection mold cavity, or too much release agent is used, it will make the surface of the plastic parts dark without luster, in this regard, it is necessary to remove oil and water stains in time, and limit the amount of release agent.

C. If the demoulding inclination of plastic parts is too small, it is difficult to demoulding, and the force is too large during demoulding, which makes the surface luster of plastic parts poor, in this regard, the demoulding inclination should be appropriately increased.

D. If the injection mold exhaust is poor, too much gas stays in the model, which also leads to poor luster, it is necessary to check and correct the mold exhaust system.

E. If the cross-sectional area of the injection gate and the runner is too small or suddenly changes, the plastic melt flows under too much shear force during the flow, resulting in turbulent flow, resulting in poor luster, in this regard, the cross-sectional area of the gate and the runner should be appropriately increased.

2) injection molding process

A. If the injection speed is small, the surface of the plastic parts is not dense, and the luster is poor, the injection speed can be appropriately increased.

B. For thick wall plastic parts, such as insufficient cooling, the surface will be hairy and the luster will be dark, in this regard, the cooling system should be improved.

C. If the pressure is insufficient, the pressure holding time is short, so that the density of plastic parts is not enough and the luster is poor, the pressure holding pressure and the pressure holding time should be increased

D. If the plastic melt temperature is too low, making the fluidity poor, easy to lead to poor luster, in this regard, should be appropriate to increase the melt temperature.

E. For the plastic parts made of crystalline resins, such as PE, PP, POM, etc., such as uneven cooling will lead to poor luster, in this regard, the cooling system should be improved to make it uniformly cooled.

F. If the injection speed is too large, and the gate cross-sectional area is too small, the gate will be dark and poor luster near the gate, for which the injection speed can be appropriately reduced and the gate cross-sectional area can be increased.

3) Plastic raw materials

A. The size difference of plastic raw materials is large, making it difficult to uniform plasticize, and the luster is poor, in this regard, the plastic raw materials should be screened.

B. Excessive addition of recycled materials in plastic raw materials affects the uniform plasticization of melt and poor luster, in this regard, the amount of recycled materials added should be reduced.

C. Some plastic raw materials will decompose and discolor at high temperature leading to poor luster, in this regard, raw materials with better temperature resistance should be selected.

D. The content of water or volatile substances in plastic raw materials is too high, volatilized into gas when heated, condensed in the cavity and melt, resulting in poor luster of plastic parts, which should be pre-dried plastic raw materials.

E. The dispersion of some additives is too poor and the luster of the plastic parts is poor, which should be changed to flow performance good additive.

F. Plastic raw materials mixed with foreign bodies, miscellany or insoluble materials, they can not be uniformly mixed with other raw materials and lead to poor luster, which should be strictly excluded in advance.

G. If the amount of lubricant is too little, the fluidity of the melt is poor, the surface of the plastic parts is not dense, making the luster poor, in this regard, the amount of lubricant should be appropriately increased.