How to solve the lusterless surface of plastic injection molded parts

Low gloss means a dull and non-glossy surface and low transparency of transparent products. There are many reasons for poor gloss. General product surface gloss defects can be divided into the following three categories: mold failure, improper molding conditions, and improper use of raw materials.

Injection mold failure

Since the surface of the plastic part is a reproduction of the surface of the mold cavity of the injection mold, if the surface of the injection mold has defects such as scratches, corrosion, microporosity, etc., it will be reproduced on the surface of the plastic part and produce a poor gloss. If the surface of the mold cavity is oily and wet, the surface of the plastic part will be darker. Therefore, the surface of the mold cavity of the injection mold should have a good glossy finish. The surface of the mold cavity must be kept clean and oil and water stains must be removed in time. The type and amount of mold release agent should be appropriate.

The temperature of the injection mold also has a great influence on the surface quality of the plastic parts. Usually, different types of plastics have different surface gloss at different temperature conditions, and the injection mold temperature should not be too high or too low, which may lead to poor gloss.

In addition, the injection mold release slope is too small, the thickness of the section is abruptly changed, the rib is too thick and the gate and sprue cross-section is too small, the shearing effect of the pouring system is too large, the injection mold exhaust is poor and other faults will affect the surface quality of the plastic parts, resulting in poor surface gloss.

Improper use of raw materials

Raw materials do not meet the requirements can also lead to plastic parts with poor surface gloss.

Cause: The moisture content in the molding raw materials is too high, and the volatile components condense and shrink in the cavity wall of the injection mold and during the molding process, resulting in poor surface gloss of the plastic parts. Treatment: The raw materials should be dried in advance.

Discoloration of raw materials or colorants leads to poor gloss. High temperature resistant raw materials and colorants should be used.

The fluidity of raw materials is too poor, the surface of plastic parts is not dense and the gloss is poor. Change the resin with better flowability or add the right amount of lubricant and increase the processing temperature.

The raw materials are mixed with impurities, and should be replaced with new materials in time.

Improper molding conditions

If the injection speed is too fast or too slow, the injection pressure is too low, the holding time is too short, the booster pressure is not enough, the nozzle hole is too small or the temperature is too low, the dispersion of fiber-reinforced plastic is too poor, the cylinder temperature is too low, the melt is poorly plasticized and the supply is insufficient, all these conditions may lead to poor surface gloss of plastic parts. For the reasons arising should be specific analysis on the specific causes, and then make the corresponding adjustments.

Of course, in daily production, the problems encountered may be much more than the above-mentioned aspects, and it is necessary to rely on the past rich experience and relevant knowledge to solve. # Injection molding processing