How to solve the uneven color of injection molded products?
Uneven color can be caused by uneven distribution of pigments, especially when injection molded products are colored by masterbatches, toners or liquid pigments. At temperatures lower than the recommended processing temperatures, the masterbatch or pigment cannot be completely homogenized.
When the molding temperature is too high, or the residual time of the barrel is too long, it is also easy to cause thermal degradation of pigments or plastics, resulting in uneven color.
When the material is plasticized or homogenized at the correct temperature, if it is injected too quickly when passing through the cross-section of the feed, frictional heat may be generated that can cause degradation of the pigment and change of color. In general, when using color masterbatches, the compatibility of the chemical and physical properties of the pigment and the resin to be colored by the dissolved solution should be ensured.
Causes and solutions related to processing parameters:
1. The material is not evenly mixed, which reduces the speed of the screw, increases the temperature of the barrel, and increases the back pressure of the screw.
2. The melting temperature is too low, which increases the temperature of the barrel and increases the back pressure of the screw.
3. The back pressure of the screw is too low, and the back pressure of the screw is increased.
4. The screw speed is too high, reduce the screw speed.
Design-related causes and solutions:
1. If the screw stroke is too long, use a barrel with a larger diameter or a larger length diameter.
2. The residence time of the melt in the barrel is short, and the barrel with a larger diameter or a larger length and diameter is used.
3. The screw L:D is too low, and the barrel with a large length and diameter ratio is used
4. The screw compression ratio is low, and the screw with a high compression ratio is used.
5. There is no shear section and mixed section, and cut and mixed section are provided.
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