6 Common Masterbatch Coloring Problems and Solutions | KCI Masterbatch

1. Stripe-like pigment bands appear on the product under sunlight

This issue should be analyzed from both plastic material properties and the molding process:

1. The injection molding temperature is not properly controlled, preventing the masterbatch from fully mixing with the resin inside the mixing chamber.
2. The injection molding machine does not apply enough back pressure, resulting in poor screw mixing performance.
3. The masterbatch has poor dispersion, or the resin is not properly plasticized.

Possible process adjustments:

1. Slightly increase the temperature near the feeding section of the mixing chamber.
2. Apply appropriate back pressure to the injection molding machine.

If the problem remains after these adjustments, it may be caused by poor dispersion or compatibility between the masterbatch and resin. In this case, it is recommended to contact the masterbatch supplier for further technical support.

2. The final product color is too dark or too light after adding the recommended ratio

Although this issue may seem simple, there are several possible causes:

1. The pigment concentration in the masterbatch may be too high or too low.
2. The dosage may not be measured accurately during production.
3. There may be compatibility issues between the masterbatch and resin, possibly caused by an unsuitable carrier resin.
4. The machine temperature may be improper, or the masterbatch may remain inside the machine for too long.

Recommended actions: First, check whether the resin type matches the masterbatch and confirm whether the dosage is accurate. Then adjust the machine temperature or screw speed. If the issue continues, contact the masterbatch manufacturer for support.

3. Why do products made with the same masterbatch, resin, and formula show different color shades on different injection molding machines?

This is often related to differences between injection molding machines.

Different machines may vary due to manufacturing design, years of use, or maintenance conditions. These differences affect the mechanical condition of the equipment, especially the contact between heating elements and the barrel.

As a result, the dispersion state of the masterbatch inside the barrel may vary, leading to differences in color depth or shade.

4. Why does the color change after switching to another resin brand, even when using the same masterbatch and formula?

Different resin grades may have different densities and melt flow indexes. These differences affect resin performance and compatibility with the masterbatch, which may lead to color variation.

In general, if the density and melt flow index are not significantly different, the color difference should not be too large. The color can usually be corrected by adjusting the dosage of masterbatch.

5. Will pigment migration during masterbatch storage affect product quality?

Some masterbatches contain a high concentration of pigments or dyes. In such cases, pigment migration during storage can be normal, especially when dyes are used.

However, this usually does not affect the quality of the final product. After the masterbatch is molded into the finished product, the pigment will be distributed at the normal coloring concentration inside the product.

6. Why do some injection-molded products have poor gloss?

There are several possible causes:

1. The nozzle temperature of the injection molding machine is too low.
2. The mold surface finish is poor.
3. The molding cycle is too long.
4. The masterbatch contains too much titanium dioxide.
5. The masterbatch has poor dispersion.