How to Solve Product Cracking After Adding Color Masterbatch in Injection Molding Process

Under sunlight exposure, the issue of striped pigment bands in products needs to be considered from two aspects: the physical and mechanical properties of the plastic and the plastic molding process.

The temperature of the injection molding equipment is not properly controlled, causing the color masterbatch to fail to fully mix with the resin after entering the mixing chamber.

If the injection molding machine is not set with a certain back pressure, the mixing effect of the screw will be poor.

The dispersion of the color masterbatch is poor or the resin is not properly plasticized.

In terms of process, the following adjustments can be made:

Slightly increase the temperature near the feeding port of the mixing chamber.

Apply a certain back pressure to the injection molding machine.

If the issue persists after the above adjustments, it may be due to the dispersibility or compatibility of the color masterbatch or resin. In this case, please contact the color masterbatch manufacturer for a solution.

After using a certain color masterbatch, the product appears to be prone to breakage. This may be caused by poor quality dispersants or additives selected by the manufacturer, resulting in poor dispersion and compatibility, which affects the physical and mechanical properties of the product. When using the masterbatch according to the proportions specified in the instruction manual, if the color turns out too deep (or too light), although this problem seems simple, there are actually many possible reasons, specifically:

The masterbatch was not carefully tested for color, resulting in either too little or too much pigment.

Measurement is often inaccurate during use, and the phenomenon of arbitrary measurement by small and medium-sized enterprises is widespread.

The mismatch between the color masterbatch and the resin may be due to the inappropriate selection of the masterbatch carrier or the manufacturer's arbitrary change of the resin type.

The machine temperature is inappropriate, and the color masterbatch stays in the machine for too long.

HandlerFirst, check if the type of resin matches the masterbatch and whether the measurement is accurate. Then, adjust the machine temperature or speed. If the problem persists, contact the masterbatch manufacturer.

The same color masterbatch, resin, and formula produce products with different shades on different injection molding machines.

This is often caused by the injection molding machine. Different injection molding machines, due to variations in manufacturing, usage duration, or maintenance conditions, result in differences in mechanical conditions. Especially the degree of contact between the heating element and the barrel varies, causing the dispersion state of the color masterbatch in the barrel to differ, leading to the aforementioned phenomenon.

After switching to a different brand of resin, using the same color masterbatch and formulation, the color changed. Why is this?

Different grades of resin have differences in density and melt index, resulting in variations in their properties and in their compatibility with color masterbatch, which can lead to color changes. Generally speaking, as long as the differences in density and melt index are not significant, the color variation will not be substantial and can be adjusted by modifying the amount of color masterbatch used.

Does pigment migration occur during the storage of color masterbatch affect the quality of the product?

Some masterbatches have a high pigment (or dye) content, and in such cases, migration is normal. Migration is particularly severe with masterbatches containing dyes. However, this does not affect the quality of the product, because once the masterbatch is injected into the product, the pigment is present at a normal color concentration within the product.

Why do some injection-molded products have poor glossiness?

There are several possibilities:

The nozzle temperature of the injection molding machine is too low; the mold surface finish of the injection molding machine is poor; the product molding cycle is too long; the color masterbatch contains too much titanium dioxide; the dispersion of the color masterbatch is poor.