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

color masterbatch 

Temperature of injection molding equipment is not well controlled, color masterbatch cannot be fully mixed with resin after entering mixing chamber.

Injection molding machine does not add a certain amount of back pressure, mixing effect of screw is not good.

Dispersion of color masterbatch is not good or resin plasticization is not good.

Process can be debugged as follows:

Increase temperature of part of mixing cavity near discharge port slightly

Apply a certain amount of back pressure to injection molding machine.

If it is still not good after above debugging, it may be a problem of dispersion or matching of color masterbatch and resin, you should contact masterbatch manufacturer to solve it.

After using a certain color masterbatch, product appears to be easier to crack. This may be due to poor diffusion and mutual solubility caused by poor quality of dispersant or auxiliary agent selected by manufacturer, which affects physical and mechanical properties of product. Color is too dark (too light) after using according to proportion on masterbatch instruction manual. Although this problem is simple, there are many possibilities, specifically:

Color masterbatch has not been tested carefully, and pigment is too little or too much.

Measurement is inaccurate when in use, there are a lot of random measurement by small and medium-sized enterprises.

There is a problem with matching of color masterbatch and resin. This may be caused by improper selection of carrier of color masterbatch, or manufacturer may change resin variety at will

Temperature of machine is improper, and masterbatch stays in machine for too long.

Processing procedure: Firstly, check whether resin type matches color masterbatch and whether measurement is accurate. Secondly, adjust temperature or speed of machine. If there are still problems, you should contact masterbatch manufacturer.

With same color masterbatch, resin and formula, why are colors of products injected by different injection molding machines different?

This is often caused by injection molding machine. Different injection molding machines have different mechanical conditions due to different manufacturing, use time or maintenance conditions, especially difference in the degree of close contact between heating element and barrel, which makes dispersion state of color masterbatch in barrel different. Above phenomenon will appear.

After changing to another brand of resin, color of same masterbatch and formula has changed. Why?

Density and melt index of different grades of resin will be different, so performance of resin will be different, and compatibility with color masterbatch will also be different, resulting in a color change. Generally speaking, as long as density and melt index are not much different, difference in color will not be too great. You can correct color by adjusting amount of color masterbatch.

Will migration of pigments during storage of color masterbatch affect quality of product?

Some color masterbatches have high pigment content (or dyes). In this case, migration is normal. Especially color masterbatches added with dyes will cause serious migration. But this does not affect quality of product, because after color masterbatch is injected into product, pigment is in normal color concentration in the product.

Why do some injection products have poor gloss?

There are many possibilities:

Nozzle temperature of injection molding machine is too low

PET preform mold finish of injection molding machine is not good

Product molding cycle is too long

Too much titanium dioxide in color masterbatch

Color masterbatch dispersion is not good