Appearance and color
Why white plastic yellows — optical brightener vs white masterbatch
Common reasons for yellowing, the difference between brightening and white coverage, and how to start diagnosis.
Yellowing or a dull look in a white product affects appearance even when processing runs normally, and it stands out more in products where looks matter. The cause is not always the same, so correct diagnosis saves time and cost.
Common causes include the nature of the material itself, process heat, recycled feedstock that gives an unclean base color, or a color/grade choice that does not fit the application. Sometimes the yellow impression is more visual than a large actual change in the material.
It is important to separate two things: improving appearance and reducing the yellow impression, which is the job of an optical brightener; versus adding white color and real coverage, which is the job of white masterbatch. These are different problems and the fix differs by what the product needs.
An optical brightener reduces the yellow impression and gives a brighter look, but it does not provide white coverage like white masterbatch. In some applications appearance improves by using both together after a production trial, and the choice depends on the base color and the coverage required.
The best approach is to test a small sample under the same operating conditions and compare, instead of increasing usage randomly. Testing is what determines the suitable grade and loading.