Reasons for discoloration of PVC edge banding
1. Heat, oxygen, light aging discoloration
Many people believe that to solve the problem of inconsistent color in PVC edge banding processing, as long as the yellowing profile production line is lowered in processing temperature, the color difference can be reduced. But some people also believe that PVC has a greater impact on yellowing CPE、 Stabilizers, PVC from different batches CPE、 Stabilizers and other main auxiliary materials may have different color differences during processing. In this case, even adding a certain amount of whitening agent or anti-aging agent alone will not have much effect.
The main manifestation of discoloration caused by heat, oxygen, and light aging is yellowing of profiles. Some stabilizer manufacturers claim that using their products can reduce the number of parts and lower costs compared to similar manufacturers when promoting their products. Although the results can also produce PVC profiles that appear satisfactory, in the recycling of waste and strict process temperature requirements, due to insufficient thermal stability efficiency, the damage to PVC molecular structure cannot be observed by the naked eye. Therefore, the following situations occur during production:
(1) During the processing of PVC edge banding, it was found that the color was not uniform (slight deviation in color is allowed);
(2) The profile shows obvious yellowing after heating deformation;
(3) The state is good after heating, but the profile becomes gray after being made into doors and windows for a short time. The profile does not turn yellow during normal production, but turns yellow in later window products.
In the production process of profiles, when the basic conditions such as raw materials and molds remain unchanged, if the temperature of the plasticizing and homogenization sections is increased by about 5 ℃, the resulting profiles tend to turn yellow, indicating insufficient thermal stability efficiency. Therefore, the amount of heat stabilizer added should be increased, especially when adding whitening agents such as fluorescent whitening agents in the formula. The reason for discoloration of PVC profiles is not obvious due to insufficient heat stabilizer.