Thermal, Oxygen and Photoaging Discoloration

Many people think that to solve the problem of inconsistent color in the processing of PVC seals, as long as the yellowing profile production line can reduce the processing temperature, the color difference can be reduced. However, some people believe that the yellowing of PVC, CPE, stabilizers, and other major auxiliary raw materials in different batches of PVC, CPE, stabilizers, there will be different color differences in processing. In this case, even if a certain amount of whitening agent and anti-photoaging agent are added alone, they will not play a very important role.

The main manifestation of the discoloration of heat, oxygen and light aging is yellowing of profiles. When promoting their products, some stabilizer manufacturers claim that using their products can reduce the number of parts and cost compared with similar manufacturers. Although the results can also produce PVC profiles with satisfactory appearance, they can also produce PVC profiles in waste recycling and in the strict process temperature requirements because of their heat. Insufficient stabilization efficiency and damage to the molecular structure of PVC can not be observed by the naked eye, so the following situations occur in production:

(1) When the edge of PVC seal is processed, it is found that the color is not uniform (for example, slight color deviation is allowed).

(2) The profile yellows obviously after heating deformation.

(3) After heating, the profile is in good condition, but it will turn grey in a short time when it is made into doors and windows. Profiles do not yellowing in normal production, but yellowing in later window products.

In the process of profile production, when the basic conditions of raw materials and moulds remain unchanged, if the temperature of the plasticized and homogenized sections is raised by about 5 C, the yellowing tendency of the profile will occur, which also indicates that the thermal stability efficiency is insufficient. The amount of heat stabilizer should be increased, especially when fluorescent whitening agent and other whitening additives are added to the formulation, the thermal stabilizer is insufficient for PVC and the conductivity of PVC profiles. The cause of discoloration was not obvious.