Discoloration of PVC profiles

In the production and application of PVC profiles, thermo-photo-oxidative catalytic reactions will occur. Under the action of heat and pressure, polymer biomacromolecules will be oxidized by a small amount of water, acid, alkali and other residues and air in the air. , resulting in a decrease in the relative molecular mass and a change in the macromolecular formula. This in turn causes the color tone of the PVC profile to change.

一、Discoloration of PVC profiles

1. Discoloration due to heat, oxygen and light aging

The main form of heat, oxygen, and photoaging discoloration is the yellowing of the profile. Some thickener manufacturers claim that their products can reduce the share and control the cost compared with similar manufacturers when promoting their products. The result Although it is still possible to produce profiles with satisfactory appearance, in the collection of waste materials and in the strict process temperature regulations, because of its insufficient thermal stability and high efficiency, the impact on the molecular formula of PVC cannot be observed by human eyes. Therefore, the following situations occur during production:

1. It is found that the color of PVC profiles is not uniform during production and processing (such as slight color errors are allowed);

2. The profile turns yellow obviously after heating and deformation;

3. The condition is good after heating, but the windows and doors made of PVC profiles will turn gray soon. The profile does not turn yellow during normal production, but turns yellow when it is finished as a window.

During the processing of PVC profiles, when the basic conditions such as materials and molds do not change, if the temperature of the melting section and homogenization section is increased by about 5°C, the resulting profiles will tend to turn yellow, which also shows that their thermal stability is high. If the efficiency is not enough, the amount of heat stabilizer added should be increased, especially when whitening modifiers such as optical brighteners are added to the secret formula, the heat stabilizer is not enough, and the whitening effect is not significant.