Study on Synergistic Application of Antioxidant and Light Stabilizer

The aging of the coating film is actually the result of the combined action of ultraviolet light and oxygen. This process includes two different processes: Light degradation and photooxidation.

However, UV light stabilizers and antioxidants have different stabilization mechanisms for coating films. The combined use of two stabilizers with different mechanisms of action is expected to achieve better stabilization effect than a single stabilizer, that is, synergistic effect.

The most typical are the combination of HALS and antioxidants, the combination of UV absorbers and antioxidants, and the combination of UV blockers and antioxidants.

The effect of adding antioxidants and light stabilizers to powder coating formulations was evaluated by accelerated aging and baking tests on coating films. The light stabilizer used here is the more concerned HALS light stabilizer. 

The test formula and results are shown in Table 1 and Table 2.

Through the test results, the light stabilizer is evaluated:

(1) The addition of light stabilizer will have a significant effect on the weather resistance of the powder, but will not change the yellowing resistance of the coating film.

(2) The combination of light stabilizer and antioxidant has a significant effect on the weather resistance and fading of the coating film, and the optimal dosage of the two is 1:1.

(3) The combination of light stabilizer and antioxidant in HAA system has better effect.

For examples:

The combined use of HALS light stabilizers and sulfur-containing antioxidants will produce an antagonistic effect and reduce the performance of the polymer; 

When HALS is used together with phosphorus-containing polymers, its synergistic effect at a 1:1 concentration should be guaranteed. ; 

The combination of low molecular weight HALS has only additive effect, while the combination of high molecular weight HALS and low molecular weight HALS has a synergistic effect, etc.

Conclusion

Combining light stabilizers with antioxidants in high performance powder coatings. If used properly, there will be a synergistic effect that significantly improves the weatherability of powder coatings, especially ultra-weatherable powder coatings;

If used improperly, there will be a superposition effect or even an antagonistic effect, thereby reducing the stability of the coating film.

The comprehensive application of stabilizers will develop in the direction of multifunctionality.