STABILIZATION MECHANISM OF HALS

HALS is an abbreviation for Hindered Amine Light Stabilizer, a light stabilizer with strong weather resistance functions.

During the processing or use of plastic products, radicals generated from the decomposition of polymer chains react with HALS to form a by-product of decomposition.

Decomposes hydroperoxide.

HALS can be used as a long-term UV stabilizer because the active ingredients are regenerated and the effect continues.

Step 1: The polymer chain is decomposed by UV light and the heat and pressure generated during processing, generating radicals and decomposition begins.

Step 2: Nitroxy radicals are generated and the role of HALS begins. Nitroxy radicals are generated when oxidized polymer radicals react with HALS.

Step 3: Nitroxy radicals are grafted onto polymer radicals to remove the radicals and prevent further decomposition of the plastic.

Step 4: Regeneration of nitroxy radicals, polymer decomposition begins again, and when step 1 progresses, the grafted HALS reacts with peroxy radicals and then regenerates nitroxy radicals again. Regenerated nitroxy radicals participate again in the second stage of the cycle.

As such, HALS has the property of being regenerated after radical removal, so it is widely used as a long-term weathering stabilizer.