UV absorbers and antioxidants that protect coating films from sunlight-driven fading, chalking, and embrittlement on exterior and weatherable surfaces.
UV stabilizers and antioxidants are additives that protect a coating film from two different degradation pathways: photo-degradation driven by sunlight, and thermo-oxidative degradation during cure and service. They are what keep an exterior finish from fading, chalking, and cracking. The family spans three working classes — UV absorbers, hindered amine light stabilizers (HALS), and antioxidants — and a durable exterior system usually pairs a UV absorber with a HALS.
UV absorbers convert UV energy into harmless heat before it can break polymer bonds. Octocrylene and the benzotriazole-class absorbers are common choices for clear and pigmented coatings. The honest limitation: absorbers are consumed over time and work poorly in very thin films, where too little material sits in the light path. That is why formulators combine them with a HALS, which scavenges the free radicals that drive degradation and keeps working catalytically rather than being used up. Specify an absorber for surface protection and a HALS for long-term film integrity.
Antioxidants such as BHT address the other pathway. They interrupt oxidation during high-temperature cure and over the coating's service life, protecting the resin from yellowing and embrittlement. Antioxidants are not a substitute for UV protection; they address oxidation, not photolysis. For a fully weatherable system, treat UV absorber, HALS, and antioxidant as complementary rather than interchangeable.
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