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 fromntwo different degradation pathways: photo-degradation driven by sunlight, andnthermo-oxidative degradation during cure and service. They are what keep annexterior finish from fading, chalking, and cracking. The family spans three workingnclasses u2014 UV absorbers, hindered amine light stabilizers (HALS), and antioxidants u2014 and andurable exterior system usually pairs a UV absorber with a HALS.
nnUV absorbers convert UV energy into harmless heat before it can break polymer bonds.nOctocrylene and the benzotriazole-class absorbers are common choices for clear andnpigmented coatings. The honest limitation: absorbers are consumed over time and worknpoorly in very thin films, where too little material sits in the light path. That is whynformulators combine them with a HALS, which scavenges the free radicals that drivendegradation and keeps working catalytically rather than being used up. Specify an absorbernfor surface protection and a HALS for long-term film integrity.
nnAntioxidants such as BHT address the other pathway. They interrupt oxidation duringnhigh-temperature cure and over the coating's service life, protecting the resin fromnyellowing and embrittlement. Antioxidants are not a substitute for UV protection; theynaddress oxidation, not photolysis. For a fully weatherable system, treat UV absorber,nHALS, and antioxidant as complementary rather than interchangeable.
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