Inorganic UV screens and organic UV absorbers that protect plastics from sunlight-driven chalking, yellowing, and embrittlement u2014 titanium dioxide, zinc oxide, and octocrylene for filled, pigmented, and clear systems.
UV stabilizers are additives that protect plastics from the chain scission,nchalking, and yellowing that sunlight causes. They work three ways: inorganicnscreens (titanium dioxide, zinc oxide) reflect and absorb UV, organic UV absorbers convertnUV energy to heat, and hindered amine light stabilizers (HALS) scavenge the radicals UVngenerates. Outdoor-durable polymers usually combine a screen or absorber with a HALS,nbecause each addresses a different step of the same degradation. Treat them as complementary,nnot interchangeable.
nnPigment-grade rutile titanium dioxide is the workhorse opaque UV screen for filled andnpigmented plastics; zinc oxide gives a similar inorganic block with more transparency innthin sections. Here is the genuine trade-off: pigmentary titanium dioxide can benphotocatalytic and actually accelerate chalking unless you specify a coated rutile gradenmade for durable exterior use. Specify surface-treated rutile (not anatase) wherever thenpart sees sunlight, and confirm the grade's weathering data before committing a formulation.
nnOrganic UV absorbers such as octocrylene protect clear and lightly pigmented systemsnwhere an opaque screen is not acceptable, but they are consumed over time and perform poorlynin thin films. The durable answer for most polyolefins and engineering plastics is a HALS,nwhich keeps working catalytically rather than being used up. Pair an absorber with a HALS fornreal outdoor service life. Confirm regulatory status for any organic UV absorber in yournapplication and jurisdiction.
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