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