UV penetration of Polyethylelne

Hi all,

Hope someone out there can help.

How deep does UV penetrate into PE (I’m talking about a blend which would already have carbon black pigment and UV additives)

If a PE is rated at 10 years, does this mean a 3mm part will fail in 10 years? If so does that mean a 12mm thick part will only have the top 3mm of plastic damaged by UV? Or does it penetrate the whole part?