3M product turn yellow ?

This is a very vague situation, so my answer will have to be equally broadbrushed. PU's have an extremely broad range of chemistries so to even attempt a guess at an answer would be difficult, but aromatic PU's are known for yellowing more than aliphatic PU's. I'm just not sure that that will help you at all.

Knowing the exact product and what the product was designed for would be helpful . How does it adhere to the display? Sticky adhesive? Static electricity? What is the environment that this is exposed to? UV light? High humidity? High temperature? Ozone? What additives are in the PU? Are they what's yellowing?

John Aspen Research, -

Opinions expressed herein are my own and may not represent those of my employer.

Hi John.

Thanks for your fast respond in my topic. I use this tape to protect and prevent any shape object damage the electronic equipment like sort touch key pad, LCD display, etc. This tape come in a roll with adhesive backed, the production floor temp. about 31-34 d/c, humidity about 77%, expose to sun light about 2 hours daily,but it only turn yellow colour in the air con room about 24 d/c. regards.