A couple of posts that had somewhat drifted away from the original subject removed.

 

 

On 9/16/2021 at 4:38 PM, Black arab said:

Poor quality is correct, I fitted uPVC windows ,doors in UK. The uPVC was from decuinec, Belgium company .None of the windows we fitted went yellow because of the quality yet many in the UK did.

As for cleaning we used a cream cleanser such as jif which you can get here, not same name. It won't scratch the plastic after spray with a glass cleaner all good.

From what I have been told, the plastic has to be made with a UV stabiliser in it when it is manufactured. Cheaper stuff doesn't have it so the solar UV radiation turns it yellow.

 

Don't know how true this is: 

I did a CORGI industrial gas course once and was told by one of the teachers that even that large bore, thick walled, yellow plastic pipe that the gas companies use nowadays for the gas mains can be affected by UV if left outside long enough. So the gas companies don't like to leave it sitting outside for months.

 

I'm not convinced the yellowing is from the Sun, as too much stuff indoors or even in drawers and boxes seems to turn yellow. Not do I think it has to do with the "quality" of the plastic. Not many manufactures actually "make" plastic.