Polycarbonate Greenhouse Panels Yellowing??? Why and how long does it take?

Here's a greenhouse built back in 1978 in Idaho. The polycarbonate has not ever been changed out. There are places where it is very cracked and brittle, but overall, most of the polycarbonate still is fairly resilient. It will not last much longer, but is still intact.

[@JohnGuest45]

If its still mechanical sound i`d be tempted to run some wiggle wire channels over the hoops and install poly to act as a UV blocker. If you can inflate it, you`d only need something like 4 mil (100 micron).

[@JohnDoe-id9hi]

I don't think I'd have any PE left on my greenhouse if it seen 80mph winds. Have you tried applying 303 aerospace protectant on the plastic? Try hitting a panel with weed torch and see if the yellow burns off. It works for the lower windows on my kubota RTV.

[@russlivesay9325]

Never tried a torch or 303. I emailed the manufacturer about how to extend the life and he had no chemical recommendations. I know acrylic can have a torch used to eliminate cracks/scratches, but Lexan (polycarbonate) has an extremely narrow "plastic" band melting point so running a torch causes it to bubble and ruins the surface. Furthermore, acrylic is extremely flammable once ignited, particularly within compartments (look up the Montreal world's fair), cracks very easy and would not be a good greenhouse solution. Don't know what the solution is. Keep me posted if you come up with an answer!