PVC trim expands and contracts considerably more than any wood species. Stand alone frames will deform under direct sunlight. Screwing them in is the way to go. PVC trim should remain a light color if it's painted, sun melts the stuff if it's painted a dark color. I heard that there's a special paint you can use to get darker colors but I can't think of the name off-hand.The project I am working on has a section of the deck screened in. I am making the framework that will receive the screen panels out of PVC trim boards. I have always made my screen panels out of cedar but I am considering making them out of PVC.
These are the concerns I have.
1) Will the frames be rigid enough. The architect said they do not have to have quick release hardware and could be screwed in. The frames will be 1" thick by 2 1/4" wide. Here is a picture of the frame they will go in. The lower right frame has a mockup panel in it just to show the architect how it will look from the outside. The mockup is not plowed out for screen.
I'd look into having the screens pre-made with an aluminum border, and then embedding them into a PVC frame. Could be as easy as making the frames out of 5/4 stock and plowing them out with a slot cutter, and assembling around a pre-made screen.2) Can I buy PVC screen stop? I could make them but I find small moldings milled from PVC can be to brittle. The extruded molding from advance trim works seem to be much less brittle. As you can see in this next picture the 3" thick corner brackets are plowed out to receive the screen panels. This means the top corner panels will be curved. I shutter to think how many curved cedar moldings I will snap trying to fasten them in. I am hoping to heat up PVC moldings and form them to the shape I need.