IR film vs plexiglass (PMMA)?

In trying to hunt down some IR film, I saw a lot of mentions of PMMA (polymethyl methacrylate, also known as acrylic, acrylic glass, perspex, or plexiglass). Apparently it has a super high transparency to IR, especially the bog standard 2mm thick stuff. Has anyone experimented with that?

I've tried a lot of different plastics. The only thing that has worked so far has been the IR film from Switzerland I link to on github and normal thin kitchen wrap. The latter does lower the readings a degree or so but it works.

I'm sorry but I don't have the names of the plastics I've tried. But stuff like acrylic sheets, perspex, the quite thin type you have when building RC car bodies, and just a lot of other stuff laying around. Maybe some of the things I tried simply were to thick. And don't let my bad luck discourage from testing stuff!!!