You dont need to as such.  For good cosmetic finish sheets i would avoid it as any flaw or uneveness in the release coat application may show up on the sheet.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi Warren,

Thanks both. Very helpful. Jess

Polypropylene sheet is great for making a few flat/curved sheets.  Ensure it is pure polypropylene and not coated.  Epoxy does not stick to pure polypropylene.

You will find compared to glass that it quickly picks up scratches and dulls, so take good care of it if you need to make a few sheets.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

It should be OK but do a test first. I use acrylic sheet for smooth double curvature projects, just well supported on a jig and I personally use TR104 hi-temp wax which has released perfectly so far.

Hi,