A lot of our truck mudflaps are made of polypropylene. I have access to a seemingly infinite supply of 1/4" and 5/16". I envy your 1/2". There are some issues with cutting polycarbonate. @jkopel shared this ages back but I’ve saved the pdf. @jkopel’s post
Your sheets of polypro are going to be excellent for creating all sorts of housings, boxes, containers, jigs, templates, engraving stamps etc… You’ve got a treasure trove of material!