"When I worked for a Precious Plastic project in the UK we tested injection moulding (at 220C for polypropylene) into polycarbonate moulds inside a steel liner, that worked just fine. PEEK is significantly more temperature and pressure resistant that PC though! My co-founder designed a no-touch tool for COVID made from recycled LDPE injected into printed Nylon moulds. Those moulds lasted hundreds of injections at around 170C. I don't think they ever failed. Check the team out at Relic Plastic. "