I tried to make samples from DER664 and similiar epoxy resins. These resins are solid and start to melt at 150 °C. They are still highly viscous. The resin is normally used for coatings. The companies have special techniques, but also only produce very thin layers. I need samples of at least 3 mm. Here is a data sheet: https://www.palmerholland.com/All-Products/DER-664
I tried to mix them with hardener liquid at room temperature, which difficult, but I managed it. Problem is that they are impossible to degass. I tried for longer times with different technics (slowly decrease the vacuum from 800 mbar to 200 mbar) but it just foams.
I also mixed them with ethanol or aceton and let them slowly degass at room temperature. I let them rest for several weeks, but then I had a solid skin and inside it was still liquid. I then put it in the oven and slowly increased the temperature over 24h, but it still foamed on the inside.