Resin Compatibility?

I put this in the other forum the other day, but didn’t realize that it is pretty much dead. Hopefully I am not breaking any rules double posting and that I can get some guidance here.

I am getting ready to embark on my first carbon fiber part and want to make sure that I have the correct materials/process down. I am planning to CNC cut extruded polystyrene to make base plugs from, which I plan to under cut and then coat with a layer of fiberglass and then body filler to then do the final machine pass on so that I have a hard dimensionally accurate surface I can then final sand and polish as the plug surface. I plan to use epoxy resin so the foam won’t melt on me. It is probably cheaper to buy foam that is polyester resin resistant so I could use cheaper resin here, but being able to grab a sheet from the store is easier, for now.

For the mold, I plan to use polyester resin so that I can use CSM for tighter contours, easier wetting out and to reduce overall costs.

For the carbon fiber parts, I plan to use an epoxy compatible poly/vinylester clear top/gel coat and use infusion resin for the carbon fiber layers.


  • Lowes/Home Depot XPS Foam
  • Fiberglass Cloth layer – US Composites 635 thin resin with fast hardener
  • Body filler layer – US Composites 635 thin resin with fast hardener and US Composites Fairing Compound


  • Plug Sealer – McLube 1038 Sealant and release agent
  • Plug Release – McLube 1123 High-Gloss Release agent
  • Gel Coat – US Composites Orange Tooling Gelcoat
  • CSM Layers – US Composites 404 Tooling Polyester Resin


  • Mold Sealer – McLube 1038 Sealant and release agent
  • Mold Release – McLube 1123 High-Gloss Release agent
  • Gel/Clear Coat – Duratec 904-061
  • Carbon Fiber Infusion Epoxy – Pro-Set INF-114 and INF-211 hardener

I have researched quite a bit and without just buying one of everything and testing it out, this SEEMS like the best/cheapest way forward. This is a resins only list, I know I also need to get the fiber glass and carbon fiber sheets as well as the materials for the infusion process, but the resins and release agent compatibility is what has got my head spinning at the moment.

I know I like the idea of the Duratec clearcoat as an added buffer layer between the polyester mold and the epoxy part as I have read issues where epoxy can bond to the polyester through the release agent coats sometimes, but there may be a better/cheaper option. From reading, it seems like getting the Duratec clear to stick to a semi-perm mold release is a hard process.

I know this is less “science” and more an artform on what materials are best together, but does anyone have any suggestions on better/different/cheaper/faster/whatever materials? Are there any compatibility issues with anything?

Thanks guys!

I have never had an issue with Duratec reacting with epoxy. I never used the clear additive and just polished the primer. A single coat of wax and then semi permanent mold release as a back up never failed.