Try thinking along the line’s of dry (cured) poly- with the reinforcment of your choice, and eps foam!!
I vacuum bag polyester all the time. The vacuum pump motor does not come in direct contact with the styrene fumes, and anyway styrene fumes are not that easy to ignite. Otherwise every surfboard glasser using ventilation fans with unsealed motors would have a serious history of fires. I heard stories about the old surfboard glassers chain smoking while they glassed, in the 60’s. Talk about coffin nails. The only glass shop fire I ever heard about was done intentionally for the insurance. Come to think of it, there have probably been a lot more fires lately. Tex
What do you coat a silicone rubber bag with to seal out the moisture, so it doesn’t inhibit the curing of polyester resins, leaving them sticky when de-bagged? We’ve been using nylon bag film and sealant tape and are working on switching over.