What is Extruded Polystyrene? Well, the short answer is it is the real Styrofoam. Styrofoam is a trade name for Dow Chemicals’ specific type of extruded polystyrene, mostly sold as blue insulation sheets in big box hardware stores. Owens Corning sells a pink version. Others sell yellow and other pigmented versions.
How is it different from Expanded Polystyrene? Well, instead of little polystyrene beads that are steam/heat puffed or expanded in a mold, extruded material is pushed through or extruded through fine jets (not unlike say fuel injection on a combustion engine). This results in a foam matrix somewhat similar in structure to the fibers of wood. Depending on the extrusion process varying types of flexural and compression strengths/characteristics can be achieved.
What are some limitations? The biggest concern with extruded material is outgassing and rapid heat expansion. The dreaded delamination has been an ongoing problem with extruded material. Not only does it need to be laminated in a specific manner, but also traditional sanding and finishing methods can cause catastrophic failure.
Benefits? These newly available blanks from Marko Foam are a closed cell foam formulated specifically for surfboard building, optimizing flex for high performance surfing with increased memory (rapid spring back) resulting in a more responsive, lively board that can take a beating. The closed cell structure does not absorb water. The greatest limitation of expanded polystyrene in surfboard manufacturing is its tendency to suck in water, not unlike a sponge, due to the gaps between the beads.
At Chaos Surf Company we have been playing with extruded materials since the 80’s and are proud to offer the new Extruded Flex Core as an option for your next custom board. Ask for it, you won't be dissapointed. We also offer pressure-fused EPS, iFoam/impact foam (expanded polyethylene), and traditional polyurethane.
