XPS（Extruded Poly Styrene） is made from a completely different process than the EPS foam. The XPS foam product starts as a solid polystyrene resin granule, which is then fed into an extruder or die where the granules are melted and then have critical additives mixed with this now viscous fluid. This fluid then has a blowing agent injected to make the material foamable. Under carefully controlled conditions where both heat and pressure are used, this foamable material is then forced through a fixture or die at which time the foaming takes place. The rigid foam is then trimmed into the final dimensions or blocks. This process produces a completely different cell structure to the foam from EPS.
This process provides a material called “Styrofoam”, which is a Dow Chemical trademarked name. Mistakenly, most people assume the EPS that is used for coolers and coffee cups is “Styrofoam”, but it should be correctly referred to as EPS or beaded EPS foam. Dow has been making the blue “Styrofoam” for well over 50 years, and the material has extensive use in the building trade.
While the material can be used in the production of surfboards, there are some inherent challenges. One problem is that the material is made primarily in 8 ft sheets and only 6 to 8 inches thick. This limits the size of the surfboard that is to be designed. Another problem that can cause issues is the outgassing of the foam over time. This can also cause delaminating of the fiberglass laminate. While some techniques have been developed to minimize this problem, it still remains a challenge. There have been some improvements to the manufacturing process, and the outgassing problem may be minimized and manageable.