Originally Posted by mrodgers

For the record, it is expanded polystyrene (EPS) and not "styrofoam." Styrofoam is a brand name. I have been working in manufacturing foams for 19 years and currently work in research and development with EPP and EPE in comparison to other open and closed cell foams such as EPS or polyurethane. There is shock absorption properties in "styrofoam" as that is the material's main function. The "crushability" of foam beads is the shock absorption property. EPS has less compression strength, ie, it is more easily "crushed" compared to an EPP foam. What that tells you is that the impact absorption property will diminish with an increased strength of impact. Falling off your bike at 15 mph and hitting your head on the pavement, the EPS will compress and absorb the impact rather than the impact going to your skull. Someone swinging a baseball bat at your head might create more of an impact than the EPS can absorb, ie the impact may fully compress the foam, and the impact may affect your skull more than an impact to the ground.