I remember when we had a discount on one company's helmets for our club. It was a small company called Aria Sonics, which I'm thinking is defunct by now. There was a mechanic at a bike shop saying that their testing showed that it could take multiple (up to 3) impacts while most helmets could take a single impact before the helmet would crack and not be able to reasonable take another impact. State of the art for other helmets included soft shells and something like a plastic "skeleton" (forgot what the marketing phrase was). Giro might have been the first to have that.
It was a little bit different. Anyone who has seen suitable styrofoam for bike helmets knows that they're kind of hard - much harder than packing styrofoam. And I've seen a few helmets damaged by impacts where there was a clear dent or where there was a dent and a crack. These EPP helmets were a lot like expanded polypropylene packaging. Kind of squishy to a degree, but certainly harder than most packaging materials.
It was a little bit different. Anyone who has seen suitable styrofoam for bike helmets knows that they're kind of hard - much harder than packing styrofoam. And I've seen a few helmets damaged by impacts where there was a clear dent or where there was a dent and a crack. These EPP helmets were a lot like expanded polypropylene packaging. Kind of squishy to a degree, but certainly harder than most packaging materials.
Aria Sonics continues to produce helmets from Expanded PolyPropylene (EPP), a material which recovers after a crash, confirmed by independent test lab results which Aria Sonics has provided to us. That makes it ideal for multi-impact sports such as aggressive skating. Other manufacturers have been slow to pick up on EPP due to its technical characteristics and requirement for expensive new molding equipment. Note added later: Aria Sonics went out of business in 1997 and their products are no longer available.