Vinyl nitrile (VN) is a closed-cell foam derived from synthetic rubber. This material is soft, flexible and offers good impact attenuation. Vinyl nitride is also resilient—meaning that it crushes on impact and reduces energy transfer to the head, before regaining its shape and protective qualities. For that reason, vinyl nitrile is used in football, hockey, snowsports and kayaking helmets.
Helmet manufacturers can also fine tune vinyl nitrile helmet liners to mitigate both high and low-energy impacts by utilizing multiple layers of varying-density foam. Paired with a flexible shell, vinyl nitrile is frequently featured in the latest generation of “soft shell” snowsport helmets.
Reading through the benefits above, you might be wondering why cycling helmets aren’t using vinyl nitrile. The primary reason is that VN’s ability to manage energy is diminished in warmer temperatures. That attribute alone currently rules out its use in cycling helmets. The material is also heavier than EPS and EPP.