Ultra lightweight polymer foams are engineered to be lightweight while also capable of dissipating impact energy. They are mainly used in wrestling gears and similar applications.
The microscale air pockets act just like the bubble wraps used in packaging of fragile items. The air inside these air pockets will compress and cushion the impact on the material. After the load on the material reaches a certain threshold the polymer membrane around the air pockets will start to stretch and help to dissipate even more energy. After the complete exhaustion of the entire energy capacity of the material, the material looks a lot like popped bubble wrap.