What is a Helmet made of?
What is a Helmet made of?
A hard shell to spread the blow over a crushable polystyrene foam liner that is destroyed by one impact.
The polystyrene liner is a single-use crumple zone: it absorbs energy by permanently deforming, so a helmet that has taken a real impact must be replaced even if the shell looks fine — and the damage is often invisible, hidden under the shell. Dropping a helmet on the floor from waist height does not do this, despite the folklore. Motorcycle helmets are additionally replaced on an age basis, typically around five years, because the liner materials, glues and comfort foam degrade. The single biggest determinant of protection is fit, not price: a loose helmet rotates out of position before it has a chance to work.
Component by component
| Part | Material | Why that material |
|---|---|---|
| liner | expanded polystyrene (EPS) foam | It crushes progressively, so the head decelerates over several centimetres instead of stopping instantly — the whole mechanism. |
| shell | in-moulded polycarbonate on cycle helmets; fibreglass, carbon or moulded thermoplastic on motorcycle helmets | The shell spreads a point impact across the foam and stops the helmet snagging or being punctured. |
| multi-impact liner | expanded polypropylene (EPP), in some skate and BMX helmets | EPP recovers after crushing, so it survives repeated small knocks — at the cost of absorbing a single big impact less well. |
| rotation management | a low-friction slip layer such as MIPS, or an elastomer suspension | Much brain injury comes from rotational rather than linear acceleration, and a few millimetres of slip reduces it. |
| retention | nylon webbing straps and a quick-release or double-D buckle | A helmet that moves on the head before impact protects nothing, which is why fit and strap adjustment do most of the work. |
Other clothing and kit objects
- Velcro (hook and loop) Two nylon tapes — one of stiff hooks, one of soft loops — copied directly from burdock burrs.
- Leather Animal hide whose collagen has been chemically stabilised so it cannot rot — usually with chromium salts.
- Gore-Tex A stretched PTFE membrane whose pores are far too small for a raindrop and far too big for a water vapour molecule.
- Denim A cotton twill with indigo-dyed warp and undyed weft — the dye sits on the fibre surface, which is why it fades.
- Bulletproof vest Many layers of woven aramid or polyethylene fibre that catch and deform a bullet; rifle threats need a ceramic plate.
- Zip (zipper) Teeth of metal, moulded acetal or nylon coil on a polyester tape, forced together by a wedge inside the slider.
- Synthetic leather A polyurethane or PVC skin on a textile backing — including the plant-based ones, which still need a plastic binder.
- Running shoe A knitted synthetic upper over a foam midsole and rubber outsole — about a dozen materials, all glued together.
- Shoe sole A rubber outsole for grip, a foam midsole for cushioning, and increasingly no clean way to separate them.
- Wetsuit Closed-cell neoprene foam full of nitrogen bubbles, faced with stretch jersey — the gas insulates, not the water.
- Life jacket Closed-cell foam or a CO2-inflated bladder, in a nylon cover — rated in newtons of buoyancy, not in size.
- Button Usually cast polyester resin; the good ones are shell, nut or horn, and you can tell by touch and temperature.
Common questions
- What is a Helmet made of?
- A hard shell to spread the blow over a crushable polystyrene foam liner that is destroyed by one impact.
- What is the liner of a Helmet made of?
- Expanded polystyrene (EPS) foam. It crushes progressively, so the head decelerates over several centimetres instead of stopping instantly — the whole mechanism.
- What is the shell of a Helmet made of?
- In-moulded polycarbonate on cycle helmets; fibreglass, carbon or moulded thermoplastic on motorcycle helmets. The shell spreads a point impact across the foam and stops the helmet snagging or being punctured.
Related pages
- Velcro (hook and loop) Two nylon tapes — one of stiff hooks, one of soft loops — copied directly from burdock burrs.
- Leather Animal hide whose collagen has been chemically stabilised so it cannot rot — usually with chromium salts.
- Gore-Tex A stretched PTFE membrane whose pores are far too small for a raindrop and far too big for a water vapour molecule.
- Denim A cotton twill with indigo-dyed warp and undyed weft — the dye sits on the fibre surface, which is why it fades.
- Bulletproof vest Many layers of woven aramid or polyethylene fibre that catch and deform a bullet; rifle threats need a ceramic plate.
- Zip (zipper) Teeth of metal, moulded acetal or nylon coil on a polyester tape, forced together by a wedge inside the slider.
- Synthetic leather A polyurethane or PVC skin on a textile backing — including the plant-based ones, which still need a plastic binder.
- Running shoe A knitted synthetic upper over a foam midsole and rubber outsole — about a dozen materials, all glued together.
- Pencil Stationery and paper
- Tennis ball Sport and games
- Banknote Around the house
- Golf ball Sport and games
- Paper Stationery and paper
- Glass Building materials
Sources
- Typical range compiled from manufacturer specifications — At One Place