---
title: "What is a Life jacket made of?"
description: "Closed-cell foam or a CO2-inflated bladder, in a nylon cover — rated in newtons of buoyancy, not in size. Every component, the material it uses, and the constraint t"
url: https://atoneplace.net/made-of/life-jacket/
site: "At One Place"
---

# What is a Life jacket made of?

**What is a Life jacket made of?: Closed-cell foam or a CO2-inflated bladder, in a nylon cover — rated in newtons of buoyancy, not in size.**

The distinction that matters is between a buoyancy aid and a life jacket. A 50 N buoyancy aid — the kind used for kayaking and dinghy sailing — keeps a conscious swimmer afloat but does nothing to turn an unconscious person face-up, which is what the higher ratings and the collar design are for. Inflatable jackets need real maintenance: the cylinder can be discharged or corroded, and the automatic bobbin has an expiry date, so an annual check is not optional. Kapok, the traditional plant fibre filling, was phased out because it absorbs water and loses buoyancy once the packets are punctured.

## Component by component

*Every material is a choice, and the third column is the constraint that drove it.*

| Part | Material | Why that material |
| --- | --- | --- |
| inherent buoyancy | closed-cell PVC or polyethylene foam | Foam works without any action from the wearer and cannot fail, which is why it is required for children and non-swimmers. |
| inflatable bladder | polyurethane-coated nylon, inflated by a small CO2 cylinder | It packs down to almost nothing when uninflated, so people actually wear it — the main reason inflatables save lives. |
| trigger | a water-soluble bobbin or a hydrostatic pressure valve | A bobbin fires on any wetting, including heavy spray; a hydrostatic head only fires under about 10 cm of water, avoiding false inflations. |
| cover and hardware | nylon or polyester fabric with corrosion-resistant buckles and a crotch strap | Without a crotch strap, a jacket rides up over the head in water, which is the classic failure people discover too late. |
| buoyancy rating | 50 N, 100 N, 150 N or 275 N under ISO 12402 | 50 N is a buoyancy aid for swimmers in sheltered water; only 150 N and above will reliably turn an unconscious person face-up. |

## Other clothing and kit objects

- [Velcro (hook and loop)](https://atoneplace.net/made-of/velcro/) — Two nylon tapes — one of stiff hooks, one of soft loops — copied directly from burdock burrs.
- [Leather](https://atoneplace.net/made-of/leather/) — Animal hide whose collagen has been chemically stabilised so it cannot rot — usually with chromium salts.
- [Gore-Tex](https://atoneplace.net/made-of/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](https://atoneplace.net/made-of/denim/) — A cotton twill with indigo-dyed warp and undyed weft — the dye sits on the fibre surface, which is why it fades.
- [Helmet](https://atoneplace.net/made-of/helmet/) — A hard shell to spread the blow over a crushable polystyrene foam liner that is destroyed by one impact.
- [Bulletproof vest](https://atoneplace.net/made-of/body-armor/) — Many layers of woven aramid or polyethylene fibre that catch and deform a bullet; rifle threats need a ceramic plate.
- [Zip (zipper)](https://atoneplace.net/made-of/zipper/) — Teeth of metal, moulded acetal or nylon coil on a polyester tape, forced together by a wedge inside the slider.
- [Synthetic leather](https://atoneplace.net/made-of/synthetic-leather/) — A polyurethane or PVC skin on a textile backing — including the plant-based ones, which still need a plastic binder.
- [Running shoe](https://atoneplace.net/made-of/running-shoe/) — A knitted synthetic upper over a foam midsole and rubber outsole — about a dozen materials, all glued together.
- [Shoe sole](https://atoneplace.net/made-of/shoe-sole/) — A rubber outsole for grip, a foam midsole for cushioning, and increasingly no clean way to separate them.
- [Wetsuit](https://atoneplace.net/made-of/wetsuit/) — Closed-cell neoprene foam full of nitrogen bubbles, faced with stretch jersey — the gas insulates, not the water.
- [Button](https://atoneplace.net/made-of/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 Life jacket made of?

Closed-cell foam or a CO2-inflated bladder, in a nylon cover — rated in newtons of buoyancy, not in size.

### What is the inherent buoyancy of a Life jacket made of?

Closed-cell PVC or polyethylene foam. Foam works without any action from the wearer and cannot fail, which is why it is required for children and non-swimmers.

### What is the inflatable bladder of a Life jacket made of?

Polyurethane-coated nylon, inflated by a small CO2 cylinder. It packs down to almost nothing when uninflated, so people actually wear it — the main reason inflatables save lives.

## Related pages

- [Velcro (hook and loop)](https://atoneplace.net/made-of/velcro/)
- [Leather](https://atoneplace.net/made-of/leather/)
- [Gore-Tex](https://atoneplace.net/made-of/gore-tex/)
- [Denim](https://atoneplace.net/made-of/denim/)
- [Helmet](https://atoneplace.net/made-of/helmet/)
- [Bulletproof vest](https://atoneplace.net/made-of/body-armor/)
- [Zip (zipper)](https://atoneplace.net/made-of/zipper/)
- [Synthetic leather](https://atoneplace.net/made-of/synthetic-leather/)
- [Pencil](https://atoneplace.net/made-of/pencil/)
- [Tennis ball](https://atoneplace.net/made-of/tennis-ball/)
- [Banknote](https://atoneplace.net/made-of/banknote/)
- [Golf ball](https://atoneplace.net/made-of/golf-ball/)
- [Paper](https://atoneplace.net/made-of/paper/)
- [Glass](https://atoneplace.net/made-of/glass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)