# Explain why carbon fibres used in high-performance materials are strong and stiff, yet nylon (a polyamide) can be drawn into flexible fibres, despite both being used as structural fibres.

> IB DP Chemistry Standard Level (2023 syllabus) — S2.4 From models to materials · Explain · 4 marks

> Carbon fibre composites are used in aircraft and racing cars because of their exceptional strength-to-mass ratio. Nylon fibres are used in clothing and ropes because of their flexibility and toughness.

## Mark scheme (4 marks)

1. Carbon fibres consist of layers of graphene-like sheets in which each carbon atom is covalently bonded to three others in a giant covalent/network covalent structure.
2. The strong covalent bonds within the carbon layers and van der Waals forces between aligned sheets resist stretching, giving high stiffness and strength.
3. Nylon is a polymer held together by hydrogen bonds between the amide (–NH–CO–) groups on adjacent chains.
4. Hydrogen bonds are weaker than covalent bonds and can be disrupted under stress, allowing chains to slide past one another, so nylon fibres can flex and deform without fracturing.

## Key terms

- [polyamide](https://www.gradenine.co.uk/glossary/polyamide)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-carbon-fibres-used-in-6f3b809c) · Published by Druglandscape Ltd.