# Kevlar is a condensation polymer used to make bulletproof vests and reinforced tyres. Its repeat unit contains an amide linkage between two benzene rings. Explain why Kevlar is classified as a condensation polymer rather than an addition polymer, and describe the type of monomer or monomers required to form Kevlar.

> Edexcel A-Level Chemistry (9CH0) — 18.3 Polymers · Explain · 5 marks

> Kevlar is an exceptionally strong synthetic fibre. Its repeat unit can be represented as: —[NH–C₆H₄–NH–CO–C₆H₄–CO]ₙ—

## Mark scheme (5 marks)

1. A small molecule (water / HCl) is eliminated / lost during each bond-forming step
2. Addition polymers form by addition reactions / no small molecule is lost, which is why Kevlar is NOT an addition polymer
3. Kevlar requires two different types of monomer (a diamine and a diacid / diacid chloride)
4. Each monomer must be bifunctional / have two functional groups (one at each end)
5. The amide (peptide) linkage / –CO–NH– bond is formed between the two monomers during condensation

## Key terms

- [condensation polymer](https://www.gradenine.co.uk/glossary/condensation-polymer)
- [addition polymer](https://www.gradenine.co.uk/glossary/addition-polymer)
- [amide linkage](https://www.gradenine.co.uk/glossary/amide-linkage)

## Related

- [Revision notes for Edexcel A-Level Chemistry (9CH0)](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/kevlar-is-a-condensation-polymer-used-717b9fb5) · Published by Druglandscape Ltd.