# Poly(lactic acid), PLA, is a biodegradable condensation polymer made from lactic acid monomers. It is increasingly used as an alternative to poly(ethene) in disposable packaging. Explain why PLA is classified as a condensation polymer, and describe two advantages and one disadvantage of using PLA rather than poly(ethene) for packaging.

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

> Poly(lactic acid), PLA, is formed from lactic acid (2-hydroxypropanoic acid), a monomer that contains both a hydroxyl group (–OH) and a carboxylic acid group (–COOH). PLA breaks down in the environment through hydrolysis of its ester linkages.

## Mark scheme (5 marks)

1. PLA is a condensation polymer because a small molecule (water) is eliminated/released during each polymerisation step
2. The monomers join through ester linkages/bonds formed between the –OH and –COOH groups
3. Advantage 1: PLA is biodegradable so it does not persist in landfill/oceans and causes less long-term environmental pollution
4. Advantage 2: PLA is made from a renewable/plant-based feedstock (e.g. corn starch/sugar cane), reducing dependence on crude oil/fossil fuels
5. Disadvantage: PLA has lower thermal stability / melts or deforms at lower temperatures than poly(ethene), limiting its use in hot conditions / or PLA is more expensive to produce than poly(ethene)

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/poly-lactic-acid-pla-is-a-biodegradable-3c289d3e) · Published by Druglandscape Ltd.