State that PET can be converted back into monomers and re-polymerised

Polyethylene Terephthalate (PET) – From Bottle to Building Block

What is PET?

PET is a common plastic used in water bottles, food containers and polyester fabrics. Its chemical formula can be written as \$(C{10}H{8}O{4})n\$. The “n” indicates that many repeating units are linked together to form a long chain, just like beads on a string.

Why Recycle PET?

Recycling PET saves energy, reduces waste, and keeps valuable resources in use. Think of PET as a LEGO set: you can take the bricks apart, clean them, and build a new set again.

Step 1 – Depolymerisation (Unpacking the LEGO)

Depolymerisation is the chemical “unpacking” of PET back into its original building blocks – terephthalic acid (TPA) and ethylene glycol (EG). Two main methods are used:

1. Hydrolysis – PET reacts with water (H₂O) at high temperature to give TPA and EG:

   \$\text{PET} + \text{H}_2\text{O} \rightarrow \text{TPA} + \text{EG}\$

2. Alkaline or Acidic Catalysis – Uses a catalyst to speed up the reaction, often at lower temperatures.

Step 2 – Purification (Cleaning the LEGO Bricks)

After depolymerisation, the TPA and EG are separated and purified. This is like washing LEGO bricks so they’re ready for a new build. Purity is essential for the next step.

Step 3 – Re‑Polymerisation (Building a New Set)

The purified TPA and EG are mixed again in a condensation reaction, releasing water and forming PET:

\$\text{TPA} + \text{EG} \rightarrow \text{PET} + \text{H}_2\text{O}\$

This is the same process used to make new PET from raw materials, but now we’re using recycled building blocks.

Key Takeaway

PET can be chemically recycled back into its monomers (TPA and EG) and then re‑polymerised to create new PET. This closed‑loop system reduces the need for virgin resources and helps keep plastic waste under control. 🚀

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