Depolymerisation is a process which involves breaking down the plastic polymer into its monomer units. The monomers can then be purified and used to create new plastics.

An example is the hydrolysis of polyesters using acid as a catalyst.

In the hydrolysis process, the ester linkages that hold the polymer chains together are broken. The polyesters will be broken down to form a large number of dicarboxylic acid monomers and diol monomers.

Conditions for hydrolysis of polyesters:
– An acid catalyst, usually sulfuric acid or hydrochloric acid
– Water as a reactant
– High temperature of between 80 deg C to 150 deg C