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Polymers and monomers

How is a polymer defined under REACH?

A polymer is a substance consisting of molecules characterised by the sequence of one or more types of monomer unit. Such molecules must be distributed over a range of molecular weights. Differences in the molecular weight are primarily attributable to differences in the number of monomer units.

Under REACH, a polymer is defined as a substance meeting the following criteria:

  1. Over 50 percent of the weight consists of molecules containing at least three monomer units which are covalently bound to at least one other monomer unit or other reactant; and,
  2. The amount of molecules presenting the same molecular weight must be less than 50 percent of the weight.

For further information see chapter of the Guidance on registration:

Full details on polymers are available in the Guidance for monomers and polymers:

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