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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:
- 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,
- The amount of molecules presenting the same molecular weight must be less than 50 percent of the weight.
For further information see chapter 18.104.22.168 of the Guidance on registration:
Full details on polymers are available in the Guidance for monomers and polymers: