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What is a polymer?
Note: This page isn’t a technical or general overview of polymers. It is a definition to help you comply with our regulation.
Polymers are used in a variety of everyday products such as plastics, paints, clothing and cosmetic products.
Your industrial chemical is a polymer if it meets both of the following criteria:
1. molecules are distributed over a range of molecular weights (where the difference in molecular weights is due to differences in the number of monomer units)
2. over 50% of the overall weight is made up of sequences of 3 or more monomer units and at least 1 more monomer unit or other reactant that can’t become a repeating unit in the polymer structure (this means over 50% of the substance must be polymer molecules)
Monomer units don’t have to be identical.
Do you need to register if you're introducing a polymer?
Yes, you need to register with us before you manufacture or import a polymer (or product containing a polymer) for any business-related purpose. This is an annual registration and there is a fee. After you register, you need to categorise your polymer introduction – read more in our 'Basics of importing and manufacturing chemicals' page.
Yes, you need to register with us before you manufacture or import a polymer (or product containing a polymer) for any business-related purpose. This is an annual registration and there is a fee. After you register, you need to categorise your polymer introduction – read more in our 'Basics of importing and manufacturing chemicals' page.
Our definitions
Monomer
A chemical that is capable of forming covalent bonds with 2 or more like or unlike molecules under the conditions of a polymer-forming reaction used for a process of polymer formation.
Monomer unit
A reacted form of a monomer in a polymer.
Sequence
A continuous string of monomer units within the molecule that are covalently bonded to one another and are uninterrupted by units other than monomer units.
Polymer molecule
A molecule that contains a sequence of at least 3 monomer units, which are covalently bound to at least one other monomer unit or other reactant (i.e. ‘3+1’ rule).
Other reactant
A molecule that cannot become a repeating unit in the polymer structure.
Examples - reaction between ethylene oxide and phenol to produce ethoxylated phenol
Consider the polymer forming reaction between ethylene oxide and phenol to manufacture an ethoxylated phenol.
Ethoxylated phenol (n is an integer, n greater than or equal to 1)
In this case we regard ethylene oxide as the monomer and phenol as the ‘other reactant’, as it cannot become a repeating unit in the polymer structure. That is, it cannot react with itself or an opened epoxide.
The monomer unit is the opened epoxide -(CH2-CH2-O)-
This chemical meets the definition of a polymer molecule whenever n greater than or equal to 3.
Example 1
| Monomer units | % by weight of polymer molecules |
|---|---|
| n=1 | 0 |
| n=2 | 0 |
| n=3 | 100 |
| n=4 | 0 |
| n=5 | 0 |
| n=6 | 0 |
| n=7 | 0 |
| Sum | 100 |
This substance consists of 100% polymer molecules (n greater than or equal to 3) and therefore meets criterion 2. However, it does not meet criterion 1 as the substance is not distributed over a range of molecular weights. The substance is a discrete chemical. Discrete chemicals have a definite chemical structure that can be represented by a definite molecular formula and chemical structure diagram.
This chemical does not meet our definition of a polymer.
Example 2
| Monomer units | % by weight of polymer molecules |
|---|---|
| n=1 | 40 |
| n=2 | 20 |
| n=3 | 15 |
| n=4 | 12 |
| n=5 | 8 |
| n=6 | 5 |
| n=7 | 0 |
| Sum | 100 |
This substance meets criterion 1 as the substance is distributed over a range of molecular weights. However, it does not meet criterion 2 as the substance consists of less than 50% by weight of polymer molecules, with 60% of the weight being from n=1 and n=2.
This chemical does not meet our definition of polymer.
Example 3
| Monomer units | % by weight of polymer molecules |
|---|---|
| n=1 | 5 |
| n=2 | 10 |
| n=3 | 20 |
| n=4 | 30 |
| n=5 | 20 |
| n=6 | 10 |
| n=7 | 5 |
| Sum | 100 |
This substance meets criterion 1 as the substance is distributed over a range of molecular weights. The substance also meets criterion 2 as the substance consists of over 50% by weight of polymer molecules, with 15% of the weight being from n=1 and n=2.
This chemical does meet our definition of polymer.
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