Reactive functional groups

Last update 7 April 2017

The number of Reactive Functional Groups (RFGs) in a polymer is important in determining whether it meets the PLC criteria.

You need to take RFGs into account when considering the low molecular weight species of a polymer and when determining whether cationic polymers are PLCs.

An RFG is defined as: 'an atom or associated group of atoms in a chemical substance that is intended or can be reasonably anticipated to undergo facile chemical reaction'.

RFGs are divided into three categories—low, moderate and high concern—to reflect the comparative reactivity of each functional group (see table below).

The criterion for determining the category is more qualitative than quantitative, and is based on the presence of chemically or metabolically-reactive or toxic (including eco-toxic) functional groups within the polymer.


RFGs in the low concern category generally lack reactivity, or have low adverse reactivity, in a biological setting.

There is no Functional Group Equivalent Weight (FGEW) cut-off for low concern RFGs under the PLC criteria.


RFGs in the moderate concern category have evidence of reactivity in a biological setting but the effects are not severe enough to place the functional group in the high concern category. Sufficient information must be available to be confident that the RFG is of moderate concern.

For a polymer to meet the PLC criteria, the FGEW cut-off for moderate concern RFGs is 1000.


RFGs in the high concern category have evidence of human health hazard—adverse effects in humans or conclusive evidence of severe effects in animals.

Where there is no information or insufficient or contradictory information on an RFG it defaults to the high concern category until sufficient information becomes available for it to be moved to another category.

For a polymer to meet the PLC criteria, the FGEW cut-off for high concern RFGs is 5000.

If a polymer does not meet the cut-off for moderate or high concern RFGs to meet the PLC criteria, it could still be considered a PLC if sufficient additional information is provided to negate concern caused by the RFGs present. This information should generally consist of toxicological studies on the notified polymer or a suitable analogue addressing the particular concern raised by the RFGs present.

For example, if a polymer contains sulfonyl halide RFGs with a FGEW <5000 then it would not be eligible to be a PLC under the PLC criteria as sulfonyl halides are potential sensitisers. However, if toxicological tests on the notified polymer or a suitable analogue show that the notified polymer was unlikely to be a sensitiser then it may still be acceptable for notification as a PLC.

A number of functional groups are not considered to be RFGs. These include carboxylic esters, ethers, amides, urethanes, sulfones and the nitro groups. This is provisional on the functional group not being modified to enhance its reactivity (for example, the dinitrophenyl ester of a carboxylic acid).

RFGs in their respective categories are listed in the regulations under the ICNA Act. The list is updated by notice in NICNAS's Chemical Gazette.

The following RFGs, although not listed in the regulations or represented in the table below, have been determined to be in the low concern category:

  • Imidazolidinone groups
  • Imides
  • Organic phosphate esters—however, the polymer must still meet the elemental criteria to be eligible as a PLC.

Reactive functional group categories

Low concern

Moderate concern

High concern

Carboxylic acid

Conjugated olefinic groups not contained in naturally occurring fats, oils and carboxylic acids

Pendant acrylates and methacrylates

Aliphatic hydroxyl


Unconjugated olefinic considered 'ordinary'


Butenedioic acid

Halosilanes, Hydrosilanes, Alkoxysilanes1

Conjugated olefinic groups contained in naturally occurring fats, oils and carboxylic acids


Blocked isocyanates (including ketoxime-blocked isocyanates)

Isocyanates, isothio-cyanates


Alpha or beta lactones

Unconjugated nitriles

Vinyl sulfones or analogous compounds

Halogens (except reactive halogen containing groups such as benzylic or allylic halides)

*Acid halides

*Acid anhydrides



*Methylolamides, -amines2 or –ureas



*Un-substituted positions ortho and para to phenolic hydroxyl

*Allyl ethers

*Imines (ketimines and aldimines)

Partially-hydrolysed acrylamides

Other RFGs not in low or moderate concern groups

1 Alkoxysilanes with alkoxy groups >C2 are listed as moderate concern by the United States Environmental Protection Agency (US EPA).

2 Amines are regarded as high concern RFGs. Polymers containing them are generally considered under cationic polymers.

*Denotes the group that is in the US EPA moderate concern category for which data and information to support placement in this category is unavailable to NICNAS. These RFGs will default to the high concern category pending provision of such data and information by industry and/or other parties to NICNAS.