ISO 21561-2:2016 specifies procedures for the quantitative determination of the microstructure of the butadiene and the content of styrene in solution-polymerized SBR (S-SBR) by Fourier Transform Infrared Spectrometry (FTIR) with Attenuated Total Reflection (ATR) method. The styrene content is expressed in mass % relative to the whole polymer. The vinyl, trans and cis contents are expressed in mol % relative to the butadiene content. This method is only applicable to raw rubbers.

NOTE 1 Precision as shown in Annex A may not be obtained for S-SBRs containing polystyrene block or styrene content more than 45 mass %.

NOTE 2 Only "vinyl", "trans" and "cis", are used in this part of ISO 21561. However, the expression of vinyl, trans and cis mean as follows in general:

- vinyl: vinyl unit, vinyl bond, 1,2-unit, 1,2-bond, 1,2-vinyl-unit or 1,2-vinyl-bond;

- trans: 1,4-trans unit, 1,4-trans bond, trans-1,4 unit or trans1,4 bond;

- cis: 1,4-cis unit, 1,4-cis bond, cis-1,4 unit or cis-1,4 bond.