ISO 21561-1:2015 specifies procedures for the quantitative determination of the microstructure of the butadiene and the content of styrene in solution-polymerized SBR (S-SBR) by 1H-NMR spectrometry as an absolute method and by IR spectrometry as a relative method. The styrene content is expressed in mass % relative to the whole polymer. The trans, cis and vinyl contents are expressed in mol % relative to the butadiene. These methods are applicable only for raw rubber.

NOTE 1 IR spectrometry can also give absolute values of microstructure by calibration with S-SBRs of known absolute microstructure obtained by 1H-NMR spectrometry.

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.