ISO 21561:2005
(Main)Styrene-butadiene rubber (SBR) — Determination of the microstructure of solution-polymerized SBR
Styrene-butadiene rubber (SBR) — Determination of the microstructure of solution-polymerized SBR
ISO 21561:2005 specifies procedures for the quantitative determination of the microstructure of the butadiene units and the content of styrene units 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 1,4-trans, 1,4-cis and 1,2-vinyl contents are expressed in mol % relative to the butadiene units.
Caoutchouc styrène-butadiène (SBR) — Détermination de la microstructure du SBR polymérisé en solution
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 21561
First edition
2005-12-01
Styrene-butadiene rubber (SBR) —
Determination of the microstructure of
solution-polymerized SBR
Caoutchouc styrène-butadiène (SBR) — Détermination de la
microstructure du SBR polymérisé en solution
Reference number
ISO 21561:2005(E)
©
ISO 2005
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ISO 21561:2005(E)
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ii © ISO 2005 – All rights reserved
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ISO 21561:2005(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 NMR method (absolute method) . 1
4 IR method (relative method) . 4
5 Precision. 10
6 Test report. 11
Annex A (informative) Procedure for sample-film preparation and measurement of microstructure
by FT IR spectrophotometry. 12
Bibliography . 15
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ISO 21561:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21561 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 2, Testing and analysis.
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INTERNATIONAL STANDARD ISO 21561:2005(E)
Styrene-butadiene rubber (SBR) — Determination of the
microstructure of solution-polymerized SBR
WARNING — Persons using this International Standard should be familiar with normal laboratory
practice. This standard does not purport to address all the safety problems, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices and to
ensure compliance with any national regulatory conditions.
1 Scope
This International Standard specifies procedures for the quantitative determination of the microstructure of the
1
butadiene units and the content of styrene units in solution-polymerized SBR (S-SBR) by H-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 1,4-trans, 1,4-cis and 1,2-vinyl contents are
expressed in mol % relative to the butadiene units.
NOTE IR spectrometry can also give absolute values of microstructure by calibration with S-SBRs of known absolute
1
microstructure obtained by H-NMR spectrometry.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1407, Rubber — Determination of solvent extract
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 NMR method (absolute method)
3.1 Principle
3.1.1 A small quantity of an extracted S-SBR is dissolved in deuterated-chloroform.
1
3.1.2 A H-NMR spectrum of the sample solution is measured at a 15 ppm sweep width. The peak areas of
the 1,4-bond (the sum of the 1,4-trans bond and 1,4-cis bond) and the 1,2-vinyl bond of the butadiene portion
are determined along with the peak area of styrene. The microstructure of the butadiene portion and the
styrene content are then calculated using theoretical formulae.
3.2 Reagents
3.2.1 Deuterated chloroform, CDCl , containing 0,03 % of tetramethyl silane (TMS) as internal standard.
3
The purity of the CDCl itself shall be > 99,8 %.
3
3.2.2 Anhydrous ethanol-toluene azeotrope (ETA).
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ISO 21561:2005(E)
3.2.3 Acetone.
3.3 Apparatus
1
3.3.1 H-NMR spectrometer: Fourier transform nuclear magnetic resonance (FT-NMR) spectrometer with
a resonance frequency of 150 MHz or higher.
3.3.2 Extraction apparatus, as described in ISO 1407.
3.3.3 Vacuum oven, operated at 50 °C to 60 °C.
3.3.4 Analytical balance, accurate to 0,1 mg.
3.4 Sampling
The raw rubber shall be sampled in accordance with ISO 1795.
3.5 Procedure
3.5.1 Extract rubber additives such as extender oil and antioxidant in accordance with ISO 1407, using
anhydrous ETA or acetone as the extraction solvent. Dry the extracted S-SBR under vacuum in the oven at
50 °C to 60 °C.
3.5.2 Take 15 mg to 50 mg of the extracted S-SBR and dissolve it completely in 0,5 ml of deuterated
chloroform containing 0,03 % of TMS. The concentration of this sample solution shall be selected according to
the resolution of the spectrometer used.
3.5.3 Transfer 0,5 ml of the S-SBR sample solution into an NMR tube for measurement.
1
3.5.4 Measure the H-NMR spectrum of the S-SBR solution under the following conditions:
Mode single-pulse mode
Measurement temperature room temperature to 50 °C
No. of data points 32 k
Offset 5 ppm
Sweep width 15 ppm or wider
Flip angle 30° pulse
Pulse repetition 4 s to 30 s
Accumulation 32 times to 256 times
3.6 Determination of the microstructure
1
3.6.1 Integrate the signal intensities of the H-NMR spectrum over each of the areas A, B and C defined in
1
Table 1. Figure 1 gives an example of a H-NMR spectrum showing the areas A, B and C.
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ISO 21561:2005(E)
Table 1 — Definition of signal integration areas
Area Signal integration range
A From 4,3 ppm to minimum intensity point around 5,0 ppm
From minimum intensity point around 5,0 ppm to minimum intensity point
B
around 6,1 ppm
C From minimum intensity point around 6,1 ppm to 7,7 ppm
TMS Integrated signal intensity of TMS in CDCl containing TMS
blank 3
CD From 6,1 ppm to 7,7 ppm in CDCl containing TMS
blank 3
TMS Integrated signal intensity of TMS in S-SBR sample solution
Key
X shift (ppm)
A, B, C signal integration areas
1
Figure 1 — Example of a H-NMR spectrum for an S-SBR
1
3.6.2 Measure as a solvent blank the H-NMR spectrum of the deuterated chloroform containing 0,03 % of
TMS. The TMS blank is normalized using Equation (1) and subtracted from the signal intensity of the solvent
determined from the integrated signal intensity of area C:
C =−C CD × TMS/TMS (1)
( )
calib blank blank
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ISO 21561:2005(E)
3.6.3 Calculate the content of each microstructure component (1,4-bond and 1,2-vinyl bond) of the
butadiene portion and the styrene content, using Equations (2) to (4):
C /5 ×104
()
calib
% St=× 100 (2)
C /5×+104 B/2 +A/4×54
() ()
calib
A/2
% Bd=×100 (3)
1,2
B/2+ A/4
B/2 A/− 4
% Bd=× 100 (4)
1,4
B/2+ A/4
where
C is the integrated signal intensity of area C compensated for the effect of CHCl in CDCl ;
calib 3 3
% St is the styrene content of the SBR, in mass %;
% Bd is the 1,2-vinyl bond content of the butadiene portion of the SBR, in mol %;
1,2
% Bd is the 1,4-bond content of the butadiene portion of the SBR, in mol %.
1,4
4 IR method (relative method)
4.1 Principle
4.1.1 A small quantity of extracted S-SBR is dissolved in cyclohexane and coated on a KBr plate.
–1
4.1.2 The IR spectrum of the S-SBR sample on the KBr plate is measured over the range 1 200 cm to
–1
600 cm . From the absorbances at four specified wavelengths, the contents of the 1,4-trans bond, the 1,4-cis
bond, the 1,2-vinyl bond and the styrene unit are calculated using Hampton’s method (see Reference [1] in
the Bibliography).
4.1.3 IR spectrometry can also give absolute values of microstructures by calibration with S-SBRs of known
1
absolute microstructure obtained by H-NMR spectrometry.
4.2 Reagents
4.2.1 Anhydrous ethanol-toluene azeotrope (ETA).
4.2.2 Acetone.
4.2.3 Cyclohexane.
4.3 Apparatus
4.3.1 IR spectrophotometer: Fourier transform infrared (FT-IR) spectrophotometer or double-beam IR
spectrophotometer.
4.3.2 Extraction apparatus, as described in ISO 1407.
4.3.3 Vacuum oven, operated at 50 °C to 60 °C.
4.3.4 Analytical balance, accurate to 0,1 mg.
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ISO 21561:2005(E)
4.3.5 20 ml sample vial, with cap.
4.3.6 Pasteur pipette and 10 ml pipette.
4.3.7 KBr plate, for IR spectrophotometry.
4.3.8 Holder, for KBr plate.
4.3.9 Metal spacer, of 0,1 mm thickness.
4.4 Sampling
The raw rubber shall be sampled in accordance with ISO 1795.
4.5 Procedure
4.5.1 Preparation of sample solution
4.5.1.1 Extract extender oil and antioxidant from the S-SBR in accordance with ISO 1407, using
anhydrous ETA or acetone. Dry the extracted S-SBR in a vacuum oven at 50 °C to 60 °C.
4.5.1.2 Put 0,2 g of extracted S-SBR sample in a
...
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