ISO 21561-2:2016

DRAFT INTERNATIONAL STANDARD
ISO/DIS 21561-2
ISO/TC 45/SC 2 Secretariat: JISC
Voting begins on: Voting terminates on:
2015-05-20 2015-08-20
Styrene-butadiene rubber (SBR) — Determination of the
microstructure of solution-polymerized SBR —
Part 2:
FTIR with ATR method
Caoutchouc styrène-butadiène (SBR) — Détermination de la microstructure du SBR polymérisé en
solution —
Partie 2: Méthode FTIR avec ATR
ICS: 83.060
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ISO/DIS 21561-2:2015(E)
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ISO/DIS 21561-2:2015(E)
© ISO 2015
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ISO/DIS 21561-2:2015(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Apparatus . 2
5 Calibration . 2
5.1 FTIR . 2
5.2 ATR . 2
6 Sampling . 2
7 Procedure for measuring ATR spectrum . 2
8 Determination of the microstructure of butadiene and the styrene content .3
8.1 Measurement of the absorbance for each microstructure component . 3
8.2 Calculation of microstructures . 4
8.2.1 General. 4
8.2.2 Base line correction of each absorbance peak . 4
8.2.3 Ratio of absorbance . 5
8.2.4 Second order terms . 5
8.2.5 Styrene content and microstructures in mass % by regression equations . 5
8.2.6 Microstructures in mol % . 6
9 Precision . 6
10 Test report . 6
Annex A (informative) Precision results from an interlaboratory test programme .7
Annex B (informative) Acquisition of regression equations for microstructure .10
Annex C (informative) Determination of microstructure by NMR spectrometry .12
Bibliography .16
ISO/DIS 21561-2:2015(E)
Foreword
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ISO 21561-2 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 2, Testing and analysis.
ISO 21561 consists of the following parts, under the general title Styrene-butadiene rubber (SBR) —
Determination of the microstructure of solution-polymerized SBR:
— Part 1: H-NMR and FTIR with cast-film method
— Part 2: FTIR with ATR method
iv © ISO 2015 – All rights reserved

DRAFT INTERNATIONAL STANDARD ISO/DIS 21561-2:2015(E)
Styrene-butadiene rubber (SBR) — Determination of the
microstructure of solution-polymerized SBR —
Part 2:
FTIR with ATR method
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.
CAUTION — Certain procedures specified in this International Standard may involve the use or
generation of substances, or the generation of waste, that could constitute a local environmental
hazard. Reference should be made to appropriate documentation on safe handling and disposal
after use.
1 Scope
This International Standard 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 International Standard. 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.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 Principle
The IR spectrum of the S-SBR sample is measured by FTIR with ATR. The absorbances that are
characteristic of each microstructure component and styrene at the specified wavelengths are used
to determine the content of each component by using the specific formulae presented in this standard.
ISO/DIS 21561-2:2015(E)
4 Apparatus
4.1 FTIR, of the following specifications:
— Detector: Deuterium Tri-Glycine Sulfate (DTGS) or Tri-Glycine Sulfate (TGS);
— Number of scans: 32;
−1
— Resolution: 2 cm ;
−1 −1
— Range of wavelength: 600 cm to 1 800 cm .
4.2 ATR, of the following specifications:
— Type: Single bounce ATR;
— Crystal: Diamond;
— Angle of incidence: 45°;
— Sample pressure clamp: a concave or a flat shaped clamp which is capable of maintaining a constant
pressure on the sample. The use of a torque wrench is preferable.
5 Calibration
5.1 FTIR
Adjust the optical bench alignment of FTIR spectrometer according to the manufacturer’s instruction
manual.
5.2 ATR
Set ATR in the sample chamber of FTIR and adjust the optical alignment of ATR according to the
manufacturer’s instruction manual.
6 Sampling
6.1 Prepare the test sample in accordance with ISO 1795.
NOTE The extraction of ordinary extender oils by solvent is not necessary.
6.2 Cut out a test piece from the test sample. The test piece shall have a flat surface to give good contact
with the ATR crystal and be approximately the same size as the crystal, usually a few square millimetres.
7 Procedure for measuring ATR spectrum
7.1 Set up FTIR according to the manufacturer’s instruction manual.
7.2 Set ATR in a sample chamber of FTIR.
7.3 Measure the background spectrum with the conditions shown in 4.1.
7.4 Put the test piece on the ATR crystal, and contact it as completely as possible to the crystal surface
preferably using the clamp specified in 4.2. The contact between the test piece and the crystal affects the
absorbance of ATR spectra.
2 © ISO 2015 – All rights reserved

ISO/DIS 21561-2:2015(E)
7.5 Measure the sample spectrum with the conditions shown in 4.1.
7.6 The atmosphere of the sample chamber for FTIR shall be kept consistent during the background
−1 −1
and test piece measurements in order to avoid the influences of absorbance at 668 cm and 723 cm by
CO .
8 Determination of the microstructure of butadiene and the styrene content
8.1 Measurement of the absorbance for each microstructure component
Measure the absorbance values at the wave numbers corresponding to the microstructure components
as specified in Table 1. For cis, the absorption peaks are weak and the wave number of the peaks is
affected by the styrene content of the polymer.
Table 1 — Measurement of absorbances for each microstructure component of S-SBR
Notation for Microstructure
Remarks
absorbance component
−1 −1
A10 Styrene Measure the absorbance at the peak maximum from 695 cm to 700 cm .
The wave number at this peak maximum is affected by the nature of the
polymer, such as the styrene content. When the peak maximum is visible,
−1 −1
read off the absorbance at the peak maximum from 720 cm to 730 cm .
A20 cis
If the styrene content is over 30 %, the peak of the cis bond is hidden
−1
between the two large styrene absorptions at around 758 cm and around
−1 −1
698 cm . In this case, measure the absorbance value at 726 cm .
−1 −1
A30 styrene Measure the absorbance at the peak maximum from 755 cm to 761 cm
−1 −1
A40 Vinyl Measure the absorbance at the peak maximum from 905 cm to 912 cm
−1 −1
A50 Trans Measure th
...