ISO 24076:2021

INTERNATIONAL ISO
STANDARD 24076
First edition
2021-02
Plastics — Polypropylene (PP) —
Determination of isotactic index by
low-resolution nuclear magnetic
resonance spectrometry
Plastiques — Polypropylène (PP) — Détermination de l'indice
isotactique par spectrométrie de résonance magnétique nucléaire à
basse résolution
Reference number
©
ISO 2021
© ISO 2021
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ii © ISO 2021 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Preparation of sample . 2
6.1 General . 2
6.2 Reference samples . 2
7 Method A — Ratio method . 2
7.1 Procedure . 2
7.1.1 Measurement of reference samples by n-heptane extraction . 2
7.1.2 LR-NMR measurement procedure of reference samples . 3
7.1.3 LR-NMR measurement procedure of test samples . 3
7.2 Calculation . 3
7.2.1 Calibration curve . 3
7.2.2 Calculation of isotactic index II .
na 4
8 Method B — Absolute method . 4
8.1 Procedure . 4
8.1.1 Measurement of reference samples by n-heptane extraction . 4
8.1.2 LR-NMR measurement procedure of reference samples . 4
8.1.3 LR-NMR measurement procedure of test samples . 4
8.2 Calculation . 4
8.2.1 Calibration curve . 4
8.2.2 Calculation of isotactic index II .
nb 5
9 Expression of results . 5
10 Test report . 5
Annex A (informative) Example of a calibration curve for method A . 7
Annex B (informative) Example of a calibration curve for method B . 8
Bibliography . 9
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9,
Thermoplastic materials.
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iv © ISO 2021 – All rights reserved

Introduction
The LR-NMR method in this document is a relative method established with ISO 9113 as the absolute
method. The method and concept of isotactic index of polypropylene are specified in ISO 9113, that is,
the polypropylene sample is separated into the extractable and the unextractable matter by n-heptane
extraction, and the percentage of unextractable matter in the sample is calculated as isotactic index.
Isotactic index in ISO 9113 sounds similar to tacticity (isotacticity or stereotacticity) of polymer chain,
but the concept and result are different. The result is related to but not equal to the tacticity (isotacticity
or stereotacticity) of molecular chain, which can be determined by high resolution carbon-13 nuclear
magnetic resonance and infrared method. The result of ISO 9113 is also related to crystallization,
molecular weight, chain entanglement of the sample, solvent solubility and other effects.
For solid polymers, extraction always takes a long time for the diffusion of long molecular chain from
polymer to solvent. To improve test efficiency, relative methods are developed. This document provides
a relative non-destructive method for the determination of isotactic index by low-resolution nuclear
magnetic resonance spectrometry through a calibration curve establishing with magnetic signal and
isotactic index determined by ISO 9113. No solvent is used, and the determination efficiency is improved
during samples measurement procedure except for the calibration part.
INTERNATIONAL STANDARD ISO 24076:2021(E)
Plastics — Polypropylene (PP) — Determination of
isotactic index by low-resolution nuclear magnetic
resonance spectrometry
1 Scope
This document specifies a relative method for the determination of polypropylene (PP) isotactic index
by low-resolution pulsed nuclear magnetic resonance spectroscopy (LR-NMR).
This method enables the identification and coding of types H propylene (PP-H) plastics according to
ISO 19069-1.
This method is suitable for base polymers and is not applicable for mixtures.
NOTE The direct method for the determination of polypropylene isotactic index is specified in ISO 9113.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 9113, Plastics — Polypropylene (PP) and propylene-copolymer thermoplastics — Determination of
isotactic index
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
isotactic index
II
percentage mass fraction of unextractable matter content in polypropylene, which cannot be extracted
from polypropylene by boiling n-heptane
4 Principle
The sample is placed in LR-NMR. After electromagnetic equilibration in the static magnetic field of
the NMR spectrometer and application of a 90° radio frequency pulse, the magnetization decay signal
curve from the protons of the sample is recorded. The signal of the un-extractable matter in the sample
drops much faster than that of extractable matter. In the signal curve, initial signal corresponds to
the whole sample including the un-extractable and the extractable matter, and later slower dropping
signal corresponds to the extractable matter in the sample. So, the magnetization decay signal and the
isotactic index of the sample are related.
The isotactic index is either calculated from the ratio between the magnetization decay signal of the
un-extractable part and the entire sample detected by a ratio probe (method A ratio method), or from
the ratio between the magnetization decay signal of the extractable part and the mass of the sample-
detected by an absolute probe (method B absolute method), using an appropriate calibration. The
calibration curve is constructed using the magnetization decay signal and isotactic index determined
by n-Heptane extraction method specified in ISO 9113.
5 Apparatus
Usual laboratory apparatus and glassware and, in particular, the following.
5.1 LR-NMR, of frequency 18 MHz to 25 MHz, typical of 20 MHz and 23 MHz; a probe of 10 mm
diameter for method A, or a probe of 26 mm diameter for method B; temperature of probe and magnet
field being 40 °C ± 0,1 °C.
NOTE The probe of other diameter can also be used according to instrument parameters.
5.2 Sample tube, of glass with outer diameter 10 mm ± 0,25 mm, wall thickness 0,9 mm ± 0,25 mm,
and length at least 150 mm, for method A; of glass with outer diameter 26 mm ± 0,25 mm, wall thickness
1,3 mm ± 0,25 mm, and length at least 200 mm, for method B.
NOTE The sample tube of other size can also be used according to probe parameters.
5.3 Oven, shall be capable of being maintained at the temperature of 140 °C ± 2 °C, provided with
vacuum lines of 25 kPa or less.
5.4 Thermostatic apparatus, shall be capable of being mai
...