ISO 24076:2021

Plastics - Polypropylene (PP) - Determination of isotactic index by low-resolution nuclear magnetic resonance spectrometry

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.

Plastiques — Polypropylène (PP) — Détermination de l'indice isotactique par spectrométrie de résonance magnétique nucléaire à basse résolution

General Information

• Status: Published
• Publication Date: 31-Jan-2021
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: ISO/TC 61/SC 9 - Thermoplastic materials
• Drafting Committee: ISO/TC 61/SC 9/WG 6 - Polyolefins
• Current Stage: 6060 - International Standard published
• Start Date: 01-Feb-2021
• Due Date: 08-May-2021
• Completion Date: 01-Feb-2021

Overview

ISO 24076:2021 - Plastics - Polypropylene (PP) - Determination of isotactic index by low‑resolution nuclear magnetic resonance spectrometry - specifies a relative, non‑destructive LR‑NMR method to determine the isotactic index (II) of polypropylene. The method is calibrated against the solvent‑extraction reference in ISO 9113 and is intended for base polymers (not mixtures). It supports identification and coding of PP‑H (types H propylene) plastics per ISO 19069‑1 and improves testing efficiency by avoiding solvent extraction during routine measurement.

Key topics and technical requirements

• Principle: Low‑resolution pulsed NMR records proton magnetization decay; faster‑decaying signal components correspond to unextractable (crystalline/isotactic) material and are related to isotactic index through a calibration curve.
• Two measurement approaches:
  • Method A - Ratio method: Uses a ratio probe to compare signals of unextractable vs. whole sample.
  • Method B - Absolute method: Uses an absolute probe to relate extractable‑signal to sample mass.
• Calibration: LR‑NMR results are calibrated against isotactic index values measured by the ISO 9113 n‑heptane extraction method using at least five reference samples across the relevant II range.
• Apparatus and conditions (examples from standard):
  • LR‑NMR frequency: 18–25 MHz (typical 20 or 23 MHz)
  • Probe diameters: ~10 mm (Method A) or ~26 mm (Method B)
  • Probe temperature: 40 °C ± 0.1 °C
  • Sample drying/annealing: 140 °C ± 2 °C for 2 h under ≤25 kPa
  • Sample tube dimensions specified for each method; balance required for Method B (0.0001 g precision)
• Scope limits: Suitable for base polypropylene polymers only; not applicable to mixtures.

Applications and who uses it

• Quality control laboratories - faster routine monitoring of polypropylene isotactic index without repeated solvent extraction.
• Polymer manufacturers and compounders - product classification, process monitoring, and acceptance testing of PP‑H materials.
• NMR instrument vendors and method developers - implementation of validated LR‑NMR procedures and instrument calibration services.
• Standards and conformity bodies - material coding and compliance assessment when classifying PP per ISO 19069‑1.

Related standards

• ISO 9113 - Direct (absolute) n‑heptane extraction method for polypropylene isotactic index (reference calibration method).
• ISO 19069‑1 - Coding and identification of types H propylene (PP‑H) plastics.

Keywords: ISO 24076:2021, polypropylene isotactic index, LR‑NMR, low‑resolution nuclear magnetic resonance, PP‑H, plastics testing, ISO 9113, ISO 19069‑1.

Standards Content (Sample)

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 a
...