BS ISO 24076:2021 pdf download – 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.
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/
percentage mass fraction of unextractable matter content in polypropylene, which cannot be extracted from polypropylene by boiling n-heptane
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.
7.1.2 LR-NMR measurement procedure of reference samples
188.8.131.52 Put the reference sample into a sample tube (5.2), with a depth of between 30 mm and 50 mm.
NOTE The sample amount can be specified by the spectrometer manufacturer which matches to the probe height.
184.108.40.206 Put the tube in thermostatic apparatus (5.4) for a minimum of 30 min to achieve temperature equilibration.
220.127.116.11 Transfer the tube to LR-NMR probe (5.1) within 15 s. Hold for 15 min to achieve temperature equilibration.
NOTE Experience shows that it is easy to transfer a tube from thermostatic apparatus to LR-NMR probe within 15 s.
18.104.22.168 Measure the magnetization decay signal. The typical signal range corresponding to the sample is 7 μs to 9 μs, and that of extractable matter is 50 μs to 90 μs.
NOTE For exact magnetization decay signal time, refer to the spectrometer manufacturer’s instructions.
7.1.3 LR-NMR measurement procedure of test samples
Shall be the same as that of reference samples (see 7.1.2) except that the reference sample is replaced by the test sample.
7.2.1 Calibration curve
Prepare calibration curve by plotting II’ obtained from extraction method against LR-NMR signal. An example of a calibration curve for method A is shown in Annex A.
The Formula (1) is obtained by linear regression method according to the calibration curve.
II’ is the isotactic index of the reference sample determined by n-heptane extraction specified in ISO 9113,expressed in percent (%);
N’ 1a is the average magnetization decay signal of the reference sample measured by method A;
N’ 2a is the average magnetization decay signal of the extractable matter in the reference sample measured by method A;
a is the slope of the calibration curve;
b is the intercept of the calibration curve.
7.2.2 Calculation of isotactic index II na
Isotactic index II na is given by the Formula (2).
8 Method B — Absolute method
8.1.1 Measurement of reference samples by n-heptane extraction See 7.1.1.
8.1.2 LR-NMR measurement procedure of reference samples
22.214.171.124 Weigh approximately 5 g of the reference sample, to the nearest 1 mg, put them into a sample tube (5.2) within the height of LR-NMR probe.BS ISO 24076 pdf download.