ISO 24076:2021 pdf free download – Plastics – Polypropylene (PP)一 Determination of isotactic index by low-resolution nuclear magnetic resonance spectrometry.
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 150 9113. No solvent is used, and the determination efficiency is improved during samples measurement procedure except for the calibration part.
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 maintained at the temperature of 40 °C ± 0,1 °C.
5.5 Balance, shall be accurate to the nearest 0,000 1 g, only for method B.
6 Preparation of sample
6.1 General
The test sample and the reference sample can be in the form of powder or pellets. Place at least 10 g of the sample in a glass container, and put it in the oven (53) for 2 h at 140 °C ± 2 °C under 25 kPa nitrogen vacuum or less for complete drying and annealing, then cool in a desiccator to room temperature.
6.2 Reference samples
At least five reference samples with different isotactic index shall be used. The isotactic index of reference samples shall cover the general range, and its distribution shall be homogeneous as far as possible.
NOTE The isotactic index of reference samples can be 94 % to 99 %. The reference samples can be collected by the user or offered by spectrometer manufacturer.
7 Method A — Ratio method
7.1 Procedure
7.1.1 Measurement of reference samples by n-heptane extraction
The isotactic index of reference samples shall be measured by extraction method specified in ISO 9113.