ISO 24076:2021 download.Plastics Polypropylene (PP) Determination of isotactic index by low-resolution nuclear magnetic resonance spectrometry.
The LR-NMR method in ISO 24076 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. ISO 24076 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.
ISO 24076 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.
150 9113, Plastics — Polypropylene (PP) and propylene-copolymer thermoplastics — Determination of iso tactic index
3 Terms and definitions
For the purposes of this document, the toI1owing terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
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 tollowing.
5.1 LR.NMR, of frequency 18 MHz to 25 MHz, typical of 20 Mlix 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 DC ±0.1 DC,
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 26mm ± 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 DC ± 2 DC. 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 got’ the sample in a glass container, and put it in the oven (5.3) for 2 hat 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 live 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 oltered 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.
7.1.2 LR-NMR measurement procedure of reference samples
7.1.2.1 Put the reference sample into a sample tube (52). 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.
7.1.2.2 Put the tube in thermostatic apparatus (5.4) for a minimum of 30 mm to achieve temperature equilibration.
7.1.2.3 Transier the tube to LR-NMR probe (SJJ withIn 15 s. Hold for 15 mm to achieve temperature equilibration,
NOTE Experience shows that It is easy to transfer a tube from thermostatic apparatus to LR.NMR probe within ISa.
7.1.2.4 Measure the magnetization decay signal. The typical signal range corresponding to the sample is? its to 9 its. and that of extractable matter is 50 ias to 90 ps.
NOTE For exact magnetization decay signal time, refer to the spectrometer manufacturer’s instructions.
7.1.3 LR-NMR measurement procedure of testsamples
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 Calculation
72.1 CalIbration curve
Prepare calibration curve by plotting IP obtained from extraction method against L.R-NMR signal. An example of a calibration curve for method A Is shown In Annex A.
The FurmuJj.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’,5 is the average magnetization decay signal of the reference sample measured by method A;
N’ 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.
8.2.2 Calculation of isotactic Index II Isotactic index “nh• is given by the Formula 4:
(4)
where
“nb Is the isotactic index of the test sample determined by method B. expressed in percent (%); Nzb is the average magnetization decay signal of the extractable matter in the test sample measui-ed by method B:
m is the mass of the test sample, expressed in grams (g);
a Is the slope of the calibration curve;
b is the intercept of the calibration curve.
9 Expression of results
Express the result as the arithmetic mean of the two determinations. Report the result to one decimal place. The absolute difference between two determinations shall be within 0,2 %. If this condition is not fulfilled, repeat the test.
10 Test report
The test report shall include the following particulars:
a) a reference to this document, I.e. ISO 24076:202 1;
b) the method used (method A or method B);
c) all Information necessary for the complete identification of the test sample;
d) details of the LR-NMR used;
e) results of calibration: number and isotactic index of reference samples, magnetization decay signals used for calculation, calibration curve and coefficients.