ISO 21461:2012 download free.Rubber-Determination of the aromaticity of oil in vulcanized rubber compounds.
ISO 21461 provides a method for the selective determination of potyaromaticity of oil in vulcanized nMber compounds. The method is based on nuclear magnetic resonance (NMR) spectrometry
2 Normative references
The following referenced documents are Indispensable for the application of ISO 21461 For dated references, only the edition cited apØles. For undated references, the latest edition of the referenced document (includllng any amendments) applies.
ISO 1407. Rubber— Oaf ermmanon of sotvent extracf
3 Terms and definitions
For the purposes of ISO 21461 the blowing terms and definitions apply.
3.1
PAIl
polycyctlc aromatIc hydrocarbon
organic compounds consisting of two or more aromatic rings where certain carbon atoms are common to two ow three rings
4 Reagents and materials
NI reagents shall be of recognized analytical grade unless specified in a different way.
4.1 ExtractIon
4.1.1 Acetone.
4.2 Sample preparation reagents
4.2.1 n-tlepterie, pa grade.
4.22 Nitrogen, purity reqiared >99,9%. for protecting the extract from oxidation during the drying step.
4.2.3 Hexam.thyldlslloxane (IIMDS), 99,5%. NMR grade. or t.tremethylsllane (ThiS), 99,5%. NMR grade.
— pulse phase: 30’,
— speciralwidtft-2ppmto• l2ppm:
— nurrder of scans: 256:
— relaxation delay: 2s.
6 Procedure
6.1 Sample extraction
6.1.1 Th. compound sample shall be of sufficient size to provide at least 350 mg of extracted oil. In case of tyres. refer to Annex B for sample preparation.
6.12 Pass the sample between the rolls of a laboratory mill to reduce its thickness to less than 0.7mm or. alternatively, cut the sample In pieces smaller than 1 mm 1 mm *2 mm.
6.1.3 Wrap the sample ii a small filter paper and insert it in the extractor (5.2) or fill the extractor with the smal cut pieces. Fill the flask of the extractor with acetone (4.l.t) arid extract for Bit.
6.1.4 Evaporate the extract to dryness under a stream of rtitrogen (4.2.2) to prevent oxidation.
6.2 Extract purification
6.2.1 Weigh the dned extract to the nearest 0.1 mg. Add the amount of n4ieptane (42.1) necessary to bring the concentration to 100 mglcm3 There may be some insoluble mailer. Prepare three vials containing 1 cm3 each of the n-heplane solution.
622 Condition the SPE cartridge (see 5.4.1 or 5.4.2) by eluting 5cm3 or ii) oii of n-hep(ane (42.1) using the 5cm3 cr10 cm3 syringe (see 5.4.1 or 5.42).
6.2.3 When the n1iepAane Is nearly completely eluled. transfer quantitatively the n-heptarie solution from one vial (6.2.1) onto the SPE cartndge and start the collection In a beaker or glass lest lube, Lisa an additional 0.5 cm3 nheptane portion to rinse the vial and ensure complete transfer of the evaporation residue.
6,2.4 When the n-lleplane solution is neatly absorbed onto the SPE cartridge. elule the non..polar fraction with 25 cm3 of n-heplane. During the elubon, maintain a constant solvent flow not exceeding a rate of 5 cm3iman.
62.5 Stop collecting the purified fraction when all o(lhe 25cm3 of n-heptane has been added to the SPE cartridge.
6.2.6 Evaporate the eluted residue to dryness under a stream of nitrogen (4.22) to prevent oxidation. In order to accelerate the final drying step. the sample can be put in a vacuum oven at 50 ‘C for 2 h to 3 h.
6.2.7 Weigh the dry residue to the nearest 0,1 mg and calculate the percentage of recovery.
82.8 Repeat the extract purification procedure two more times, using the other two vials prepared in advance In step 6.2.1.
6.2.9 Calculate the average value of th. three percentages of recovery (from 62.7). It the Indrddual values obtained are within t 5 % of the average, proceed to 6.3. Otherwise repeat the sample preparation until three values are within ± 5% of the average recovery.
6.3 NMR analysis
6.3.1 PrInciple
The aromatic character of the oil present in the dry residues obtained en 6.2.7 and 6.2.8 is determined by means of 1H-NMR spectroscopy.
The molecular structure of non4enear PAH with three or more fused rings contains a characteristic threesded concave area, located at the periphery of the aromatic hydrocarbon molecule; these specific hydrogen atoms in this area are called bay region hyckogens (see Figure 1)
‘H-NMR spectroscopy can identity and quantity selectively the hydrogen atoms In the bay region. wtllch are characteristic for aromatic ods.
This method describes the procedure to determine the percentage of bay region hydrogens (% H51) in a sample solution by ‘H-NMR. thus concluding on the aromatic character of the alt
The hiier the amount of bay region hydrogens. the higher is the aromaticity.
6.3.2 NMR meeaurement
6.3.2.1 Dissolve one of the dry residues obtained In 6.2.7 and 6.2.8 In a glass vial pot example, about I an3 of
CDC* (42.4) for a 5mm tube). ltnenessary. enhance dissolution by using a small magnetic stirrer or mechanical
5hakae if this is not enough, add more CDCI.
6.3.2.2 Acqure the free induction decay (FID) signal and apply a Fourier transform, multiplying by an exponential function (LB – 0,3 Hz) to obtain the spectrum (see the examples In Annex A). Adjust the resonance of the reference peak to 0.00 ppm for TMS. or to 0.06 ppm (or HUDS, respectively.
6.3.2.3 Correct the baseline of the spectrum.
8.3.2.4 Correct the baseline by using a cubc spline correction, setting points for the correction at 11.5 ppm.
10.5 ppm. 6,0 ppm, -0.5 ppm and -1.5 ppm. An example of a spectrum after phase correction and after baseline correction is shown in Figure 2.
6.3.2.5 lntegate the spectrum and record the following areas
where
Cl4 Is the Integrated area from 6.0 ppm and 9,5 ppm In deuterated chloroform containing ThIS or HMDS (4.2.4):
Waterk is the integrated area from 1,0 ppm .01,8 ppm in deutorated chloroform containing TMS or HUDS (4.2.4). This integrated signal intensity accounts for the water content in the solvent
TMS or HMDSk Is the integrated signal intensity of ThIS (or lIMOS) in deuleiated chloroform containing TMS or lIMOS (4.2,4):
TMS or HMDS Is the integrated signal intensity or TMS or HMOS wi the sample solution (4.2.4).
6.3.2.7 Optorial procedure using acalaldehyde:
In case of dltfcultles in obtaining a good phasing of th. spectrum. it Is pei’missible to add 0,6% of acataidellyde to the chloroform solution (see 4.2.5) to help phasing the spectruni: the phase correction Is done using the peaks at around 9,8 ppm (acetaldehyde) and at 0,0 ppm (TMS) or at 0,06 ppm (HMDS) Processing Is done In the some way as for the somples without acetaldehyde. with the following modiltcabons.
— The integral Ioo includes also the acetaldehyde atiphatic proton signal at around 2.2 ppm.
— The correcfron for the eliphatlc protons of the acetaldehyde is done using the Integrated signal Intensity (A.4) of the aldehydic proton ICHO at around 9,8 ppm) in the sample, as the concentration of acetaldehyde 1 likely to change with time due to the very low boding point (21 C).
— The additional correction to be applied to the Integral 13 to account far the presence of ac.