This document specifies three methods for the determination of the soluble content of polypropylene homopolymers or copolymers in xylene at 25°C:
Method A: Chemical method.
Method B: Infrared spectroscopy
Method C: Low resolution pulsed nuclear magnetic resonance.
Method A is the reference method and is used for the calibration of Methods B and C.
This document applies to the determination of the soluble content of polypropylene homopolymers or copolymers in xylene at 25°C. Materials such as additives that are soluble in xylene may affect the determination of the xylene soluble content.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, note the date of the cited documents, only the date of the corresponding version applicable to this document; do not note the date of the cited documents, the latest version (including all the revision of the list) applicable to this document.
GB/T8170 numerical modification rules and limit values of the representation and determination
3 Terminology and definitions
The following terms and definitions apply to this document.
3.1
xylene-soluble fractionw,
The mass fraction of material that does not precipitate out of the solution after the polymer has been dissolved in xylene at reflux temperature and the solution has been cooled to 25°C and held for a certain time.
4 Methods
A: Chemical method
4.1 Principle
A sample of polypropylene is dried, weighed and dissolved in xylene at reflux. The solution is then cooled to 25°C under specific conditions and kept at a constant temperature to ensure that the polypropylene is fully crystallised under these conditions. The mixture was then filtered to give a clear filtrate. The xylene in the filtrate is evaporated to obtain the xylene soluble matter and its content is calculated.
4.2 Apparatus
4.2.1 Reflux condenser, length 400 mm.
4.2.2 Flask with a volume of 500 mL.
4.2.3 Insulation mat, made of ceramic fibre.
4.2.4 Electromagnetic stirrer with temperature-controlled heating plate, thermostatic oil bath or heating block, capable of maintaining a temperature of 140 °C to 150 °C.
4.3 Reagents and materials
4.3.1 Optional xylenes are available:
4.4 Test procedure
4.4.1 Preparation of xylene
4.4.1.1 When measuring unstable powders or small granules, any of the antioxidants in 4.3.2 should be added to the xylene to prevent degradation. Antioxidants are more stable in xylene at a concentration of approx. 0.02 g/L.
The solution is heated to 80 °C to 90 °C with a temperature-controlled electromagnetic stirrer (see 4.2.4) and stirred for at least 1 h to mix the antioxidant and xylene. This heating temperature is suitable for the relatively volatile antioxidant BHT.
4.4.1.2 Degas the xylene with nitrogen, at least 1 hour every 24 hours.
4.4.2 Determination of impurities in xylene (blank test)
4.4.2.1 The purpose of the blank test is to determine whether the xylene contains obvious evaporative residues and other impurities. If the purity of the reagent is greater than or equal to 99.5% and it is used immediately after opening, the blank test may not be carried out. It is advisable to use glass containers for xylene, which should be used within 3 days of opening.
Three blanks should be taken from each batch of xylene.
4.4.2.2 Pipette (see 4.2.6) 200 mL of xylene into a clean, empty flask (see 4.2.2).
4.4.2.3 Place the filter paper (see 4.2.9) in a funnel (see 4.2.10) and place the funnel above the 250 mL flask (see 4.2.7).
4.4.3 Determination of xylene soluble matter in polypropylene
4.5 Calculation and presentation of results
4.6 Precision
Inter-laboratory precision tests were carried out in different laboratories on six polypropylene samples with different xylene soluble content and the results of the data are shown in Table B.1.
5 Method
B: Infrared spectrometry
5.1 Principle
A certain mass of polypropylene sample was dissolved in 1,2-dichlorobenzene or 1,2,4-trichlorobenzene at 145 °C to 170 °C until it was completely dissolved, and a certain volume of the solution was taken to determine its characteristic infrared absorption peak. The solution containing the soluble fraction was then cooled to 30 °C to 40 °C and held for at least 30 min to allow the soluble and crystalline fractions to separate. The solution containing the soluble fraction is then passed through a detector to determine its characteristic infrared absorption peak and the ratio of the peak areas of the two characteristic infrared absorption peaks is used to obtain the amount of soluble fraction dissolved in the solvent.
5.2 Instrumentation
5.2.1 Fully automatic soluble matter analyser with the main components being solvent storage, injection/transfer system, dissolution system, separation system, detector, waste solution, and a solvent analyzer.
The main components of the instrument are solvent storage, injection/transfer system, dissolution system, separation system, detector, waste liquid storage, data acquisition and data processing system. As the solution is transferred between systems, the systems and their connecting lines should be at high temperatures to avoid unwanted crystallisation of the polymer as it dissolves.
5.2.2 Solvent reservoirs or waste reservoirs, containers (bottles, etc.) should be capable of holding sufficient volume of solvent and waste to ensure continuity and uniformity of solvent delivery during the test. The container material should be inert to solvents and glass containers are recommended.
5.3 Reagents and materials
5.3.1 The reagents available are:
--1,2,4-trichlorobenzene, purity greater than or equal to 99%;
--1,2-o-dichlorobenzene, purity greater than or equal to 99%.
5.4.1.1 To prevent degradation, add any one of the antioxidants in 5.3.2 to the reagent, which is better stabilised at a concentration of about 0.3 g/1.
5.4.1.2 If necessary, heat the solution to 80 °C~90 °C with a temperature-controlled electromagnetic stirrer (see 4.2.4) and stir for at least 1 h to mix the antioxidant and the reagent.
6 Method
C: Low resolution pulsed NMR method
6.1 Principle
This method is based on the different relaxation times of the protons of different structures in the sample during the free induction decay process of NMR, and by comparing the different decay signals of different structural features, the NMR signal response value of the sample is obtained. A calibration curve was established using a series of reference polypropylene samples with known xylene soluble content at 25°C obtained by Method A. The calibration curve and the NMR signal response of the polypropylene samples were then used to obtain the xylene soluble content of the polypropylene samples.
6.2 Instrumentation
6.2.1 Low resolution pulsed NMR spectrometer:
a) Operating frequency: 18 MHz to 25 MHz;
b) Probe type: absolute or relative
c) Magnet temperature: set according to the specific requirements of the instrument, control accuracy: ±0.01 °C. 6.2.2 Analytical balance, accuracy 0.1 mg.
6.2.3 Sample tube, made of non-conductive material without hydrogen atoms, e.g. glass, etc.
6.3 Test procedure
6.3.1 Sample preparation
6.3.1.1 If necessary, the specimen should be processed as described in 4.4.3.1.
6.3.1.2 The appropriate amount of sample is quickly loaded into a clean sample tube (see 6.2.3) and sealed immediately to prevent any change in sample moisture. The sample tube with the specified amount of sample for the instrument is then inserted into the jack which has been preheated in the thermostat (see 6.2.4) and preheated for 30 min. The preheating temperature is kept at the same temperature as the probe.
7 Test report
Appendix A (informative) Comparison of this document with ISO 16152:2005 structure numbering
Appendix B (informative) Statistical results of precision data
Bibliography
1 Scope 2 Normative references 3 Terminology and definitions 4 Methods 5 Method 6 Method 7 Test report Appendix A (informative) Comparison of this document with ISO 16152:2005 structure numbering Appendix B (informative) Statistical results of precision data Bibliography
1 Scope
This document specifies three methods for the determination of the soluble content of polypropylene homopolymers or copolymers in xylene at 25°C:
Method A: Chemical method.
Method B: Infrared spectroscopy
Method C: Low resolution pulsed nuclear magnetic resonance.
Method A is the reference method and is used for the calibration of Methods B and C.
This document applies to the determination of the soluble content of polypropylene homopolymers or copolymers in xylene at 25°C. Materials such as additives that are soluble in xylene may affect the determination of the xylene soluble content.
2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, note the date of the cited documents, only the date of the corresponding version applicable to this document; do not note the date of the cited documents, the latest version (including all the revision of the list) applicable to this document.
GB/T8170 numerical modification rules and limit values of the representation and determination
3 Terminology and definitions
The following terms and definitions apply to this document.
3.1
xylene-soluble fractionw,
The mass fraction of material that does not precipitate out of the solution after the polymer has been dissolved in xylene at reflux temperature and the solution has been cooled to 25°C and held for a certain time.
4 Methods
A: Chemical method
4.1 Principle
A sample of polypropylene is dried, weighed and dissolved in xylene at reflux. The solution is then cooled to 25°C under specific conditions and kept at a constant temperature to ensure that the polypropylene is fully crystallised under these conditions. The mixture was then filtered to give a clear filtrate. The xylene in the filtrate is evaporated to obtain the xylene soluble matter and its content is calculated.
4.2 Apparatus
4.2.1 Reflux condenser, length 400 mm.
4.2.2 Flask with a volume of 500 mL.
4.2.3 Insulation mat, made of ceramic fibre.
4.2.4 Electromagnetic stirrer with temperature-controlled heating plate, thermostatic oil bath or heating block, capable of maintaining a temperature of 140 °C to 150 °C.
4.3 Reagents and materials
4.3.1 Optional xylenes are available:
4.4 Test procedure
4.4.1 Preparation of xylene
4.4.1.1 When measuring unstable powders or small granules, any of the antioxidants in 4.3.2 should be added to the xylene to prevent degradation. Antioxidants are more stable in xylene at a concentration of approx. 0.02 g/L.
The solution is heated to 80 °C to 90 °C with a temperature-controlled electromagnetic stirrer (see 4.2.4) and stirred for at least 1 h to mix the antioxidant and xylene. This heating temperature is suitable for the relatively volatile antioxidant BHT.
4.4.1.2 Degas the xylene with nitrogen, at least 1 hour every 24 hours.
4.4.2 Determination of impurities in xylene (blank test)
4.4.2.1 The purpose of the blank test is to determine whether the xylene contains obvious evaporative residues and other impurities. If the purity of the reagent is greater than or equal to 99.5% and it is used immediately after opening, the blank test may not be carried out. It is advisable to use glass containers for xylene, which should be used within 3 days of opening.
Three blanks should be taken from each batch of xylene.
4.4.2.2 Pipette (see 4.2.6) 200 mL of xylene into a clean, empty flask (see 4.2.2).
4.4.2.3 Place the filter paper (see 4.2.9) in a funnel (see 4.2.10) and place the funnel above the 250 mL flask (see 4.2.7).
4.4.3 Determination of xylene soluble matter in polypropylene
4.5 Calculation and presentation of results
4.6 Precision
Inter-laboratory precision tests were carried out in different laboratories on six polypropylene samples with different xylene soluble content and the results of the data are shown in Table B.1.
5 Method
B: Infrared spectrometry
5.1 Principle
A certain mass of polypropylene sample was dissolved in 1,2-dichlorobenzene or 1,2,4-trichlorobenzene at 145 °C to 170 °C until it was completely dissolved, and a certain volume of the solution was taken to determine its characteristic infrared absorption peak. The solution containing the soluble fraction was then cooled to 30 °C to 40 °C and held for at least 30 min to allow the soluble and crystalline fractions to separate. The solution containing the soluble fraction is then passed through a detector to determine its characteristic infrared absorption peak and the ratio of the peak areas of the two characteristic infrared absorption peaks is used to obtain the amount of soluble fraction dissolved in the solvent.
5.2 Instrumentation
5.2.1 Fully automatic soluble matter analyser with the main components being solvent storage, injection/transfer system, dissolution system, separation system, detector, waste solution, and a solvent analyzer.
The main components of the instrument are solvent storage, injection/transfer system, dissolution system, separation system, detector, waste liquid storage, data acquisition and data processing system. As the solution is transferred between systems, the systems and their connecting lines should be at high temperatures to avoid unwanted crystallisation of the polymer as it dissolves.
5.2.2 Solvent reservoirs or waste reservoirs, containers (bottles, etc.) should be capable of holding sufficient volume of solvent and waste to ensure continuity and uniformity of solvent delivery during the test. The container material should be inert to solvents and glass containers are recommended.
5.3 Reagents and materials
5.3.1 The reagents available are:
--1,2,4-trichlorobenzene, purity greater than or equal to 99%;
--1,2-o-dichlorobenzene, purity greater than or equal to 99%.
5.3.2 Optional antioxidants are:
--Butylhydroxytoluene (antioxidant BHT);
--Tetrakis[methyl-(3,5-di-tert-butyl-4-hydroxyphenyl propionate)]pentaerythritol ester (antioxidant 1010).
5.4 Test procedure
5.4.1 Preparation of solvents
5.4.1.1 To prevent degradation, add any one of the antioxidants in 5.3.2 to the reagent, which is better stabilised at a concentration of about 0.3 g/1.
5.4.1.2 If necessary, heat the solution to 80 °C~90 °C with a temperature-controlled electromagnetic stirrer (see 4.2.4) and stir for at least 1 h to mix the antioxidant and the reagent.
6 Method
C: Low resolution pulsed NMR method
6.1 Principle
This method is based on the different relaxation times of the protons of different structures in the sample during the free induction decay process of NMR, and by comparing the different decay signals of different structural features, the NMR signal response value of the sample is obtained. A calibration curve was established using a series of reference polypropylene samples with known xylene soluble content at 25°C obtained by Method A. The calibration curve and the NMR signal response of the polypropylene samples were then used to obtain the xylene soluble content of the polypropylene samples.
6.2 Instrumentation
6.2.1 Low resolution pulsed NMR spectrometer:
a) Operating frequency: 18 MHz to 25 MHz;
b) Probe type: absolute or relative
c) Magnet temperature: set according to the specific requirements of the instrument, control accuracy: ±0.01 °C. 6.2.2 Analytical balance, accuracy 0.1 mg.
6.2.3 Sample tube, made of non-conductive material without hydrogen atoms, e.g. glass, etc.
6.3 Test procedure
6.3.1 Sample preparation
6.3.1.1 If necessary, the specimen should be processed as described in 4.4.3.1.
6.3.1.2 The appropriate amount of sample is quickly loaded into a clean sample tube (see 6.2.3) and sealed immediately to prevent any change in sample moisture. The sample tube with the specified amount of sample for the instrument is then inserted into the jack which has been preheated in the thermostat (see 6.2.4) and preheated for 30 min. The preheating temperature is kept at the same temperature as the probe.
7 Test report
Appendix A (informative) Comparison of this document with ISO 16152:2005 structure numbering
Appendix B (informative) Statistical results of precision data
Bibliography
Contents of GB/T 24282-2021
1 Scope
2 Normative references
3 Terminology and definitions
4 Methods
5 Method
6 Method
7 Test report
Appendix A (informative) Comparison of this document with ISO 16152:2005 structure numbering
Appendix B (informative) Statistical results of precision data
Bibliography
