fractionation and subsequent analysis of the individual fractions by SEC-FTIR has
been found to be an effective method for the determination of the chemical
composition per molar mass slice [45]. This approach provides an average chemical
composition per molar mass fraction; however, the CCD cannot be obtained since
each molar mass fraction can be heterogeneous with respect to chemical
composition.
The most recent development in the field of polyolefin analysis is the introduction of HT-HPLC that allows fractionation of polyolefins with respect to their
chemical composition. Since final materials properties are dependent on MMD
and CCD, fractionation with respect to both parameters is required. MMD and CCD
overlap with each other; hence, a 2D mapping of this multivariate distribution
(separation according to chemical composition and molar mass) is required. This
mapping can be realized by HT-2D-LC. In a previous study, the individual
components in selected TREF fractions of IPC were fractionated and analysed by
the combination of P-TREF, HT-HPLC and HT-2D-LC [113, 114]. The analysis of
the TREF fractions was accomplished by coupling HT-SEC to advanced thermal
analysis. The analysis of TREF-SEC fractions by HyperDSC and Flash DSC
1 revealed that the fractions had complex molecular structures and exhibited
complex thermal behaviours.
3.4.3.1 Aim
In this study, two complex IPC samples with different chemical compositions shall
be analysed to evaluate the effectiveness of cross-fractionation techniques, obtained
by a combination of various analytical separation methods as a tool for complex
polyolefin characterization. The P-TREF fractionation will be the initial step that
will provide different fractions, including EPR, EP-segmented copolymers and iPP.
These fractions can still have distributions with respect to chemical composition
and molar mass. Different coupled methods, namely SEC-FTIR, HT-HPLC-FTIR
and HT-2D-LC, will be used for the analysis of the P-TREF fractions. In HT-2DLC, the chemically homogeneous fractions obtained by HT-HPLC in the first
dimension will be analysed for MMD by HT-SEC in the second dimension. For
CCD analysis, HT-HPLC will be coupled to FTIR spectroscopy via the
LC-Transform interface. The coupling to FTIR will reveal information on the
ethylene and propylene contents of the samples, and also the ethylene and propylene crystallinities.
3.4.3.2 Materials
• Polymers. Two non-stabilized IPCs (designated 3V and 3VA) (SASOL
Polymers, Secunda, South Africa). Molar mass dispersity and comonomer
content of the samples are given as follows: 3V: 10.5 mol% ethylene, isotacticity
88.8 % (mmmm), M w 228 kg/mol, M w /M n 3.5; 3VA: 11.8 mol% ethylene,
isotacticity 87.5 % (mmmm), M w 361 kg/mol, M w /M n 6.0.
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3 Column-Based Chromatographic Techniques
been found to be an effective method for the determination of the chemical
composition per molar mass slice [45]. This approach provides an average chemical
composition per molar mass fraction; however, the CCD cannot be obtained since
each molar mass fraction can be heterogeneous with respect to chemical
composition.
The most recent development in the field of polyolefin analysis is the introduction of HT-HPLC that allows fractionation of polyolefins with respect to their
chemical composition. Since final materials properties are dependent on MMD
and CCD, fractionation with respect to both parameters is required. MMD and CCD
overlap with each other; hence, a 2D mapping of this multivariate distribution
(separation according to chemical composition and molar mass) is required. This
mapping can be realized by HT-2D-LC. In a previous study, the individual
components in selected TREF fractions of IPC were fractionated and analysed by
the combination of P-TREF, HT-HPLC and HT-2D-LC [113, 114]. The analysis of
the TREF fractions was accomplished by coupling HT-SEC to advanced thermal
analysis. The analysis of TREF-SEC fractions by HyperDSC and Flash DSC
1 revealed that the fractions had complex molecular structures and exhibited
complex thermal behaviours.
3.4.3.1 Aim
In this study, two complex IPC samples with different chemical compositions shall
be analysed to evaluate the effectiveness of cross-fractionation techniques, obtained
by a combination of various analytical separation methods as a tool for complex
polyolefin characterization. The P-TREF fractionation will be the initial step that
will provide different fractions, including EPR, EP-segmented copolymers and iPP.
These fractions can still have distributions with respect to chemical composition
and molar mass. Different coupled methods, namely SEC-FTIR, HT-HPLC-FTIR
and HT-2D-LC, will be used for the analysis of the P-TREF fractions. In HT-2DLC, the chemically homogeneous fractions obtained by HT-HPLC in the first
dimension will be analysed for MMD by HT-SEC in the second dimension. For
CCD analysis, HT-HPLC will be coupled to FTIR spectroscopy via the
LC-Transform interface. The coupling to FTIR will reveal information on the
ethylene and propylene contents of the samples, and also the ethylene and propylene crystallinities.
3.4.3.2 Materials
• Polymers. Two non-stabilized IPCs (designated 3V and 3VA) (SASOL
Polymers, Secunda, South Africa). Molar mass dispersity and comonomer
content of the samples are given as follows: 3V: 10.5 mol% ethylene, isotacticity
88.8 % (mmmm), M w 228 kg/mol, M w /M n 3.5; 3VA: 11.8 mol% ethylene,
isotacticity 87.5 % (mmmm), M w 361 kg/mol, M w /M n 6.0.
130
3 Column-Based Chromatographic Techniques