Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (40)
- Posterpräsentation (28)
- Vortrag (11)
- Beitrag zu einem Tagungsband (6)
- Forschungsbericht (4)
- Beitrag zu einem Sammelband (3)
Schlagworte
- CRM (1)
- Chromatographie (1)
- Coupling methods (1)
- Intrinsic viscosity (1)
- Kopplung (1)
- Light scattering (LS) (1)
- Liquid chromatography (1)
- MALDI-TOF MS (1)
- MALDI-TOF-MS (1)
- Molar mass determination (1)
Eingeladener Vortrag
- nein (11)
Two-dimensional polymer characterization is used for a simultaneous analysis of molar masses and chemical heterogeneities (e.g., end groups, copolymer composition, etc.). This principle is based on coupling of two different chromatographic modes. Liquid adsorption chromatography at critical conditions (LACCC) is applied for a separation according to the chemical heterogeneity, whereas in the second-dimension fractions are analyzed with regard to their molar mass distribution by means of size exclusion chromatography (SEC). Because appropriate standards for a calibration of the SEC are seldom available, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS) was used to substitute the SEC. The LACCC-MALDI MS coupling enables acquiring additional structural information on copolymer composition, which can considerably enhance the performance of this coupled method.
This article reports round-robin tests dealing with static light scattering (LS), size exclusion chromatography (SEC), and viscometry measurements of 10 reference materials of various polymer classes: poly(styrene)s (PS), poly(methyl methacrylate)s (PMMA), poly(ethylene oxide)s (PEO), and poly(lactide)s (PLA).
In the certificates, molar masses and intrinsic viscosities as well as their uncertainties are specified. Additional values from nuclear magnetic resonance (NMR), infrared spectroscopy (IR), differential scanning calorimetry (DSC), melt flow index (MFR), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), which were determined exclusively in BAM laboratories are given, as well.
These results represent the base for the BAM certification work of creating polymer reference materials according to the BAM Guidelines for the Production and Certification of BAM Reference Materials, a version of the European guidelines (BCR/01/97). These samples are available for third-party user.
Dynamische Beanspruchung von Bauteilen aus Polyolefinen und ihr Einfluß auf die Spannungsrißbildung
(1978)
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a useful new technique for the determination of the chemical structure and the molar mass distribution of poly(ethylene oxides). Investigating different alkyloxy and aryloxy polyethylene oxides, we have shown that MALDI-MS gives accurate molar masses, provided that the oligomer masses are above 400 g/mol. Below 400 g/mol, mass discrimination effects have to be taken into account. A perfect fit of MALDI-MS with data, determined independently by supercritical fluid chromatography and high performance liquid chromatography, was obtained.
The hydrolytic degradation of technical poly(ethylene terephthalate) (PET) was investigated by means of different methods such as size-exclusion chromatography (SEC), viscometry, light-scattering, thin-layer chromatography, end-group titration, and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The long-term degradation was simulated by exposing PET filament yarns to aqueous neutral conditions at 90°C for up to 18 weeks. By means of MALDI-MS and thin-layer chromatography, the formation of different oligomers was obtained during polymer degradation. As expected, an ester scission process was found generating acid terminated oligomers (H-[GT]m-OH) and T-[GT]m-OH and ethylene glycol terminated oligomers (H-[GT]m-G), where G is an ethylene glycol unit and T is a terephthalic acid unit. Additionally, the scission of the ester bonds during the chemical treatment led to a strong decrease in the number of cyclic oligomers ([GT]m). The occurrence of di-acid terminated species demonstrated a high degree of degradation.