Vincent Mathot

Simultaneous Synchrotron WAXD and Fast Scanning (Chip) Calorimetry: On the (Isothermal) Crystallization of HDPE and PA11 at High Supercoolings and Cooling Rates up to 200 °C s−1

An experimental setup, making use of a Flash DSC 1 prototype, is presented in which materials can be studied simultaneously by fast scanning calorimetry (FSC) and synchrotron wide angle X-ray diffraction (WAXD). Accumulation of multiple, identical measurements results in high quality, millisecond WAXD patterns. Patterns at every degree during the crystallization and melting of high density polyethylene at FSC typical scanning rates from 20 up to 200 °C s(-1) are discussed in terms of the temperature and scanning rate dependent material crystallinities and crystal densities. Interestingly, the combined approach reveals FSC thermal lag issues, for which can be corrected. For polyamide 11, isothermal solidification at high supercooling yields a mesomorphic phase in less than a second, whereas at very low supercooling crystals are obtained. At intermediate supercooling, mixtures of mesomorphic and crystalline material are generated at a ratio proportional to the supercooling. This ratio is constant over the isothermal solidification time.

Combination of TREF, high-temperature HPLC, FTIR and HPer DSC for the comprehensive analysis of complex polypropylene copolymers

AbstractA novel, powerful analytical technique, preparative temperature rising elution fractionation (prep TREF)/high-temperature (HT)-HPLC/Fourier transform infrared spectroscopy (FTIR)/high-performance differential scanning calorimetry (HPer DSC)), has been introduced to study the correlation between the polymer chain microstructure and the thermal behaviour of various components in a complex impact polypropylene copolymer (IPC). For the comprehensive analysis of this complex material, in a first step, prep TREF is used to produce less complex but still heterogeneous fractions. These chemically heterogeneous fractions are completely separated by using a highly selective chromatographic separation method—high-temperature solvent gradient HPLC. The detailed structural and thermal analysis of the HPLC fractions was conducted by offline coupling of HT-HPLC with FTIR spectroscopy and a novel DSC method—HPer DSC. Three chemically different components were identified in the mid-elution temperature TREF fractions. For the first component, identified as isotactic polypropylene homopolymer by FTIR, the macromolecular chain length is found to be an important factor affecting the melting and crystallisation behaviour. The second component relates to ethylene–propylene copolymer molecules with varying ethylene monomer distributions and propylene tacticity distributions. For the polyethylene component (last eluting component in all semi-crystalline TREF fractions), it was found that branching produced defects in the long crystallisable ethylene sequences that affected the thermal properties. The different species exhibit distinctively different melting and crystallisation behaviour, as documented by HPer DSC. Using this novel approach of hyphenated techniques, the chain structure and melting and crystallisation behaviour of different components in a complex copolymer were investigated systematically. Fractionation and analysis of complex ethylene -propylene copolymers by using HT-HPLC-FTIR and HT-HPLC-HPer DSC

Upscaling of the hot-melt extrusion process: Comparison between laboratory scale and pilot scale production of solid dispersions with miconazole and Kollicoat IR

Since only limited amount of drug is available in early development stages, the extruder design has evolved towards smaller batch sizes, with a more simple design. An in dept study about the consequences of the differences in design is mandatory and little can be found in literature. Miconazole and Kollicoat IR were used as model drug and carrier for this study. Two series of solid dispersions were made with a laboratory scale (internal circulation-simple screw design) and a pilot scale extruder (continuous throughput-modular screw design). Efforts were made to match the operating parameters as close as possible (residence time, extrusion temperature and screw speed). The samples were analyzed with modulated DSC straight after production and after exact 24h and 15 days storage at -26 °C. The kinetic miscibility of the samples prepared with the laboratory scale extruder was slightly higher than the samples prepared with the pilot scale extruder. As the solid dispersions with high drug load were unstable over time, demixing occurred, slightly faster for the samples prepared with the laboratory scale extruder. After 15 days, the levels of molecular mixing were comparable, pointing to the predictive value of samples prepared on laboratory scale.

Full Dissolution and Crystallization of Polyamide 6 and Polyamide 4.6 in Water and Ethanol

The full dissolution and crystallization of PA6 in water and PA4.6 in water and ethanol under pressure are described. Dissolution of PA6 in water is very fast and effective: it is completed during heating at 5◦C/min in a DSC without stirring. It drastically lowers subsequent crystallization and melting temperatures. The maximum depression of the crystallization and melting temperatures is approximately 60◦C. This temperature depression of the transitions is independent of concentration over a large range (10–70 m% PA6 in water). Dissolving PA6 in water during a DSC cycle causes a moderate shift of the molar mass distribution to lower values. The DSC based crystallinities at 110◦C for PA6-water are fairly independent of concentration but higher values are obtained compared to pure PA6. From WAXD-measurements and crystal structure calculations in the case of PA6 it is concluded that α-type crystallites grow from the melt as well as from water based solutions. Furthermore, water does not enter the crystallites. PA4.6 in water and ethanol shows a similar behavior as PA6 but the transition temperature depressions are larger and the plateau in the temperature – m% plot is narrower for both

Combining Fast Scanning Chip Calorimetry with Structural and Morphological Characterization Techniques

Thanks to the development of fast-scanning (chip-based) calorimeters (FSC) it is nowadays possible to achieve very high cooling rates, which enabled the study of polymer crystallization at large supercoolings, in conditions similar to what is experienced in real industrial processes. In such extreme conditions formation of structures very different from those commonly obtained under relatively slow cooling can occur.