Polypropylene metal functionalised POSS nanocomposites: A study by thermogravimetric analysis

Dimeric and oligomeric Al and Zn-containing isobutyl silsesquioxanes (POSS) were studied to investigate their thermal stability both in inert and oxidant atmosphere, by means of Differential Scanning Calorimetry (DSC) and thermogravimetric analyses (TGA).Thermo-oxidative degradation leads to an important solid residue yield, as a consequence of the POSS oxidation to a thermally stable ceramic phase.The study of the differences in degradation pathways of both metal POSS derivatives clearly shows a competition between two possible mechanisms for product thermal behaviour, namely evaporation and oxidation.The metal POSS compounds were incorporated via melt blending into a PP matrix and the composites thermal properties were studied by thermogravimetric analyses.Thermo-oxidative degradation of composites is strongly affected by the presence of metal containing POSS, resulting in an improved thermal stability, in terms of higher weight loss temperature.     

Crossed characterisation of polymer-layered silicate (PLS) nanocomposite morphology: TEM, X-ray diffraction, rheology and solid-state nuclear magnetic resonance measurements

As the nanocomposite properties dramatically depend on the dispersion state of the filler in the matrix, it is essential to develop technical methods to characterise the nanodispersion both qualitatively and quantitatively. In this study, complete characterisations of the nanodispersion of organomodified clays in polyamide 6, polypropylene and poly(butylene terephtalate) are presented and discussed using different analytical tools. All four characterisation methods have been evaluated experimentally. TEM has been used to qualitatively characterise the dispersion. As TEM picture might be not fully representative of the whole sample, many pictures have to be analysed to mirror the global repartition. XRD is particularly adapted to the study of intercalated morphology of nanocomposite since the distance between two platelets can be calculated but needs TEM to provide more complete conclusions. Melt rheology and solid-state NMR are bulk analyses. During the measurement the sample is representative of the material. Rheology is relatively simple to make measurements and to get semi-quantitative data. In connection with NMR, we can get quantitative measurements on the degree of nanodispersion in the nanocomposite.     

Sample Preparation of Energy Materials for X‐ray Nanotomography with Micromanipulation

X‐ray nanotomography presents an unprecedented opportunity to study energy storage/conversion materials at nanometer scales in three dimensions, with both elemental and chemical sensitivity. A critical step in obtaining high‐quality X‐ray nanotomography data is reliable sample preparation to ensure that the entire sample fits within the field of view of the X‐ray microscope. Although focused‐ion‐beam lift‐out has previously been used for large sample (few to tens of microns) preparation, a difficult undercut and lift‐out procedure results in a time‐consuming sample preparation process. Herein, we propose a much simpler and direct sample preparation method to resolve the issues that block the view of the sample base after milling and during the lift‐out process. This method is applied on a solid‐oxide fuel cell and a lithium‐ion battery electrode, before numerous critical 3D morphological parameters are extracted, which are highly relevant to their electrochemical performance. A broad application of this method for microstructure study with X‐ray nanotomography is discussed and presented.     

Effect of expanded graphite/layered-silicate clay on thermal, mechanical and fire retardant properties of poly(lactic acid)

Preparation of PLA based nanocomposites was carried out by using two different nanofillers: expanded graphite and organically modified montmorillonite. The addition and co-addition of these nanofillers to PLA using the melt-blending technique provides nanocomposites that showed significant enhancements in rigidity, thermal stability and fire retardancy of the polymer matrix. The presence of dispersed graphite nanolayers in PLA significantly accelerated the polyester crystallization, whereas the essential increase of thermal resistance is mainly connected to the addition of organoclay. The structure of the nanocomposites was examined by Wide Angle X-ray Scattering Analysis and Transmission Electron Microscopy. The improvement of thermal and mechanical properties obtained by the presence of both nanoparticles in PLA were associated to the good (co)dispersion and to the co-reinforcement effect, whilst the fire retardant properties were found to be related to the combined additive action of both nanofillers.     

Study of the mechanism of intumescence in fire retardant polymers: Part III—Effect of urea on the ammonium polyphosphate-pentaerythritol system

Urea, which is commonly used as a ‘blowing’ co-additive in intumescent coatings, is shown to depress intumescence when it is added to ammonium polyphosphate-pentaerythritol mixtures incorporated into the bulk of polypropylene. Concurrently, the fire retardant properties of the intumescent additive are depressed in the presence of urea although, in this case, a smaller amount of flammable hydrocarbons is evolved in the thermal degradation of the polymer.