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Saint-Christol-lès-Alès, France

Puerta-Falla G.,University of California at Los Angeles | Balonis M.,University of California at Los Angeles | Le Saout G.,Center Des Materiaux Of Lecole Des Mines Dales | Kumar A.,University of California at Los Angeles | And 4 more authors.
Journal of Materials Science | Year: 2016

The addition of slightly (CaCO3) and highly soluble (Na2CO3) carbonate salts is expected to favor the formation of carboaluminate phases in hydrated calcium aluminate cements (CACs). A multi-method approach including X-ray diffraction, thermogravimetric analysis, and thermodynamic calculations is applied to highlight that the “conversion phenomena” in CACs cannot be mitigated by the formation of carboaluminate phases (monocarboaluminate: Mc and hemicarboaluminate: Hc) which are anticipated to form following the addition of carbonate salts. Here, carboaluminate phase formation is shown to depend on three factors: (1) water availability, (2) carbonate content of the salts, and their ability to mobilize CO3 2− species in solution, and (3) lime content associated with the carbonate salt. The latter two factors are linked to the composition and solubility of the carbonate agent. It is concluded that limestone (CaCO3), despite being a source of calcium and carbonate species, contributes only slightly to carboaluminate phase formation due to its low solubility and slow dissolution rate. Soluble carbonate salts (Na2CO3) fail to boost carboaluminate phase formation as the availability of Ca2+ ions and water are limiting. Detailed thermodynamic calculations are used to elucidate conditions that affect the formation of carboaluminate phases. © 2016 Springer Science+Business Media New York Source


Viretto A.,Center Des Materiaux Of Lecole Des Mines Dales | Sonnier R.,Center Des Materiaux Of Lecole Des Mines Dales | Taguet A.,Center Des Materiaux Of Lecole Des Mines Dales | Otazaghine B.,Center Des Materiaux Of Lecole Des Mines Dales | And 3 more authors.
Fire and Materials | Year: 2016

Magnesium dihydroxide (MDH) was evaluated as char promoter into different polymers exhibiting various chemical structures. Char promotion was characterized using thermogravimetric analysis and pyrolysis-combustion flow calorimetry. Gases released during pyrolysis were identified using pyrolysis coupled gas chromatography/mass spectrometry and thermogravimetric analysis coupled Fourier transform infrared spectroscopy. Relationships between the MDH effect (according to the char content and its thermal stability) and the chemical structure of the host polymers were identified. It was shown that MDH can be a good char promoter for aromatic polyesters such as polybutylene terephtalate and polyethylene terephtalate. Char promotion can be considered as one of the main mode-of-action of MDH at low or moderate filler content. An optimum was observed at approximately 20wt.% of MDH. Magnesium oxide was also studied as substitute to MDH to avoid hydrolysis phenomena due to the water release. But it was demonstrated that MDH was more efficient as a char promoter for polybutylene terephtalate than magnesium oxide. © Copyright 2015 John Wiley & Sons, Ltd. Source


Sonnier R.,Center Des Materiaux Of Lecole Des Mines Dales | Bokobza L.,Center Des Materiaux Of Lecole Des Mines Dales | Concha-Lozano N.,Center Des Materiaux Of Lecole Des Mines Dales
Polymers for Advanced Technologies | Year: 2015

Poly(dimethylsiloxane) (PDMS) filled with low contents of multiwall carbon nanotubes (MWCNT) was prepared using different ways to monitor the dispersion of MWCNT. The influence of the dispersion on thermal conductivity and transmittance was measured. High degree of transparence can be achieved with 0.02 phr of well dispersed MWCNT. Time-to-ignition (TTI) was also measured on 2- or 4-mm-thick specimens heated using radiative unidirectional source. Time-to-ignition was found to decrease with the incorporation of MWCNT because more heat is absorbed at the surface. Higher time-to-ignition was observed for partially translucent composites, due to different absorption in-depth profiles. It can be assumed that time-to-ignition can be controlled by the dispersion of MWCNT into the polymeric matrix. © 2015 John Wiley & Sons, Ltd. Source


Courtat J.,University Claude Bernard Lyon 1 | Melis F.,University Claude Bernard Lyon 1 | Taulemesse J.-M.,Center Des Materiaux Of Lecole Des Mines Dales | Bounor-Legare V.,University Claude Bernard Lyon 1 | And 3 more authors.
Polymer Degradation and Stability | Year: 2015

Abstract Surface modification of various silicas by phosphorous agents was carried out with the aim to use these particles as flame retardant additive in a polypropylene matrice (PP) at low content (10 wt%). Thermal and flammability properties of PP/modified silica (PP-Tm-10%, PP-Zm-10%) were studied using TGA, PCFC and cone calorimeter and compared to those conferred by pure silica (PP-T-10%, PP-Z-10%). Quite surprisingly the untreated fillers induce the most significant reduction of peak of Heat Release Rate (50% decrease) while the surface modification by phosphorous agents does not lead to the expected effect on the fire behavior of PP composite. This phenomenon was related to the morphology and rheological behavior of the various PP composites. Indeed, the higher the storage modulus at low frequencies is, the better the fire behavior is, because of the induced barrier effect. Moreover, the addition of non modified silicas leads to a decrease of 10 s of the TTI. This phenomenon was related to the formation of bubbles after the PP melting during cone calorimeter test. © 2015 Elsevier Ltd. Source


Sonnier R.,Center Des Materiaux Of Lecole Des Mines Dales | Viretto A.,Center Des Materiaux Of Lecole Des Mines Dales | Dumazert L.,Center Des Materiaux Of Lecole Des Mines Dales | Gallard B.,Center Des Materiaux Of Lecole Des Mines Dales
Combustion and Flame | Year: 2016

A method to distinguish the mass loss rates corresponding to each of the two decomposition steps in binary blends is proposed. This method is suitable for cone calorimeter test and all other tests measuring continuously mass loss and heat release in an independent way. Heat release rate curves recalculated from the method well fit the experimental ones. Several systems including copolymers, polymers filled with inert or hydrated fillers and binary blends were studied. It appears that the decomposition of these materials is complex because the decomposition rate of one component influences the decomposition rate of the second one. These interactions depend on the materials, their content and also the external heat flux. Concerning binary blends, first results show the decomposition of the most thermally stable polymer is delayed because the temperature within the material is maintained close to the pyrolysis temperature of the least thermally stable polymer. Longer is the delay, higher is the decomposition rate of the most thermally stable polymer. In some cases, this polymer can decompose at higher rate (but later) than the least stable polymer. © 2016 The Combustion Institute. Source

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