Soutenance de thèse : Ahmad HAMADEH

Εtude des interactions silice – silane par spectroscopie ΙR et modélisation multivariée

Abstract

18/12/2019 –  10H30 – Salle de conférence du CNRT

This work deals with the study of the reaction mechanisms of silane TESPT – a coupling agent widely used in the pneumatic industry – with silica in the presence of 1,3-diphenylguanidine (DPG), an accelerator used during the step of mixing. For this purpose, we studied by IR spectroscopy and by multivariate modelling the interactions of each of these two compounds alone, then the two compounds in mixture, on the surface of the silica according to the temperature.
The results obtained show that the reactivity of TESPT, on the one hand, and DPG on the other hand, can be satisfactorily modelled by three components, whether these compounds are alone or mixed on the silica. We verified that the TESPT beyond the ambient temperature undergo a preliminary hydrolysis reaction followed at a higher temperature by a grafting reaction with the silica or by co-condensation with a neighbouring molecule. As for the DPG – adsorbed on silanol groups of silica – it gathers in dimers by going beyond the ambient temperature, and it is involved in an equilibrium with them. These dimers decompose at a higher temperature to release aniline in the gas phase and produce on the silica surface – in dynamic vacuum – compounds that appear to be phenylcyanamide molecules grafted onto the silica or oligomers of phenylcyanamide (and / or aniline). These surface products can be quickly hydrolysed in the presence of water.
While no species or specific component resulting from the interaction of DPG with TESPT could be demonstrated, our results show that TESPT decreases the amount of species produced (at the silica surface) by the decomposition of the DPG in dynamic vacuum, and that DPG significantly influences the reactivity of TESPT by promoting the formation of siloxane bridging.