A Kinetic Analysis of a Thermal Curing Reaction of a Silicon Resin in Solid State

Abstract

The curing mechanism of a silicon resin, pure or mixed with catalyst is discussed here. The silicon resin is a polymethylsilsesquioxane containing hydroxyl and ethoxy side groups which ensure the condensation. Side-products of this condensation are water and ethanol. The solid curing catalyst used is the aluminium acetylacetonate. Former studies have been developed on liquid solutions of silicon resins and catalysts in solvent, ensuring the complete contact between species -with maximum efficiency-, this work proposes a solid state mixing and questions the real utility of the catalyst. This work is divided in three parts: the first one is about resin behavior and reactions occurring under non-isothermal conditions, using different methods as Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The second step deals with kinetic analysis under isothermal conditions at different T. The last part is about stability in time of the system resin and catalyst.

Direct Ink Writing of a Preceramic Polymer and Fillers to Produce Hardystonite (Ca2ZnSi2O7) Bioceramic Scaffolds

“…These findings suggest that the oxidation of the Si-CH 3 groups in the silicone preceramic polymer, which starts above 350°C, 21 was at least partly responsible for the formation of the cracks, since it is a very exothermic reaction. 22,23 As described in the following paragraph, this formulation did not form hardystonite, but wollastonite, as the main ceramic phase; nonetheless, this result showed the potential of using a heat treatment in inert atmosphere that could be applied to other silicate ceramic systems. It is also relevant to notice that the volume change associated with the formation of hardystonite (from a stoichiometric amount of SiO 2 , ZnO, and CaO) is À10.2 vol%, while for wollastonite (from a stoichiometric amount of SiO 2 and CaO) is À9.2 vol%.…”

“…The few cracks [see, in particular, Fig. 22,23 As described in the following paragraph, this formulation did not form hardystonite, but wollastonite, as the main ceramic phase; nonetheless, this result showed the potential of using a heat treatment in inert atmosphere that could be applied to other silicate ceramic systems. Figure 7 shows an image of the cross section of a scaffold fired in air (a) and in nitrogen (b), revealing that the material constituting the strut was microporous (average pore size of 1 lm, max pore size <10 lm).…”