minus Polysiloxane composites with ndash xA wt

−Polysiloxane composites with 20–70 wt% epoxy powder as sacrificial filler were successfully employed as precursors of mechanically strong pyrolytic SiOC foams. The chosen epoxy was easy to pulverise and – due to a high content of polyoxypropylene chains – it PD 153035 HCL degraded practically quantitatively during the pyrolysis in nitrogen.−Larger monoliths can be easily prepared, and display relatively good shape constancy during pyrolysis.−SiOC foam densities between 1.31 and 0.62 g/cm3 were achieved, corresponding to macro-porosities of 35–69%.−The use of a polymer sacrificial filler with a wide size distribution led to a hierarchical structure of the macro-pores in the SiOC foams.−Compressive strength between 15 and 38 MPa was achieved, depending on the foam density: the best strength was obtained at the porosity of 56% (density: 0.87 g/cm3), while in the case of denser foams, their strength was reduced by pyrolysis cracks. In lighter foams (porosity >56%), the strength decreases due to thinner pore walls.−The most promising foam (with 56% porosity) displayed an elastic modulus of 10 GPa.