Crosslinking Behavior of UV-Cured Polyorganosilazane as Polymer-Derived Ceramic Precursor in Ambient and Nitrogen Atmosphere

Polymer-derived ceramics (PDCs) based on silicon precursor represent an outstanding
material for ceramic coatings thanks to their extraordinary versatile processibility. A promising
example of a silicone precursor, polyorganosilazane (Durazane 1800), was studied concerning its
crosslinking behavior by mixing it with three different photoinitiators, and curing it by two different
UV-LED sources under both nitrogen and ambient atmosphere. The chemical conversion during
polymerization and pyrolysis was monitored by FTIR spectroscopy. Pyrolysis was performed in a
nitrogen atmosphere at 950 C. The results demonstrate that polyorganosilazane can be cured by
the energy-efficient UV-LED source at room temperature in nitrogen and ambient atmosphere. In
nitrogen atmosphere, already common reactions for polysilazanes, including polyaddition of the
vinyl group, dehydrogenation reactions, hydrosilylation, and transamination reaction, are responsible
for crosslinking. Meanwhile, in ambient atmosphere, hydrolysis and polycondensation reactions
occur next to the aforementioned reactions. In addition, the type of photoinitiator has an influence
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on the conversion of the reactive bonds and the chemical composition of the resulting ceramic.
Furthermore, thermogravimetric analysis (TGA) was conducted in order to measure the ceramic
yield of the cured samples as well as to study their decomposition. The ceramic yield was observed
in the range of 72 to 78% depending on the composition and the curing atmosphere. The curing
atmosphere significantly impacts the chemical composition of the resulting ceramics. Depending
on the chosen atmosphere, either silicon carbonitride (SiCN) or a partially oxidized SiCN(O) can
be produced.