Alkyl- and arylsilsesquiazanes: effect of the R group on polymer degradation and ceramic char composition

• DOI: 10.1007/bf01082152
• Publication Date: 2005-02-02T10:43:42Z
• Authors: Gary T. Burns; Timothy P. Angelotti; Larry F. Hanneman; Grish Chandra; John A. Moore
• Keywords: Inert gas; Percolation (cognitive psychology); Carbon fibers; Thermal Stability

A series of alkyl- and arylsilsesquiazanes [RSi(NH)3/2] was prepared by the ammonolysis of the corresponding RSiCl3. Each polymer was pyrolysed to 1200° C in an inert atmosphere to give amorphous Si-C-N ceramic chars. The major volatile products in the pyrolysis effluent were identified and quantified by a combination of TGA-GCMS, TGA-GCFTIR and pyrolysis-capillary GC techniques. Mechanistic aspects correlating the alkyl/aryl group on the polymer structure, decomposition and ceramic char composition were studied. Oxidative stability of the ceramic chars fits percolation theory. The oxygen contents of ceramic chars containing ⩽ 25 wt% carbon increased 1 to 2% after 12 h at 1200° C. At higher levels of carbon the chars were completely oxidized to SiO2.