The incorporation of silicon into thermosetting polymers at the molecular level has been shown to have several significant effects, beyond improving thermo-oxidative stability, as demonstrated by studies of silicon-containing cyanate ester resins.  These effects are generally traceable to the enhanced flexibility afforded by the substitution of C-Si for C-C bonds, and include increased free volume and thermal expansion.  In cyanate esters, the increased specific volume leads to a decrease in cyanurate ring density, which may explain the reduced water uptake in silicon-containing cyanate esters at high conversions.  In addition, the increased flexibility provides for a greater degree of cure at lower temperatures than would otherwise be possible, leading, counter-intuitively, to a higher glass transition temperature for a given cure schedule.  Due to the molecular level mechanisms involved, many of these effects are expected to be present in other silicon-containing thermosetting resins as well.

Effects of silicon substitution in the main chain network segments of polycyanurates

243rd National Meeting (2012)

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