Is the silicon-nitrogen bond in KiON polymers more reactive than a primary amine or a polyol when it is reacted with an isocyanate or an epoxy?
KiON polysilazanes are EXTREMELY reactive at room temperature toward aromatic isocyanates (e.g. TDI, MDI). The reaction is exothermic and a significant amount of heat is evolved. For this reason, it is important to EXERCISE EXTREME CAUTION when reacting KiON polymers with aromatic isocyanates. Cross sections of no more than about 0.5 inches should be attempted in unfilled compositions. Particulate fillers such as silicon carbide and aluminum metal can be used to ameliorate this exotherm. The reaction of KiON polysilazanes with aliphatic isocyanates (e.g. HMDI trimer, IPDI) is less pronounced. While KiON polysilazanes will cure aliphatic isocyanates over the course of several hours, often some heat (60°-70° C) is required to effect a complete cure. The reaction of KiON polymers with epoxy resins is slow and requires significant heating (>160° C). Even so, cure can be incomplete and depends on the exact structure of the epoxy resin.