A cyanate ester resin mixture with at least one cyanate ester resin, an isocyanate foaming resin, other co-curatives such as polyol or epoxy compounds, a surfactant, and a catalyst/water can react to form a foaming resin that can be cured at a temperature greater than 50° C. to form a cyanate ester foam. The cyanate ester foam can be heated to a temperature greater than 400° C. in a non-oxidative atmosphere to provide a carbonaceous char foam.