Copolymerization of a silicon-containing spiroorthoester with a phosphorus-containing diglycidyl compound: Influence on flame retardancy and shrinkage

The cationic copolymerization of spiroorthoesters with diglycidyl compounds to introduce silicon and phosphorus has been carried out with ytterbium triflate as an initiator. The curing process was studied by differential scanning calorimetry and monitored by Fourier transform infrared spectroscopy. The thermomechanical and thermogravimetric properties were evaluated. The incorporation of phosphorus or silicon into the network increased the limiting oxygen index values, thus improving the flame retardancy of the materials. The shrinkage during the crosslinking of all mixtures was lower than that observed in conventional epoxy resins.