Preparation and film properties of tri(3,4-epoxycyclohexylmethyl) phosphate based cationically UV curing coatings

A facile synthesis of phosphorus-containing trifunctional cycloaliphatic epoxide resin, tri(3,4-epoxycyclohexylmethyl) phosphate (TECP), used for cationically UV curing coatings as a reactive-type flame retardant, was proposed. The molecular structure was confirmed by FTIR, ¹H NMR and ³¹P NMR spectroscopic analysis. A series of flame retardant formulations by incorporating into a commercial difunctional cycloaliphatic epoxide resin, CYRACURE™ UVR-6110, were prepared, and exposed to a medium pressure lamp to form the cured films under the presence of diaryliodonium hexafluorophosphate salt as a cationic photoinitiator. Their flame retardancy examined by the limiting oxygen index showed the improvement up to 27 for 50 wt% TECP addition compared with 21 for pure UVR-6110. The T_s and T_g decreased from 86 °C and 131 °C to 55 °C and 91 °C, respectively, by using dynamic mechanical thermal analysis, whereas the tensile strength showed a slight increase (11%) with 50 wt% TECP addition. The thermogravimetric analysis (TGA) and real-time Fourier transform infrared spectroscopy (RT-FTIR) measurement demonstrated the condensed-phase flame retardant mechanism.