Flame retardancy and thermal property of novel UV-curable epoxy acrylate coatings modified by melamine-based hyperbranched polyphosphonate acrylate

A novel melamine-based hyperbranched polyphosphonate acrylate (MHPA), successfully synthesized via the Michael addition polymerization of 2-(2-amino-ethylamino)-4,6-bisethylamino-1,3,5-triazine with tri(acryloyloxyethyl) phosphate, was blended with the epoxy acrylate (EA) to prepare UV-cured flame retardant coatings. The study of their flammability revealed that MHPA can improve the flame retardancy and the sample with 45 wt% MHPA (EA3) showed a good intumescent behavior when combusted. The results of their thermal degradation displayed that MHPA had a dual effect on the thermal stability of EA: leading to its earlier degradation catalyzed by acidic species from the relatively weak phosphorus-bearing parts, but improving the thermal stability of the char layer at high temperature due to the formed intumescent phosphorus-carbon compounds. Besides, the total release amount of gas products of EA3 was much lower than that of pure EA and various flammable gases like hydrocarbons and highly toxic CO were also reduced