Covalent organic framework with Cu-containing compounds for enhancing flame retardancy and smoke suppression effects on epoxy resin

To enhance the flame retardancy and smoke suppression effects of epoxy resin (EP), three inorganic compounds of copper modified covalent organic frameworks (COFs), COFs@CuO, COFs@Cu 2 O, COFs@Cu(OH) 2 are synthesized. The flame retardancy of EP can be significantly uprated by adding only 2 wt% COFs@Cu 2 O. The PHRR and THR yield of EP/COFs@Cu 2 O decrease by 36.6% and 20.4% compared with that of unmixed EP, respectively. The smoke density of EP/COFs@CuO reduces by 54.3% compared with that of pure epoxy. Moreover, the peak CO yield (COPR) of EP/COFs@Cu 2 O nanocomposites is 42.8% lower than that of unmixed EP. In addition, the impulse strength of EP/COFs@CuO augment 50.7% than that of pure epoxy, and the tensile strength of EP/COFs@CuO is 80.0% higher than that of EP/COFs. The synergy between metallic inorganic compounds and COFs is investigated. This work proves a guidance for preparation of high safety EP.