In situ growth of nano-MOFs on ammonium polyphosphate particles for boosting flame retardancy, smoke suppression and mechanical properties of epoxy

ZIF-8@APP was prepared by in situ growth of ZIF-8 on the surface of ammonium polyphosphate (APP) through co-precipitation method. The ZIF-8@APP/EP composites were prepared by adding ZIF-8@APP into epoxy resin (EP). The composites with loading of ZIF-8@APP showed good flame retardancy, smoke suppression and mechanical properties simultaneously. The limiting oxygen index (LOI) of the flame retarded composites containing 10 wt% of ZIF-8@APP was 32.6% and the UL-94 test reached V-0. Meanwhile, the peak heat release rate and total heat release of the composites with 5 wt% of ZIF-8@APP were reduced by 60.8 and 35.5% compared with pristine epoxy resin. The ZIF-8 particles on APP improved interface actions between APP and EP matrix, which led to the enhancement in mechanical properties of the flame-retardant composites. Graphical abstract