Preparation of nano ZIF-8@short carbon fibers and its effects on the flame retardancy, smoke suppression and mechanical properties of epoxy composites

The nano ZIF-8 on short carbon fibers (ZIF-8@SCFs) were prepared in situ growth. The composites were manufactured using ZIF-8@SCFs, ammonium polyphosphate (APP) and epoxy resin (EP) to improve the flame retardant and mechanical properties. Oxygen index tester, horizontal and vertical combustion tester, cone calorimeter and universal electronic tensile machine were used to investigate the flame retardant and mechanical properties of EP composite materials. The experimental results show that when the addition amount of ZIF-8@SCFs is 1wt% (the mass ratio of APP to ZIF-8@SCFs is 4∶1), the limiting oxygen index of the composite material increases from 25.7% to 28.1%, and UL-94 reaches V-1 level. The peak heat release rate (pHRR) and total smoke production (TSP) are reduced evidently compared with the sample with only 5wt% of APP. Besides, the tensile strength, flexural strength, elastic modulus and elongation at break of the composite material are increased by 86%, 81%, 20% and 75%, respectively, which solves the problem that the addition of inorganic flame-retardant destroys the mechanical properties of EP. The prepared composites could be applied in practice.