Synergistic effect between zeolitic imidazolate framework-8 and expandable graphite to improve the flame retardancy and smoke suppression of polyurethane elastomer

Zeolitic imidazolate framework-8 (ZIF-8) was synthesized at room temperature, and then added with expandable graphite (EG) to polyurethane elastomer (PUE) to study their flame retardancy and smoke suppression of PUE. The results showed that when the total flame retardant was 3 wt % and the ratio of ZIF-8 and EG was 1:3, it had the best effect on the flame retardancy and smoke suppression of PUE. Compared with pure PUE, the peak heat release rate, the total heat release, and the maximum smoke density values of Z1E3 decreased by 83.4, 42.6, and 22.4%, respectively. Moreover, the limited oxygen index value of Z1E3 increased to 30.2% and its UL-94 vertical burning test reached V-1 rating. This was because ZIF-8 synergized with EG to make the intumescent char layer compact, resulting in improved flame retardancy and smoke suppression of PUE. The specific mechanism of flame retardancy and smoke suppression is also discussed in this article. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48048.