# Flame Retardance and Smoke Suppression of CFA/APP/LDHs/EVA Composite
## 3 Results and Discussion
### Flame Retardance and Smoke Suppression Mechanism of Composites
Thus, the LDH-Cu shows the better flame retardance among composites. To verify the effect of CO\({}_{2}\), Figure 8 shows the production rate of CO\({}_{2}\) (CO\({}_{2}\)P) curves of EVA and composites. A crucial relationship between HRR and CO\({}_{2}\)P was obtained. The shapes of CO\({}_{2}\)P curves are consistent with the HRR curves. The peak values of CO\({}_{2}\)P (pk-CO\({}_{2}\)P) time of the pure EVA, ALDH-0, ELDH-Ni, ELDH-Co, and ELDH-Cu are 235, 67, 125, 145 and 112 s, respectively. The above pk-CO\({}_{2}\)P times are same as the pk-HRR time. The result indicates that when the production rate of CO\({}_{2}\) reaches to the pk-CO\({}_{2}\)P values, the HRR of samples reaches the pk-HRR values. Additionally, from the cone calorimeter test data, one can know that the MCO\({}_{2}\)Y is the mean release yield of CO\({}_{2}\) of burning materials. The MCO\({}_{2}\)Y values of EVA, ELDH-0, ELDH-Ni, ELDH-Co and ELDH-Cu are 2.315, 2.408, 2.857, 2.638 and 2.834 kg/kg, respectively. The MCO\({}_{2}\)Y values of composites significantly increase because of the addition of LDHs. ELDH-Ni, ELDH-Co and ELDH-Cu release more CO\({}_{2}\), which dilutes the flammable gases during combustion. Therefore, the composites with LDHs show reduced pk-HRR values compared to pure EVA and ELDH-0. This finding confirmed that the release yield and production rates of CO\({}_{2}\) essentially mirror the HRR data [2]. It is well known that most injuries and deaths result from the smoke and toxic gases in the case of fire [37]. From Figure 9A, it can be seen that the peak values of smoke production rate (pk-SPR) of ELDH-0, ELDH-Ni, ELDH-Co and ELDH-Cu are 0.053, 0.054, 0.057 and 0.036 m\({}^{2}\)/s, respectively. These values are significantly lower than that of EVA (0.109 m\({}^{2}\)/s). Moreover, the pk-SPR time of ELDH-Ni and ELDH-Co are extended to 994 and 793 s, respectively. They are much longer than the 89 s of ELDH-0 and 251 s of EVA. Moreover, Figure 9B shows the production rate of CO (COP) curves of EVA and composites. The COP curves of all composites are significantly declined compared with EVA. The peak values of COP (pk-COP) for ELDH-Ni, ELDH-Co and ELDH-Cu are 0.0022, 0.0026, and 0.0025 g/s, respectively. They are obviously smaller than 0.0038 g/s of ELDH-0 and 0.0128 g/s of EVA. Simultaneously, MCOY is the mean release yield of CO of burning materials. The MCOY value of EVA is 0.031 kg/kg, while the MCOY values of ELDH-0, ELDH-Ni, ELDH-Co and ELDH-Cu decrease to 0.0234, 0.00765, 0.0194 and 0.0102 kg/kg, respectively. MCOY values of composites show an evident decrease compared with EVA. In particular, ELDH-Ni has the smallest MCOY value among composites. The extension of pk-SPR time, the reduction of pk-SPR, pk-COP and MCOY for composites are important contributions to people's evacuation and the rescue of firefighters. At the same time, the relationship between the CO\({}_{2}\) and CO release is observed by the cone calorimeter test. When the MCO\({}_{2}\)Y is increased, the pk-COP and MCOY values are decreased. That is, the change tendency of the MCO\({}_{2}\)Y values is precisely opposite to the change tendency of pk-COP and MCOY values for EVA and composites. Figure 8: Production rate of CO\({}_{2}\) (CO\({}_{2}\)P) curves of EVA and composites. (**a**) EVA; (**b**) ELDH-0; (**c**) ELDH-Ni; (**d**) ELDH-Co; and (**e**) ELDH-Cu. Figure 9: (**A**) Smoke production rate (SPR); and (**B**) production rate of CO (COP) curves of EVA and composites. (**a**) EVA; (**b**) ELDH-0; (**c**) ELDH-Ni; (**d**) ELDH-Co; and (**e**) ELDH-Cu.