FIGURE 6 Digital photos of PU foam (a, b ) and
MMT/PAAS-PU (c, d ) before and after burring. SEM images of
MMT/PAAS-PU before (e, f ) and after (g, h ) burring.
Subsequently, the effect of MMT/PAAS coating on the flame retardancy of
PU foam was studied by using a cone calorimetric test (CCT). The results
are shown in Fig.7 and the characteristic parameters are shown
in Table 2 . The most obvious should be shown to slow its
ignition time. The time to ignition (TTI) of PU foam is 6s, while that
of MMT/PAAS-PU is 10s. After the material was ignited, the heat release
rate (HRR) of PU foam was almost higher than that of the MMT/PAAS-PU
throughout the test (Fig. 7a ). Especially, its peak HRR (PHRR)
was 381.42 kW/m3, 53.39% higher than that of
MMT/PAAS-PU (177.80 kW/m3). Furthermore, the total
heat release (THR) of PU foam is 40.69% larger (Fig.7b ).
Unlike completely burned-out PU foam, MMT/PAAS-PU self-extinguished
during the test (Fig. S7 in Supporting Information). Based on
the above results, the MMT/PAAS coating will effectively improve the
flame retardant properties and reduce damage even after ignition.
Relatively, the peak mass loss rate (PMLR) is also higher than that of
MMT/PAAS-PU, indicating that under a certain fire intensity, the degree
of pyrolysis, volatilization, and combustion is more intense. Since the
MMT/PAAS coating has an ordered layered structure and the structure
remains after combustion, it plays a good role in the gas barriers.
Therefore, compared with PU foam, its peak effective heat combustion
(PEHC, reflecting the combustion degree of volatile gas in gas phase
flame), total smoke production (TSP), peak CO yield (PCOY) and peak
CO2 yield (PCO2Y) decreased by 15.76%,
53.03%, 47.58%, and 70.15%, respectively. The smoke produce rate
(SPR) is always lower than PU foam (Fig.7c ) during the whole
test. In a real fire, more than half of the deaths are caused by
particulate matter and toxic gases (especially CO) generated by
combustion.[47] MMT/PAAS coating in this study can
effectively suppress smoke, which may greatly save people’s lives in
real fires.
TABLE 2 The resulting parameters of CCT for PU foam and
MMT/PAAS-PU