Peak heat release rate organoclays

Flammabihty studies using cone calorimetry at 50 kW m heat flux showed that incorporation of 5 wt% organoclay reduced peak heat release rate (PHRR) by 23-27% and total heat release (THR) values by 4—11%, depending on the clay modification. However, no simple correlation was observed between the FR efficiency and the degree of day exfoliation. The synergistic effect was observed for the combination of ammonium polyphosphate and 5 wt% amount of nanoday, which resulted in the total reduction of the PHRR of polyester resin in the range 60-70%. 

The great improvements in flame retardancy caused by the organoclays also opened the possibility of decreasing the level of ATH within the EVA polymer matrix. The content of ATH needed to maintain 200 kW/m as a peak heat release rate could be decreased from 65 to 45 wt% by the presence of only 5 wt% organoclays within the EVA polymer matrix. Reduction in the total amount of these fillers resulted in improved mechanical and rheological properties of the EVA-based nanocomposite. 

In addition, several studies have reported the use of conventional ATH in combination with other types of nanofillers, particularly organoclays, to improve the FR properties of polymer nanocomposites [12, 13]. Organoclays are not considered as FR despite their ability to decrease peak heat release rates of several polymers under firelike conditions... 

Beyer clearly observed a delay in thermal degradation using TGA (in air) with the addition of a small amount of organoclay to EVA-ATH composite [20]. The char of the EVA-ATH-organoclay compound formed in a cone calorimeter was rigid, with only a few small cracks, whereas the char of the EVA-ATH composite was much less rigid (reduced mechanical strength) and had many big cracks. These observations allowed the author to explain the reduction of the peak heat release rate to 100 kW/m for the nanocomposite, compared to 200 kW/m for the EVA-ATH composite [21]. 

The nanodispersed nanoadditives usually show enhanced fire performance and CCA has been the most powerful tool in analyzing the flammability of the PNs. In most cases, the PNs, as seen in Figure 11.20, show a significantly reduced peak HRR in the CCA curve. More examples of this are seen in PA-6/clay nanocomposite, which shows a 63% reduction in the peak HRR at 5% loading (Figure 11.2898 in which the heat release rate as a function of time for pure PA-6 and its clay nanocomposites is shown) and in poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposite,99 which shows a reduction of the peak HRR at about 50% at 5% organoclay loading. 

---