## 3 Results and Discussion
Furthermore, the temperature of degradation of OMT is lower than that attained for ABS, as also [PERSON] et al. [44] observed. Plus, it can see that even if OMT and FR are used separately, weaker TTI times are obtained, if compared with reABS. This appears due to the weak thermal stability of OMT and FR, while when these two components are used together a synergy between them occurs and TTI times of nanocomposites are improved. On the other hand, [PERSON] et al. [45] who used a cone calorimeter with a heat flux of 35 kW/m\({}^{2}\), obtained a time of ignition of 39 s for pristine ABS and 51 s for ABS with 30% APP filler. Other researchers, as [PERSON] et al. [46], obtained a TTI of 24 s for ABS with a 50 kW/m\({}^{2}\) external heat flux, which is in line with our result. A different TTI time for ABS shows that for a comprehensive approach, several factors have to be considered, as for example: the monomers (acrylonitrile, butadiene-styrene) concentration [47], the manufacturing method, the products supplier (i.e., with regard to their purity, chemical composition etc.) or the external heat flux value of the cone calorimeter. When the residue values are discussed, one can say that the residues of particles act as barriers against heat transport and thus decrease the heating rates of the developed nanocomposites. Additionally, the multilayer silicate heat-shielding layer slows down the escape of volatile products generated from the degrading polymer, as was explained also by [PERSON] et al. [14] and [PERSON] et al. [16]. Precisely, [PERSON] et al. [16] affirmed that the barrier effect of exfoliated layered silicates delays the thermal degradation in the nanocomposite, while [PERSON] et al. [14] noticed the same behavior for graphene layers in an PC/ABS matrix. The same effect of the protective layer formed during combustion was observed by [PERSON] et al. [42] which compared two types of organically modified montmorillonite mixed in ABS and noticed similar PHRR for both cases. From the results in Table 4 it may be seen that the residue increases by adding both OMT and FR to almost 19%, larger values being obtained with the wt% increase of both clay and fire retardant. Nevertheless, the addition of clay to the reABS results in a 155%-296% increase in the residue while on adding the Exolit mixture to the base composite, the residue increases to 560%. Finally, the released heat versus time for reABS and when combined with OMT and FR is shown in Figure 1, while Figures 2 and 3 show the results for reABS with 1% OMT and 2% OMT with different percentages of fire retardant (from 15%-20%). Overall, it can be affirmed that the reABS burning is faster and more violent and this is decreased by adding different amounts of OMT and FR. This behavior was also observed by [PERSON] et al. [33] who added 2% montmorillonite in ABS and by [PERSON] et al. [1] who added 25 wt% FR in pristine ABS and obtained a four-times decrease of PHRR. In Figure 1 it is possible to observe that 15% of FR dramatically decreases the heat release, while OMT is responsible for more modest decreases. In the first case, the FR delays the burning as a consequence of the char layer formation (i.e., the same phenomenon was acknowledged also by [PERSON] et al. [1]) while adding higher percentages of OMT decreases the heat release (delaying the maximum point) due to migration of the OMT to the specimen surface. This phenomenon was also encountered by other research groups who studied these nanocomposites (see for example [1; 42; 44]). As a further comment, [PERSON] et al. [42] who used 5% modified montmorillonite + ABS, also observed that the montmorillonite tactoids have a tendency to accumulate together on the surface of the burning material and create a compact protective layer. The same phenomenon was noticed by [PERSON] et al. [43] when they tested the thermal degradation of ABS +5% OMT.