Combination effects of carbon nanotubes, MMT and phosphorus flame retardant on fire and thermal resistance of fiber-reinforced epoxy composites

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The present work aims to enhance thermal stability and flame retardancy of the epoxy/glass composites containing carbon nanotubes (CNTs). To achieve this purpose ammonium polyphosphate (APP) as a micro filler and montmorillonite (MMT) as nanofiller have been used. Since good dispersion is necessary to achieve thermal and flame resistivity in nanocomposites, it was found that combination of ultrasonication and high shear flow can result in a good dispersion of nanoparticles in polymer matrix. Thus, all samples were prepared according to this method. In order to study thermal resistance and flame retardancy of the samples, thermal gravimetric analysis (TGA) and limiting oxygen index (LOI) have been employed, respectively. TGA results showed that combination of 0.5 wt% CNTs with either 5 wt% MMT or 15 wt% APP can increase the initial thermal decomposition temperature up to 62 °C for the former polymer composite and 47 °C for the latter one. Overall stabilization effect (OSE) and integral procedure decomposition temperature (IPDT) parameters have also been calculated from TGA data. These results showed that the sample containing a combination of APP and CNT has the highest value of OSE. Moreover, IPDT of this sample has increased about 9 % compared with the neat epoxy. LOI of the samples showed that the addition of MMT and CNTs together could increase LOI about 8 % and introduction of APP to these samples increased LOI about 10 %, as well.