Investigating Thermal Stability and Flame Retardant Properties of Synthesized Halloysite Nanotubes (HNT)/Ethylene Propylene Diene Monomer (EPDM) Nanocomposites

In this work, Halloysite Nanotube (HNT) was synthesized, using a modified method, from kaolin clay. The scanning electron microscopy (SEM) of the synthesized HNT revealed that many of the nanotubes were tubular; however, spherical and semi-spherical, platy and semi rolled structures were also observed. Fire retardant EPDM compounds composed of typical flame retardants (FR), deca-bromo diphenyl oxide (DBDPO), antimony oxide (Sb2O3), talc and carbon black were prepared. Three elastomer compounds, with 5, 10 and 20 wt.% of synthesized HNT, and one more compound with 10 wt.% of synthesized HNT and 10 wt.% of conventional flame retardants were prepared and formed by a two roll mill. A TEM micrograph was presented to prove the well dispersion of HNT in polymer matrix. The flammability, thermal stability and tensile strength of the compounds were compared to that of typical fire retarded EPDM. The results showed that the typical flame retardants diminish the tensile strength and elongation at break of EPDM elastomers; in addition, these compounds showed the lowest thermal stability among the typical formulations. The extent of flammability of the compounds was characterized using the cone calorimetry technique. The compound containing 5 wt.% HNT showed the highest tensile strength, the least flammability and the highest thermal stability compared to the other compounds. This was related to the good dispersion and also on the tubular structure of the synthesized nanotubes. The peak of heat release rate (PHRR) and total heat release (THR) as well as the amount of hazardous gas emission for the sample having the highest mechanical response was smaller than those with conventional micro-filler flame retardants.