Combustion and mechanical properties of natural rubber based on carboxyl modified carbon nanotubes and intumescent flame retardant

The flame retardant natural rubber (NR) composites were prepared using carboxyl modified multi-walled carbon nanotubes (CMCNTs) and traditional intumescent flame retardant with the ratio among ammonium polyphosphate (APP), melamine (MEL), and pentaerythritol (PER) of 3/1/1. The flame retardancy and thermal stability, and mechanical properties of NR composites were investigated by the LOI test, UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), and tensile test, respectively. The results showed that NR/IFR3/2.0CMCNT had good flame retardancy and past the UL-94 test V-2 rating. The peak of heat release rate (pHRR), the peak of smoke production rate (pSPR), and the total smoke production (TSP) of NR/IFR3/2.0CMCNT were lower than those of NR/IFR3, which were reduced by 4.4%, 12.1%, and 26.3%, respectively. In addition, CMCNTs can improve the elongation at the break of NR composites with the increase of CMCNTs under the condition of low load CMCNTs.