Evaluation of fire performance of linear low-density polyethylene containing novel intumescent flame retardant

Abstract

A novel single-molecule intumescent flame retardant, melamine salt of montmorillonite phosphate (MMP), was synthesized and characterized by FTIR and XRD. The effect of MMP on the thermal stability and flammability properties of linear low-density polyethylene (LLDPE) was studied by thermogravimetric analysis, vertical burning test (UL-94V), and cone calorimeter. In addition, the synergistic effect between MMP and low concentrations from zinc borate (ZB) on LLDPE thermal stability and flammability properties was investigated. The results showed that addition of MMP and MMP/ZB to LLDPE improved the thermal stability at high temperatures and enhanced the char formation at 750 °C. UL-94V test results presented that LLDPE achieved V-0 rating at (30%MMP/5%ZB) loading level. The cone calorimeter data showed that MMP and MMP/ZB considerably reduced peak of heat release rate, mean heat release rate, total heat release, and mean mass loss rate of LLDPE. The data of fire performance index, fire growth rate index, and maximum average rate of heat emission indicated that MMP and MMP/ZB additives reduced the fire risks of LLDPE. The digital photographs, SEM images, and EDXS analysis for the char residue after cone calorimeter test showed the formation of coherent, compact, and thermally stable char layer on the polymer composites surfaces.