Synergistic effect of chitosan-based flame retardant and modified clay on the flammability properties of LLDPE

The synergistic effect of melamine salt of chitosan phosphate (MCHP) and organic modified montmorillonite (OMMT) on the thermal stability and flammability properties of linear low density polyethylene (LLDPE) was studied. MCHP was synthesized by reaction of chitosan phosphate with melamine. OMMT was formed by the reaction of cetyl trimethyl ammonium bromide (CTAB) with sodium montmorillonite. The structures of MCHP and OMMT were characterized by FTIR and 1H NMR. The thermogravimetric analysis of various LLDPE composites showed that the addition of OMMT to MCHP effectively improved the thermal stability of LLDPE and increased the char residues. The flammability properties of LLDPE composites demonstrated that addition of 1 wt% OMMT to 30 wt% MCHP promoted achieving V-0 rating in UL-94 test. Moreover, it participated remarkably in decreasing the peak of heat release rate (pHRR), total heat release (THR), CO and CO2 emissions, and fire growth index (FGI). This indicated that addition of OMMT/MCHP reduced the fire risks of LLDPE. The digital photographs and SEM images of char formed after cone calorimeter test showed that addition of 1 wt% OMMT with MCHP promoted the formation of coherent and compact char layer.