Synergistic effect of OMMT and Ni₂O₃ on the flame retardancy of LLDPE/EVA composites with magnesium hydroxide

Organically modified montmorillonite (OMMT) and Ni2O3 were simultaneously introduced into flame-retardant linear low-density polyethylene/ethylene-vinyl acetate/magnesium hydroxide (LEM) composites. Compared with the LEM composite, the thermal stability, and tensile properties of LEM/ remained basically unchanged when 5 wt% of OMMT/Ni2O3 was substituted for MH. The LOI value increased a little from 27.2 to 27.7%. The data from cone calorimeter test showed that the first and second peak heat release rate was reduced by 19% and 67%, respectively. The total heat release and total smoke production showed a significant reduction by 18% and 36% after incorporation of OMMT/Ni2O3, respectively. The mechanism study indicated that the combination of OMMT/Ni2O3 cooperates promote the carbonization of the polymer itself into carbon naotubes, which form a more cohesive char layer with magnesium hydroxide during combustion. This is the core factor responsible for the synergistic effect on reducing the heat release and smoke production in the LEM composite.