Percolation effect of active carbon on vulcanization, combustion and mechanical properties of flame retardant ethylene vinyl-acetate rubber

The effect of bamboo based active carbon (AC) on vulcanization, combustion and mechanical properties of intumescent flame retardant ethylene vinyl-acetate rubber (EVM) was studied. The study of vulcanization property indicates that a network is formed due to the percolation effect of AC in EVM. With the increase of AC content, the maximum torque and viscosity of flame retardant EVM increase. The rheological and swelling measurements show that the percolation effect of AC improves the shear viscosity and crosslink density of flame retardant EVM which is benefit for the improved flame retardancy and mechanical properties. The analysis of microstructure demonstrates the formation of the network of AC from microscopic viewpoint. The results of combustion and mechanical tests prove that there is synergistic effect between AC and intumescent flame retardant (IFR) and the flame retardancy of EVM is improved due to the percolation effect of AC. The optimum flame retardancy is obtained when the mass ratio of IFR and AC is 37:3. The limit oxide index (LOI) achieves 33.6% and 28.7% when the addition of flame retardant is 40% and 25% respectively. Besides, the heat release also decreases significantly. The tensile strength of flame retardant EVM improves with the increasing of AC, while the elongation at break decreases. AC shows its superiority in balancing the vulcanization, flame retardancy, and mechanical properties of flame retardant EVM, which is conductive to improve its comprehensive performance.