Effect of ethylene-acrylic acid copolymer on flame retardancy and properties of LLDPE/EAA/MH composites

Halogen-free flame retardant linear low density polyethylene (LLDPE)/ethylene-acrylic acid copolymer (EAA) blends were prepared in a melt process using magnesium hydroxide (MH) as flame retardant. The effect of EAA on flame retardancy and properties of LLDPE/EAA/MH composites was studied. The flammability of composites was investigated using Limiting Oxygen Index (LOI) and Cone calorimeter test. The results showed that the introduction of EAA into composites apparently increased LOI from 28% to 39%, meanwhile, reduced heat release rate (HRR) and smoke production rate (SPR) according to Cone calorimeter results, which was mainly due to the uniform dispersion of MH as a result of hydrogen bonding and acid-base reaction between MH and EAA. This improved interfacial adhesion was confirmed by Scanning Electronic Microscopy (SEM). Thermogravimetric analysis (TGA) showed that EAA could enhance the thermal oxidative stability of composites. It was attributed to the formation of a stable barrier to prevent the heat and mass transfer in fire, which was confirmed by the observation of fire performance with Cone calorimeter. The crystallization and rheological behaviour of composites were studied using Differential scanning calorimeter (DSC) and oscillatory rheological measurements. Mechanical test results indicated that the addition of EAA could increase the elongation at break and impact strength of composites.