Synergic flame retardancy mechanism of montmorillonite in the nano-sized hydroxyl aluminum oxalate/LDPE/EPDM system

Nano-sized hydroxyl aluminum oxalate (nano-HAO) and montmorillonite (MMT) were mixed into low density polyethylene (LDPE)/ethylene propylene diene rubber (EPDM) system via melt compounding method. By means of LOI and UL94 horizontal burning tests, MMT and nano-HAO together exhibited better performance on flame-retarding LDPE/EPDM composites than how they performed individually, which proved that there existed a synergistic effect between MMT and nano-HAO on flame retardancy. Furthermore, through the analysis of Fourier transform IR spectra (FTIR), scanning electron microscope (SEM), and the thermogravimetric and differential thermal analysis (TG–DTA), the mechanism of the synergistic flame retardance was proposed as when MMT was added into nano-HAO/LDPE/EPDM composites, a laminated structure formed in the char layer and thus the transmission speeds of heat, oxygen, flammable mass and vapor were adjusted. So the process of combustion was retarded owing to lack of oxygen and heat.