Combination Effect of Organics-Modified Montmorillonite with Intumescent Flame Retardants on Thermal Stability and Fire Behavior of Polyethylene Nanocomposites

A combination effect was observed between organics-modified montmorillonite (OMMT) and a novel intumescent flame retardant, diphenylmethanamine spirocyclic pentaerythritol bisphosphonate (PSPD), in low-density polyethylene (LDPE) nanocomposites. The results from X-ray diffraction and transmission electron microscopy showed that montmorillonite can achieve better dispersion in LDPE/PSPD blend matrix, and exfoliated LDPE/PSPD/OMMT nanocomposites are formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis and cone calorimeter tests. The combination effect of PSPD and montmorillonite improved thermal stability and reduced significantly the flammability (including heat release rate, total heat release, average mass loss rate, etc.). The peak heat release rate of LDPE/PSPD/OMMT is reduced by about 51% compared with pure LDPE. The morphology and composition of residues generated after cone calorimeter tests were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. The scanning electron microscopy images showed that the compact and dense intumescent char is formed for LDPE/PSPD/OMMT nanocomposite after combustion. The results of X-ray photoelectron spectroscopy confirmed that the carbon content of the char for LDPE/PSPD/OMMT increases obviously by the combination effect of PSPD and montmorillonite. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1285-1291, 2011