Comparative investigation on combustion property and smoke toxicity of epoxy resin filled with α- and δ-MnO₂ nanosheets

Manganese dioxide (MnO₂) as a promising green material has attracted widely attention in virtue of its outstanding chemical and physical properties. Herein, MnO₂ nanosheets with α- and δ- crystal structures were used to comparatively study the influence of crystal structures on the fire resistance of EP resin. Cone calorimeter results confirmed that δ-MnO₂ nanosheets achieved better improvements than α-MnO₂ nanosheets in reducing the PHRR and THR values as well as suppressing smoke release during combustion process. Moreover, Raman data and SEM tests showed that δ-MnO₂ nanosheets could effectively promote the char dense of char residues of EP composites. TG-IR results also indicated that the pyrolysis toxic products were significantly decreased after the incorporation of δ-MnO₂ nanosheets. By the way, the mechanical property of EP/δ-MnO₂ 2% composites had no obvious reduction compared with pristine EP resin, which would not restrict the application of EP resin in fields requiring high mechanical properties.