Abstract: Polypropylene (PP)/intumescent flame retardant (IFR) composites and PP/IFR/organic montmorillonite (OMMT) nanocomposites were prepared by melt blending method. Synergistic effect between IFR and OMMT on flame retardant properties in PP matrix and the mechanical properties of the composites were investigated. The synergistic flame retardant mechanism was explored. It was observed that PP/IFR/OMMT nanocomposites had a higher oxygen index and a lower peak heat release rate than PP/IFR composites. Especially, the material reached UL 94 V-0 level when 18.5% of IFR and 1.5% OMMT were introduced, while material without OMMT was zero level. SEM micrograph of char residue after combustion showed that OMMT played a reinforcing on the cell, so that the PP/IFR/OMMT nanocomposites exhibited better flame retardant performance than PP/IFR composites. The impact strength of PP/IFR/OMMT nanocomposites was improved, however, the tensile strength was declined based on PP/IFR composites.

Key words: polypropylene, intumescent flame retardant, organic montmorillonite, flame retardant property, mechanical property