Abstract: Polypropylene /intumescent flame retardant / organic montmorillonite (PP/IFR/OMMT) composites were prepared by direct melting intercalation. The synergistic flame retarding effect of OMMT and IFR was investigated. The composite was characterized by X-ray diffraction, limiting oxygen index, thermal analysis, etc. It was found that the layers of OMMT were intercalated by PP chain. There was a clear synergistic retarding effect between OMMT and IFR. When 2 phr of OMMT was introduced, the limiting oxygen index was 30 %, and the carbon residue increased obviously. With increasing contents of OMMT, the tensile strength, bending strength and impact strength of composites increased, and then decreased. When 3 phr of OMMT was introduced, the tensile strength, bending strength and impact strength of composites reached the maximum value.

Key words: polypropylene, organic montmorillonite, intumescent flame retardant, synergistic retarding