Preparation of Exfoliated Organo-Montmorillonite and Its Effect on Flame Retardancy and Mechanical Properties of Polypropylene

In this study, a new type of ammonium polyphosphate-intercalated organic montmorillonite (APP/OMt) was synthesized using in-situ polymerization, and the chemical structure and surface morphology of APP/OMt was confirmed by FT-IR, XRD, EDS and SEM. Moreover, the intumescent flame retardant (IFR) composed of APP/OMt, pentaerythritol (PER) and melamine (MA) was added into polypropylene (PP) to fabricate the PP/IFRAPP/OMt composites, and their flame-retardant and mechanical properties were characterized systematically. When the additive mass of the flame retardants was 30 %, the limiting oxygen index (LOI) value reached 33.3 %, and the UL-94 test passed the V-0 level when the added amount was only 20 %. Especially, compared to the counterpart of IFRAPP, the addition of IFRAPP/OMt dramatically decreased the released smoke of PP during combustion, and the quality of carbon layer after combustion was obviously improved. The flame-retardant mechanism of IFRAPP/OMt was deeply explored. In addition, the mechanical properties of PP composites with IFRAPP/OMt were significantly improved compared with IFRAPP. The enhanced flame retardancy and mechanical strength were attributed to the synergistic effect between OMt and IFR particles along with improved the dispersion of IFRAPP/OMt within the PP matrix.