Polypropylene/clay nanocomposites prepared by in situ grafting–melt intercalation with a novel co-intercalating monomer

Polypropylene (PP)/clay nanocomposites were prepared by melt-compounding PP with organomontmorillonite (PMT), using maleic anhydride grafted polypropylene (PP-g-MA) as the primary compatibilizer and N-imidazol-O-(bicyclo pentaerythritol phosphate)-O-(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X-ray diffraction patterns indicated that the larger interlayer spacing of PMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d-spacing further increased with the addition of PP-g-MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI-containing PP nanocomposites exhibited better thermal stability than PEBI-free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (Tg) shifted slightly to low temperature with the incorporation of clay for PP/PMT hybrids. PEBI-containing PP/PMT composites gave a lower Tg value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame-retardancy properties of PP nano-composites were highly improved with the incorporation of PEBI