Effects of dihydrogen phosphate intercalated layered double hydroxides on the crystal behaviors and flammability of polypropylene

Mg-Al-H2PO4- layered double hydroxides (LDHs) was prepared by anion exchange method, and polypropylene (PP)-LDH composites were prepared by melt compounding. The dispersion of LDH in PP matrix was characterized by Transmission electron microscope and X-ray diffraction (XRD), and the results showed that both exfoliation structures and aggregation structures can be found in the composites. The effects of LDH on the crystal behaviors of PP was investigated by XRD and Differential scanning calorimetry (DSC), and it indicated that LDH can induce the formation of crystal and serve as a heterogeneous nucleating agent in PP. The significant decrease of both the crystallization and the melting enthalpy (H-c and H-m) was observed in PP composite at the presence of LDH platelets. Both the peak heat release rate and total heat release (THR) were significantly decreased after the addition of treated LDH. The possible chemical structural change in the condensed phase of PP composite during heating was studied by Fourier transform infrared spectroscopy (FT-IR). The mechanism of modified LDH in improving the fire performance of PP and the possible relationship between flame retardancy and crystal behavior have been proposed and discussed. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3645-3651, 2013