Synergistic effect of epoxy/organophilic montorillonite nanocomposites and triphenyl phosphate on flame retardance enhancement of polypropylene

Epoxy/organophilic montorillonite (Epoxy/OMMT) nanocomposites were prepared by epoxy intercalated into the interlayer of OMMT, and flame retardant polypropylene (PP) was obtained with Epoxy/OMMT nanocomposites and triphenyl phosphate (TPP) mixture as flame retardant agent. The effect of epoxy sorts, mass ratio of OMMT and Epoxy, and the contents of Epoxy/OMMT and TPP on properties of PP were studied. It was found that there is a remarkable synergistic flame retardant effect of novolac epoxy/organophilic montorillonite (NE/OMMT) and TPP on PP. Flame retardant PP with oxygen index (OI) value of 36.5%, peak heat release rate (PHRR) of 654 kW/m(2), notched Izod impact strength of 6.93 kJ/m(2) and tensile strength of 30.56 MPa was obtained when the mass ratio of OMMT and NE is 5:100, the content of NE/OMMT and TPP is 13.33 and 6.67wt.%, respectively. The materials were characterized via X-Ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectrum (FT-IR), and thermogravimetry (TG). The XRD results and TEM photograph indicate OMMT is exfoliated in PP matrix when the mass ratio of OMMT and NE is lower than 10:100. The TG results show the evaporation of TPP is greatly hampered by NE/OMMT nanocomposite. PP with NE/OMMT-TPP has an onset weight loss temperature 31.7 degrees C higher than PP with NE-TPP because of the shielding effect of OMMT layers. The FT-IR spectra indicate phosphoric acid is generated from TPP and carboxylic acid and phenyl ether are generated from NE under thermal degradation, which further results in the formation of thermally stable char. This charring process is also affirmed by the wide thermally stable zone at 380-550 degrees C in TG curves of PP with NE/OMMT-TPP or NE-TPP.