Synergistic effect of montmorillonite and nano-Sb2O3/brominated polystyrene on the flame retardancy of polypropylene matrix composites

Sb 2 O 3 nanoparticles (nano-Sb 2 O 3 ), montmorillonite (MMT) and brominated polystyrene (BPS) were used to enhance flame retardancy of polypropylene (PP) in the work, in which nano-Sb 2 O 3 was modified by cetyl trimethyl ammonium bromide and polyethylene glycol and MMT was modified by silane coupling agent. PP matrix flame retardant composites were prepared by melt blending after pre-mixing by high energy ball milling technique. Then, the flame retardancy, thermal stability behaviour, crystallization performance and tensile strength of PP matrix composites (nano-Sb 2 O 3 /MMT/BPS-PP, nano-Sb 2 O 3 /BPS-PP) were investigated. The results show that MMT can significantly improve the thermal stability and flame retardancy of PP matrix due to improving the strength of char layer and forming barrier effect. Compared with 3.5%nano-Sb 2 O 3 /8%BPS-PP composites, the limiting oxygen index of 3.5%nano-Sb 2 O 3 /3%MMT/8%BPS-PP composites was increased from 26.9% to 29.0% and its UL94 grade was achieved to V-0 level. Moreover, MMT and nano-Sb 2 O 3 can increase the crystallinity and tensile strength of PP matrix composites because of the heterogeneous nucleation effect of MMT and nano-Sb 2 O 3 particles on the crystallization of PP matrix.