Enhancement of wollastonite on flame retardancy and mechanical properties of PP/IFR composite

Wollastonite, a natural calcium metasilicate possessing acicular crystal habit structure, was used together with intumescent flame retardant (IFR) to flame retard polypropylene (PP). The synergistic effects between wollastonite and IFR were investigated using limiting oxygen index (LOI) test, cone calorimeter test, thermogravimetric analysis, scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS), etc. The results revealed that wollastonite could effectively improve mechanical properties and flame retardancy of the PP/IFR composite. When 2.0 wt% wollastonite substituted for the same amount of IFR in the composite, the impact strength was enhanced from 4.6 kJ/m 2 to 6.8 kJ/m 2 , which was increased by 47.1%. Meanwhile, the LOI was increased from 33.0% to 35.5%, a UL‐94V‐0 rating was achieved and the peak heat release rate decreased substantially from 314.4 kW/m 2 to 262.8 kW/m 2 . Furthermore, the SEM‐EDS results provided positive evidence that the quality of char layer of the PP/IFR/wollastonite was superior to that of the PP/IFR composite due to synergism between wollastonite and IFR. POLYM. COMPOS., 35:158–166, 2014. © 2013 Society of Plastics Engineers