Synergistic Effect of Novel Synergists-Transition Metal Ion-incorporated Nickel Phosphates with Intumescent Flame Retardants in Polypropylene

The two kinds of transition metal ion-incorporated nickel phosphates (TMIVSB-1) were synthesized by the hydrothermal method. The flame retardancy and thermal behavior of intumescent flame retardants (IFR), with and without TMIVSB-1 for PP, were investigated by LOI, UL-94 test, thermogravimetric analyses (TGA) and cone calorimetry. TMIVSB-1 can obviously improve the flame retardant behavior of IFR systems according to the results of LOI values and UL-94 test. The results of LOI show that 2 wt% TMIVSB-1 can increase the LOI value by 3-5 unit compared with that of PP/IFR composite. The UL-94 test shows that PP with 20% IFR burns and has no rating, but the addition of a small content 2 wt% of TMIVSB-1 with 18 wt% of IFR can reach a UL-94 V-0 rating. TGA results show that the thermal stability of PP/IFR/TMIVSB-1 increases obviously more than that of PP/IFR when the temperature is above 265C. From cone calorimetry results, it can be observed that the HRR peaks are not obviously decreased, but the burning time of PP/IFR/FeVSB-1 (351s) and PP/IFR/ZnVSB-1 (380s) is obviously prolonged compared with that of PP/IFR (303s). The real time FTIR spectra (RTFTIR) demonstrates that the addition of TMIVSB-1 further staves the decomposition of the PP composites. The scanning electron microscopy (SEM) indicates the quality of char forming of PP/IFR/ TMIVSB-1 is superior to that of PP/IFR.