Investigation on Flame Retardancy and Antidripping of New Intumescent Flame Retardant Polypropylene Film

A novel intumescent flame retardant (IFR) system consisting of a novel char forming agent (CFA), modified ammonium polyphosphate (MAPP), a synergistic agent (4A zeolite) and an antidripping agent (SN3300) was used in an intumescent flame retardant polypropylene film (IFR-PP film). The original ammonium polyphosphate (OAPP) was modified by octadecylamine to enhance its compatibility with the PP matrix. According to the results obtained from the flame retardancy tests, MAPP had a higher efficiency than OAPP, and the IFR-PP film without the antidripping agent reached a high limiting oxygen index (LOT) value, but it failed to pass UL-94 VTM-0 rating (0.2 mm). The reasonable loading of SN3300 was 0.10 similar to 0.15 wt.% (26 wt.% loading of IFR). Greater or smaller loadings did not help the samples to pass VTM-0 rating, and even deteriorated the flame-retardancy of the film. Based on thermogravimetric analytical data, the IFR enhanced the thermal stability of composites at high temperature and effectively increased the char residue. The cone results demonstrated that the IFR could reduce the flammability of PP films based on reduced heat release rate (HRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP); also IFR containing MAPP became more effective in reducing smoke release than one containing OAPP. The mechanical properties test results showed that films containing MAPP had better tensile strength and tear strength. The morphological structures observed by scanning electron microscopy (SEM) showed that MAPP had much better compatibility with a PP matrix than OAPP, and it made the char layer become more homogeneous and dense.