Halogen Free Flame Retardant Agents for Polypropylene in Wire Coating Process

The Re2Sn2O7 (Re = Nd, Sm, Gd) on the enhancement of fire safety and physical performance of Polyolefin/IFR cable materials

Polyolefin (PO) cables used in confined spaces need to have low smoke, low heat release, low toxic gas release and excellent physical properties. In this work, a series of rare earth stannates Re₂Sn₂O₇ (RES, Re = Nd, Sm, Gd) with high temperature catalytic performance were prepared by hydrothermal method for synergistic flame retardant PO/IFR. The flame retardancy, heat release, smoke density, toxic gas release and physical properties of PO composites were thoroughly studied in detail. The RES could enhance the vertical burning rating and the limiting oxygen index (LOI) of PO/IFR composites. Moreover, the residual char of the thermogravimetric analysis increased from 9.7% to 11.4 wt% after the RES added in PO/IFR system. Interestingly, the PO/IFR system containing Gd₂Sn₂O₇ exhibits the lowest peak heat release rate of 233.7 kW/m². Excellent flame resistance due to the formation of a complete and compact protective char layer. In addition, the toxic release of PO during combustion is also effectively reduced by introducing the RES. The tube furnace combustion test shows that the emission of carbon oxide (CO) and hydrogen cyanide (HCN) of PO/IFR/Gd₂Sn₂O₇ are the lowest. It can be attributed to the catalytic effect of rare earth elements and the blocking effect of the dense char layer. In addition, compared with the PO/IFR composites, the PO/IFR/RES system demonstrate higher mechanical properties and volume resistivity. Therefore, the addition of RES has a positive effect on improving the physical properties and fire safety properties of the PO/IFR cable composites, especially suitable for using in confined spaces.