In this work, expandable graphite (EG) was introduced to the composite of polypropylene/magnesium hydroxide (PP/MH) by melt compounding, fire performance, thermal degradation behavior, and acid resistance of the PP/MH/EG composites were investigated. The results demonstrate that the flame retardant efficiency of MH is very low by itself and there is a noticeable synergism between MH and EG in PP. The addition of proper EG can enhance flame retardancy, smoke suppression, and acid resistance of the PP/MH composite significantly at the same time.Replacing 8.7 wt% MH with 8.7 wt% EG reduces the filling grade needed for V-0 from 63 wt% MH to 56.5 wt% MH/EG mixture. The presence of EG on the composite surface hinders acid erosion of MH. There is no chemical reaction between MH and EG. Continuous intumescent char can be produced on the composite surface upon combustion, which is responsible for the much-improved flame retardancy and smoke suppression, regardless of the presence of MH on the surface area.

Nano-sized carbon black (CB) was introduced to ethylene vinyl acetate/magnesium hydroxide (EVA/MH) composite by melt compounding and the EVA/MH/CB ternary composites were investigated in terms of their thermal, flame retardant, mechanical, and electrical properties. The results indicate that the introduction of MH and CB has no impact on thermal degradation mechanism of EVA, but inhibits its degradation substantially. The presence of CB can hinder thermo-oxidative degradation and increase thermal stability of the EVA/MH composite significantly. The addition of CB increases the flame-retardant efficiency of MH effectively. The EVA/MH/CB composite with 3.6% CB can achieve V-0 rating and its peak heat release rate is 23% smaller than that of the EVA/MH composite, which only achieves V-2 rating in UL-94 test. The improvement in flame retardancy happens in condensed phase. On the whole, the introduction of proper CB can enhance the thermal and flame-retardant properties of EVA/MH composite considerably without damaging its mechanical and electrical performances. This work provides a simple and cost-effective method to further increase the properties of EVA/MH composite for wire and cable industry.