Influence of ferric hydroxide on smoke suppression properties and combustion behavior of intumescent flame retardant silicone rubber composites

New silicone rubbers(SR)-based hybrid material containing intumescent flame retardant (IFR) and ferric hydroxide (FeOOH) has been developed in order to improve flame retardancy of SR. The synergistic effects of FeOOH with IFR in halogen-free flame retardant SR/IFR blends have been studied by cone calorimeter test (CCT) and thermogravimetric analysis (TG). The data obtained from the CCT indicate that the SR/IFR/FeOOH sample with 4.0 mass% FeOOH has the lowest HRR, SPR, TSR, THR, and SF among all samples. The digital photo graphs give positive evidence that there is a synergistic effect between IFR with FeOOH. The TG results reveal that FeOOH can enhance the thermal stability of SR/IFR/FeOOH at high temperature. Besides the traditional investigations on cone calorimeter tests, an intensive study on the thermo-degradation kinetics was carried out to reveal the mechanism of the outstanding flame retarding performance of the SR/IFR/FeOOH. FeOOH can improve the flame retardancy, increase the thermal stability during the whole process of degradation, and strengthen the ability to form a thermally stable and condensed barrier for heat and mass transfer. These attractive features of SR/IFR/FeOOH suggest that the method proposed herein is a good approach to prepare very effective flame retardants and corresponding super flame retarding SR.