The encapsulation of intumescent flame retardants by poly-siloxane for thermoplastic polyolefin: Fire safety and water resistance

The flammability of thermoplastic polyolefins (TPO) is a prior concern related to fire disasters. The fire safety strategy for TPO has not been settled because of serious waterproof property deteriorations caused by the presence of flame retardant additives. This work reported an encapsulation of conventional intumescent flame retardant (IFR) additives by a poly-siloxane (Si-IFR) and its application in TPO composites. The fire behavior characterization revealed that the peak heat release rate and smoke density of the TPO/Si-IFR sample was decreased by 26.5% and 24.0% respectively compared with that of the TPO/IFR sample. The flame retardant mechanism analysis suggested that the poly-siloxane coated IFR formed compact char layers through Si-O structures and nano-silica attachment on the carbonous layer. Notably, the flame retardancy and mechanical property for the TPO/Si-IFR sample were almost unchanged after being soaked in water for 7 days at 70°C. Consequently, this work proved that the poly-siloxane encapsulated IFR was an effective additive for producing flame retardant and water resistant TPO composites.