Sodium silicate monohydrate (NSH), glass frits (GF) and aluminum hydroxide (ATH) were incorporated into room temperature vulcanized (RTV) silicone rubber (SR) as char reinforcing materials to improve the fire resistance of intumescent flame retardant silicone rubber. SR composites containing only intumescent flame retardant such as phosphorus nitrogen composite flame retardant (NH2‐C) and expandable graphite (EG) were used as comparison samples. Limiting oxygen index (LOI) test, vertical burning test (UL‐94), flame resistance test, scanning electron microscopy (SEM) and X‐ray diffraction spectroscopy tests, as well as volume variation and compression strength of char residues were used to discuss the effects of the above‐mentioned fillers on the fire resistance, char residue strength and char integrity of SR composites. The results showed that SR composite filled with only intumescent flame retardants EG and NH2‐C had excellent flame retardancy. After adding ATH, the char residue was relatively dense and had good compressive strength, but its thermal insulation performance was reduced. GF or NSH reduced the flame retardancy of SR composites, but it obviously played a role in binding combustion residues, forming new crystals and improving the stability of char residues.
In order to improve fire resistance performances of sealant for pipe penetration, a novel ceramizable silicone rubber (CSR) composite was developed. The CSR composite was prepared by glass frits (GF), aluminum hydroxide (ATH), phosphorus-nitrogen flame retardant (NH 2 C) as functional fillers to get a silicone rubber with reinforced char residues. The effects of ATH, GF, and NH 2 C content on the mechanical and flame retardant properties were studied by orthogonal designed experiments. The scanning electronic microscopy and X-ray diffraction were used to characterize the microstructure and phase composition after the sintering test, and subsequently to explore the fire resistance mechanism of the CSR composite. Experimental results indicated the optimum composition of CSR (by weight percent) was 18% GF, 18% ATH, and 25% phosphorus-nitrogen flame retardant. The surface flammability and marine A class pipe penetration fire tests were untiled to evaluate the fire resistance of the CSR with optimal proportion. The results show the optimal CSR can achieve the A-60 grade in the pipe penetration fire test and possess superior low flame spread flammability. Its application in pipe penetration sealing would be an effective strategy to prevent the flame propagation.
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