Preparation and Properties of Silicone Rubber-based Intumescent Fireproof Sealing Material
An intumescent fireproof sealing system with room temperature vulcanized silicone rubber(SR)as matrix,sodium silicate(NSH)as expansion filler and ammonium polyphosphate(APP)as flame retardant was designed,and the effects of different modulus expansion agents on the properties of the material were investigated.The SR composites were prepared via blending pouring method.The thermal stability and flame retardancy of SR composites were measured by vertical burning test(UL-94),limiting oxygen index(LOI)and thermogravimetric analysis(TGA).Moreover,the important indexes of the sealing material were characterized by expansion test and fire resistance test.The morphology of char residues after UL-94 test and fire resistance test were observed by scanning electron microscopy(SEM).The results showed that the high modulus sodium silicate had better thermal expansion effect,and the 2.8 modulus sodium silicate had the best expansion fireproof performance.The sample with only expansive agent had no grade in the flame-retardant test,but by adding a small amount of flame retardant,the limiting oxygen index increased to 30.9％,and passed the UL-94 test V-0 grade.The study of mechanism found that the outer layer of the material was transformed into a thin-walled hollow microsphere stacking structure when exposed to fire,forming a strong expansion barrier layer.Concomitantly,the expansion barrier layer efficiently exerts the gas phase flame retardant effect of the flame retardant.In addition,the prepared sample can reach the 3 h level of fire sealing test for cracks.
Sealing materialRoom temperature vulcanized silicone rubberAmmonium polyphosphateSodium silicat
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