| Steel structures are extensively used in modern buildings because of its high strength, good toughness and excellent shock resistance. But the strength of steel decreases rapidly when its temperature exceeds 540?. To improve fire resistance of steel structure, one of the most effective methods is to paint intumescent fire retardant coating on steel surface. In order to investigate the synergistic effects of components in intumescent coating, the reaserch focused on the effects of intumescent flame retardant system, resin and inorganic fillers on the performance of fire retardancy.In this paper, the main research works are as follows:1. The synergistic effect during the char formation between ammonium polyphosphate ?APP? and pentaerythritol ?PER? was studied, the result showed that PER reacted with APP to generate phosphocarbonaceous esters from 180? to 320?, which dehydrated and cyclized of at 320??550?, and finally formed graphite-like fragment at 600??750?. When the ratio of APP and PER was 3:1, generated the maximum char yield. The effects of APP, PER, and MEL content in the intumescent flame retardant on the fire resistant performance of the coating were researched, the results demonstrated that the coating show best fire endurance and maximum expansion rate when each content of APP, PER and MEL were 55.6%,22.2% and 22.2%. The effects of thermal degradation temperature of APP and APP/PER mass ratio on the fire resistant performance of the coating were investigated, the results indicated that, due to the formation of intumescent char layer with good heat insulation, the peak back temperature rising rate dropped to 25.7?/min form 35.1?/min, with fire endurance increased by 20.5min, especially when the mass ration of AP462 and PER was3:1.2. The effects of acrylic resin on the expansion rate and fire endurance were studied, results demonstrated that the foaming expansion property of the coating was closely related to its melt viscosity at the stage of high temperature. The Tg of resin and the initial pyrolysis temperature of intumescent flame retardant system should be matched within a certain temperature range. The melt viscosity was suit for the expansion of the char layer when the Tg was within the range of 65? and 80 ?. Then the effects of mass ratio between acrylic resin and intumescent flame retardant on the expansion rate and acid resistance of the coating were investigated, results indicated that the expansion rate was 25.3 and fire resistant was 39.5min when the mass ratio was 1:2.3. The effects of fillers and their content on the fire resistance of the coating were investigated, results indicated that fire resistant and the strength of intumescent char layer were enhanced when adding appropriate amount of TiO2 and EG. The thermal conductivity of intumescent char layer was 0.0414 W·m-1·K-1 after adding 2.5% EG, because EG has a greater impact on the thermal conductivity of intumescent char layer. In addition, the effects of three kinds of layered silicate filler on the fire resistance performance of the coatings were studied, the results indicated that kaolin with crystal structure of 1:1 type of Al-O octahedrons and Si-O tetrahedrons could elevated the thermal stability of char layer at the stage of high temperature. |
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