钢结构作为主要的建筑结构类型之一，由于其耐热性能差，在火灾中易发生变形而导致坍塌事故，因此需对其采取有效的防火保护措施，目前多采用喷涂水性防火涂料的办法。为了解决水性防火涂料防火性能差、耐水性差等问题，本文将三聚氰胺聚磷酸盐（MPP）和三嗪成炭剂（CFA）复配作为阻燃剂应用于钢结构防火涂料中，采用实验方法对涂料的防火性能进行研究，并初步揭示其防火机理，具体研究内容如下：

首先选取了丙烯酸、苯丙、硅丙、纯丙四种乳液作为钢结构防火涂料的成膜物质，采用模拟大板燃烧、锥形量热测试和热重（TG）实验研究了成膜物质的种类对涂料耐火性能和热稳定性的影响。结果表明，丙烯酸防火涂料的钢板背温最低为268℃，热释放速率峰值（PHRR）和总热释放量（THR）最小，丙烯酸乳胶膜的热稳定性最高。表明丙烯酸防火涂料的防火性能最好，与MPP/CFA膨胀阻燃体系匹配度最佳。

将丙烯酸作为钢结构防火涂料的成膜物质，通过模拟大板燃烧法和锥形量热测试实验研究了MPP和CFA的配比以及阻燃剂含量对涂料耐火性能的影响，设计正交试验方案优化防火涂料配方，并与传统的聚磷酸铵/季戊四醇/三聚氰胺（P-C-N）防火涂料进行防火性能和耐水性能对比。结果表明，当MPP:CFA=1:3，阻燃剂MPP/CFA含量为35%时，钢板最高背温、PHRR和THR值均最低。与P-C-N防火涂料相比，MPP/CFA涂层的吸水率降低了71.5%，THR降低了20.4%，总产烟量降低了31.4%，MPP/CFA防火涂料表现出较好的耐水性、防火性能和抑烟性能。

最后通过TG、SEM、FTIR、XRD等测试得到防火涂料的热解行为、物质变化和残炭形貌等实验参数，分析防火涂料燃烧和热解过程中的变化规律，综合分析其成炭机理。结果表明，MPP/CFA防火涂料的热分解过程主要分为四个阶段，燃烧后形成较为连续、致密的炭层，MPP受热分解生成的多聚磷酸与CFA产生的三嗪环形成的含有交联结构的磷碳炭层起主要隔热隔氧作用，同时兼有气相阻燃作用，提高了防火涂料的防火性能。

As one of the main types of building structures, steel structure is prone to collapse due to its poor heat resistance and deformation in fire. Therefore, effective fire protection measures need to be taken. At present, the method of spraying water-based fire retardant coating is mostly used. In order to solve the problems of poor fire resistance and water resistance of waterborne fire retardant coatings, the compound of melamine polyphosphate (MPP) and triazine charring agent (CFA) is used as flame retardant in steel structure fire retardant coatings. The fire resistance of coatings is studied by experimental methods, and its fire resistance mechanism is preliminarily revealed. The specific research contents are as follows:

First, four kinds of lotion, acrylic acid, styrene acrylic, silicon acrylic and acrylic acrylic emulsion were selected as the film forming material of steel structure fire retardant coating. The effects of film forming substances on the fire resistance and thermal stability of the coating were studied by simulating plate combustion, cone calorimeter and thermogravimetric (TG). The results show that the minimum back temperature of steel plate of acrylic fire retardant coating is 268 ℃, the peak heat release rate (phrr) and total heat release (THR) are the smallest, and the thermal stability of acrylic emulsion film is the highest. It shows that acrylic fire retardant coating has the best fire resistance and the best matching degree with MPP/CFA intumescent flame retardant system.

Acrylic acid was used as the film-forming material of steel structure fire retardant coating. The effects of the ratio of MPP and CFA and the content of flame retardant on the fire resistance of the coating were studied by simulated large plate combustion method and cone calorimetry. The orthogonal test scheme was designed to optimize the formula of fire retardant coating, and the fire resistance and water resistance were compared with the traditional ammonium polyphosphate/pentaerythritol / melamine (P-C-N) fire retardant coating. The results show that when MPP: CFA = 1:3 and the content of flame retardant MPP/CFA is 35%, the maximum back temperature, phrr and thr of the steel plate are the lowest. Compared with P-C-N fire retardant coating, the water absorption of MPP/CFA coating is reduced by 71.5%, THR is reduced by 20.4%, and the total smoke production is reduced by 31.4%. MPP/CFA fire retardant coating shows better water resistance, fire resistance and smoke suppression.

Finally, through TG, SEM, FTIR, XRD and other tests, the experimental parameters such as pyrolysis behavior, material change and residual carbon morphology of the fire retardant coating are obtained, the change law in the combustion and pyrolysis process of the fire retardant coating is analyzed, and its charring mechanism is comprehensively analyzed. The results show that the thermal decomposition process of MPP/CFA fire retardant coating is mainly divided into four stages. After combustion, a relatively continuous and dense carbon layer is formed. The phosphorus carbon layer with cross-linked structure formed by the polyphosphoric acid produced by MPP thermal decomposition and the triazine ring produced by CFA plays the main role of heat insulation and oxygen isolation, and also has the role of gas-phase flame retardant, which improves the fire resistance of the fire retardant coating.