Damage Of Intumescent Fire Retardant Coatings And Its Influence On Thermal Insulation Performance

Intumescent steel structure fireproof coatings have been widely used due to their advantages such as light weight,good finish,and not being limited by the geometric shape of components.However,at present,the design and use of fire-resistant coatings for intumescent steel structures are based on the assumption that the integrity of the coating is good.In fact,the structure of the carbon layer of the fire-resistant coatings for intumescent steel structures is constantly changing during the expansion and expansion process under high temperature,The adhesion of the coating to the substrate and the mechanical properties of the coating will decrease,which will cause damage to the coating.After the coating is damaged,the temperature rise conditions of the components will change,which will cause the change of the refractory time.The existing research mainly includes two aspects: one is that most of the studies improve the adhesion and mechanical properties of coatings from the perspective of formulation design;the other is that most of these studies are performed on coatings at normal temperature,and the research at high temperature is very less.It is unknown whether the influencing factors,the mechanism and the rules of the damage of the fire-resistant coating of the expanded steel structure are damaged,and what is the change in the thermal insulation performance of the coating after the damage.To this end,the following research has been carried out:(1)Test of adhesion between small plate and substrate.64 small plate test pieces were tested for the adhesion strength between the coating and the substrate,including 32 forward adhesion tests and 32 tangential adhesion tests.The substrate type,coating expansion state,and surface treatment were examined.Effect on the adhesion between the coating and the substrate.(2)Test of adhesion between small plate and substrate.64 small plate test pieces were tested for the adhesion between the coating and the substrate,including 32 forward adhesion tests and 32 tangential adhesion tests.The substrate type,coating expansion state,and surface treatment were examined.Effect on the adhesion between the coating and the substrate and the damaged interface.(3)Fire temperature test on long columns.Four long columns were subjected to a constant-load temperature rise test to investigate the influence of the substrate material(Q235 steel and 304 stainless steel),surface treatment(sandblasting,carbon fiber cloth)on the damage of the coating and the influence of the damage on the temperature of the steel substrate.The research shows that the damage mode and degree of fire-resistant coatings of intumescent steel structures under fire are affected by many factors such as the geometric characteristics of the substrate,the loading conditions and the interface treatment.When the coating is in the carbon layer stage,cracks have already appeared,and the application of carbon fiber cloth is not conducive to the integrity of the coating and will cause the coating to fall off in a wide range.The shape of the substrate,external load,and surface treatment have certain effects on the damage of the coating and the temperature of the substrate.When the cross-sectional shape is similar and the substrate is the same,the temperature of the short column is 21.7% higher than that of the small steel plate at 30 minutes,and the substrate temperature of the I-shaped long column is 36.23% higher than that of the small steel plate.11.12%;the temperature of long T-loaded long column is 13% higher than that of short T-shaped column.The temperature of the 304 test piece and the sand blasted test piece were about 93.8 ° C and 35.08 ° C higher than the carbon fiber cloth test piece,respectively.