Abstract
Shape-stabilized phase change material (SSPCM) is a promising thermal energy storage material in energy-saving buildings. However, its flammability leads to a fire risk. The conventional bulk addition method has a limited flame-retardant effect. Herein, a series of surface coatings with various flame retardants were introduced to improve flame retardance of SSPCM. The results showed that all of the coatings had flame-retardant effects on SSPCM; In particular, the EG coating performed the best: the horizontal burning time was the longest, the limiting oxygen index was above 30%, the V0 classification was obtained, the peak heat release rate was sharply decreased from 1137.0 to 392.5 kW/m2 and the burning process was prolonged with the least total smoke production. The flame-retardant mechanism was discussed. As paraffin easily evaporated from the SSPCM at a moderate temperature, it caused flames. After being surface coated, the EG-based coatings first hindered the volatilization of paraffin at a moderate temperature, then expanded and formed thick porous carbon layers at a high temperature to block the transfer of combustibles, oxygen and heat between the bulk and the environment. Therefore, the surface coating strategy achieved a desirable flame-retardant level with fewer flame retardants.
Highlights
IntroductionReactive flame retardants can strengthen the char residue in the matrix and insulate the exchange of volatile products and heat, while the inert gases generated can dilute the oxygen and combustible gas concentration to some degree
Efficient energy-saving technologies are urgently required in buildings so as to address the massive energy consumption and greenhouse gas emissions due to rapid urbanization and modernization [1].Introducing phase change materials into building envelops is a passive and cost-effective technology to improve energy utilization efficiency [2,3,4]
With expandable graphite (EG) coating achieved good flame-retardant properties with fewer flame retardants. Why did these different flame-retardant effects happen on shape-stabilized phase change material (SSPCM)? Was it owing to the different flammability nature between SSPCM and traditional polymers? In this study, we investigated the effects of coatings containing various flame retardants such as Talc, organic montmorillonite (OMMT), EG, ammonium polyphosphate (APP), intumescent flame retardants (IFRs)
Summary
Reactive flame retardants can strengthen the char residue in the matrix and insulate the exchange of volatile products and heat, while the inert gases generated can dilute the oxygen and combustible gas concentration to some degree. All of these flame retardants contribute to the failure of the fire triangle and enhance the flame retardancy of SSPCM. Cai et al [13] investigated the synergistic effect between EG and APP, helping to enhance the thermal stability and to suppress the flammability of HDPE/paraffin composites This was ascribed to the formation of the heat-insulated phosphor-carbonaceous char residue from the reaction of APP and EG, accompanied by the capture of. This work will be helpful to choose appropriate flame retardants and prepare
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