The experimental study presented herein investigates the influence of the substrate thermal conditions on the behaviour of thin intumescent coatings. Steel plates coated with a commercially available solvent-based thin intumescent coating were exposed to a constant incident radiant heat flux of 50 kW/m² in accordance with the heat-transfer rate inducing system (H-TRIS) test method. The influence of different substrate thermal conditions was investigated using sample holders capable of controlling the thermal boundary conditions at the unexposed surface of tested steel plates and comparing them to coated timber samples. Experimental results evidence that the substrate thermal conditions govern the swelling of intumescent coatings, thus their effectiveness in protecting load-bearing structural elements. The substrate temperature controls the swelling of intumescent coatings because it defines the temperature experienced by the reacting virgin coating located close to the coating-substrate interface. The physical and thermal properties of the substrate control the capacity of the system to concentrate/dissipate heat in proximity of the coating-substrate interface. In this way, the substrate thermal conditions govern the temperature evolution of the reacting intumescent coating, consequently the swelling process. Accordingly, high swelling rates were recorded for highly insulating conditions (timber substrate), while low swelling rates for poorly insulating conditions (water-cooled heat sink).

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基材热条件对薄膨胀涂层溶胀的影响

本文提出的实验研究调查了基材热条件对薄膨胀涂层行为的影响。涂有市售溶剂型薄膨胀涂层的钢板暴露于 50 kW/m ²的恒定入射辐射热通量根据传热率诱导系统（H-TRIS）测试方法。使用能够控制受试钢板未暴露表面的热边界条件并将它们与涂层木材样品进行比较的样品架，研究了不同基材热条件的影响。实验结果证明，基材热条件控制膨胀涂层的溶胀，因此它们在保护承重结构元件方面是有效的。基材温度控制膨胀涂层的溶胀，因为它定义了靠近涂层-基材界面的反应原始涂层所经历的温度。基材的物理和热特性控制系统在涂层-基材界面附近集中/散发热量的能力。通过这种方式，基材的热条件控制着膨胀涂层的反应温度演变，从而控制溶胀过程。因此，在高度绝缘的条件下（木材基材）记录了高膨胀率，而在绝缘差的条件下（水冷散热器）记录了低膨胀率。