No abstract

The development and use of intumescent heat-insulating materials is important for ensuring fire safety and refractoriness of various structures exposed to powerful sources of heat energy [1][2][3][4][5]. Under heat loading such materials can increase in thickness by a factor of greater than several tens [3][4][5], forming a heat-insulating layer with a low thermal conductivity and thereby protecting the wall of the structure against damage. The number of such materials and the cost of thermal tests for their certification and prediction of heatinsulating properties constantly increase [5]. In this connection, it seems reasonable to use an approach that includes a study of the physical and chemical processes occurring in heated layers of intumescent coatings and their identification and mathematical description. This makes it possible to construct physically plausible mathematical models that can give well-founded predictions in the development of new, more effective coatings.Attempts to realize this approach have been undertaken by Buckmaster et al. [1][2][3][4]. Thus, for example, some heat-and mass-transfer mechanisms in a fire-insulation coating based on chlorosulfonated polyethylene (CSPE) and thermally expansible graphite (TEG) have been studied [3, 4]. Intumescence and thermal" destruction of the binder were found to proceed in the same temperature interval. This feature and also the high porosity of the heat-insulating layer significantly complicate identification of the observed physicochemical processes; therefore, it is necessary to split them into simpler processes, study them sequentially, and identify each of them separately. This experimental procedure is described in detail in [6], where a diagram of preliminary and basic experiments is given. In the first stage, the thermophysical characteristics of intumescent material were determined [8] over a wide temperature range by solution of the inverse problem of heat conduction for each individual stabilization temperature using the method of stabilized states [7]. The macrokinetic constants for the first step of thermal dest uction of the polymer binder were found using the results of dynamic exp,.riments [4]. This process is exothermic and can be described by a first-order solid-state reaction with a temperature dependence in the form of Arrhenius' law. The adiabatic regime of the first step of this reaction was found to be similar to the ignition process of condensed substances [9, 10].In this paper, a most complete model of intumescent material is proposed and the thermal destruction of the polymer binder and intumescence of the filler are identified over the studied temperature range using experimental data on the temperature fields and the dynamics of growth of the heat-insulation layer under heat loading.1. Experimental Procedure and Physical Concepts of the Processes. In accordance with the procedure of [6], we split spatially the processes in the physicochemical experiment and consider the diagram of the experiment shown in Fig. 1. The studied ...

No abstract

No abstract

No abstract