This work discusses the thermal-structural behaviour of an 'inorganic'based intumescent coating. On exposure to heat, this fire-retardant system undergoes particular physical phenomena: (i) Thermo-chemical decomposition reactions; (ii) Formation of numerous micro-scale pores in its internal structure; (iii) Geometrical volume (thickness) expansions; (iv) Variations in its thermal boundaries. These simultaneous occurrences interact with each other's progressions with time. In order to evaluate the coating's thermal insulation performance and to optimise its performance, this study aims to clearly interpret the combined thermal-structural behaviour. This research program is constructed in four stages: • To identify the thermo-kinetic and -physical characteristics of the polymer compound, this work analyses the experimental data, obtained from Thermogravimetric Analysis, Differential Scanning Calorimetry, Electronic Furnace, and Cone Calorimeter tests; • To accurately quantify the net heat absorbed by the swelling specimen tested with the cone calorimetry, this study investigates (i) the irradiance intensification on the sample's top surface moving toward the heater, (ii) the heat transfer through the surface area of its perimeter being progressively extended, (iii) the convective fluid motions driven in testing and the corresponding coefficients, and (iv) the radiant mechanism generated in testing and the corresponding radiative properties; • To quantitatively assess the thermal insulation performance of the coating, this work numerically simulates the heat transfer mechanism through its porous structure, and analyses individual contributions of the component modes of heat transfer, by adopting 'effective' thermal conductivity; • To comprehensively explain the thermal-structural behaviour of the coating, this study proposes a series of sequential steps of mass and volume changes as a function of temperature, and numerically simulates the process of intumescence. All the findings gained from the previous three stages are applied in this simulation, which is verified by comparison with the experimental data. From this work, it can be identified that the performance of this refractory product is significantly affected by (i) endothermic water vaporisation with dehydration and dehydroxylation, (ii) effective thermal conductivity of its multi-cellular structure, (iii) length of the heat penetration path across its expanding volume, and (iv) radiant heat emission on its heated surfaces. The interacting behaviour of the inorganic-based intumescent coating is systematically analysed, from microscopic thermo-kinetic characteristics to macroscopic behaviours in relation to heat transfer and thermal expansion, in this study. Hence, it can contribute to further studies on intumescent-type materials and their practical development.
Thermal-structural behaviour of inorganic intumescent system
Kang, S. (Author). 2016
Student thesis: Doctoral Thesis