Design and optimization of an intumescent flame retardant coating using thermal degradation kinetics and Taguchi's experimental design

Two supplementary approaches in terms of thermal degradation kinetics and Taguchi's experimental design were employed toward developing a design effort for intumescent coatings. A model intumescent system including ammonium polyphosphate (APP), pentaerythritol (PER), melamine (MEL), thermoplastic acrylic resin and liquid hydrocarbon resin was chosen and then subjected to thermogravimetric analysis and heat insulation tests to provide experimental data. Kinetic analysis of the thermogravimetric data based on the Friedman and Kissinger methods revealed that activation energy (Ea) and reaction order (n) could be used as parameters to accurately judge whether the selected intumescent components represented coordinated thermal characteristics. Examination of the calculated Ea and n values showed that the decomposition of thermoplastic acrylic resin and liquid hydrocarbon resin occurred first and that the APP, PER and MEL components were degraded immediately after. Such a degradation sequence was quite consistent with the functional mechanism of intumescent systems. In addition, simultaneous implementation of analysis of variance and mean effect assessment on the Taguchi data demonstrated that the designed formulation, based on the optimized coupling of 10 g MEL into APP/PER 25 g/11 g, exhibited the highest fireproofing time among the prepared coating samples. The APP content had the most important contribution to the flame retardant behaviour, and APP versus PER interactions showed the highest severity index. Scanning electron microscopy showed that the higher flame retardancy of the optimized sample was related to the presence of a large number of micropores in the expanded charring layer structure. Copyright (C) 2012 Society of Chemical Industry