Casein-magnesium composite as an intumescent fire retardant coating for wood

Fire hazard associated to wood and wood-based products is a clear shortcoming of natural building materials and hence the use of fire retardants is mandated by national building codes. In this study, we have synthesized a simple and green fire retardant composite using magnesium hydroxide (Mg(OH)2) with casein protein and tested its performance as self-adhesive coating paste. The thermogravimetric analyses indicated that casein-magnesium composites are able to produce thermally stable insulating magnesium oxide (MgO) that suppresses the fire spread as a result of the synergistic combination of physical and chemical actions—the intumescent action of casein, formation of char and thermally stable MgO, and the simultaneous release of water vapor retained by the casein. The most effective performance was obtained with a sample (coating weight of 1080 g/m2) for which the ignition time of pinewood substrate was increased by 147%, while the smoke production rate and the peak heat release rate were decreased by 53% and 30%, respectively.