Milk-derived casein protein reacted with magnesium hydroxide and showed to be an effective PIN FR coating for timber. The reaction was carried out at 70°C with sodium hydroxide and the resulting compound was then spread on 20 mm scotch pine wood samples and dried at room temperature. The coating showed to have penetrated around 0.5 mm into the wood. Peak heat release was reduced by nearly 45%, time to ignition was more than doubled and smoke release was reduced by around 30% with c. 1 kg (dry weight) coating per m2. The authors conclude that the casein acts as an adhesive to between the magnesium hydroxide and the wood, contributes to an intumescent effect, and retains water released by the magnesium hydroxide in fire. The composite releases magnesium oxide layers with a high surface area which absorb smoke and gases. Information on the aesthetic impacts of the coating on the timber and on possible durability (resistance to moisture and weathering) are not assessed.
“Casein-magnesium composite as an intumescent fire retardant coating for wood”, M. Uddin et al., Fire Safety Journal 112 (2020) 102943 https://doi.org/10.1016/j.firesaf.2019.102943