Cyclic phosphate ester was reacted with magnesium hydroxide (1 – 6 %) and then tested with melamine formaldehyde and pentaerythritol (at ratios 1:1 to 1:4) as a flame retardant coating on 4 mm plywood (250 g/m2 coating). The magnesium containing coating achieved flame spread rating, total heat release and total smoke release respectively 34%, 29% and 55% lower than a cyclic phosphate ester only coating. Analysis shows that the presence of magnesium increases char production and improves char structure, with more phosphorus-rich cross-linked and aromatic structures in the char.
“Synthesis and application of novel magnesium phosphate ester flame retardants for transparent intumescent fire-retardant coatings applied on wood substrates”, L. Yan, Progress in Organic Coatings 129 (2019) 327–337, https://doi.org/10.1016/j.porgcoat.2019.01.013