Biobased P-N-Si transparent PIN FR coating

The biological phosphorus molecule, phytic acid, was reacted with a N-Si cation to produce a PIN FR coating for wood. Phytic acid is widely present in seeds and grains and is nature’s phosphorus storage molecule. Phytic acid sodium salt was here reacted with N-[3-(trimethoxysilyl) propyl]-N,N,N-trimethylammonium at 60°C. The resulting molecule was coated onto wood by brushing at 500 g/m², resulting in a cross-linked polysiloxane. The coating remained transparent and did not damage the wood fibre grain. When the phytic acid and N-Si compound were reacted at a 1:1 ratio, the resulting coating increased LOI (Limiting Oxygen Index) from 26 (untreated wood) to 36, reduced peak heat release rate by around -20% and reduced total smoke release by around two thirds. Fire performance was achieved by development of a strong intumescent char layer.

“Highly Transparent Fire-resistant Coatings with Intumescent Three-source Integration”, X-L. Zeng et al., Chinese J. Polym. Sci. 2024, 42, 907–915, https://doi.org/10.1 007/s10118-024-3100-1 Image: Wiki – Harbinary.