Charge Regulated Diffusion of Silica Nanoparticles into Wood for Flame Retardant Transparent Wood

The preparation of wood substrates modified by charged inorganic nano­particles (NPs) diffusing into the internal cell wall structure is investigated for generating functional properties. The flammability problem of wood biocom­posites is addressed. NPs applied from colloidal sols carry charge to stabilize them against aggregation. The influence of charge on particle diffusion and adsorption should play a role for their spatial distribution and localization in the wood substrate biocomposite. It is hypothesized that improved disper­sion, infiltration, and stability of NPs into the wood structure can be achieved by charge control diffusion, also restricting NP agglomeration and limiting distribution to the wood cell wall. Cationic and anionic silica NPs of ≈30 nm are therefore allowed to diffuse into bleached wood. The influence of charge on distribution in wood is investigated as a function of initial sol concentra­tion. Transparent wood is fabricated by in situ polymerization of a thiol­ene in the wood pore space. These biocomposites demonstrate excellent flame retardancy with self­extinguishing characteristics. The approach has poten­tial for commercial fabrication of flame retardant transparent composites for glazing and other building applications.