In-situ synthesis and assembly of nanospheres (Py1H2PW, Py2H1PW, and Py3PW) in wood to promote flame retardation

Hybrid wood is a composite with the advantages of both wood and inorganic material. Here, a novel hybrid wood was fabricated from wood and nanospheres by the in-situ assembly of phosphotungstic acid (HPW) and pyridine (PY) at room temperature. The uniformly distributed amphiphilic PY-PW nanospheres provided controllable particle size and acid properties by changing the HPW-PY molar. Examination under Scanning electron microscopy (SEM) showed the presence of a uniform nanosphere coating by the nanospheres, and FE-SEM/EDS showed even distribution on the cell walls. The successful synthesis of the nanospheres in the wood was confirmed by Transmission electron microscopy (TEM). The PY-PW/wood hybrid was also resistant to leaching, attributed to the amphiphilicity of the nanospheres. The hybrid wood also showed superior flame retardation, with a UL-94 V-0 rating, and significantly reduced the peak heat release rate (pk-HRR) and total smoke release (TSR) values of the untreated wood by 44.7 % and 51.7 %, respectively. The enhanced flame retardation was attributed to synergistic effects and catalytic carbon reactions resulting from high-density nitrogen/phosphorus/oxygen cross-linking in the carbon layer in the condensed phase and the removal of combustible gases by free radicals. This hybrid wood material has potential application for the development of fire-safe wood.