Leach-resistant modified bamboo with fire-retardant and anti-mildew properties via in situ synthesis

To ensure the long-term fire-retardant (FR) and anti-mildew (AM) of bamboo materials when employed in outdoor settings susceptible to rainfall exposure, high durability is essential. In this study, we achieved water-leaching resistance of FR and AM bamboo through the in situ synthesis of phosphotungstic acid (PW) and silver nitrate (AG) via vacuum-pressure impregnation. The successful synthesis of the nanospheres within the bamboo (referred to as PWAG-B) was confirmed by TEM, FTIR, and XPS. These nanospheres remained intact within the bamboo cell wall after being subjected to a leaching test, with only a negligible mass loss of 0.88 % and virtually no traces of Ag and W in the leachate for PWAG-B1. Furthermore, the treated bamboo exhibited superior AM properties, with complete resistance against two types of mildew, namely Botryodiplodia theobromae and Alternaria alternate, as well as stain fungi including Aspergillus niger and Penicillum citrinum. Notably, the treated bamboo displayed reduced thermal and smoke parameters in comparison to untreated bamboo, along with a delayed ignition time. This long-term AM and FR bamboo has the potential for the development of eco-friendly outdoor building materials.