Recent research has shown that fluorides such as NaF have potential as a wood preservative against termite attack (Pan and Wang, 2015). However, NaF has high leaching susceptibility because of its solubility (40 g/l ) which can reduce its efficacy over long term. Metal fluoride nanoparticles such as MgF2 and CaF2 present a viable alternative to water soluble fluoride-based wood preservatives as they have low water solubility. The solubility of MgF2 is 130 mg/l and that of CaF2 is 16 mg/l. It is found that synthesis of low-water soluble fluorides as nanoparticles allow them to be introduced into wood specimens. These homo-dispersed nano metal fluorides are synthesized as sols using fluorolytic sol-gel synthesis (Krahl et al. 2016). Wood specimens treated with fluoride sols of MgF2 and CaF2 have been tested against subterranean termites (Coptotermes formosanus) in accordance with EN 117. Coptotermes formosanus is a species that causes significant decay of wood especially in Taiwan, Japan, and southern United States (Chang and Cheng 2002). After eight-week testing according to EN 117, the specimens treated with nano metal fluorides had an average rating of 1.2 while the control specimens had an average rating of 4. Moreover, after the eight-week test almost all termites exposed to treated specimens were dead, while the termites exposed to untreated specimens had average 55% survival. Thus, the nano metal fluoride treated wood specimens were toxic to termites leading to the observed high mortality and low rating. A preliminary analysis of the protists in the gut of the termites exposed to nano metal fluoride treated wood specimens found that the number of gut protists were lower than those exposed to untreated specimens.

Download document (129 kb)
free for the members of IRG. Available if purchased.

Purchase this document