Sitting on the deck to drink your morning cup of coffee is a great way to start the day—but not when your deck is rotting. Fortunately wood products are protected with wood preservatives, often with chromate copper arsenate (CCA) . But growing concerns over the safety and health effects of CCA as a wood treatment have led to the development of organic biocides—substances that protect against biological infestation—such as tebuconazole.
Xiaochu Ding, a researcher at Michigan Technological University in Michigan, USA and colleagues published a new process using nanoparticles to deliver organic biocides into wood.
Wood can be treated with just a solution of tebuconzole, but retention of the biocide is poor and the majority of it is leached out over time. Biocide leaching leaves wood less-protected from biological attacks and can have detrimental environmental effects. By incorporating the biocide into nanoparticles, the team was able control the release of biocide and reduce the amount leached.
The nanoparticles—about 150 nanometers in diameter—consist of chitosan, methyl methacrylate (MMA) and tebuconazole combined together. Chitosan is a polymer derived from chitin, a structural material found in the exoskeleton of some crustaceans, insects, and micro-organisms. Crab and shrimp shells are the most common source of this natural polymer . Methyl methacrylate is water-hating organic compound, used to form the transparent plastic poly(methyl methacrylate).
What’s special about these nanoparticles is that they are amphiphilic, mean they have both water-loving and water-hating areas. The amphiphilic design allows the water-hating core (MMA) to control the release rate, while the water-loving shell (chitosan) forms a stable suspension in water.
The team reported the nanoparticle-treated wood was effectively protected from decay against a brown rot fungus (G. trabeum). More importantly, the nanoparticle-treated wood only leached 9% of the biocide, significantly less that treatment with the biocide solution alone.
Ding, X., Richter, D., Matuana, L., & Heiden, P. (2011). Efficient one-pot synthesis and loading of self-assembled amphiphilic chitosan nanoparticles for low-leaching wood preservation Carbohydrate Polymers, 86 (1), 58-64 DOI: 10.1016/j.carbpol.2011.04.002