ls nanotechnologythe next front in wood preserving?

L.TorrNc rHE PoPULARTTy of wood I \ pressure treated with micronized wood preservatives, researchers are experimenting with even smaller "nanotech" particles, to further prevent leaching.

A team of Michigan Technological University scientists is preparing to reveal their findings, following a fiveyear study of nanotechnology in wood preservation.

"It's a new method that uses nanoparticles to deliver preservatives into the lumber," said chemistry professor Patricia Heiden. "In our experiments, it reduced the leaching of biocidesby 90Vo;'

The nanoparticles are tiny spheres of gelatin or chitosan (a material found in the shells of shrimp and other shellfish) chemically modified to surround the fungicide tebuconazole. The little spheres require no special handling.

"You just pressure-treat the wood in the usual wav." Heiden said. "We used tebuconazole as an organic preservative-donated by Lanxess Corp., Pittsburgh, Pa.-and copper oxide nanoparticles we made ourselves as an inorganic preservative. Our main goal was to study how we could reduce the leaching."

The initial tests show that nanoparticle-treated wood is just as resistant to rot and insects as conventionally treated lumber. The researchers have now moved their tests from the confines of MTU to the warm, wet weather of Hawaii. "Most of the work is already done, but we are testing a few other things out of curiosity," Heiden said.

The research is funded by the U.S. Environmental Protection Agency, under the program name

"Environmentally Benign

Manufacturing & Processing 2005GO-AI." The preliminary study was completed last year and one group of findings has been published so far, with several more in the offing.

The researchers had completed similar studies before, using petroleum-based components and dilute conditions. "We used gelatin and chitosan (biopolymers) and methyl methacrylate (MMA, which is petroleum based and is used to make plexiglass),"

Heiden explained. "We made the nanoparticle in water by a simple combination of gelatin or chitosan with methyl methacrylate, an initiator, and the tebuconazole biocide and heated for a few hours. We then isolated the nanoparticles or diluted to the appropriate volume to treat the wood. We found that these nanoparticles reduced the leaching by 90Vo or so, and were effective in soil jar studies. We have treated field stakes to make sure we could penetrate wood completely, but did not do field studres.

MTU scientists initially tried to use some commercial copper-based preservative systems, according to Heiden, "but they were highly formulated and we did not always know with what, so we made a simple 'inhouse' ACQ system and also a simple copper oxide nanoparticle, made in a solution method rather than by any sort of a mechanical reduction system of copper carbonate." She found the results "rather surprising," saying that the nature of the copper oxide surfaces influenced how much the nanoparticles leached and promising to share further information in the coming months.

Here's what she can divulge: "The organic nanoparticles definitely reduce leaching of organic biocide, and the reduction is substantial compared to a straight solution or emulsion treatment of organic biocide, even without the use of a surfactant. In our work, we found that the use of a chitosan shell did not reduce the leaching of copper oxide nanoparticles."

John Lounsbury, managing editor and co-founder of Global Economic Intersection, speculates that the new technology could result in preservatives that are both more effective and more affordable. Current preservatives for residential use, says Lounsbury, "are much more expensive than the older most common compound used before 2004 (CCA), so manufacturers try to use less of it. That leads to at least 12 different grades of treated wood product today and makes choosing the correct wood for each application a process that requires greater care."

So while he optimistically has his "fingers crossed" about the viability of nanotechnology, questions remain: "How expensive is the nanotech process?" he asks. "Does the reduced leaching mean that much less of the expensive treatment chemicals can be used? And, can nanotech processing mean that more toxic chemicals that have been phased out-or never

By Carla Waldemar