Final Report: Environmentally Safe Wood PreservativesEPA Contract Number: EPD04046
Title: Environmentally Safe Wood Preservatives
Investigators: Stockel, Richard F.
Small Business: Princeton Trade and Technology Inc.
EPA Contact: Manager, SBIR Program
Project Period: March 1, 2004 through August 31, 2004
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2004) RFA Text | Recipients Lists
Research Category: Nanotechnology , SBIR - Nanotechnology , Small Business Innovation Research (SBIR)
The goal of this research project was to develop a novel class of environmentally safe wood preservatives using known fungicidal agents already approved by the U.S. Environmental Protection Agency (EPA) and/or the U.S. Food and Drug Administration. Princeton Trade & Technology, Inc., doing business as Novaflux Technologies, developed a technology that relies on forming nanostructured complexes in which the members of the complex are based on EPA-approved biocides. The components of the complex are selected to have complementary biological activity necessary to prevent wood decay over a prolonged period of time. Selecting the most effective complexes has been the primary aim of this study.
The novel technology developed in Phase I is based on using a new class of safe wood preservatives that use existing EPA-approved biocides. The wood preservatives are completely organic and therefore environmentally friendly, in contrast with wood preservatives manufactured prior to December 31, 2003, which contain the toxic heavy metal agent chromated copper arsenate, and current products containing copper such as copper-quat or copper-azoles. This innovative technology is applicable for use in construction repair and wood materials used for residential structural applications.
Novaflux Technologies’ main innovation relies on making novel nanostructure complexes and using them as effective wood preservatives. The chemical forces that hold these complexes together include a combination of electrostatic and hydrophobic bonding. The balance between the two types of forces may be tailored by selecting the member compounds for building the complexes. The latter are normally selected from EPA-approved substances and the final materials are free of heavy metals. The complexes formed may bear a net charge, either anionic or cationic, but are mostly neutral, and are tailored to possess broad-spectrum functions, including fungicidal, bactericidal, as well as ultraviolet and weathering protection. Notably, the proposed complexes can be made to be water repellant as well.
The first task of the study involved the development of methods to form the nanostructure complexes. Entirely green chemistry methods have been developed to make the complexes in the aqueous environment. Although the complexes made could be used to treat wood as nano-emulsions, Novaflux Technologies decided to test them in a simple vehicle to avoid complications in interpreting the data. More than 20 complexes were successfully made and evaluated for leaching and wood decay performance. All complexes and controls were evaluated for decay using the standard soil block test. Aggressive brown-rot fungus Gloeophyllum trabeum was the choice organism in this screening study.
Leaching studies indicated that computing the amount of complex leached or retained in wood samples using weight measurement as a basis does not produce accurate results. This is complicated by the fact that untreated wood itself suffers weight loss when subjected to the standard leaching procedure. To overcome these difficulties, methods to apply a correction factor have been devised based on the weight loss of untreated wood samples and using direct elemental analysis of the wood samples to accurately assess the leaching profile of candidate preservatives used in the study. When such methodology was employed, the generated data showed that the complexes could be successfully incorporated into wood. For the purposes of this research project, all wood samples were treated at a concentration of 1 percent in a simple vehicle.
This development work has been successful in defining promising cation-anion complexes for more comprehensive development during Phase II. Approximately 6 candidate combination complexes were selected from more than 20 original possibilities. The candidate anions and cations are known as active preservatives by themselves and are registered as environmentally safe compounds. Because the complexes are based on simple electrostatic precipitation/bonding, EPA registration is expected to be straightforward and fast. New discoveries made during this research project are expected to increase the technical feasibility of developing a new class of safe wood preservatives. These include:
- Binary and ternary complexes could be made to supply broad-spectrum biological and other wood preservative functions. Stoichiometric ratios can be adjusted to deliver the required functionability.
- The complexes to be developed are expected to function as “sustained release” agents that could preserve wood for prolonged periods of time against decay. Such functions can be adjusted by selecting agents with specific stability/dissociation constants.
- The leaching properties of the complexes can be tailored by selecting their composition and stability in wood structures.
The stability constant of the complexes appears to be a critical parameter controlling both leaching properties and bioavailability in wood structure. Several complexes formed between known fungicidal anions and cations showed no activity against fungal decay by G. trabeum. Novaflux Technologies believes that such complexes may possess high stability constants that retard the dissociation and bioavailability of the complexes, thus diminishing their function as effective wood preservatives. Means to design the complexes have been developed such that they would possess sufficient dissociation constants in wood samples, and thus could effectively function as sustained-release wood preservatives. This new innovation will be further used to develop the selected candidate complexes during Phase II.