Lignin–Propiconazole Nanocapsules are an Effective Bio-Based Wood Preservative

In the modern forest industry, the need for bio-based, renewable, and environmentally-benign wood preservatives is increasing. The world harvests approximately 1700 million m3 of wood annually for use in a variety of applications. Unfortunately, when exposed to moisture, wood products are at high risk of decay by wood degrading fungi. Preservatives are used to prevent or limit decay, and there has been an increasing interest in developing wood preservatives from renewable materials. For this work, the effectiveness of water-dispersible, double-shell, lignin nanocapsules encapsulating the fungicide propiconazole, as a sustainable wood preservative, was evaluated. The system was tested for its biocidal efficacy against brown rot decay by Gloeophyllum trabeum in southern yellow pine wood using both dip and pressure treatments. The preservative successfully penetrated the wood block during pressure treatment, and following 3 months of soil-jar incubation, only wood blocks pressure-treated with either the double-shelled-propiconazole nanocapsule system or the conventional exterior wood preservative, chromated copper arsenate (CCA), showed less weight loss (19.95 ± 2.05 and 16.40 ± 3.80%, respectively) compared to the control (41.58 ± 9.51%). Additionally, the novel preservative system exhibited enhanced antifungal resistance compared to its individual constituents, as confirmed with Kirby–Bauer disk diffusion tests. The double-shell lignin nanocapsule exhibited radical quenching activity against DPPH of 75.9 ± 4.2%, and this could have contributed to the enhanced antifungal activity of the double-shell lignin nanocapsule–propiconazole system. This novel preservative system can be considered as a potential bio-based antifungal wood preservative.