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    Hybrid Approach for Wood Modification: Characterization and Evaluation of Weathering Resistance of Coatings on Acetylated Wood

    Year: 2021

    Journal: Coatings, Volume 11, JUN

    Authors: Sandak, Anna; Foldvari-Nagy, Edit; Poohphajai, Faksawat; Diaz, Rene Herrera; Gordobil, Oihana; Sajincic, Nezka; Ponnuchamy, Veerapandian; Sandak, Jakub

    Organizations: European Commission (Horizon2020 Widespread-2-Teaming program) [739574]; Republic of Slovenia (European Regional Development Fund); infrastructural ARRS program [IO-0035]; MIUR-Italy [RBSI14Y7Y4]; ARRS-Slovenia [BI-IT/18-20-007, BI/US-20-054, BI-AT/20-21-014, J7-9404]; umbrella of ERA-NET Cofund ForestValue by the Ministry of Education, Science and Sport of the Republic of Slovenia [773324]; European Union's Horizon 2020 research and innovation programme

    Keywords: wood modification; natural weathering; acetylation; coatings; service life performance; aesthetic

    Wood, as a biological material, is sensitive to environmental conditions and microorganisms; therefore, wood products require protective measures to extend their service life in outdoor applications. Several modification processes are available for the improvement of wood properties, including commercially available solutions. Among the chemical treatments, acetylation by acetic anhydride is one of the most effective methods to induce chemical changes in the constitutive polymers at the cellular wall level. Acetylation reduces wood shrinkage-swelling, increases its durability against biotic agents, improves UV resistance and reduces surface erosion. However, even if the expected service life for external cladding of acetylated wood is estimated to be 60 years, the aesthetics change rapidly during the first years of exposure. Hybrid, or fusion, modification includes processes where the positive effect of a single treatment can be multiplied by merging with additional follow-up modifications. This report presents results of the performance tests of wood samples that, besides the modification by means of acetylation, were additionally protected with seven commercially available coatings. Natural weathering was conducted in Northern Italy for 15 months. Samples were characterized with numerous instruments by measuring samples collected from the stand every three months. Superior performance was observed on samples that merged both treatments. It is due to the combined effect of the wood acetylation and surface coating. Limited shrinkage/swelling of the bulk substrate due to chemical treatment substantially reduced stresses of the coating film. Hybrid process, compared to sole acetylation of wood, assured superior visual performance of the wood surface by preserving its original appearance.
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