Tannin- caprolactam and Tannin- PEG formulations as outdoor wood preservatives: Biological Properties

Key Message: This article presents the enhancement in boron fixation as well as the improved biological resistance against fungi and termites for wood samples treated with tannin-caprolactam and tannin-PEG formulations. Context: Although the recently developed tannin-boron wood preservatives have shown high biological protection, they presented also average resistance against weathering. The tannin-caprolactam formulations have shown improved weathering resistances and dimensional stability. Aims: For this reason, more detailed biological tests were performed to evaluate the influence of the caprolactam and PEG on the biological resistance. Methods: In this paper, the boron leaching of the tannin-caprolactam and tannin-PEG impregnated Scots pine specimens was observed and the biocidal effect against fungi (Antrodia spp. and Coniophora puteana) and insects (Reticulitermes flavipes and Hylotrupes bajulus) were determined according to the guidelines of EN 113, EN 117, and EN 47. Results: The advanced formulations containing PEG have shown interesting resistance against fungal decay, but very low penetration and weak resistance against larvae while the tannin-caprolactam preservatives have shown overall improved biological performances and higher boron fixations. Conclusion: The biocidal activity of the caprolactam-added formulations was overall enhanced and therefore these formulations are confirmed to be an interesting alternative for the wood preservation in outdoor environment. (Résumé d'auteur

Tannin- caprolactam and Tannin- PEG formulations as outdoor wood preservatives: Weathering properties

International audienceAbstractKey messageThis article presents the leaching, fire and weathering resistance improvements of samples treated with tannin-based wood preservatives added of caprolactam. PEG-added formulations show limited applicability. The FT-IR and13C-NMR analyses of the caprolactam-added formulations show some evidences of copolymerization.ContextTannin-boron wood preservatives are known for their high resistance against leaching, biological attacks, fire as well as for the good mechanical properties that they impart to wood. These properties promoted these formulations for being a candidate for the protection of green buildings. However, the low elasticity of these polymers and their dark colour implied limited weathering resistances.AimsThe aim of the study is to find suitable additives for tannin-based formulations to overcome their limited weathering resistances, without compromising the other properties.MethodsTreatment, leaching and fire tests, dimensional stability as well as artificial and natural weathering of the timber treated with caprolactam-added and PEG-added formulations were performed. FT-IR and 13C-NMR of the formulations were presented.ResultsThe presence of caprolactam improved the properties of the formulation with particularly significant results in terms of resistance against leaching and dimensional stability. These enhancements were imparted also to the weathering resistance of the tannin-caprolactam formulations. Indeed, the colour changes during the artificial and natural exposures were stable for longer periods. FT-IR and 13C-NMR investigations of the advanced formulations were led, and covalent copolymerization of the caprolactam with the tannin-hexamine polymer was observed.ConclusionThe tannin formulations with caprolactam improved the durability of the wood specimens, while the PEG-tannin presented strong application drawbacks

Heat treatment of poplar plywood: modifications in physical, mechanical and durability properties

Plywood made of poplar are limited to indoor usages since poplar exhibits a rather low natural durability. Recently, wood heat treatments have been applied to improve properties such as decay susceptibility and dimensional stability. This study examines the potential of exposing poplar plywood to heat treatment to extend the potential of applications of this engineered wood product to outdoor end uses, and new markets accordingly. Plywood panels were glued with two different adhesive formulations based on the same melamine-urea-formaldehyde (MUF) resin to compare their respective ability to resist to the heat treatment. These different plywoods were thermally modified in saturated steam conditions at 215 °C for 2 hours following the ThermoWood® process, up to reach 14% in mass loss. The durability improvement brought by the heat treatment was assessed in order to evaluate any possible outdoor uses for such plywood. After all the conducted analyses, the potential to use heat treated poplar plywoods in humid interior and protected exterior service conditions was confirmed.ANR-10-EQPX-16 XYLOFOREST laboratoire Mixte Public/privé qui associe les Arts et Métiers (campus de Cluny) et l’entreprise Brugèr

Advanced tannin based wood preservatives

Protecting timber with natural products is one of the most significant challenge in wood technology since decades, but recently also the political institutions show the need for this challenge to be win. Tannin-based wood preservatives were studied for a long time (Laks et al. 1988), but only combining the knowledge in tannin chemistry developed in more recent years (Pichelin et al. 1999) it was possible to produce tannin-based formulations that enabled to fix in the timber structure resisting Jeaching (Thevenon et al. 2009). The first generation of water resistant tannin-based wood preservative presented very good mechanical properties, enhancement of fire resistance and also outstanding biocide properties (Tondi et al. 2012). Unforlunately, the weathering tests underlined the limit of these innovative formulations: On the one hand the dark color of the treated sample brings to higher absorption of UV-light with the consequence of breaking down the tannin polymer and on the other hand the rigid tannin polymer did not resist the continuous dimensional changes of wood (Tondi et al. 2013). With this work we would like to present a second generation of tannin wood preservative in which the effect of polyethylene glycol and caprolactam have been studied. The latter have been added to the tannin-based formulation in order to increase the elasticity of the tannin polymer whether with a blend or with a real copolymer. The results of these tests have shown a considerable improvement of the properties of the sample treated with tannin-caprolactam solution especially in terms of resistance against water and biological attacks. Some improvements have been registered also for the dimensional stability and for the weathering even if these enhancements do not solve the problem completely yet

Impregnation of Scots pine and beech with tannin solutions: effect of viscosity and wood anatomy in wood infiltration

none6mixedTondi G; Thevenon MF; Mies B; Standfest G; Petutschnigg A; Wieland STondi, G; Thevenon, Mf; Mies, B; Standfest, G; Petutschnigg, A; Wieland,

Heat treatment of poplar plywood: modifications in physical, mechanical and durability properties

International audiencePlywood made of poplar are limited to indoor usages since poplar exhibits a rather low natural durability. Recently, wood heat treatments have been applied to improve properties such as decay susceptibility and dimensional stability. This study examines the potential of exposing poplar plywood to heat treatment to extend the potential of applications of this engineered wood product to outdoor end uses, and new markets accordingly. Plywood panels were glued with two different adhesive formulations based on the same melamine-urea-formaldehyde (MUF) resin to compare their respective ability to resist to the heat treatment. These different plywoods were thermally modified in saturated steam conditions at 215 °C for 2 hours following the ThermoWood® process, up to reach 14% in mass loss. The durability improvement brought by the heat treatment was assessed in order to evaluate any possible outdoor uses for such plywood. After all the conducted analyses, the potential to use heat treated poplar plywoods in humid interior and protected exterior service conditions was confirmed