Tannin-caprolactam and Tannin-PEG formulations as outdoor wood preservatives: weathering properties Gianluca Tondi, Jinbo Hu, Filippo Rizzo, Janez Buh, Sergej Medved, Alexander Petutschnigg, Marie-France Thevenon To cite this version: Gianluca Tondi, Jinbo Hu, Filippo Rizzo, Janez Buh, Sergej Medved, et al.. Tannin-caprolactam and Tannin-PEG formulations as outdoor wood preservatives: weathering properties. Annals of Forest Science, Springer Nature (since 2011)/EDP Science (until 2010), 2017, 74 (1), pp.19. 10.1007/s13595- 016-0605-y. hal-01710371 HAL Id: hal-01710371 https://hal.archives-ouvertes.fr/hal-01710371 Submitted on 15 Feb 2018 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Annals of Forest Science (2017) 74: 19 DOI 10.1007/s13595-016-0605-y ORIGINAL PAPER Tannin-caprolactam and Tannin-PEG formulations as outdoor wood preservatives: weathering properties Gianluca Tondi1 & Jinbo Hu2,3 & Filippo Rizzo1 & Janez Buh4 & Sergej Medved4 & Alexander Petutschnigg1 & Marie-France Thevenon3 Received: 7 August 2016 /Accepted: 21 October 2016 /Published online: 15 February 2017 # The Author(s) 2017. This article is published with open access at Springerlink.com Abstract & Context Tannin-boron wood preservatives are known for & Key message This article presents the leaching, fire and their high resistance against leaching, biological attacks, fire weathering resistance improvements of samples treated as well as for the good mechanical properties that they impart with tannin-based wood preservatives added of to wood. These properties promoted these formulations for caprolactam. PEG-added formulations show limited ap- being a candidate for the protection of green buildings. plicability. The FT-IR and 13C-NMR analyses of the However, the low elasticity of these polymers and their dark caprolactam-added formulations show some evidences of colour implied limited weathering resistances. copolymerization. & Aims The aim of the study is to find suitable additives for tannin-based formulations to overcome their limited weathering resistances, without compromising the other properties. Handling Editor: Jean-Michel Leban & Methods Treatment, leaching and fire tests, dimensional sta- Contribution of the co-authors bility as well as artificial and natural weathering of the timber Gianluca Tondi: research leader, formulation developer, publication treated with caprolactam-added and PEG-added formulations writing and data analysis were performed. FT-IR and 13C-NMR of the formulations Jinbo Hu: sample preparation and fire testing were presented. Filippo Rizzo: responsible for the weathering test and the CIELAB & system Results The presence of caprolactam improved the proper- Janez Buh: sample preparation and retention studies ties of the formulation with particularly significant results in Sergej Medved: writing terms of resistance against leaching and dimensional stability. Alexander Petutschnigg: multivariate data analysis These enhancements were imparted also to the weathering Marie-France Thevenon: research leader, publication writing and sample preparation resistance of the tannin-caprolactam formulations. Indeed, * Gianluca Tondi Marie-France Thevenon [email protected] [email protected] * Jinbo Hu [email protected] 1 Forest Product Technology and Timber Construction Department, Salzburg University of Applied Sciences, Marktstraße 136a, 5431, Filippo Rizzo Kuchl, Austria [email protected] 2 College of Material Science and Engineering, Central South University of Forestry and Technology, Shaoshan South Road, No. Janez Buh 498, Changsha 410018, China [email protected] 3 Research Unit BIOWooEB, TA B 114/16, CIRAD, Cedex 5, Sergej Medved 34398 Montpellier, France [email protected] 4 Biotechnical Faculty, Department of Wood Science and Technology, Alexander Petutschnigg University of Ljubljana, Rozna dolina, cesta VIII/34, [email protected] 1000 Ljubljana, Slovenia 19 Page 2 of 12 Annals of Forest Science (2017) 74: 19 the colour changes during the artificial and natural exposures Okuda 1998; Taylor et al. 2006; Tascioglu et al. 2012)inthe were stable for longer periods. FT-IR and 13C-NMR investi- following years. A significant breakthrough in the chemistry gations of the advanced formulations were led, and covalent of flavonoid tannins was that their condensation reactions oc- copolymerization of the caprolactam with the tannin- curred with similar extent as phenol and resorcinol (Pizzi hexamine polymer was observed. 1980; Pichelin et al. 1999), and therefore, it was possible to & Conclusion The tannin formulations with caprolactam im- oppose the long-standing leaching problem of tannin in the proved the durability of the wood specimens, while the PEG- wood preservation field and hence raise this approach to a new tannin presented strong application drawbacks. level. The technology uses the polymerization of tannins and Keywords Condensed tannin . Timber protection . CIELAB consists in infiltrating the activated oligomers of flavonoid in system . Natural copolymer . Multivariate data analysis . PCA the wood with a successive in situ polymerization catalysed by heat (Thevenon et al. 2010). This can also be obtained in the presence of an active ingredient such as boric acid. Such 1 Introduction associations allow combining the effects of both ingredients, using boric acid at a very low level and observe the restrictions In former times, universal solutions for preserving wood were on the use of boron compounds (2008/58/EC 2008), avoid used: Creosote, pentachlorophenol and then chromate-copper- boric acid leaching and increase performances and service life arsenate (CCA) were dominating the market warranting very of such treated timber (Obanda et al. 2008). long service life (Richardson 1993; Ruddick 2011). Since over Original formulations based on tannin-boric acid synergy a decade, bans and restrictions on the use of these wood preser- have shown outstanding preservation properties against bio- vatives have focused attention on technological developments of logic attack and fire and have also improved mechanical prop- alternatives in wood protection area (Evans 2003; Schultz et al. erties (Tondi et al. 2012b; Tondi et al. 2014). However, the 2007; 98/8/EC 1998; 2003/2/EC 2003; 2011/71/EU 2011). tannin-based treatment does not improve significantly the As the wood protection sector is getting under scrutiny, weathering resistance (Tondi et al. 2012c). The tannin poly- different alternative systems, mainly based on natural solu- mer indeed is rigid and dark, and these two conditions carry (i) tions, are receiving more attention (Singh and Singh 2012; to mechanical polymer cracking during the continuous dimen- Mai et al. 2004). Amongst different approaches, the addition sional changes occurring when the wood is exposed outdoors of hydrophobic substances in order to hinder the access to and (ii) to higher radical degradation due to light exposure water enhancing the durability of wood especially against (Tondi et al. 2013b). fungal agents is one of the most suited solutions. Wood pro- The idea of adding other template components to the orig- tection can be improved by the use of oil and waxes (Treu inal formulation considers two different technological ap- et al. 2004; Lesar and Humar 2011), as well as tall oil, a proaches: Firstly, an unreactive polyether such as polyethyl- secondary product of the pulp and paper industry (Hyvönen ene glycol (PEG) was added as “steric hindering” filler to et al. 2006), or pyrolysis fractions (Temiz et al. 2010;Palanti decrease the amount of cross-links in the hardened network, et al. 2011;Mazela2007). Other alternative solutions based on and secondly, a polymerizable molecule such as caprolactam, lactic acid and proteins were also studied with promising re- which can polymerize to polyamides producing protein-like sults (Nöel et al. 2009a,b;Thevenonetal.1997; Thévenon polymers, was added to actively participate to the synthesis of and Pizzi 2003; Polus-Ratajczak and Mazela 2004). Other a more linear copolymer (Pizzi 1994). Both approaches were researchers have published studies in which the hydrophobic considered to enable the polymer to become more elastic and matrix was mixed to an active biocide in order to enhance its clearer with the objective of producing high-performance protective effect (Evans et al. 2009; Temiz et al. 2008; Yang wood preservatives. Retentions, resistances against leaching et al. 2006). and fire, dimensional stability and colour changes during nat- The technology applied in this work exploits the properties ural and artificial weathering are described in this paper, and of tannins to its utmost as: On one hand, they are easily soluble preliminary FT-IR and 13C-NMR investigations on the ad- in water, and therefore, they can penetrate into wood (Tondi vanced tannin-based formulations are also presented. et al. 2013a), and on the other hand, they can polymerize in situ increasing the hydrophobicity of the wood surface