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Impregnation of Wood Products Past, Present and Future Work
Published in Tatjana Stevanovic, Chemistry of Lignocellulosics: Current Trends, 2018
Diane Schorr, Stéphanie Sabrina Vanslambrouck, Véronic Landry
Oils and waxes are commercially used in water repellent finishes and wood preservatives. Literature also reports their use to impregnate wood substrates by using thermal treatment (oil and waxes at high temperatures to decrease their viscosity) and vacuum-pressure processes. Although these processes are not new, a renewed interest is to be expected as they used bio-based products, which are mostly safe and easy to use. The resulted densified wood has improved properties such as dimensional stability (Wang et al. 2015), photodegradation (Lesar et al. 2011a) and even improved mechanical properties (Kakavas et al. 2014). Due to environmental concerns, natural oils such as vegetable oil (soybean oil, linseed oil) or even waxes, such as beeswax, Carnauba wax, Montan wax (obtained by solvent extraction of certain types of lignite or brown coal), are preferred. Fadl and Basta (2005) modified the wood by vapor phase acetylation or by swelling phase acetylation before impregnating it with novolac resin and linseed oil. They observed that using the vapor phase acetylation before impregnation led to higher dimensional stability compared to the liquid phase acetylation. However, liquid phase acetylation improved the impregnation process of resins and oils compared to the vapor phase acetylation. They observed that increasing the curing time and the impregnation temperature with linseed oil improved water repellency and dimensional stability of the wood contrary to the impregnation with novolac resin where these properties decreased. Neither the novolac resin nor the linseed oil led to covalent bonds with the wood cell walls, however both formed hygroscopic insoluble polymer. Awoyemi et al. (2009) studied the curing treatment of the wood in oil with and without cooling time after oil treatment. They showed that the wettability, the water uptake and the swelling properties decreased with a better retention caused by the addition of the process in oil cooling. The authors explained these results by a better oil impregnation during the cooling process. To improve other properties such as decay resistance, some additional products can be mixed with the wax such as boron compounds to limit the moisture content and the wood sorption wood. As a result, mold and fungi growth was decreased (Lesar et al. 2011b).
Chemical modification of montan resin by peracetic acid and agricultural application of its modified products
Published in Journal of the Air & Waste Management Association, 2020
Hui-Fen Zhang, Hao Qin, Bao-Cai Li, Yi Qin, Huan-Hong Wang, Bing Zhang, Mi Zhang
Lignite is a kind of coal with a low degree of coalification and a high content of moisture (Dong, Yun, and Cao 2008). Recently, with the development of many upgrading technologies, including gasification, liquefaction, pyrolysis, and preparation of lignite-based products (Cao 2015; Dosodia et al. 2009; Gao et al. 2019; Mathur, Majumder, and Chatterjee 2007; Pande and Sharma 2002; Sharma and Dhawan 2018; Sharma and Giri 1994; Wang et al. 2019; Zhao, Wang, and Liu 2007), utilization of lignite by a clean and efficient way, instead of its combustion directly as a fuel, has been preferred by many countries and their governments. Montan wax is a chemical product extracted from lignite. Due to the wide application and good performance, it has been the higher valuable product than other lignite-based chemical products, especially refined montan wax. Technically, the crude montan wax was prepared from lignite by direct extraction using organic solvent and contained a high content of montan resin. After removal of montan resin, it could be prepared into deresination montan wax, which could be further oxidized into refined montan wax by bleaching step. Deresination and refined montan wax are two main wax products in the market, which are widely used in aerospace, metallurgy, packaging, printing, and paper-making industries, etc. However, the deresination and refinement processes are accompanied by the production of a large amount of montan resin (MR).
The effect of microorganisms on the biomodification of montan resin from lignite
Published in Journal of the Air & Waste Management Association, 2021
Yi Qin, Huan-Hong Wang, Hui-Fen Zhang, Wei-Feng Dai, Shi-Yun Jiao, Bao-Cai Li, Mi Zhang
Refined montan wax is an important coal-based chemical product that has been widely used because of its high performance for precision casting, spaceflight, and aero aviation (Zhang et al. 2016). The removal of montan resin (MR) from crude wax is a central step in the production of refined montan wax (Guo et al. 2014; Huang et al. 2017). The average MR content in crude montan wax extracted directly from lignite is generally 26%, and more than 20 tons of MR are recovered from every one hundred tons of crude montan wax (Li 1982). MR is an industrial by-product that has not been reused in any field to date.