Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion

Abstract

Nonbiocidal techniques for wood protection have become more and more important in the last few years. One of the possible treatments to enhance wood durability is use of water repellents. In this research, the influence of one of the possible water repellents, the montan wax emulsion, on the moisturizing and the sorption characteristics of impregnated wood was investigated. To achieve a better protection against wood decay fungi, wood was impregnated with montan wax emulsion enriched with boric acid. The equilibrium moisture content (MC) was monitored during the adsorption and the desorption processes at five levels of relative air humidity (RH 1 ¼ 20%, RH 2 ¼ 33%, RH 3 ¼ 65%, RH 4 ¼ 88%, and RH 5 ¼ 98%). Water repellence efficiency was monitored in the chamber with high RH (87%) and during dipping in the water. Impregnated samples were also exposed outdoors in a covered position for 5 months to determine MC changes according to changes in outdoor humidity and temperature. The results showed that the sorption properties of the impregnated wood are strongly related to retention of preservative solutions after impregnation and its composition. Montan wax reduced equilibrium MC of the impregnated wood up to 25% (relatively), whereas specimens impregnated with combination of montan wax and boric acid resulted in decreased MC in some cases and in increased MC in some cases. The Guggenheim-Andersen-deBoer model of sorption isotherms was fitted to experimental data to explain the sorption mechanisms.

Influence of Artificial and Natural Weathering on the Hydrophobicity and Surface Properties of Wood

“…Furthermore, thermally modified wood treated with wax (PaTmWa) showed fairly low changes after being subjected to the most severe aging method (OutDW), with a ΔΕ of only 4.0. The positive effect of waxes on photo degradation has been reported (Lesar et al 2011a), and it is mainly explained by the fact that waxes absorb part of the UV spectra and that waxes limit quinone leaching because of the reduced MC of wood. Zlahtic and Humar (2016).…”

“…In order to upgrade the wood properties (durability, hydrophobicity), wood samples (Table 1) were treated with various solutions including (1) a 10% natural wax suspension mixed with distilled water (Lesar et al 2011a); (2) tung oil (Humar and Lesar 2013); and (3) commercial copper-ethanolamine formulation (CuEA) (Silvanolin, Silvaprodukt), which contains five ingredients: copper(II) hydroxide, ethanolamine, quaternary ammonium compound, octanoic acid, and boric acid (Humar and Lesar 2008). The concentration of active ingredients and consequent retention conformed to the Class 3 requirements (above ground and uncovered (EN 335 2013)).…”

Dimensional Stabilization of Wood

“…Paraffin wax [59] was used as a water repellent, which decreased the hygroscopicity level of beech. The equilibrium moisture content of wood impregnated with montan wax reduced by up to 25 %, while treatment with a mixture of montan wax and boric acid did not exhibit consistent results for different compositions [55]. Bleached soft wood pulp treated with various concentrations of paraffin and microcrystalline petroleum waxes resulted in an increase in water resistance [52].…”

“…Because of their hydrophobic properties, waxes are widely used in the coating industry as water repellents for wood surfaces and paper materials [25, 51••, 52, 53]. Their use as woodmodifying agents also improves dimensional stability, weathering durability, white-rot and brown-rot fungi resistance, and mechanical properties [54][55][56][57]. Wax treatment physically fills the large cell lumens to slow the sorption rate of moisture.…”

Thermal modification of Southern pine combined with wax emulsion preimpregnation: effect on hydrophobicity and dimensional stability

“…Wax emulsion found already wide industrial applications for the improvement of water repellency of wood (Lesar et al 2011a). For instance, 2.5% wax emulsion was reported to decrease the water absorption significantly (Evans et al 2009).…”