1. Introduction

The use Wof wood in buildings should be promoted when it is possible, as it is a bio-based material with great properties and aesthetics. Other materials, such as steel and concrete, are sometimes preferred to wood as they are considered mored used outdoors is exposed to many sources of degradation. Each of these sources (UV, moisture, decay fungi, wind, dust, etc.) bring their own contribution to the degradation, but they can also interact together [1,2]. dMoisturable. It is however possible to efficiently protecte is one of the most important agents of wood from decay and damages with simple treatments.

Wood protectdegradation, as it provokes dimensional could mainly be separated in two broad and complementary categories: impregnation treatments and coatings. Impregnationhanges, allows the growth of decay fungi and molds, promotes the leaching of wood treatments are used to penetrate wood cavities with hydrophobic and/or biocidalnd water-soluble wood compounds and improve its durability against insects, decay fungi, molds and, and so forth. After an extended period, the dimensional changes ^{[1][2][3][4][5][6]}. Some reactwivell chemicals, like acetic anhydride and formaldehyde, can also be used to modify the chemical nature of the cell wallmake the wood warp, crack, and lose its coating, exposing unprotected wood to environmental hazards and improve their propertieshastening its degradation ^[7][8][3,4].

Unlike Wwood impregnationused indoor, where humidity is usually relies on pressure and vacuum methods to allow for a rapid and deep penetration of the treatmentslower and more effectively controlled, wood exposed outdoor is subject to a vast range ^[9][10].of Cmoatings can be very diverse, from penetrating oils to film-forming alkyds and acrylicsisture conditions (dry periods, wet periods, rain, snow) ^[11][5]. Theyse can prevent the weathering from abiotic elements (wind, sand, rainvariations in humidity are the source of the dimensional changes, etc), decrease the exchanges ofy influence the moisture, and block the UV rays from the sun with pigment content of the wood, which shrinks and UV absorbersswells accordingly ^{[12][13][14][15]}[3]. ThIn orde natural look of ther to reduce its degradation, wood surface can be preservemust therefore be treated with clear coatings, or altered to hidden with increasing amount of pigments.

An preservatives and good building designs must be encouraqugeousd [5]. iImpregnation treatment was recently developed to allow for the impregnation of wood through diffusion after a simple dipping, preventing the need for pressure and vacuum ^[16]. Is with different resins (phenolic, amino, silane, acrylic) can mitigate the intake of liquid wat uses the abilities of tertiary amine oxides to diffuse into the wood and solubilize organic compounds, like biocides, to protectr, but protection against air moisture is mainly achieved through wood from biodegradation and dimensional changesmodification (acetylation, esterification, thermal treatments, etc.) ^[17][18][6,7,8,9,10]. IWhen a previous paper, we showed that this treatment could nearly inhibit the fungal degradation bymoisture content above 20% is reached, decay fungi can develop Rhodonia placenta and dfecrease the dimensionalast on the wood cell materials, changes in eastern white pine (Pinus strobus L) ing its mechanical and wchite spruce (Picea glauca Memical propench (Voss)) by 29% and 24%, respectively, whilerties [11]. barelyA increasing their dengreat diversity ^[19].of Iorgan another paper, we determined that the treatment did improve the penetric and inorganic biocides can be impregnated to prevent the biodegradation of thefrom decay fungicides, but only longitudinally. Meanwhile, the antiseptic amine oxides could penetrate perpendicularly to the grain, granting fungal protection below the surface. We also found that the treatment allowed to and mold, such as triazoles, copper oxides and carbonates, borates, and quaternary compounds [12,13,14]. iImpregnate enough fungicide to respect the EN standards, even after 2 weeks of leaching by immersionion treatments are often carried out ^[20].

Iin authis paper, we brought the treatment one step further by adding acrylic resins to its composition. It allowed for both the impregnation and the coating of wood in a single step. After characterizingoclaves, where methods employing vacuum and/or pressure can be used to ease the treatment solutions and the dry films, we testeds into the wood structure [15,16].

To the adhesion of the films, their permeability to water and air moisture, and the impregnation depth of an indigo blue dye (Fig. 1). The adhesion andffectively protect the surface of wood, diverse coatings can be used. They can be water permeability tests were combined with artificial aging. The main results are summarized in the next section and discussed in further details in the paperborne or solvent borne, usually contain an alkyd or acrylic resin, and have different levels of transparency [5,17,18].

Figure 1. Experimental procedure of the study

2. Main results

2.1. Properties of the treatments

They treatment solutions were prepared using a factorial design with acrylic resins and amine oxides (AO)  conditions as the factors. They would contain no resin (R0) or one of three commercial resins (R1, R2, R3), and either no amine (AO0), only dimethyldodecylamine oxide (DDAO)(AO1), or a mix of DDAO and dimethylhcan also contain various nanocomponents, such as nanoparticles, nanoclays and nanoxides, to improve their properties (resistance to weathering and decay, hydrophobicity, UV absorption, fire-proofing, etc.) [19,20,21]. Bexadecalmine oxide (DHAO)(AO2).

We use ofound that both the amine oxides and the acrylic resins increased the viscosity of the treatment solutions. Consequentlye increasingly strict legislations surrounding vocs (volatile organic compounds), the dry films of the treatments containing amine oxides were also thicker. The amine oxides usually led to a faster drying time and ause of solvent-based coatings is decreasing to prioritize waterborne formulations [22]. lowTher Tg, particularly for AO2.

Table 1. latter are much Prmoperties of the treatment solutions (at 65 ^oC) and of re permeable, but have betthe dry coatings.

*Theser aging properties are providend by the supplier of the acrylica higher flexibility [23,24,25]. reThisin las

2.2. Permeability to water

The permeability to water of the treatments was studied by comparing the mass of water absorbed by treated and untreated samples after 30 minutes of soaking ^[21]. The water repellent efficiency (WRE) was calculated with eq. 1:

WRE (%) = 100 x ((M_ua - M_ub) - (M_ta - M_tb))/(M_ua - M_ub)

where M_ua and M_ub represent the mass (in grams) of untreated samples after and before soaking, and M_ta and M_tb the mass (in grams) of treated samples after and before soaking, respectively. The samples for this test were either unaged or aged for 14 cycles (Table 2).

Table 2.t Cponditions of one cycle of artificial aging.

The results showed that the amine oxides reduced the permeability to water of uncoated samples (R0-AO1 and R0-AO2), but increased the permeability of the coated ones. It was attributed to the amine oxides being less hydrophilic than the wood cells, but more than the acrylic resins. In both scenarios, the treatments with DHAO (AO2) were less hydrophilic. All three resins reduced significantly the permeability to water of white spruce before aging. They however did not perform well after aging as the samples were cracked, which greatly increased the absorption of water. This cracking was attributed to the freezing of trapped water into the wood during the aging cycles.

Figure 2. Water repellent efficiency (WRE) of the white spruce before and after artificial aging.

Figure 3. Water repellent efficiency (WRE) of the white pine before and after artificial aging.

In the case of white pine, R2 and R3 did not perform well before aging, which would be caused by an insufficient protection of the latewood (Fig. 4). The WRE of these samples however increased by a large margin after artificial aging, as the resins still managed to prevent these samples from cracking during the aging process.

Figure 4.int is crucial, as it Optical microscopy of the transverse plane of white spruce and white pine treated with R1-AO1 and R2-AO1. The arrows indicate the presence of resin at the surface of the latewood.

2.3. Permeability to moisture

The permeability to moisture was investigated with sorption isotherms. It was observed that, for uncoated samples, the absorption of moisture was greater and faster than for untreated samples. It was attributed to the ability of amine oxides to make hydrogen bonds with water, which added many sites into the wood for water adsorption ^[22]. The resins did not seem to reduce the absorption of water. Conversely, their EMC was much higher than the uncoated samples, suggesting that the coatings absorbed a lot of moisture. On the other hand, they did slow down the uptake of moisture.

Figure 5. Equilibriumlows them to follow the dimensional changes of wood mowisture content (EMC)thout failing [26]. ofAlkyd the samples (left) resins leand time elapsed after reaching the equilibrium (right) o a better wetting and at the different steps during the sorpdeeper penetration isotherms in white pine.

Figure 6. Eqnto the wood suilibrium moisture content (EMC) of the samples (left) astrate than acrylic resinds, time elapsed after reaching the equilibrium (right) at which increases their mechanical anchoring and improves the different steps during the sorption isotherms in white spruce.

2.4. Adhesion

The adhesion of the acrylic resins was tested with pull-off tests using 20 mm dollies glued to their surface. The samples used for this test were artificially aged for 0, 1, 7, or 14 cycles (Table 2).

Although the adhesion was quite low for all the treatments, the fracture occurred at the wood/coating interface for all the treatments, except some aged R2-AO1 pine samples and some unaged R2-AO2 spruce samples. It was found that the amine oxides decreased the adhesion of the coatings, particularly for AO2, which would result from a lower Tg. The artificial aging improved the adhesion of the coatings after the first cycle, as water soluble compounds were lost. The adhesion remained higher up to the seventh cycles, but then decreased as the bounds between the wood and the coatings began to break.

Figure 7.r adhesion. However, acrylics are more Tflensile strength required to pull-off the dollies from white pine (left) and white spruce (right)

2.5. Impregnation depth

The impregnation depth of organic fungicides was estimated with an indigo blue dye. To do this, cubic samples were treated with solutions containing the dye. These samples were then sawn open and the penetration of the indigo was measured with an optical microscope.

The penetration of the indigo dye was only observed longitudinally. In the case of the white pine, the less viscous solutions, primarily those without any resin, penetrated slightly into the earlywood and deeper into the more permeable latewood. However, as a result of the greater capillary forces, the white spruce samples, as well as the pine samples treated with solutions containing a resin, were only impregnated in the earlywood. The impregnation depth was usually inversely proportional to the viscosity of the treatment solution.

Figure 9. Impregnxible, lose less flexibility while aging, and allow better exchation depth of the indigo dye in the white pine (earlywood and latewood) and the earlywood of the white spruceges of moisture, which makes them overall more durable [27,28].

3. Conclusion

After treating wood samples with solutions combining a buffered amine oxide impregnation system and acrylic resins, the following statements could be made:

• The combination of the two parts of the treatments successfully allowed both the coating and the impregnation of wood in a single step.

• The two parts of the treatments affected the properties of the treatment solutions and of the dry films.

• The impregnation system usually led to a loss of adhesion of the coatings.

• The impregnation system slightly increased the permeability to water of the coatings.

• The impregnation system did not impair the impermeability to moisture of the coatings.

• The acrylic resins decreased the impregnation depth as a result of the higher viscosity of the solutions.

Accordingly, it was established that the practical side of the addition of an acrylic resin to an impregnation treatment would be paid with some performances. While much work should be done to optimize the treatment and lessen this side-effect, it can still be useful in specific situations, like sidings protected from the rain, which are not affected too much by the adhesion and water permeability of the coating. Adding more layers of coating could also help to improve the overall performances and durability of the coating.