The finishing quality of wood products depends on the material's surface and its intrinsic properties. Dynamic wettability is a simple and efficient way to understand the behavior of materials related to solidliquid interactions according to theoretical and practical perspectives. Thus, we sought to investigate the wettability of Imbuia (Ocotea spp.), Red oak (Quercus spp.), and Pine (Pinus elliottii) woods and its effects before and after sanding. Through the sessile drop technique, we evaluated contact angle and work of adhesion. Sanding changed the samples' surface quality due to the decrease in contact angle and the increase in the work of adhesion. In addition, the droplet spreading and adsorption observed on the surface of the woods are an indicator of wettability. Pine and Red oak had their dynamic contact angle reduced by up to 43 %. However, Imbuia was less susceptible to the effects of sanding, since it was found to be a more hydrophobic species; thus, this wood has a more stable surface in terms of dynamic wettability. This may be a result of the effect of low molecular weight compounds on the surface of Imbuia wood. The preparation of the wood surface depends on a synergy between the finishing processes and the chemical composition of the surface. Therefore, the results found can indicate which coatings are more suited to these woods.
A simple method to extract pyrolytic lignin from bio-oil is under agitation in water or organic solvent. This process produces a water-insoluble fraction (pyrolytic lignin) and a water-soluble fraction (WS). In this study, we used a physical fractionation technique with water as a liquid agent to separate the two fractions of the fast pyrolysis bio-oil and obtain the WS — the object of study — to test its efficiency as a protective agent for lignocellulosic materials. The study aimed to investigate the efficiency of the aqueous phase (WS) as a water-repellent agent when impregnated into Pinus elliotti wood. To obtain WS, we used two bio-oil:water ratios (1:50 and 1:100) and two agitation speeds (17,000 and 8,500 RPM); they were respectively named WS50 and WS100, both with an average yield of 61% WS. Gas chromatography coupled with mass spectrometry (GC-MS), thermogravimetry (TGA), contact angle, and scanning electron microscopy (SEM) were used to characterize the WS and the veneers impregnated with it. There were no morphological changes on their surface, especially regarding the non-coating of the wood pits; meanwhile, the TGA showed visible changes in the degree of thermal degradation of the impregnated material related to the chemical composition of the WS identified in the GC-MS. There was a significant increase, on average 62%, in the apparent contact angle of the impregnated wood, approximately 126°. The WS has shown to be efficient as a protective agent by converting the hydrophilic surface of Pinus elliotti into a hydrophobic one, and this effect partially remained after 45 days of exposure.
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