Abstract
Wood protection through chemical modification has received increasing interest over the last decades due to the environmental issues related to conventional biocides or protecting products. Consequently, a wide range of new treatments are developed in laboratories, which are later scaled up in the industrial environment. The main goal of modifying wood for indoor–outdoor application is to change its hydrophilic character, which in turn improves the intrinsic properties of the material and its durability against external factors. Wood can be esterified through its hydroxyl groups to obtain a hydrophobic and photo-stable material. Chemical modifications of Pinus radiata D. Don wood using hexanoyl chloride (P6), dodecanoyl chloride (P12), and stearoyl chloride (P18) were carried out at different concentrations. Esterification was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) technique combined with a discriminatory analysis. Weight percent gain was associated with the number of carbons of the aliphatic chain of the fatty acid (P6 > P12 > P18). Moreover, an increase of wood density as a consequence of modification treatments was observed. A substantial improvement of the hydrophobicity of wood was observed by dynamic contact angle measurements. In addition, the effect of ultraviolet (UV) radiation on color changes was reduced with the treatments. Furthermore, the P6 treatment presented acceptable values of modulus of elasticity (MOE) and modulus of rupture (MOR), being suitable for similar mechanical uses as non-treated pinewood. However, only treatments P12 and P18 enhanced thermal resistance of the pinewood in an oxidative atmosphere.
Highlights
Wood is the most widely used bio-based material for indoor–outdoor applications due to its availability, low price, acceptable mechanical properties, ease of processing, renewability, and appearance, among others
Solid Radiata pinewood was chemically modified with three different fatty acid chlorides in order to study the effect of the esterification on the physical-chemical, mechanical, and thermal properties of wood
FT-IR spectroscopy confirmed the esterification by showing spectral differences between control and esterified wood, especially in the treatment with shorter chain (P6), followed by P12 and P18, regardless of product concentration
Summary
Wood is the most widely used bio-based material for indoor–outdoor applications due to its availability, low price, acceptable mechanical properties, ease of processing, renewability, and appearance, among others The properties of this anisotropic material are derived from the wood cell wall structure and composition. Several wood modification techniques have been developed during the last decades [3], by means of heat treatments at mild temperatures (up to 220 ◦ C) in different atmospheres [4] or by using chemical reagents that interact with hydroxyl groups of wood. Another way of ensuring long-term durability is coating the wood surface with protective formulations [5]. The most prominent chemical modification process and the impregnation method of solid wood are acetylation and furfurylation, which have been extensively studied and are exploited at an industrial-scale level under different patents [1]
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