Metal Oxide Sol-Gels ( , AlO(OH), and ) to Improve the Mechanical Performance of Wood Substrates

Wood is a renewable material widely used in many applications due to its unique properties and distinctive look. However, as wood is organically constituted, it is slowly destroyed by the long-term impact of oxygen, UV radiations, water, and biological attacks (Mahltig et al., 2008). Therefore, protective treatments are necessary to improve the mechanical, thermal, and chemical properties of wood. In order to improve the mechanical properties of sugar maple (Acer saccharum Marsh.), as this species is widely used in the wood products industry, samples of sugar maple were impregnated with sols of metal oxides (AlO(OH), SiO2, and ZrO2). The weight gain and two different techniques of microscopy were used to evaluate the efficiency of the impregnation in the wood samples. The mechanical properties were evaluated using hardness test, scratch test, and impact test. It was shown that the maple samples impregnated with ZrO2 led to the greatest improvement of the mechanical properties. 1. Introduction Wood is a renewable material widely used in many applications, such as outdoor (sidings, shingles, etc.) and indoor products (hardwood floors, kitchen cabinets, furniture, etc.), due to its excellent properties and distinctive look. However, as wood is organically constituted, it is slowly destroyed by the long-term impact of oxygen, UV radiations, water, and biological attacks [1]. Therefore, protective treatments have to be used to increase its life in service. In addition the growing environmental concerns push the industry to develop and use nontoxic wood preservatives [2, 3]. Recently, it has been observed that one promising method to improve and provide new properties for wood materials is to modify the wood surface by the deposition of hybrid inorganic-organic materials with the sol-gel process. Hybrid inorganic-organic materials offer the opportunity to combine the desirable properties (i.e., toughness, elasticity, etc.) of organic polymers with those of inorganic solids (i.e., hardness, chemical resistance, etc.) [4]. The sol-gel process is simple, low cost, and it allows room-temperature deposition of hybrid inorganic-organic thin films on a wide range of substrates, including wood [2, 3]. This technique is appropriate for commodity production such as wood product industry. Depending on the sol-gel synthesized, various wood properties can be improved, such as color retention, mechanical properties, dimensional stability, and more. Over the last two decades, the sol-gel process has been the subject of many studies. However, most of the studies on sol-gel