Modification of Water Uptake Capacity of Wood Using Colloidal Solution by Impregnation Technique
Creators: name: Davoodi, Amir
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2020
Subjects: Nano-particle

description: Hygroscopic properties are important characteristics of a material that is used in building construction. Wood is an anisotropic, heterogeneous and hygroscopic material. Given the cellular structure of wood as well as capillary action in the Lumina, the level of water uptake in wood is significant. Such amount of water uptake makes the wood susceptible to dimensional instabilities, causes alterations in the mechanical properties, and potential for degradation of the material. Various approaches have been investigated to modify the hydrophilic nature of lignocellulosic materials, including surface modifications using silane treatments, acetylation, wax etc. Although these surface modifications can decrease the rate of water uptake by the materials, the amount of water uptake at saturation remains unchanged. In fact, the lumen diameter is so small that the rise of liquid, even with a hydrophobic surface, can still occur. Therefore, the only way to halt the water uptake driven by capillary action in lignocellulosic materials is to apply a uniform cover on the material surface in addition to filling the lumen with dense material. In the current research project, the vascular structure of softwood (Spruce) is obstructed by silica nanoparticles using the impregnation technique as one of the advanced methods to reduce the water absorption capacity in wood. This process can form a thin film of nanoparticles on solid objects with complex geometries. In addition, the technique can fill up the cavities and voids of porous materials and prevent the capillary action inside the Lumina. In this method, the wood specimen is dipped into the solution, silica 40 (wt. %) colloidal solution. Then the solvent is evaporated which results in the formation of nanoparticles in the form of thin films or particulates. The former may change the moisture absorption on the surface and the later reduces the capillarity of the vascular system. This project aims to find the optimal impregnation condition to minimize the water uptake capacity of wood in order to increase wood physical and mechanical stabilities. Three immersing times (i.e. short, medium, and long) were used to coat wooden samples with the silica colloidal solution. The samples were conditioned in wet environments with specificiii relative time and then their weight as percentage change were examined. To investigate the capability of the method to obstruct the vascular structure of the wood samples, the characteristic process was done in the next step by some common tests such as X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Water Contact Angle (WCA), etc. The results from the experiments show that dip-coating the wood samples with silica nanoparticle colloidal solution had effect on the amount of water absorption, but significant levels of reduction in water attraction was achieved with considering the other effective parameters such as duration of each set, the number of sets that are conducted, and impregnation in vacuumed condition. More research is needed to quantify the benefits of using nanoparticle in these applications.