Densification of timber: a review on the process, material properties, and application

Abstract

Timber densification is a process that has been around since the early 1900s and is predominantly used to enhance the structural properties of timber. The process of densification provides the timber with a greater mechanical strength, hardness, abrasion resistance, and dimensional stability in comparison to its virgin counterparts. It alters the cellular structure of the timber through compression, chemical impregnation, or the combination of the two. This in turn closes the voids of the timber or fills the porosity of the cell wall structure, increasing the density of the timber and, therefore, changing its properties. Several processes are reported in literature which produce densified timber, considering the effect of various parameters, such as the compression ratio, and the temperature on the mechanical properties of the densified timber. This paper presents an overview of the current processes of timber densification and its corresponding effects. The material properties of densified timber, applications, and possible future directions are also explored, as the potential of this innovative material is still not fully realised.

Quebracho Tannin Bio-Based Adhesives for Plywood

“…Thickness and therefore the degree of compression is influenced by the moisture content of veneers, press time and temperature. An elongated press time with a higher temperature influences the chemical wood structure due to a shift toward the glass transition of the singular chemical wood constituents while softening the natural polymeric cellular fiber composite character of wood [ 47 ].…”

Numerical Simulation of the Deformation Behavior of Softwood Tracheids for the Calculation of the Mechanical Properties of Wood–Polymer Composites

“…The presented modeling approach thus maps the material behavior determined by measurement with sufficient accuracy. The remaining discrepancies can be explained by growth-related fluctuations in dimensions, wall thickness and cellulose fiber content of the tracheids, as well as the mutual support of the cell walls in the tracheid network and the multiaxial load conditions in the solid wood [10]. This behavior could be represented realistically by arranging and compressing the developed EW and LW tracheid models, such as a larger network similar to reference [27].…”

“…To exploit the material potential of softwood, its structural composition must be considered during processing. This includes, on the one hand, utilizing the excellent mechanical properties in the growth, respectively, longitudinal direction and, on the other hand, the specific compaction of the porous softwood structure while retaining the strengthgiving components [10]. Figure 1 show a comparison of the material properties of red beech and pine [11] as well as the hypothetical achievable properties of pine at 50% compression.…”

Effect of Bleaching and Hot-Pressing Conditions on Mechanical Properties of Compressed Wood

“…CW can reduce the porosity or void space of the wood and make highly compact wood, leading to better mechanical properties. There are many different approaches for fabricating CW [ 1 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]: thermo-hydro-mechanical (THM), thermo-mechanical, heat treatment, chemical, surface densification, steam treatment, non-steaming densification, and so on [ 10 , 11 ]. The thermo-mechanical method uses an open hot- press without controlling the humidity and moisture content.…”