For centuries wood has been a popular and traditional material for various applications and its timeless appeal continues to endure in modern times. Its versatility, sustainability, and aesthetic qualities make it a preferred choice for a wide range of building uses, from commercial to residential applications.
As the popularity of wood continues to grow in the construction and design industry, manufacturers are actively developing new technologies to expand the product offerings. This effort caters to the increasing demand and aims to elevate the performance and sustainability of wood in construction and design applications. Among these methods, thermal modification stands out as a process that transforms wood into a material with improved durability, stability, and aesthetic qualities. This article delves into the various aspects of thermally modified wood, exploring the process and the remarkable benefits it brings.
Thermal modification is an eco-friendly process that involves altering wood using heat energy, omitting the use of additional chemicals. The heart of the process lies in the thermal modification itself. Wood undergoes controlled heating in an oxygen-deprived environment, while gradually raising the heat to the desired temperature. Precise control is exercised to ensure uniform heating throughout the material. This process induces structural changes within the wood, enhancing its properties without risking combustion.
The wood is maintained at an elevated temperature for a specified duration, allowing the thermal modification to permeate its cellular structure. This cooking phase is pivotal for achieving the desired physical and chemical transformations. The controlled application of elevated temperatures in the absence of oxygen leads to several changes in the cellular components of wood, including hemicellulose, cellulose, and lignin—which are three major components that contribute to the overall mechanical properties of wood.
Hemicellulose Decomposition
Hemicellulose, a polymer comprised of sugars found in timber, constitutes a significant portion of wood, accounting for 20-35% of its dry weight. It plays a crucial role in moisture absorption and facilitates cross-linking among cellular components. During thermal modification, hemicellulose undergoes decomposition, leading to a decrease in its content. This process releases water vapor and other volatile compounds from the timber. The reduced hemicellulose content decreases the timber’s capacity to absorb and release moisture, thereby improving its overall stability.
Cellulose Crystallinity
Cellulose, a fibrous structure serving as the primary constituent of wood fiber, plays a pivotal role in enhancing the strength and rigidity of wood. The crystalline regions of cellulose are well-organized and tightly packed. The degree of cellulose crystallinity in wood influences the wood’s physical properties, such as strength and stiffness. The heat treatment causes the cellulose chains to become more ordered and crystalline, increasing its stiffness. This alteration contributes to improved dimensional stability and reduced susceptibility to swelling and shrinking when exposed to changes in moisture levels.
Lignin Modification
Lignin is a complex polymer that holds cellulose fibers together. It acts as a binding substance and provides structural support and rigidity to wood. At higher temperatures during thermal modification, lignin depolymerizes and breaks down into smaller fragments. The heat energy then redistributes and recondenses these broken lignin fragments. The reorganization of these fragments can contribute to an increase in lignin content, resulting in altered characteristics such as improved dimensional stability.
Lignin is the primary contributor to the natural brown color of wood. Various wood processing methods can modify or eliminate lignin content, thereby influencing the wood’s color. Thermal modification tends to contribute to the enhanced coloration of the wood, often resulting in a darker and more uniform appearance.
Cooling Phase
Following the thermal modification, a carefully managed cooling phase follows to prevent abrupt temperature changes that could compromise the integrity of the modified wood. By managing the cooling phase correctly, the risk of structural damage to the wood is minimized. Slow cooling helps prevent surface irregularities, such as warping or cupping, which might occur if the wood experiences sudden temperature fluctuations.
In summary, thermal modification process changes the cellular characteristics and interaction among hemicellulose, cellulose, and lignin. These alterations enhance the mechanical properties of the wood, resulting in improved dimensional stability, reduced susceptibility to moisture absorption, and increased resistance to decay.
Thermally Modified Wood Cladding
Thermally modified wood has gained significant attention in recent years as an excellent option for wood cladding. The result is a material with enhanced durability, stability, and resistance to decay, making it particularly well-suited for exterior applications.
SylvaTM and Abodo® are two examples of wood species that undergo thermal modification to enhance their performance as cladding materials.
Sylva is created from North American Red Oak, known for its attractive grain patterns and warm, reddish-brown hues. When thermally modified, it not only retains these aesthetic qualities but also gains increased resistance to decay, insects, and other environmental factors. This makes it an excellent choice for exterior cladding, where it can provide both visual appeal and long-term durability.
Abodo Vulcan thermally modified wood cladding is created from New Zealand plantation timber. The thermal modification process gives Vulcan cladding superior stability and reduced resin content. It’s naturally durable so the timber doesn’t require any chemical preservatives, and has a beautiful, consistent brown tone.
The versatility of thermally modified wood and its eco-friendly attributes establish it as a compelling choice for building materials across various applications, spanning from interior to exterior and encompassing both residential and commercial settings. As the building industry seeks sustainable and high-performance materials, the journey into the world of thermally modified wood opens doors to innovation and a more resilient future for wood-based products.
Contact us to find out how you can integrate Thermally Modified products into your upcoming project.
