Why to thermo-modify the wood?

Why to thermo-modify the wood?

Thermally Modified Wood (LTM) is increasingly known all over the world due to the benefits that this process produces at all levels of the supply chain. Through the heat treatment, the wood acquires greater durability and stability, is much less sensitive to shrinkage and swelling, acquires considerable resistance to parasite infestation and gains an elegant livery that is homogeneous over the entire thickness of the material.

The goal was to optimize the process technology developed by BIGonDRY on aspects related to costs, environmental impact, safety and standardization of the production of thermally modified wood (LTM) with proven characteristics of durability, stability and appearance.

The products that arise within these processes are to be considered totally bio-compatible, as no chemicals of any kind are applied. This process gives wood a strong competitiveness with respect to alternative materials, including wood modified with other technologies or natural wood as it acquires greater durability and stability, avoiding having to chemically treat the wood and also eliminating the possibility of infestations by insects and obtaining a homogeneous dark color on the wood throughout the thickness.

The BIGonDRY-THW system is a process in the presence of saturated steam, which thanks to the slight overpressure, allows you to work at a temperature close to 230°C in an environment in the absence of oxygen, exploiting the natural production of gas from the wood (steam during first phase and gas from pyrolysis during the High Temperature phase) and, if necessary, by the controlled evaporation of a direct source of water supplied by the system. Consequently, the BIGonDRY-THW system uses a minimum amount of steam which allows to reach an ecological approach to the process with the following advantages:

  • a lower energy requirement compared to other HT systems that use high quantities of superheated steam;
  • limited emission of gas into the environment;
  • a highly competitive plant cost

The quality and performance of the products are proven in the field by customer satisfaction and by the collaboration with independent research and experimentation institutes in Italy.

BIGonDRY also pays close attention to the environment and recent analyzes carried out on high temperature cycles for gaseous, liquid and solid emissions from the plant have revealed reassuring data. BIGonDRY is able to equip THW heat treatment plants with very effective filtering systems to reduce at best, also minimizing the consumption of “clean” water, thus having an economic as well as environmental saving. Furthermore, the extractives contained in the recycled water should not be underestimated, which often contribute to improving not only the appearance of the heat-treated wood but also its quality as it can absorb some of the extractives previously dissolved in the liquid and thus re-acquire some chemically important substances for the effects of durability and the improvement of some physical characteristics.

The technical staff of BIGonDRY is constantly looking for improvements in both drying and heat treatment programs, continually trying not only to obtain a product that is increasingly suited to market demands but also with environment and energy saving.

The very important phases of final conditioning distinguish the product and its stability, in fact in these phases the humidity regained through controlled humidification phases allow to confer the dimensional stability that characterizes this product. This treatment phase is essential in order to make the material suitable for subsequent processing and provide the end customer with a durable, resistant but also easily workable material.

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Insights

Spruce

Picea abies Karst.

The Spruce is widespread in Europe and Central Asia, suitable for alpine climates and has the ability to adapt to the climatic situation in which it is found by developing suitable characteristics. It is easily workable and has favorable characteristics for the construction of musical instruments and for internal building uses. The heat treatment carried out with the BIGonDRY THW plant has effects on the physical and mechanical properties of the spruce wood. It has particularly positive consequences as regards the dimensional stability parameters and durability reaching class 2.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C

Douglas

Pseudotsuga menziesii

Originating from the west coast of the United States of America, Douglas prefers temperate and humid climates. It is one of the tallest plants in the world, its stem can reach 75m in height but remains moderately limited in diameter. It is used in construction: boats, bridges, houses, carpentry in general, railway axles, precisely because of its lightness, strength, elasticity and resistance to atmospheric agents. The heat treatment carried out with the BIGonDRY THW plant has effects on the physical and mechanical properties. It minimally affects the density of the heat-treated material at various temperatures, but has a very positive effect on dimensional stability. As far as durability is concerned, there is a class improvement based on the heat treatment temperature, class 2 is obtained.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C

Scots pine

Pinus sylvestris L

Its distribution is extremely vast, some species prefer temperate climates while other species can be found on the northern edges of the tropics. It grows very tall and its branches tend upwards and its foliage is needle-like. Its mechanical properties are fair, durability is a cross between classes 4 and 5. The heat treatment carried out with the BIGonDRY THW plant has effects on the physical and mechanical properties of the Scots pine. In particular, we have an increase of over 50% in dimensional stability and an improvement in durability up to class 2.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C

Maritime Pine

Pinus pinaster Aiton

The Maritime Pine develops mainly near the coasts of the Mediterranean Sea, in fact it owes its name to its predisposition to grow in sandy areas. It develops very high trunks and dominated by a crown consisting of dense green needles. It is used a lot for the extraction of its resin, less for its own wood despite being easily workable. The heat treatment carried out with the BIGonDRY THW plant has a very positive effect on increasing dimensional stability and compressive strength. The parameter that is most positively affected by heat treatments is durability. The improvements are especially noticeable at the high temperatures in which class 1 is reached.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C

Beech

Fagus sylvatica L.

The Beech, thanks to its ability to adapt to growth in different climatic conditions, has a varied distribution. It is a very long-lived, slow-growing plant, characterized by slightly tapered stems and a very thin greyish bark. Its wood is valued for being hard and compact and this makes it suitable for the construction of furniture, kitchen utensils and for being turned. The benefits brought about by thermal modification in terms of dimensional stability are considerable: an anti-swelling efficiency of almost 60% is achieved. Durability passes from class 5 to class 2 thus having an extremely positive effect and considerably extending the life expectancy of the wood.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C

Ash

Fraxinus spp.

The Ash has a tendency to grow in environments with a temperate climate. It develops very tall with a cylindrical and particularly straight trunk. Strongly known for the uses that can be made of bark and leaves for medicinal and medicinal purposes and also excellent as a fuel and therefore for the production of firewood and appreciated for its ease of processing, resistance and elasticity. The heat treatment causes a great benefit regarding the dimensional stability, the efficiency against the reabsorption of moisture and the consequent swelling will be more than double compared to the untreated material. The durability is the property that is most positively affected by heat treatment and in fact reaches class 1.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C
Application examples

Poplar

Populus spp.

Poplar is widespread throughout the northern hemisphere, the bark is smooth in young specimens and then becomes rough over time. The color of the wood tends to be white-light yellow. It is highly appreciated for its light weight and is used in the paper industry, packaging and the manufacture of plywood panels. The heat treatment carried out with the BIGonDRY THW plant has a very positive effect on dimensional stability, improving it by about 50%. The positive effects of the heat treatment are also shown in the compressive strength parameters and in the modulus of elasticity. The most surprising data, however, is the improvement in durability that reaches class 1 with heat treatment.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C

Oak

Quercus petraea Liebl.

The Oak is widespread throughout Europe with the exception of the Italian islands. It therefore prefers continental climates and goes to altitudes up to 1000 meters. Its natural wood is considered valuable for its density and heaviness and for its light brown color. It is used for the production of floors, furniture and barrels for the aging of fine liqueurs. The heat treatment carried out with the BIGonDRY THW plant gives a significant improvement in terms of dimensional stability, the effects of moisture reabsorption and swelling caused by the same are reduced by about 55%. Durability is already very good for natural wood, the treatment enhances this characteristic.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C
Application examples

Tulipier

Liriodendron tulipifera L.

Tulipier is a species of wood native to the United States of America, more precisely from the eastern part. However, it is also cultivated throughout Europe as an ornamental plant. Being a tree that grows tall and straight, it provides wood which, with its characteristics of workability, stability and specific weight, make it suitable for a large number of uses. It has a whitish color, evident veining with dark or greenish flames. The heat treatment carried out with the BIGonDRY THW system has positive effects regarding dimensional stability, which define an improvement in hygroscopic efficiency, and anti-swelling that reaches up to 50%. The life expectancy of this wood species extends a lot once subjected to heat treatment, in fact we have reached class 2.

Waterproofness
Elasticity
Swelling
Durability
Pressure
Examples of thermal variation
Natural
160°C
185°C
200°C
215°C
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