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ThermoWood® Process

ThermoWood® - thermal modification process has been developed and patented by VTT Technical Research Centre of Finland.

Process can be divided into three phases:

1. Temperature increase

Wood temperature is raised rapidly using heat and steam to a level of around 100 °C. Thereafter the temperature is increased steadily to 130 °C. Raw material can be green of pre-dried wood. Steam is used to prevent cracking of the wood. It also affects the chemical changes taking place in the wood. Moisture content reduces to nearly zero.

2. Actual thermal modification

During actual thermal modification phase the temperature is increased to a level of 185-215 °C. Temperature depends on the desired treatment class. When the target level has been reached, the temperature remains constant 2-3 hours. Steam is used to prevent the wood from burning in high temperatures and it also affects to the chemical changes in the wood.

 



Diagram of the production process

3. Cooling and re-conditioning

The temperature is reduced by using water spraying as cooling media. Conditioning and re-moisturing takes place to bring the wood moisture content to a level of 4-6 percent.

When the temperature is raised or lowered, a special adjustment system is used in order to prevent surface and inside splitting and checking. Customised adjustment values are used for different wood species and dimensions.

The raw material can be green or kiln-dried wood. If the process is begun with green wood, the wood can be dried in a very fast high-temperature drying process. The method is suitable for softwood and hardwood species. However, the process must be optimised separately for each wood species.

What is Thermowood ?

Thermowood is a heat treatment process with 320C, steam and air circulation. The iner part of the wood becomes 185C-212C and depending on the thickness and to the beginning moisture of the wood it’s a process which takes 48-144 hours.

With the Thermowood process most of the negativeness of the wood is minimized and beeen abolished.
Because of the high temperature applied to the wood, the cellulose chains are broken down, acids are to be resolved, purified from microorganisms and insects, the fattening environment of the fungi’s are removed. The big percentage of the resin is thrown out of the wood and the rest is cristallized so that it becomes harmless.

At the Thermowood process fort he heat treatment the moisture content of the wood is decreased at the decreased at the beginning to 0%. At the conditioning phase 4-6% moisture is given to the wood. With this application the wood becomes resistant against bending, shrinkages and movings.

Being attentive during getting timber form around wood for Thermowood is very important. For this Novawood makes it’s researches in all around the world in choosing the right rawmaterial.
The quality of the timber on which the Thermowood process will be done has high importance.

As a principle the heat treatment process can be done on all wood species the species we do
Thermowood are as followings; Pine, Spruce, Ash, Oak, Beech, Birch, Apsen, Iroko, Tali and Movengui.

During the process all methods to the parameters are applied different regarding the wood species.

The machineries and equipments used by Novawood are certified by the International Thermowood Association and are equipped with the last technology. Besides Novawood is a member of the Association as well.

The Thermowood plant exists at the Industrial Zone of Gerede Bolu and it’s Turkey’s first and only Thermowood manufacturing plant.

Standard ThermoWood treatment classes

ThermoWood has two standard treatment classes, Thermo-S and Thermo-D.

Thermo-S

The letter 'S' in 'Thermo-S' stands for 'stability'. Along with appearance, stability is a key property in the end use applications of the products in this treatment class. The average tangential swelling and shrinkage due to moisture for Thermo-S class treated wood is 6-8%. Thermo-S class ThermoWood is classified as relatively durable according to the standard EN 113; i.e., its natural resistance to decay meets class 3 requirements.

Recommended end use applications for Thermo-S class heat-treated timber:

Thermo-S Softwood Thermo-S Hardwood
- building components
- furnishing in dry conditions
- fixtures in dry conditions
- furniture
- garden furniture
- sauna benches
- door and window components 		- furnishing
- fixtures
- furniture
- flooring
- sauna structures
- garden furniture

Thermo-D

The letter 'D' in 'Thermo-D' stands for 'durability'. Along with appearance, biological durability is a key property in the end use applications of products in this treatment class. The average tangential swelling and shrinkage due to moisture for Thermo-D class treated wood is 5-6%. Thermo-D class ThermoWood is classified as durable according to the EN 113 standard; i.e., its natural resistance to decay meets class 2 requirements.

Recommended end use applications for Thermo-D class heat-treated timber:

Thermo-D Softwood Thermo-D Hardwood
- cladding
- outer doors
- shutters
- environmental constructions
- sauna and bathroom furnishing
- flooring
- garden furniture 		End use applications as in Thermo-S.
If a darker colour is desired, Thermo-D should be used.

Summary of the effects of the ThermoWood process on wood properties, by treatment class

Softwoods (pine and spruce)

Thermo-S Thermo- D
Treatment temperature 190 °C 212 °C
Weather resistance + ++
Dimensional stability + ++
Bending strength no change -
Colour darkness + + +

Hardwoods (irocco, tali, ash, oak, birch and aspen)

Thermo-S Thermo- D
Treatment temperature 185 °C 200 °C
Weather resistance no change +
Dimensional stability + +
Bending strength no change -
Colour darkness + + +



     
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info@novawood.com.tr