CHEMICAL PROCESSING OF THE TIMBER

 

Photo: lv.kompass.com

Chemical processing of the timber is a way, how to get the necessary characteristics from the popular nowadays wooden materials. The durability of the size and form, variations of different colors and tones, different durability ratio and all the other characteristics, which are necessary for resolving different building projects, also in the “North House” building of the wooden carcass house chemically processed timber is in use.

Do not be scared of a word “chemical”, because the chemical processing of the timber is regulated by the environment applicable requirements within the country and the EU. There are two ways of chemical processing – by impregnating in timber factories by producing ready-made, deeply processed timber or by processing on the construction site, where the timber is processed manually with chemical protection acid.

Chemical processing provides changes of the characteristics of the timber by strengthening, hardening, making forms, the ability of absorption of color humidity and also fire protection. The timber is protected against the humidity, fire influence, insects, fungi, mold and provide several physical characteristics to provide a fitting of the material for building concrete projects.

Protection of fungi infections and insect damages

Naturally, the timber is sensible to microorganism and insect influence. As a part of nature, it is included in a food chain and is nice for all the types of mold and green fungi, timber structure damaging insects and tree rodents. The aim of the chemical processing is to provide a safe timber protection.

Processing for the protection of the fire

Despite the fact, that in a contact with fire timber burns, it is possible to control the timing of the burning process. It is possible to be achieved in a chemical way by covering a protective acid against the fire. It has a very significant role in an agrarian stage of the fire by lasting all the space at the moment when the fire starts. In several occasions, it is possible to fully eliminate the ignition.

In the impregnation, there are special protective colors in use. These colors in the contact with a fire swell and insulate the timber surface against the fire, which is a very effective resolution.

Chemical processing for stabilizing sizes

Stabilizing of sizes is a method for reduction of wood felling and cutting, which is used in specific areas – wooden sculptures, dishes, etc. the creation of objects. Stabilizing of sizes reduce and eliminate appearing of cracks in the timber material, wood becomes hard and does not change its form. For stabilizing there is resin in use, which fills all the moss and structure, the result is almost impermeable material, which is possible to pull hard. A resin is reusable.

For stabilizing is necessary the timber with a humidity under 10%, wet timber will not stabilize. During the process, it is possible to paint the timber in any color by adding to the resin necessary amount of the pigment. The wood is then immersed in a vacuum stabilization chamber. The capacity of the vacuum is gradually increasing to avoid a resin excessive foaming. As far as resin foam stops to go out from the wood, the vacuum has been switched off and the material starts to swell with a resin. The finished process is when the material is not able to swim anymore. If the timber continues to swim, the vacuum process repeats. To finish the process, wood parts are wrapped in aluminum foil and preserved in a preheated oven at about 90 degrees Celsius. Stabilization process is finished, when the timber became hard and fully dry, and the resin is crystallized. Before the use, allow standing for 24-48 h, depending on the thickness of the material.

How deep Tanalith E enters the wood // Photo: iveja.lv

Increasing of the hardness

This method usually is necessary for pine tree materials to get a similar hardness to oak. There are different ways, how to increase the hardness of the timber, but the most popular are these – fire hardening method, applying polycarbonate or epoxy coating.

Hardening with a fire (heat) – for this method is necessary a fire heat, which pushes out unnecessary humidity from the timber. Doing work such like this, you have to be experienced, patient and caring, precise – by providing smooth, applicable temperature. Too high temperature may cause ignition.

Polycarbonate resin coating

Applying polycarbonate resin material does not change the wood texture, but the material is hardened. Mostly available in the concentrated form and, according to the manufacturer’s instructions, should be diluted with water. Apply the material on a thin layer of cleaned, soft wood. Then place it in a cool, dry place. To achieve greater hardness, cover so many polycarbonate coils until you reach the desired degree of hardness.

Increase hardness with epoxy application

The method is used to harden existing, well-built objects when the wooden surface becomes soiled. Applying the epoxy layer, the fibers are bonded and hardened. Working with epoxy is fast, done by amateur forces. The wood must be clean before application, but the main condition is to act according to the epoxy instructions. The application is carried out manually, in thick, with a brush. Depending on the thickness of the wood, it should be allowed to dry for a few hours or even for several days until the surface is completely dry. Then the epoxy is deep into the wood. Accelerating the drying process and increasing hardness can be achieved by reducing the temperature of the environment.

Processing against humidity

It is possible to process timber by reducing humidity swellability and gap appearing. EU standards (EU 335-1, 351-1 and 599-1) require several classes of material impregnation according to the humidity environment, in which the material is used.

Class 1 – for use in situations where the wood or wood product is under the cover and is not in contact with water and moisture.

Class 2 – Applicable in situations where the wood or wood product is under the cover, there is no direct contact with water, but a damp environment can cause occasional wetting.

Class 3 – for use in situations where the wood or wood product does not have a cover, and there is no direct contact with the ground, but it is either continuously exposed to weather conditions or is weatherproof, but subject to moisture.

Class 4 – for use in situations where the wood or wood product is in direct contact with the ground and water, therefore it is subject to constant moistening.

Class 5 – Applies to situations where the wood or wood product is in direct, constant contact with salt water.

The most of impregnation materials are toxic and dangerous for the environment, they have to be used in accordance to the instructions by applying appropriate protective and personal security events.

Chemical aid for the timber is possible to classify by the origin:

  • water basis;
  • oil basis;
  • an organic solver basis.

The most popular chemical processing aid nowadays is made on the water basis with copper. Sometimes it can consist of chromium, boric acid, etc. connections. At the end water basis, chemical timber processing aids make processed timber with a dry, able to paint layer, without a smell.

From on the oil-based chemical processing aids, the most popular is creosote. Despite the fact that creosote is an effective timber processing aid and it does not soluble in the water, it is noticed as a carcinogenic and is usable only, when in the situation there is no other similar processing material.

The most popular methods of timber chemical processing

The most popular methods for the chemical processing at the moment are two – Betel process method and Rüping process. Other methods include impregnation by spraying, wood acetylation, hot oil impregnation, light organic solvents, silicone compounds, immersion (for wet wood), etc.

More information about the Betel method

In the process of the method, there are metal oxides in use by using vacuum and pressure cycle changes. The method can be called as filled cell method because the vacuum makes an ability for each timber cell to fill with an impregnation, so timber swells as much as possible. First, a vacuum is created in the pressure vessel, creating a vacuum in the tree. Then press in the dish has filled an impregnants. When the vessel is full, the vacuum is switched off and a high pressure is switched on. (more than 1200 kPa, which helps to swell impregnants into a timber. After a concrete time limit – according to the size of the timber material and wooden material sizes, the normal pressure is on. The last work – by switching not a huge pressure to cut off impregnation surplus – eliminate timber material dripping, when save.

Rüping method

In this processing method, there are creosote impregnants under the pressure in use. The first thing is pressure making –  100-700 kPa when the air in the timber cells is pushed. In a pressure vessel filled impregnants fills empty timber cells. After that the pressure becomes normal and a pushed air output unnecessary liquid from cells. Similarly, as in the Betel method, the process is closed with a vacuum stage, where an unnecessary amount of the impregnation is outputted from the timber.

Processing for getting back the humidity

Processing of the layer with a covering color includes one system with different processing aspects, where each has its own function. The priming process includes reducing of the humidity swellability, stabilize the timber surface and prepare it for the next processing stage.

Processed with an oil color surface repulse the water good enough. Wood that is used outdoors should be regularly treated with wood oil to prevent drying, water absorption, cracking, and staining.

Chemical painting

Sometimes timber painting is called timber beice. For example, iron vitriol liquid makes timber brown-grey tone. The surface is similar to an old wood, so this method is used for the new wood patching.

Timber chemical processing becomes more and more important, because it provides long-lasting of the timber, helps to save forest resources, lets to use in the building useful wood types, lets to use alternative materials, reduces the necessity for the demand, gives economic and social costs. Timber chemical processing is a significant requirement for making a long-lasting timber carcass house.