Overview of Materials Used in the Project

2.1.2.5. Method of peeling tree bark

This method limits the intrusion of termites that damage fresh wood and termites that damage tree bark. After harvesting, the bark is usually peeled (except for some specialized types of wood that need to keep the bark). Peeling the bark dries the wood quickly, reducing humidity, creating unfavorable conditions for harmful organisms to penetrate fresh wood. (Nguyen Thi Bich Ngoc et al., 2006 [9]

2.1.2.6. Method of drying wood

Drying wood is a way to preserve forest products from some insects that damage fresh wood. Wood with high moisture content is stacked on top of each other or placed on pallets exposed to the air or put in the oven to dry.

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With this method, in addition to eliminating harmful factors caused by living organisms, it also limits non-living factors such as warping and cracking in wood.

When stacking wood for drying, avoid letting light or wind blow directly onto the top of the tree or wooden plank. This causes the moisture to escape too quickly, leading to the wood cracking.

Arranging the bars must be technically correct: stimulate the walls, the distance between the bars must be even, and the bars between the planks must be in a straight line. The distance between the bars depends on the type of wood, board thickness, and the size of the bars is usually 2.5 cm thick and 5 - 6 cm wide. (Nguyen Thi Bich Ngoc et al., 2006).[9]

2.1.2.7. Smoking and soaking methods

This method is applied empirically. The method of smoking bamboo, wood, and rattan on the stove helps the bamboo and rattan dry quickly and prevent mold. On the other hand, on the surface there will be a layer of soot with a chemical composition similar to plastic oil products that can prevent mold and bamboo beetles.

The method of soaking bamboo and wood in ponds or mud for a period of 6 months to 1 year or longer will limit mold. This method will change the chemical composition of wood, specifically reducing the sugar and starch content in bamboo and wood. (Nguyen Thi Bich Ngoc et al., 2006). [9]

2.1.2.8. Method of impregnating standing trees

This method is called soaking live trees (trees that have not been cut down). Taking advantage of the characteristics of the tree, it must absorb water and mineral salts from the soil through the root system, following the vessels leading up to the leaves to form resin after photosynthesis to nourish the tree. This method will block the flow of resin and replace it with a preservative solution, which will follow the circuit and distribute in the tree. (Nguyen Thi Bich Ngoc et al., 2006).[9]

2.1.2.9. Plastic replacement method

After 2-3 days of cutting wood, the sap is still in a liquid state and will move if there is a push from the base to the top of the log.

Taking advantage of this characteristic, people use the preparation solution on one end of the log (the root side). Thanks to the pressure difference of the solution at the root end and the tip of the log, the impregnating solution will press into the joints. circuit, gradually pushing the plastic to one side and replacing the position of the plastic in the gaps.

Impregnation time depends on the type of wood, on average 5 - 12 days.

One week after finishing the soaking process, the skin can be peeled and depending on the drying time corresponding to moisture requirements, it can be used.

The amount of medicine consumed for this method is about 400 - 500kg/m3 of liquid medicine solution. The concentration of the soaked drug solution depends on the type of drug used. (Nguyen Thi Tuyen, 2008).[14]

2.1.2.10. Spraying and sweeping methods

+ Scanning method

It is the most rudimentary preservation method, often encountered in actual production, such as in temporary preservation of wood in wharfs for a short period of time and preservation of the surface layer of wooden objects.

+ Spray method

The spray method is faster than the scanning method, however, because the waste of this method is too large, especially for small details, the scope of use is limited.

Preservative effect: temporary, preserving the surface layer. It also has certain importance in some cases such as additional preservation of items in vulnerable places of constructions such as under bridges, ceilings, and swept nooks and crannies. (Nguyen Thi Tuyen, 2008).[14]

2.1.3. Overview of materials used in the project

2.1.3.1. Wood materials

- White pine.

- The age of pine wood is 10 years old.

- Some properties and characteristics of Pine wood:

+ Appearance: Pine trees have reddish brown bark. The root has a darker color and when old, it peels into pieces. Young branches are pale yellow or tawny, without hair.

+ Structure of Pine wood: Pine wood has a yellow-brown core, distinct heartwood and heartwood, rough grain, no veins, tracheids account for 90% of the wood volume and length. 3.29 0.59mm, soft tissue cells are arranged along the tree trunk, wood rays are arranged horizontally in the tree trunk, accounting for 5-6% of the wood volume, the number of vertical sap ducts is 1.06 tubes/mm 2 .

+ Mechanical and physical properties of Pine wood:

- Elasticity of wood: Is the change in size of wood when the wood's moisture content changes from 0% to the saturated moisture content of the wood grain and vice versa, the saturated moisture content of the wood grain drops to 0%.

- Volume of wood: 0.45g/cm 3 .

- Strength limit when compressed across the grain:

+Comprehension across the entire grain in the tangential direction: 22 (Kg/cm 2 )

+Comprehensive cross-grain compression in the radial direction: 22 (Kg/cm 2 )

+ Local grain transverse compression in the tangential direction: 38 (Kg/cm 2 )

+ Local grain transverse compression in the radial direction: 40 (Kg/cm 2 )

- Compulsivity:

+ Reluctance calculated by cross section: 500 (Kg/cm 2 )

+ Resistance calculated according to radial section: 400 (Kg/cm 2 )

+ Reluctance calculated according to tangential section: 450 (Kg/cm 2 )

- Surface limit for static bending:

+ Strength limit in radial direction: 420 (Kg/cm 2 )

+ Tangential strength limit: 450 (Kg/cm 2 )

2.1.3.2. Raw materials for preparations

Eucalyptus tree is also known as Eucalyptus, scientific name is Eucalyptus, in the Myrtus family, Myrtaceae.

There are more than 700 species of eucalyptus, most native to Australia, and a small number found in New Guinea and Indonesia and one in the far northern Philippines and Taiwan. Eucalyptus species have been grown in tropical and subtropical regions including the Americas, Europe, Africa, the Mediterranean region, the Middle East, China, the Indian peninsula...

Seed rings were planted in our country around the 1950s and showed that some species are very suitable for the soil and climate of Vietnam, especially they can be planted in concentrated forests or dispersed in Residential land of people from the plains to the plains and highlands.

In Vietnam, only about 10 types of Eucalyptus are imported such as:

+ Red eucalyptus: Eucalyptus camaldulensis is suitable for the plains.

+ White eucalyptus: Eu.alba, suitable for areas near the sea.

+ Small-leaved eucalyptus: Eu. Tereticornis, suitable for the hills of Thua Thien - Hue.

+ Eucalyptus willow: Eu. Exserta, suitable for the highlands of Northern Vietnam.

+ Lemon eucalyptus: Eu. Citriodora, suitable for lowland areas, leaves contain lemongrass essential oil.

+ Gourd-leaved eucalyptus: Eu.globules, suitable for the highlands.

+ Large eucalyptus: Eu.grandis, suitable for alluvial soils.

+ Wet eucalyptus: Eu.saligna, suitable for the Da Lat highlands.

+ Eucalyptus Black Apricot: Eu. Maidenii, suitable for highland areas like Lam Dong, etc

Characteristics of Eucalyptus Tree:

The Eucalyptus tree (Eucalyptus camaldulensis Dehn.) is a large tree with soft, cork bark that peels off into patches to reveal light-colored trunk bark, young branches with 4 edges, young leaves growing opposite, sessile, leaf blades ovoid, green like covered with wax. Old leaves grow alternately with sickle-shaped leaf blades that are narrower and longer than young leaves. The leaf blades have sacs that secrete essential oils. Flowers grow in the leaf axils. Cup-shaped fruit.

The leaves are spear-shaped or crescent-shaped, the stem is short and slightly twisted, the leaf blade is long and narrow (in E. exserta) brittle and wider (in E. camaldulensis), 1 - 5 cm wide, 8 - 18 cm long. . Both sides of the leaves are green with a little light yellow, scattered with many small yellow dots. When you look at the leaves in front of the light, you see many tiny essential oil-secreting sacs. Secondary veins radiate from the midrib, meeting at the edge of the leaf. When crushed, the leaves have a special strong aroma, the smell is milder than in E. camaldulensis. The aroma is hot, slightly bitter, then feels cool and pleasant.

Uses of Eucalyptus Tree:

Leaves: White eucalyptus or willow eucalyptus leaves can be used to replace green eucalyptus leaves (E. globulus), which have been used for a long time in European countries.

Form of use: suppressant, inhaler, or mixed into dosage forms such as eucalyptus leaf alcoholic syrup, used to treat coughs, disinfect the respiratory tract, treat respiratory infections, coughs, asthma, etc.

Essential oils are used as cajuput essential oil. However, up to now, Eucalyptus in Vietnam has not been exploited on an industrial scale like Melaleuca. Also in the scope of exploratory and proposed research.

Lemon eucalyptus essential oil was widely used by the Department of Ear, Nose, and Throat at Bach Mai Hospital during the years of resistance against the Americans to treat coughs, sore throats, and disinfect the respiratory tract.

In Vietnam, because eucalyptus wood is usually cut down for about 5-7 years to make pillars in construction and to make pulp or chipboard called okal board (panneau de copaux), it is believed that eucalyptus is a soft and poor quality

when making household furniture, while in Australia, Eucalyptus forests are over 70-80 years old, the trees are up to 50-60 meters tall, the average diameter is up to a meter and the wood is used for many purposes from making pulp, plywood, chipboard, pillars to household carpentry, house construction as well as heavy construction projects.

With the above research results, it shows that in Vietnam there is no research on using eucalyptus bark and leaves in the process of preserving wood, so the implementation of the topic of using Eucalyptus leaves and bark in preservation Wood is of great significance.

2.1.3.2. Factors affecting the drug permeability of wood

+ Type of wood:

The permeability of different types of wood. Even on the same tree, the heartwood and heartwood are also different. Due to the very complex structure of wood, the main path for the preservative solution is the system of xylem vessels, tracheids and horizontal pores. If the size of this system is large, the drug permeability increases. Therefore, volume is a factor that needs attention.

Factors in wood structure affect drug absorption and sealing capacity. The occlusive body is a type of substance extracted from protoplasm, which acts as a plug to prevent fluid from entering the vascular tube.

+ Soaking method:

Mix the solution to concentrations of 15%, 25%, 35%. Then soak the wood in different concentrations, use a wood soaking tool to add enough solution to cover the wood and then dry it so that the wood's humidity is <20.

+ Type of drug, amount of drug, drug concentration

Different types of medicine have different amounts of drug absorbed. In the same drug, when changing the solution concentration, the amount of preservative will affect the ability to absorb the drug. There are a few cases where soaking wood with high humidity with a high concentration of drug solution changes the absorption of the drug into the wood. From permeation according to the capillary principle to permeation according to the principle of diffusion.

+ Wood humidity:

With the normal soaking method, the moisture content above the wood grain saturation point sometimes cannot determine the amount of drug absorbed by the weight method. Therefore, during the soaking process, we need to pay attention to the moisture content of the wood.

2.1.3.3. Preservative products

+ Requirements of preservative products:

- Highly toxic to organisms harmful to forest products in general.

- Not toxic to humans and livestock.

- Long-term stability of drugs in forest products when used in different environments.

- Easy to absorb, penetrates deeply into forest products.

- Does not affect the properties of wood and minimizes the possibility of wood burning, does not affect the mechanical strength of wood.

- Does not affect the adhesive film and surface jewelry process.

- Does not corrode metal.

- Does not pollute the environment.

- Cheap price, popular, easy to use.

+ Mechanism of action of preservatives with mushrooms:

Each mushroom species has a suitable humidity threshold for growth, in addition to other conditions such as oxygen, temperature, light and pH. To prevent fungi from damaging forest products, people often apply technical measures that change the living conditions of fungi or poison their food source with forest product preservatives. The preservative is effective against fungi when impregnated in wood, first of all it creates an environment completely different from that of unimpregnated wood, it deprives the spores of favorable conditions for germination. mushrooms, moreover, the preservative also immediately destroys the fungal spores. The active ingredients of the preservative penetrate into the spores and react with the main components of the spores, causing the spores to not germinate. . The results summarize the above effects of the product

Preservation means causing the fungus to be deformed in shape or destroyed right on the wood soaked in preservatives.

+ Mechanism of action of preservatives on insects:

Preservatives used to prevent insects can be treated directly to kill insects or with a layer of toxic chemicals that prevent insects from accessing food sources. The mechanism of action of preservatives on insects is that they can paralyze the nervous system due to direct contact with the preservative or when the insects eat wood that has been impregnated with the preservative. The product has the effect of destroying bacteria and digestive enzymes in the insect intestine, making food indigestible.

+ Mechanism of permeation of preservatives:

The process of permeating the preservative into the wood is due to one or more processes, including capillary processes, diffusion effects or external pressure. These effects, depending on each specific case, can be independent or occur at the same time.

+ Capillary permeation:

According to the document: Forest products and forest product preservation, volume 2 of the University of Forestry published in 1992, the capillary process is described as follows:

When soaking wood in an environment that is a preservative solution, the solution penetrates into the wood thanks to capillary pressure. This phenomenon occurs when wood has moisture below the grain saturation point. When a solid object is immersed in a liquid, according to physical laws, the interface between the liquid, the solid and the air will create a curved surface due to the surface tension of the liquid and the level of wetness of the solid where it is located. The interface between the solid and the fluid creates an angle and therefore two different types of positive and negative capillary pressures appear. When the capillary pressure is positive, the drug absorption will be poor and vice versa, when the capillary pressure is negative, the drug absorption will be better.

In fact, because wood cells have a heterogeneous and isotropic structure and some types of wood also have resinous oils that hinder the penetration of the product and determining the parameters will be difficult.

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