Method for stabilizing wood size (chemical method)

Chemical method

Chemical method refers to the chemical reaction using wood components, but it does not necessarily mean that it causes chemical reactions.

Often clear. The chemical methods described below are limited to what kind of ingredients or raw are consumed to some extent.

What became the ingredient. In fact, some of the methods carried out in physical law are accompanied to some extent.

A chemical reaction.

1

. Heat treatment

The dimensional stability can be obtained by heat treatment of the cellulose material. There are many explanations for its mechanism, but the main

What is going to work is the chemical change of hemicellulose, especially polysaccharide aldehyde, to form hygroscopic acid.

The compound, in turn, combines the cellulose chains with each other by hydrogen bonding.

The dimensional stability of the wood treated by heat treatment. Burmester et al. found that teak is stable in size.

The main reason for good sex is that the amount of hemicellulose which is easily hydrolyzed is small, and other tree species can be reduced by half after heat treatment.

Cellulose content, sometimes even smaller than the moisture absorption and swelling of the sleeve wood

Chow and other research

It shows that when the white spruce veneer is heated and treated in the atmosphere, the color intensity of the village surface is different, and the hydroxyl content is

Reduced, the crystallinity of cellulose decreased.

The dimensional stability obtained is different depending on the heat treatment conditions.

When the quality reduction rate is

When it is more than 20 %, the rate of swelling (shrinkage) in the atmosphere becomes low, and it does not change in nitrogen.

The closed container is instead raised. The order in which the processing environment facilitates dimensional stabilization is vacuum > atmosphere > cooking.

The results of treatment in molten metal are similar to those in vacuum.

When the relative humidity is in the lower range of 45 % to 55 %, the heat treatment material is resistant to expansion (shrinkage)

The rate and the moisture resistance rate are the highest, and both values ​​decrease as the relative humidity becomes higher.

The 1300- year-old Cooper used in the Horyuji Temple in Japan has an anti-swelling rate of about 40 %. visible

Generally, woods that have been aged for many years have reduced hygroscopicity, and the dimensional changes produced during moisture absorption and desorption are small.

It can be considered that many years of aging is a long-term heat treatment at low temperatures.

Starnm

The study found that various cellulosic materials were obtained from the rate of mass reduction and the rate of swelling.

Heat treatment reaction activation energy is almost always

117 04KJ/mol or so. However, if you join 2 . 5 % chlorine

Zinc as a catalyst, in

The reaction rate of heating yellow pinewood at 150 °C is about no more than

The reaction rate of the agent is increased

16 times. In this way, if the wood is first placed in a low concentration metal salt solution

Dip or spray, and then a short heat treatment can achieve good dimensional stability.

( 2 ) Other properties of the heat treated material. Mechanical properties: although heat treatment can improve wood

Inch stability, but the mechanical properties are worse. Thickness is

3 . Zmm 's North American cedar veneer in molten metal

Heating, when the rate of expansion (shrinkage)

At 40 %, various mechanical strength indicators are lower than untreated materials.

Such as the decrease in bending strength

17 %, hardness decreased by 21 %, toughness decreased by 40 %, wear resistance decreased by 60 %

Generally, hardwoods fall more than softwoods because hardwoods contain more hemicellulose than softwoods.

Prime.

Heat treatment can increase the thermoplasticity of the wood. Lignin is a thermoplastic component that is high in high temperatures.

(temperature

165 ~ 175 °C, pressure 9 stone 1 ~ 10 2 8 MPa , water content 6 % ~ 10 %) compression

In the case of the material, the equilibrium swelling and recovery after compression become smaller.

Corrosion resistance: heating the yellow cedar tree between 180 °C brass hot plate, when the expansion resistance

To

At 40 %, almost no decay occurred. The reason is that the hygroscopicity is lowered and the fungi cannot be satisfied.

The moisture necessary for living.

Gluing: The drying process of the veneer is essentially the heat treatment process, making the surface hydrophobic performance

High, especially in wood with a high content of natural resins, is more pronounced and makes glue difficult.

In addition to solid wood, heat treatment is also advantageous for dimensional stabilization of wood-based panels. In system

When the particle board is used, the moisture content of the wood chip is near the fiber saturation point, and the ruler can be heated by a closed container to obtain a ruler.

A well-stabilized particleboard will be in the form of a board

Treated in saturated steam at 175 °C for 10 min , thickening

Both rate and rebound resilience are small.

2

. Acetylation

This treatment is to replace the hydrophilic hydroxyl group with a hydrophobic acetic acid group ( CHCO- ).

(-

MH ). Due to the introduction of acetic acid in the wood, it can be considered as a ruler caused by compatibilization.

Stabilized.

This reaction can be carried out in the liquid phase or in the gas phase. Reaction can occur without catalyst, but there is catalysis

The reaction rate of the agent will increase. In addition, the wood is pre-expanded to make the acetate more uniform.

When acetylating wood, if the amount of acetyl is small, it is only acetylated on the surface of microfibrils, such as acetyl.

When the amount of the base is large, it can be acetylated inside the microfibrils. That is, when the amount of acetyl group is low, the acetate material is relatively wet.

The degree increases and decreases, but the amount of high acetic acid base increases.

( 2 ) Acetylation method.

There are several ways to acetylate wood:

1 pyridine pretreatment - gas phase treatment in an equal amount of anhydrous acetic acid and pyridine mixed liquid;

2 urea-monoammonium sulfate mixed solution pretreatment, one drying, one gas phase treatment in glacial acetic acid;

Pretreatment of 3 potassium acetate solution - drying one in the vapor phase of dimethylformamide and glacial acetic acid solution vapor

deal with;

4 Dilute glacial acetic acid with xylene solution to a concentration of 25 %, and use this liquid for liquid phase

Reason. This method is suitable for handling larger sizes of wood.

Gas phase treatment at 130 °C with 85 % glacial acetic acid and 15 % dimethylformamide

Pine wood specimen [

L.0cm(T)X1.0cm ( R ) X13.0cm ( L ) 2 5h , can

Achieving uniform acetateization tends to make the anti-expansion ratio of the various grain directions of the wood uniform.

( 3 ) The nature of the acetated village. Mechanical properties: due to the expansion agent used, the presence or absence of catalysts and species

Class, reaction conditions or tree species vary. The horizontal compressive strength, hardness and toughness are improved to some extent, but the resistance

The shear strength is reduced. The effect of acetic acidation on stress relaxation is significant.

Physical properties: moisture inhibition rate is slightly lower than anti-expansion (shrinkage) rate, moisture resistance and resistance at different relative humidity

The expansion (shrinkage) rate is almost constant; the permeability of the gas is deteriorated, and the rate of diffusion of water is slow; in organic liquids

The expansion ratio is reduced; the coefficient of linear expansion due to heat becomes large; the color of the material becomes white when irradiated with ultraviolet rays.

, but

The brightness is almost constant; the pits caused by drying are less occluded.

Gluing: Gluing of wood when glued with thermosetting resin due to the reduction of free hydroxyl groups

Can be reduced, the damage of the rubber layer is increased.

Corrosion resistance: pretreatment with 1 % zinc chloride, followed by gas phase treatment of yellow yellow at 120 °C with glacial acetic acid

Fir veneer, the rate of expansion (shrinkage) is reached

70 % ( 30 % acetic acid ), no decay, there are

Insect and anti-ant effect.

3.

Isocyanate

In 1970, he began to use the isocyanate in wood gluing wood modification. Advantage

It is easy to react with water, alcohol, ammonia, acid, etc. The disadvantage is that it is toxic. When the wood size is stable

Commonly used phenyl isocyanate (

Hl ), 4 , 4 '- M phenylmethane, M isocyanate ( M ' DI ), methyl isocyanide

Acid ester, butyl isocyanate, urethane prepolymer or methyl isocyanate with methyl methacrylate

The mixture is subjected to gas phase treatment or liquid phase treatment.

With methyl isocyanate monomethyl methacrylate, the water content of wood is higher when the gas phase is treated at 130 °C.

High, the less the rate of increase in the quality of the wood; the rate of expansion (shrinkage) of the treated material increases with the increase in mass

Becomes high.

When gas phase treatment with phenyl isocyanate ( TDI ) (nitrogen, 120 °C), the closer to the surface of the wood

The easier it is to react, the resulting carbamate is almost always crosslinked with the wood component, so the initial reaction is not

Very fast,

The moisture resistance rate and the expansion resistance of the TDI treated material increase with the increase of the amount of nitrogen, and

Good dimensional stability at high relative humidity compared to low humidity.

The compressive strength and flexural strength of the diisocyanate treated material increase, especially the polymer content

More, the more the horizontal compressive strength is increased, the less the toughness that occurs when the phenolic resin is not treated.

Phenomenon, and slightly increased. However, the toughness of wood treated with methyl isocyanate monodimethylformamide

Abrasion resistance decreases

25 %.

Wood treated with methyl isocyanate-methyl methacrylate has good weatherability; methyl isocyanide

The acid treated wood has a certain corrosion resistance.

4

. Polymerization (manufacturing wood-plastic composite, WPC )

Wood plastic composite (

WPC) vinyl monomer is injected in the timber is then radiation using high-energy radiation

Shooting or coupling of organic monomers with wood components by means of initiators and heat

Or a new material formed by filling a polymer cell cavity with a polymer. This material is

1961

come out,

In the 1970s , he entered the US market. In 1964 , he was listed as one of the world's top ten sciences by the US News Agency.

One of the achievements.

There are many ways to make wood-plastic composites, but there are two commonly used ones, namely radiation method and

Catalyst method. Either way, first choose the monomer, initiator and expansion agent.

Commonly used monomers are a class of vinyl compounds having unsaturated double bonds, mainly comprising: styrene.

Methyl methacrylate, acrylonitrile, acrylic acid, vinyl chloride, ethylene, propylene, ethyl acrylate, B

Acid ethylene, maleic anhydride, etc.

One of the compounds can be selected as a monomer when used.

The two compounds were formulated as a mixed solution as a monomer.

Initiators are a class of compounds that are readily decomposed to form free radicals to initiate free radical polymerization.

There are two types of commonly used initiators: one is an organic peroxy compound (such as benzoyl peroxide); the other is

It is an azo compound (such as azobisisobutyr).

Adding a bulking agent to the monomer solution can increase the impregnation rate of the hard-to-inject wood. Common wood expansion

The agent is ethanol, dioxane, ammonium formate, dimethylformate or the like.

Wood-plastic composite has the dual advantages of wood and polymer, and its hygroscopicity and water absorption are untreated.

Significantly reduced material, excellent volume stability, and high shrinkage resistance

70 % or so. In addition,

Mechanical strength, surface properties, corrosion resistance and weather resistance are all significantly improved compared to untreated materials.

Kitchenware Storage Shelf

The kitchen is also an important place for home storage, but some home kitchens are small, so storage is also a problem. In addition to making cabinets, the storage rack is a very important tool in the kitchen. There are so many things in the kitchen. The kitchen will look more neat and orderly only if the pots and pans and various household appliances are properly stored.

1. When space is limited, you can make full use of the vertical space in the kitchen. Some light objects can be directly mounted on the wall. A stainless steel frame is hung on the wall, and a solid wood partition is placed on the partition. Small objects that are often used can be placed on the partition. It not only meets the requirements of storage, but also saves space.

2. The facade of the refrigerator is also a good storage space. The shelves that can be adsorbed by magnets can be used. For example, items such as frequently used kitchen paper fresh-keeping film can be placed on the refrigerator, ready for use.
3. Put a storage rack behind the sink to make it look like a hook. Kitchen tools such as soup spoon filter and egg beater can be hung up without taking up too much space and are convenient to use.

Kitchenware Storage Shelf,Kitchen Organizer,Kitchen Collection Shelf,Kitchen Storage Rack,Kitchen Items Storage

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