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About MDF board application powder coating

About MDF board application powder coating

  • Categories:Industry News
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  • Time of issue:2020-12-11
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(Summary description)Plain MDF began as a product developed in the mid-1960s. The United States built the first Plain MDF plant in 1966. The English name of the Plain MDF is Plain MDF, Plain MDF for short, and Plain MDF for Chinese abbreviation.

Plain MDF in our country uses agricultural residues or sub-small fuelwood as the main raw material. At present, most of the solid wood furniture is not 100% made of solid wood, more of it is made of solid wood and board. A large part of the furniture chooses medium density fiberboard as the main material.

Plain MDF is made of wood fiber or other plant fiber as raw material, and synthetic resin, such as urea-formaldehyde resin or other adhesives, is pressed under heating and pressurizing conditions. This density board is generally at a density of 0.5-0.8g/cm3. Plain MDF is easy to form and even more convenient.

About MDF board application powder coating

(Summary description)Plain MDF began as a product developed in the mid-1960s. The United States built the first Plain MDF plant in 1966. The English name of the Plain MDF is Plain MDF, Plain MDF for short, and Plain MDF for Chinese abbreviation.

Plain MDF in our country uses agricultural residues or sub-small fuelwood as the main raw material. At present, most of the solid wood furniture is not 100% made of solid wood, more of it is made of solid wood and board. A large part of the furniture chooses medium density fiberboard as the main material.

Plain MDF is made of wood fiber or other plant fiber as raw material, and synthetic resin, such as urea-formaldehyde resin or other adhesives, is pressed under heating and pressurizing conditions. This density board is generally at a density of 0.5-0.8g/cm3. Plain MDF is easy to form and even more convenient.

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2020-12-11
  • Views:0
Information

Plain MDF in our country uses agricultural residues or sub-small fuelwood as the main raw material. At present, most of the solid wood furniture is not 100% made of solid wood, more of it is made of solid wood and board, and a large part of the furniture chooses Plain MDF as the main material.

 

Plain MDF is made of wood fiber or other plant fiber as raw material, and synthetic resin, such as urea-formaldehyde resin or other adhesives, is pressed under heating and pressurizing conditions. This density board is generally at a density of 0.5-0.8g/cm3. Plain MDF is easy to form and even more convenient.

 

1 Introduction

 

According to national standards, Plain MDF can be divided into EO grade, El grade and E2 grade according to its free formaldehyde content.

 

E2 grade formaldehyde emission is 5mg/L: El grade formaldehyde emission is 1.5mg/L, EO grade formaldehyde emission is O.5mg/L, and formaldehyde content exceeding 30mg/L is regarded as a defective product.

 

General furniture uses EO and El grade density boards. Recently, the Plain MDF decoration process includes low and high pressure melamine veneer, plastic film veneer, paint spraying, and the resin coating of the veneer material itself contains organic solvents such as formaldehyde.

 

In addition, the porosity of Plain MDF is large. After spraying, the pores of wood fiber will affect the formation of many formaldehyde and other substances in the use process after the furniture is formed, which will cause great harm to the human body. In addition, people now have increased awareness of environmental protection and desire for a healthy living environment. , The requirements for Plain MDF boards are getting higher and higher, and the advantages of powder coatings are becoming more obvious.

 

Generally, the curing temperature of powder is around 190, and the rapid curing at low temperature is also limited to above 140. Most powders can only be applied to conductive heat-sensitive materials, and the application range is limited to general hardware.

 

Once the temperature of the Plain MDF sheet exceeds 140, the inside of the sheet will crack and the external peeling will occur. Therefore, the powder coating applied to the Plain MDF sheet will also be restricted. Many well-known powder factories are launching their own Plain MDF powder. There are not many successful cases and the scope of application is limited.

 

There are also many processes for spraying Plain MDF powder on the market, most of which are water-based UV primers and powder coating spray covers. Recently, powder manufacturers are also vigorously promoting the use of foundation powder.

 

Due to technical shortcomings, there are still many flaws in application. Water-based UV primer powder spray surface is the mainstream at present, but the non-pipelined process makes its application stagnant, and its inability to mass production limits its development prospects, and foundation powder surface The main difficulty is that the conductivity of the base powder and poor shape retention during double-layer curing of the sheet become difficult.

 

After years of investment and development, our company has now formed its own unique Plain MDF powder coating, which has sand patterns and flat surfaces for customers to choose. The curing conditions have also broken through to complete curing at 120 degrees for 3.5 minutes. Able to meet the customer's choice.

 

2 test

 

2.1 Test equipment

Plain MDF powder coating, water-based UV coating. Conductive paint, Plain MDF board (E2 level).

 

2.2 Experimental steps

Remove wood fibers and burrs from the Plain MDF board, blow off the dust and polish the residue with compressed air, and seal it with water-based UV paint after completion.

 

Generally, the spraying thickness is 30-40μm, and then conduct conductive coating treatment, then polish, and finally powder spray, then infrared curing, heating in sections, frequency reduction step by step, and furnace temperature less than 120;

 

The conveyor chain speed is 2 m/min, the melting voltage upper limit is 120V, the lower limit voltage is 135V, the solidification voltage upper limit is 100V, the lower limit voltage is 110V, the exhaust speed is 50HZ, and the air temperature is 180°C. The moisture content of the board MDF is 7.5%.

 

The powder coatings were tested by several well-known manufacturers and several samples from our company. The test results are as shown in Figure a. Finally, the HC-13 formulation was selected for testing and passed the constant power control.

 

The heating tunnel is a fast energy transmission section in the first stage. This part of the test takes about 35 seconds to promote rapid leveling and partial solidification of the powder, and then gradually reduce the power to the end.

 

The entire process is about 5 minutes, and the furnace temperature is controlled within 130 degrees to keep the powder completely solidified. At the same time, the temperature and time are controlled so that the MDF board cannot appear cracks and peeling.

  

 

 

The powder coating has been fully cured, the powder coating has good adhesion to the surface of the board, the gloss is moderate and meets the requirements, and the water resistance and cold liquid resistance test results are intact.

 

Because the powder is completely solidified, the VOC inside the Plain MDF board is sealed, almost shielding the release of formaldehyde, the product after MDF powder spraying can be directly used as indoor furniture.

 

3 Results and discussion

 

In the entire application test process, we should fully understand the characteristics of Plain MDF powder before electrostatic spraying, such as electrical conductivity, thermal conductivity, and determination of water content.

 

In addition, we must pay attention to some characteristics of the board, such as density, thickness, adhesive strength and the variety of adhesives. In addition, the choice of infrared light source and the level of moisture content directly affect the electrification of the board.

 

Generally, resistance <105Ω is regarded as a conductor, and resistance>10100 is regarded as an insulator. The conductivity of MDF is mainly determined by its moisture content. Under normal temperature and pressure, moisture content>10%, good conductivity, but excessive moisture, After the plate is cured by powder spraying, bubbles and cracks in the plate will appear in the coating film, which will cause the product to fail to meet the requirements;

 

However, if the water content is less than 4%, the resistance of the board is too large, it is not conductive, and becomes an insulator. The moisture content of powder sprayed MDF board should be controlled between 6%-9%, and its surface resistance is 105-108Ω, which is beneficial to spraying and construction.

 

The thermal conductivity of Plain MDF sheet is very poor. The main reason is its low thermal conductivity (0.07w/(m.k), which is a poor conductor of heat, and the thermal conductivity is close to air (0.02w/(m.k)).

 

If you use a common heating mode, such as hot air circulation, to heat the Plain MDF board, due to its poor thermal conductivity, it takes a long time and temperature to reach the curing temperature and curing time, which will cause a large difference in temperature between the surface and the inner layer. Uneven heating of the plate will cause the MDF to deform and crack.

 

The infrared radiation technology is the best way to penetrate the surface layer of the powder to simultaneously heat the inner layer of the powder, uniform and rapid curing, which can effectively solve the problem of overcoming the Plain MDF board.

 

And we know that infrared wavelengths are divided into long, medium and short wavelength bands. Long-wave wavelengths are generally 4μm, medium-wave wavelengths are generally 2-4μm, and short-wave wavelengths are generally 2μm, depending on the wavelength.

 

It can be concluded that long-wave can only heat the surface of the coating, but cannot heat the inside of the coating. The short-wave infrared has strong penetrating power and will heat into the interior of the sheet, which will cause the interior of the Plain MDF to heat up, causing moisture and volatile substances to escape directly. Affect the appearance of powder coating. The mid-wave infrared heating will uniformly heat the inside and outside of the coating, which can achieve the best effect.

 

The development of Plain MDF powder coating technology is mainly due to the application and development of new technologies. The first choice is the synthesis and manufacturing of low-temperature fast resins, as well as the rapid development of curing agents and accelerators, which led to the rapid development of Plain MDF powders. It is currently on a large scale. Promotion and application, and construction is becoming more and more efficient, creating more value for customers.

 

With the improvement of peoples environmental protection and health awareness, the improvement of relevant laws and regulations, and the investment of more and more companies and raw material companies, the future direction will be more clear, and more powder coatings will be used on Plain MDF boards. It will be broader.

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