Dry goods | furniture coating knowledge and then finishing, want to read this article is enough!

Furniture paint, also known as wood paint, generally refers to the surface of wood furniture special paint. In the panel furniture industry, the quality of paint is inextricably linked to the quality of furniture, and the environmental protection of paint determines the environmental protection of furniture. A certain understanding of paint is a must for every furniture practitioner. Therefore, this article combs out 10 common sense of furniture coating for practitioners to answer questions.

How to classify many furniture paints on the market?

A: In general, there are six kinds of furniture coatings:

PU (polyurethane paint) is widely used in high-end furniture, which has two kinds of water and oil. Its advantage is high hardness, the disadvantage is easy to yellow.

The NC, PU, PE, etc. are named after the film-forming substance, while UV (photocurable paint) is named after the curing way of the paint and cured into a film under ultraviolet light. Its advantages are fast drying and environmental protection; The disadvantage is that the cost is higher and the irregular object is more difficult to operate.

Water-based paint is the future development trend of environmental protection coatings. Its advantages and disadvantages have been explained in many previous articles, and this article will not be repeated.

Two. Paint = paint? What's the difference between the two?

First of all, paint ≠ paint, the two have a difference in definition. Early paints were mostly made from vegetable oil, hence the name paint. Later, synthetic resin completely refers to vegetable oil, and then it is not appropriate to name paint, so it is changed to paint.

In short, the word paint can cover liquid paint and solid powder coating, which can basically refer to various products in the industry; But paint is only liquid paint, which belongs to a kind of paint.

Three. The difference between primer and top paint?

Primer is the material applied directly to the surface of the furniture, that is, the first layer of the paint system. The primer is generally firmly attached to the surface and is used to reduce costs and fill the finish.

The top paint is the final coating of the coating, and the anti-oxidation, anti-yellowing, feel and gloss should be reflected in the quality of the top paint. Generally, the thickness of the paint film can be increased by increasing the number of top paint layers.

So why in the paint process, the primer should be brushed first?

Because the primer is designed for the purpose of filling. Good filling and sanding, and low cost. If you do not brush the primer and use the topcoat directly, it will lead to high cost and poor filling effect.

In addition, the standard for painting primer is that the wood eye should be filled thoroughly. That is, smooth paint film effect can be obtained by grinding.

4. Why should some paints be used together with adjuvants?

In general, in addition to the main paint, some paints also need to be combined with curing agents, accelerators, diluents, etc. Taking PU paint as an example, PU paint emphasizes the common use of main paint, curing agent and diluent. Different PU paints have different dilution systems and different solid content. If the use of unmatched diluent or curing agent, it will affect the crosslinking reaction of the paint, resulting in insufficient hardness, dry, film cracking and other problems.

In addition, AC acid curing paint is two-liquid type (main paint + curing agent); PE unsaturated polyester paint for three liquid type (main paint, accelerator, curing agent).

Only the main paint can be painted: NC nitro paint (single liquid self-drying type); UV light curing paint (single liquid curing type).

5. Are there any environmental requirements for painting?

The answer is clearly yes. A good paint level is not only related to the quality of the paint, but also closely related to the environment of the operation. Specifically, the environment needs to meet the following conditions:

1. Temperature: The best temperature should be 15℃ - 25℃.

2. Humidity: The appropriate ambient humidity is 30% -- 70%.

3. Ventilation is required.

4. Ensure environmental cleanliness.

5. Get good light.

Six. Paint after the phenomenon of flow hanging, how to solve?

Flow hanging is a very common problem in paint construction. In general, there are the following reasons:

1. Too much thinner

2. The temperature of the construction site is low, and the paint dries slowly

3. Paint brushes that are too large, too long, or too soft

4. When brushing uneven objects, thick surfaces are easy to hang

5. The brushed surface is not clean and cannot be attached after brushing.

According to the above summary to find the root cause, according to the specific situation to develop reasonable solution measures, can effectively avoid the phenomenon of flow hanging.

Seven. What causes the paint cracking?

There are many reasons for paint cracking.

In general, the hardness of the top paint is too high, the flexibility is poor, the coating is too thick, the surface layer is not dry, the drying agent is too much, the surface layer is too dry, the paint is not matched, the hardness of the bottom layer is too big, the paint is expired, the pigment and the resin are layered, the mixing is uneven and easy to crack, the environment is harsh and other reasons may cause the paint to crack.

Eight. Wood moisture content will affect the quality of coating?

It will affect. The moisture content of general wood should be controlled at 8-12%. If the moisture content exceeds the controlled moisture content, the wood of the furniture appears wet, and the coating dries slowly when finishing, which will reduce the adhesion of the paint film and make the volatile type such as nitrocellulose paint white. Will make the curing dry type of paint, such as PU paint produce bubbles, pinholes and other paint film defects.

When the climate is dry, the water content of the wood evaporates and shrinks, which is easy to crack and destroy the surface of the paint film. Therefore, the wood for furniture must be dried, and the moisture content should be controlled within the specified range.

9. Why will nitro paint film white, how to prevent?

The phenomenon of turbidity or milky white paint film after film formation is called white paint film, also known as white, white, whitening and so on. The causes of whitening of nitrocellulose paint film during spraying are as follows:

1. The solvent release of nitrocellulose paint is better, and the solvent is relatively easier to volatilize into the atmosphere in NC paint;

2, NC paint formula contains more volatile solvents;

The above two points are the precognitive conditions of whitening.

3, the solvent quickly volatilizes, absorbs the internal energy of the wet film of the just sprayed NC paint film, so that the surface temperature of the wet film instantly drops 2-30C, providing a "cold bed" for "condensation";

4, the high temperature and high humidity environment, so that the high content of water vapor around the wet film quickly condenses into droplets on the "cold bed";

The above two points are the process of whitening. After the process is produced, the result will be whiteness.

5, the poor miscibility of micro-beads and wet film, resulting in turbidity or milky phenomenon, called "white".

Measures to prevent nitrocellulose paint (NC) film whitening are as follows:

1. Check the effect of the oil-water separator when spraying, and remove the water in the compressed air in time;

2. Adopt proper and accurate methods to keep the interior painting environment in line with the requirements;

3. Under high temperature and high humidity environment, when the construction produces whitening phenomenon, whitening water can be added.

10. Why do bubbles, pinholes and other defects occur?

When applying glue, there is often such a problem: there are many large and small bubbles on the surface of the coating, and then the bubbles burst or are worn out during the grinding of the paint film to form dense pinhole-like holes.

The reasons for such blistering and pinholes are as follows:

1. There is gas in the coating, which breaks through the coating to form bubbles, and then breaks or wears out to form pinholes;

2. The spray air pressure is too high, and too much air is mixed into the paint;

3. The coating surface is attached with oil, dust, sweat, etc.

4. The temperature difference between the coating and the coated surface is too large;

5. Improper use of diluent, excessive addition of curing agent or wrong curing agent;

6. The paint itself is brought into the bubbles, and the bubbles generated when stirring are not eliminated.

All in all, there are many reasons for foaming and pinholes. According to the above reasons, the coating process conditions can be checked, the appropriate coating viscosity can be adjusted, the appropriate amount of diluent and curing agent can be used, and the coating thickness can be controlled.