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    Home > Coatings News > Paints and Coatings Market > Wood coating technical service knowledge

    Wood coating technical service knowledge

    • Last Update: 2020-11-29
    • Source: Internet
    • Author: User
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    Paint is a kind of furniture raw materials, furniture surface decoration, improve the taste of furniture plays a very important role. Paints that are available in home improvement often vary widely in price, so how do you evaluate the performance of paints? Is the paint you choose worth it? In this regard, it can simply be evaluated from the following aspects: the surface performance of
    paint: the surface performance of paint refers to the general more intuitive perception, such as paint leveling, flow resistance, dryness, sanding, color accuracy and other performance.
    the intrinsic properties of paint: the evaluation of the intrinsic performance of paint is an important indicator to determine the quality of paint
    the
    .
    Viscosity indicator: viscosity varies greatly with temperature, so sometimes the viscosity varies greatly during the winter and summer rainy seasons, which is not an unstable paint quality, which is often a mistake for some furniture manufacturers.
    2. Non-volatile content index: also known as solid content, this indicator is the only indicator to evaluate the effective content of paint. At present, there is a misconception in the furniture industry that the higher the viscosity of the paint, the more water it can meet, the more cost-effective, without considering the effective content of the paint. In fact, the water in the paint will eventually all evaporate into the air, and will not remain on the surface of the work piece, the more water that hooks, the greater the actual waste, and seriously affect the environment. Therefore, low viscosity, high solid paint is the mainstream of the development of the furniture industry.
    3. Hardness: Hardness is divided into 6H, 5H, 4H3H, 2H, H, F, HB, 2B, 3B, 4B, 5B, 6B, etc. 14 grades, ordinary paint film hardness is generally between B-3H, paint film hardness is only a simple indicator of the performance of esqueer paint film, not hardness is generally good.
    4. Adhesion: Adhesion is an important indicator of the degree of closeness between paint and substrate, and also a sign of whether paint will fall during long-term use of furniture.
    5. Warping: it is an important index of the flexibility of the paint film. Paint film flexibility is a sign of furniture in the long-term use process will not crack, peeling.
    6. Impact resistance: it is also an important index of the flexibility of the paint film. The significance of this index to metal paint is particularly obvious, the better the resistance, then the more difficult the paint film in the impact conditions appear white, off-layer phenomenon.
    7. Cold resistance: refers to the paint film in low temperature conditions of cold resistance. This performance is a prerequisite for determining whether furniture Chinese mainland use in cold winter areas such as the northern part of the country.
    8. Heat resistance: The adoption of this performance is to ensure that the paint film in general conditions of use for hot water, teapots and other daily necessities of the heat requirements.
    9. Temperature resistance: This indicator is a higher level of paint film requirements. Only paint film that can withstand the hot and cold cycle test can obtain the basic conditions for safe use in any climate.
    10. Yellow degeneration: is the paint film in the process of use of color preservation performance of the indicators, generally using UV light or before and after the sun color difference, to quantify the degree of color change. The smaller the color difference, the better the color preservation, and the better the design of the paint film under the test conditions should have a small color difference.
    The problem in the use of paint and solve the problem
    1, paint peeling: may be the surface is too smooth, if the original paint is light paint or powder (plus untreated slurry paint), the new paint on the surface will not stick. Or it could be wood decay or rusty metal, or it could peel off due to poor paint quality. Small areas of paint peeled off, polished with fine yarn paper, then coated with putty, painted with primer, and then repainted. Large areas of shedding must be completely peeled off and repainted.
    2, bubbles, needle eyes: the solvent in the coating film is not completely volatile, the surface has been dried, resulting in the surface is volatile to the top, if the top is broken is the needle eye, if not broken into bubbles. Therefore:
    (1) if the table drys too fast, when the bubbles, curing agents and water reaction products carbon dioxide left in the paint, etc. can not run away;
    (2) one-time thick coating; insufficient inter-layer interval;
    (3) construction temperature is too high, resulting in too much table drying, curing agent and water reaction too much to produce excessive carbon dioxide;
    (4) coating (including thinners) or the surface of the coating moisture content is too high, the ambient temperature is too high, will lead to the curing agent and water side reaction to produce a large number of carbon dioxide bubbles;
    (5) Too much curing agent, especially at high temperatures more easily foaming
    prevention, solution:
    (1) adjust the speed of solvent volatilization, appropriate addition of slow-drying solvents, such as cyclosterone, CAC, etc.;, set aside for about 20 minutes to allow the air brought in during the mixing process to evaporate;
    (2) cannot be coated thick at a time; the interval between each spray is not too short; and
    (3) controls the temperature of the spray room and the drying room, such as in hot summer, It is advisable to spray in the morning or evening when the temperature is low, avoid direct sunlight, etc., sometimes the coating has just moved from the hot sun into the coating room, the coated object temperature is often very high, need to be placed cool for a period of time until room temperature after application;
    (4) Avoid the construction of places where the ambient temperature is too high, especially after grinding the water to wait for the surface moisture to dry fully dry, sweating the hands in summer, try to avoid touching the coating by hand before spraying,
    (5) correctly match the curing agent, in the high temperature and humidity season, slightly reduce the ratio of the curing agent.
    3, cracks appear: this situation mostly with chemical paint remover or hot air spray gun to remove the paint, and then repaint. If the fracture range is not large, then you can use sand scrubs or dry and wet sandpaper water, grind off the broken paint, after the surface is polished smooth, putty, paint the primer, and then repaint.
    4, flow hanging phenomenon:
    a. white blank surface uneven, complex geometry; b. spray gun and workware is too close;
    c. too much spray at a time; d. paint ratio dilution dose too much;
    e. construction environment temperature is too low; f. level interval time is not enough;
    g. Diluent volatility is too slow;
    prevention and treatment methods:
    (1) white blank table processing flat, complex geometry of the work to be sprayed multiple times;
    (2) spray gun and workware to maintain a distance of 20-30CM;
    (3) to reduce air pressure, Control the amount and quantity of oil;
    (4) reduce the number of thinners, construction viscosity should be about 16 inches (4 cups);
    (5) if the construction site temperature is too low, the construction site temperature should be controlled before construction;
    (6) spray coating should be in the first layer of paint film after the basic surface drying,
    (7) replaced with fast-drying diluent
    ; Moldy color change: This problem occurs mostly on wet paint surfaces, such as water vapor condensation on glass and metal surfaces often resulting in brown-black stains. At this time can be used fungicides, according to the instructions of the instructions to deal with moldy parts, after the mold killed, clean the surface, and then repaint.
    6, stains: paint surfaces produce stains for many reasons. For example: water in latex paint dissolves the material on the wall and rusts out of the paint surface, and rust spots are produced on the wall that is rubbed with steel wool. There are stains and so on in the leakage of dark pipes in the wall. In order to prevent stains, you can first brush a layer of aluminum powder primer, if there has been a stain, you can first remove the stain on the latex paint, brush layer aluminum powder primer, and then repaint.
    7, loss of luster: the reason is not on the primer, or the primer and the inner paint is not dry on the direct light paint, the result of the paint is absorbed by wood and lose luster. The bad light paint is also a reason. Use dry and wet sandpaper to grind off the old paint, brush to polish the dust, wipe the surface with a clean damper cloth, after drying out, and then repaint it. It is important to note that paint in very low temperatures can also lose its luster when the paint film is dry.
    8, orange peel, wrinkles: the coating film is not fully smooth flow is dry.
    (1) the paint is too thick;
    (2) the pressure is too high, the nozzle is too close to the work piece or too far away;
    (3) the thinner type is not right;
    (4) the ambient temperature is too high;
    prevention, solution:
    (1) paint is adjusted to the construction viscosity (4 cup) about 16-18;
    (2) reduce air pressure, spray and workware distance to be maintained at about 20-30CM, paint film should not spray too thin;
    (3) thinner type to be used in support of the selection of appropriate slow-drying solvents;
    (4) adjust the temperature of the spray room, control the exhaust flow.
    9, the cause of the granulation phenomenon (very poor feel):
    a. poor construction environment, too much dust; b. spraying is too small, pressure is too big paint atomization is not good;
    c. spray room ventilation is not good, the construction of the space in the spray room to retain a layer of paint mist;
    d. the use of curing agent has been bad;
    e. paint and curing agent after too long, paint has been glued.
    prevention and control, solutions:
    (1) alter the spray room to purify the air, clean the spray room, control the entry of unrelated personnel;
    (2) adjust the size of the spray gun nozzle, paint spray the best spray caliber of about 1.5mm, adjust the pressure;
    (3) the distance between the gun and the work piece is maintained at the optimum distance;
    (4) make the spray room well ventilated, no more foggy air in the spray room during construction,
    to use a good quality curing agent, paint mixed with the curing agent should be used within 4 hours.
    10, paint is not dry:
    (1) paint or the surface of the coating contains water,
    alcohol, oil or wax and other foreign substances, resulting in curing agent consumption
    ;
    prevention, solution:
    (1) select the specified thinner (excluding water, alcohol, acid). In particular, banana water, which contains a large number of alcohol solvents, will consume a large number of curing agents, and now there are still a lot of small furniture factories do not choose matching thinners, especially when making primers, often lead to primer dry, sometimes the surface looks dry, but in fact the same as curing agents are consumed by a large number of alcohol solvents, Resin is not well cross-linked, the result is that the primer hardness is not enough, polished sticky sandpaper or very easy to wear, medium or surface coating, there will be bite bottom, foaming, abundance difference, poor hardness, poor adhesion and many other problems
    ;
    (3) PU paint is slow to dry when room temperature is below 5 degrees C.
    11, paint stick to the bug: try to remove the bug when the paint is not dry, and then use a brush with a little paint gently repair the surface. If the paint has dried, it will have to wait for the paint film to harden before removing the bugs, so as not to make the surface a mess.
    12, painted wood surface dark spots: may be the wood section before painting unsealed, by the sun, wood section heat, resin from the wood towel seepage caused. At this point, the paint can be scraped with a scraper, and then fine sandpaper polished to reveal the wood section, with a sealing paint to seal the wood section, to be dried through, and then repainted.
    13, bite bottom, loss of light whitening:
    (1) upper and lower coating does not match, the inter-layer time is too short to dilute with high-strength solvent spray;
    (2) the temperature is too low in the spray room humidity is too high, the ventilation environment is too poor resulting in the paint film whitening loss of luster;
    (3) the paint has too much water and thinner added, not up to the thickness of the paint film,
    (4) construction site humidity is too high.
    prevention, solution:
    (1) upper and lower coatings supporting the use of inter-layer construction time extended to dry and re-sprayed a second time, replace diluted solvents.
    (2) renovation of construction sites, ventilation environment, the best construction temperature control at 25 degrees C relative humidity in about 70%;
    (3) adjust the paint ratio and construction viscosity (15-17),
    (4) construction, to avoid high humidity occasions and weather.
    14. Oil: After coating, the surface of the paint is caused by uneven pressure.
    (1) paint is contaminated is the main reason. Contaminated channels are:
    a. spray system, the supply of compressed air containing oil pollution - check the air compressor submarine valve, remove the oil, water, check the effect of oil and water separators;
    b. Packaging tank, open tank is contaminated with oil, fat - with a clean container paint, paint before, first wash with Tianna water;
    c. Operator's hand with oil, especially in winter hands with oily skin care products, in grinding, painting easy to cause paint pollution - operators confirm that there is no grease on hand, it is best to wash hands with soap or Tianna water;
    d. Contamination of substrates, including dusting, oil pollution, long storage time after grinding - confirm that there is no contamination on the substrate, if the previous grinding interval is too long, re-polishing;
    e. Contamination of the bottom coating, Including primer, medium coating due to the use of too many additives (such as leveling agent), and additives will move to the upper layer of the paint film, the bottom is applied too hard, not enough polishing, individual places are leaking - another grinding, confirm that the polishing thoroughly.
    (2) Plus the effects of electric field, magnetic field,
    because paint is a bad conductor of electricity, in the process of stirring, spraying, due to friction will produce a large amount of static electricity, when a strong applied electromagnetic field exists, will lead to serious oil. Such as the nearby use of welding machines, DC generators, the presence of instruments with strong magnetic fields, etc. - confirm that to be painted without the presence of the above situation before coating.
    (3) the operator with a strong static electricity, as described in (2), the paint surface often accumulated a large amount of static electricity, when the operator has enough static electricity, will lead to oil. This kind of situation often occurs in winter and plum rainy season,
    (4) paint production process, the additive is not stirred, resulting in the local additive content is too high;
    (5) the resin itself poor quality, such as molecular weight distribution is too wide sticky through the low
    paint use common sense
    1, temperature, humidity: the normal use of the paint temperature at 15-35 degrees C, relative humidity does not exceed 80%, beyond the above temperature and humidity limit, before use must To our technical department, the construction temperature of paint too low will make the paint film slow dry or not dry, at this time, if forced construction paint, will lead to late paint cracking;
    storage time of the oil depth after 2 and 0 all:
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