Analysis and countermeasures of several common film coating diseases

Whitening
in the construction of fast-drying paint, often appear whitening phenomenon, and the coating film lost light can not be restored. These coatings are mainly nitro paint, perchloroethylene paint, phosphate primer, thermoplastic acrylic magnetic paint and so on. The reasons and measures are as follows:
(1) the operating environment humidity is too high, solvent rapid evaporation takes away a large amount of heat, resulting in local wet film surface temperature dropped below the "dew point", so that water vapor condensation seeps into the wet film, resulting in emulsified white film, water eventually evaporated to create a gap and replaced by air, and eventually formed a holeless white filmThe relative humidity of the control environment is below 70% and the temperature is around 20 degrees C.
(2) paint solvents are volatile too quickly. Choose a diluent with suitable volatility, or add some slow volatile strong solvents to the raw material to adjust the volatility of the dilute material, such as dipropanosyl alcohol, cycloxitong, butyl acetate, butanol, glycol with ethylene esters and so on.
(3) the surface temperature of the coating is too low. The workbeat can be heated to a temperature 10 degrees Celsius above the ambient temperature.
(4) wet film contains moisture. Checkpaint, thin material contains moisture, air compressor oil moisture higher failure, there is a negative period of discharge of air compressor and oil moisture high water.
(5) thinner is not selected properly. The real solvent in the thin material is volatile too fast, the non-solvent evaporation is slow, when the wet film is dry, with its solvent volatile, the resin is insoluble in the non-solvent and the starting white.
lasing
in the spray, the paint is silky spray, affecting the appearance of the coating film, easy to appear this problem is acrylic paint, vinyl chloride paint, chlorinated rubber paint, epoxy paint and so on.
(1) paint construction viscosity is too large, atomization is not good, easy to produce silky spray, adjust the construction viscosity.
(2) the solubility of the dilute material is not enough, the dilution is too poor. Strong solvents are added to enhance the solubility of the rare material.
(3) coating resin molecular weight is too high, in the normal construction of solids, viscosity is very large. Increase the amount of thinner.
Retract hole
When the surface strain of the coating and the surface of the substrate vary greatly, it is easy to cause the paint to wet the substrate is not good, the angle of the angle becomes large, so that the paint has the tendency to maintain the pick and exposed to the coating surface. The aperture size is generally 0.1 to 2mm. In particular, varnishes and paints with fewer pigments are more prone to this defect and are not easy to repair.
(1) paint its own reasons, such as paint surface pressure is too large, poor mobility, resulting in poor wetting and poor bubble release.
(2) the substrate surface has oil or water, resulting in poor wetting of the coating film.
(3) smooth old paint film is also easy to wet the coating film. Give proper polishing.
(4) paint is mixed with oil, such as compressed air.
(5) the bottom coating contains silicone oil additives or plastic surfaces with release agents, the surface of the substrate is too low, there is poor wetting. Remove the low polarity surface by polishing.
(6) drying room air dirty, but also easy to cause shrink holes.
(7) wet film is contaminated with water, oil and other spray lakes.
bubbles and pores
are the bubbles left by the coating film during the coating drying process, when the bubbles trapped in the coating film force their way through the coating film escape. Unbreakable so that the coating film bulging is called a bubble. Bubbles can be air bubbles formed when the paint is stirred, or solvent bubbles formed by the sharp evaporation of the solvent when drying.
(1) solvent evaporates too quickly. Adjust solvent volatility and extend flash drying time.
(2) base coating is not dry and contains solvents. Wait for the bottom layer to dry out before re-painting.
(3) paint viscosity is too high. According to the construction specifications to exchange thin.
(4) paint is stirred too vigorously, or sprayed immediately after stirring. Add some desosting agent or alcohol solvent and set aside for 30min after stirring.
(5) brush is applied, the brush moves too fast or the bristles are too hard.
heats up sharply when baked with a thick coating (6) thick coating or water-like paint. Extend the flash drying time and heating process.
(7) is coated with residual moisture. Add a surface blow-drying process, or improve the drying effect.
pinhole
is a small hole on the surface of the coating that has been pierced by the tip of the needle, similar to a leather pore with a aperture of about 100 m.
(1) varnish is poorly refined and contains impurities.
(2) paint in the solvent volatile fast, and dosing more.
(3) pigment dispersion is poor.
(4) paint surface pressure, high viscosity, poor mobility, poor bubble release.
(5) paint-based mutual solubility is poor, with the ambient temperature decreased and locally deserated or increased viscosity, easy to cause particles and pinholes, such as asphalt paint is most likely to produce this defect.
(6) paint for a long time stirring, forming numerous fine air bubbles.
(7) is not cooled, so that the wet film solvent steamed out sharply.
(8) coating film is too thick and the table is drying too fast.
(9) operating environment is too high, or water is brought into the coating film when sprayed.
(10) flash dry is not enough. Baking heats up too fast.
hair
hair flowers are color paint surface color incogenity, the appearance of spots and stripes and other resulting color messy appearance defects.
(1) paint is unevenly dispersed, or the slurry is not mixed sufficiently when the color is toned. Such problems occur more easily, such as gray, light blue, green paint, etc.
(2) the solubility of the material is poor, or the viscosity is not proper, is not conducive to pigment, color paste even dispersion.
(3) thick coating film on the upper and lower layers of conflow, if the density of the two pigments is very different, easy to flower to form a hexagonal pattern.