Water-based polyurethane coating spraying tips

Spraying method is one of the main methods in the construction of water-based polyurethane coatings, can obtain a thin and uniform coating film, for heterogeneous parts, small holes, gaps, concave and convex places, the coating can be evenly distributed; for spraying large pieces, this method is faster and more effective than painting. The construction by spraying method must also master some operational tricks: 

1. Use clean water to adjust the waterborne polyurethane paint to a suitable spraying viscosity, measured with a Tu-4 viscometer, the suitable viscosity is generally 20~30 seconds.

If there is no viscometer for a while, visual inspection can be used: use a stick (iron or wooden stick) to stir the paint and then pick it up to a height of 20cm and stop to observe, if the paint does not break the line in a short time (a few seconds), it is too thick; if the line is broken as soon as it leaves the upper edge of the barrel, it is too thin; to stop at a height of 20cm, the paint becomes a straight line and instantly breaks off into a downward drip, this viscosity is more suitable.

2. Air pressure is best controlled at 0.3 to 0.4 MPa (3 to 4 kg force/cm2). If the pressure is too small, the atomisation of the paint will be poor and pockmarks will form on the surface; if the pressure is too large, it is easy to hang and the paint mist will be too large, which will waste materials and affect the health of the operator.

3,The distance between the nozzle and the surface of the object is generally 30~40cm. Too close to easy to hang; too far away from the paint mist is not uniform, easy to appear pockmark, and nozzle from the surface of the object far away from the paint mist in the way to scatter caused waste.

The specific size of the distance should be adjusted according to the type of paint, viscosity and the size of the air pressure. Slow dry paint spraying distance can be far away, fast dry paint spraying, the distance can be closer; viscosity thick when a little closer, viscosity can be a little farther; air pressure, the distance can be farther, the pressure can be a little closer; the so-called near a little far is a small range of adjustment between 1cm ~ 5cm, if more than this range, it is difficult to obtain the ideal water-based polyurethane paint film.

4, The gun can be moved up and down, left and right, preferably at a speed of 10 to 12 m / min even operation, the nozzle should be straight in the object surface spraying, minimize oblique spraying.

When spraying to both ends of the object, the trigger hand of the gun should be quickly loosened, so that the paint mist is reduced, because the two ends of the object, often to receive more than two spraying, is the easiest place to cause the flow of hanging.

5, when spraying to the next pressure on the previous 1/3 or 1/4, so that there will be no leakage of spraying phenomenon. When spraying fast drying paint, you need to spray it all at once in order. The effect of spraying is not ideal.

6、When spraying in the open outdoor area, pay attention to the wind direction (not suitable for operation in high winds), the operator should stand in the downwind direction to prevent the paint mist from being blown by the wind onto the sprayed water-based polyurethane paint film resulting in an unsightly granular surface.

7. The order of spraying is: first difficult, then easy, first inside, then outside. First high place after low place, first small area after large area. This will not cause the sprayed paint mist to splash onto the sprayed paint film and destroy the sprayed water-based polyurethane film.