In the process of coating construction, it is often necessary to reduce its viscosity, and three methods are usually used: adding solvent (diluent), heating and shearing and stirring. The three methods have their own advantages and disadvantages, and they should be used with caution.
(1) Solvent (thinner)
For the convenience of storage and transportation, the paint is often made into a viscous state with high solid content. When in use, solvent (thinner) is added to dilute it to make it reach the viscosity required for construction. Dilute with human thinner and stir evenly to obtain the desired viscosity coating. Ease of use and obvious effect are the biggest advantages of this method. The disadvantage is that organic solvents are volatile organic compounds (VOC), which will pollute the environment, and the cost of use is also high, and the viscosity obtained by simply preparing according to the instructions is not accurate. Because the viscosity of the paint will change with the ambient temperature and humidity during preparation, it is often necessary to make further adjustments according to the actual situation and experience. The solvent-diluted paint should not be left for too long, because the solvent will evaporate and the viscosity will change after being exposed to the air for a long time.
(2) Heating
The viscosity of the paint will change greatly with the temperature. As the temperature rises, the viscosity will decrease significantly. Therefore, attention should be paid to adjusting the viscosity of the paint during construction in different seasons. For coatings with higher viscosity, thermal spraying with a Spray Gun equipped with a heating device can obtain better construction results, which is also the principle of decreasing viscosity with increasing temperature. The disadvantage of reducing the viscosity by heating is that it consumes more energy and requires the use of specialized equipment. Conversely, in order to ensure that the viscosity of the coating remains stable during construction, and to ensure a constant temperature in the working environment, it is generally required to keep the temperature at around 20-25°C.
(3) cut
Reducing the viscosity of coatings by shearing is a widely used method in the spraying process. But it should be noted that it is valid for non-Newtonian pseudoplastic and plastic fluids. Moreover, only one stable delivery pressure is often used in the pressure-feed spraying process system, and the viscosity of the pseudoplastic fluid will change under shearing, so the spraying pressure will not be changed accordingly, and the spraying effect will be affected. It is necessary to minimize the shearing effect during the spraying process, such as reducing the number of openings of the Spray Gun, reducing the change of fluid pressure in the delivery pipeline, etc.
