(1) In transparent varnish, the addition of matting agent must not produce hard precipitation during storage or affect the transparency of the final paint film. Therefore, as mentioned above, the matting agent treated with organic matter is the best choice. Some other benefits can be brought by matting agents treated with organics, such as smooth surface and enhanced anti-scuffing properties.
(2) In the color paint system, the precipitation of matting agent is not a problem because of the addition of pigment, which has a much larger specific gravity than the matting agent. For cost-saving considerations, you can choose no surface treatment of matting agent, but sometimes, in order to improve the feel of the paint film and anti-scuffing, you can also choose the organic treatment of matting agent.
When individual particles are far apart, the ion atmosphere has not yet overlapped, and only gravity works. That is, in the second minimum area in the figure, the total potential energy is negative. At this time, the particles attract each other to produce soft and reversible flocs. As the distance decreases, the ion atmosphere overlaps, as shown in the figure
As shown in the second minimum 2-7(b), the repulsive force begins to appear, and the total potential energy gradually rises to a positive value. -Gravity But at this time, the gravitational force also increases as the distance decreases, and the maximum repulsive first minimum potential energy Vmax appears at a certain distance. The distance shrinks again, and the gravitational force takes the upper hand. The potential energy begins to drop in the potential energy curve of the interaction between the particles in Fig. 2-8, and enters the first minimal area in Fig. 28, and the particles will form hard aggregates. If V mmx is less than 2 to 3 times the kinetic energy (kT), due to the gravitational force VA, agglomeration will occur between particles. If there is a polymer dispersant adsorption layer around the particles, the situation is different. what chemicals are in wax If Vmax is above 20~25kT, there will be no aggregation between particles due to the repulsive force.
(2-13) where m is the mass;
V—particle velocity; k—boltzmann constant; kT—average energy of particle thermal motion. VR is the repulsive force, and its magnitude is the same as the electric potential of the diffusion double layer. It decreases exponentially with the increase of distance. The decrease is determined by the Debye length K. When the particle size is a1/K, Vk can be obtained by the following formula :
Where E is the dielectric constant of liquid; h is the distance between particles;
a~particle radius; in a heterogeneous dispersion system, the situation is different from the previous ones.
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