Wetting Agents and Dispersion Geometry
Paint is essentially a dispersion system consisting of a binder, solvent and pigment. Used in furniture manufacturing to protect wood and give it a decorative appearance, paint's main components are binder, pigment and solvent, along with a mixture of other auxiliary materials. The binder portion consists of resin. The organic and inorganic pigments and fillers that give paint its color are also quite important in the mixture. Binder, pigment and additives (auxiliary substances) are the non-volatile parts of the system, while the volatile part is the solvent.
Wetting Agents and Dispersion Geometry
Paint is essentially a dispersion system composed of binder, solvent and pigment. The main components of paint used in furniture manufacturing to protect wood and provide a decorative appearance are binder, pigment and solvent, along with other auxiliary materials.
The binder portion consists of resin. Organic and inorganic pigments and fillers that provide color to the paint are also important in the mixture. The binder, pigment and additives (auxiliary materials) form the non-volatile portion of the system. The volatile portion is the solvent.
Wetting agents (auxiliary materials) are added to paint in very small amounts alongside the binder, pigment and solvent, and they have very important effects during manufacturing, storage, paint application and in improving paint film characteristics.
Additives not only modify the technical properties of the paint but also have properties that increase pigment efficiency.
Expected properties of a good wetting and dispersion agent:
• Good pigment wetting property,
• Should assist in grinding pigment particles,
• Should provide stabilization of pigment particles,
• Should provide color fastness,
• Should reduce viscosity,
• Storage stability
• Compatibility with the system.
Wetting agents should be added before powder materials.
These agents adsorb onto the particle surface and replace the air around the particles with liquid.
Wetting and Dispersion Process
The dispersion process is the mechanical distribution of particles in bulk and their homogeneous distribution in the liquid system at particle size. While inorganic pigments such as titanium dioxide disperse well with mechanical blades in the system, organic pigments are more difficult to disperse.
Wetting and dispersion agents enable a good dispersion process by creating a new particle surface while also shortening the dispersion time. The wetting agent amount should be optimally adjusted.
If the wetting agent amount is used sparingly, low efficiency is obtained and the desired grind level is not reached. As the dispersion time increases due to insufficient wetting agent, costs rise. If excessive wetting agent is used, settling occurs.
The most important point for ideal pigment stabilization is the adsorption of wetting and dispersion agents onto the pigment surface. The possible interactions in this process are ionic bonding, dipole interaction and hydrogen bonding.
According to this, stabilization types are as follows:
1. Electrostatic stabilization,
2. Steric stabilization,
3. Electrosteric stabilization.
Solvent-based systems generally employ steric stabilization.
In steric stabilization, the hydrophilic part of the wetting agent adsorbs onto the pigment surface. The pigment surface is thus coated and becomes stable against settling.
Wetting and dispersion agents should prevent or enable controlled settling (soft settling).
Dispersion Geometry
There is a specific geometry that must be observed in the dispersion process. This geometry is indexed to the diameter (a) of the blade used in dispersion.
The diameter of the container in which dispersion will be performed (2a) should be a maximum of twice the diameter of the dispersion blade. During the dispersion process, the dispersion blade should be positioned at a height of ½ a from the bottom.
The height of the mixture to be dispersed inside the dispersion container can be a maximum of 4 times the diameter of the dispersion blade, but a height of 2 times is preferred and optimal results are obtained at this height.
Pigment Properties
The particle size and shape of pigments directly determines their surface area. Pigment particle size determines transparency and opacity, and as pigment particle size decreases, adhesion increases. Very good wetting of pigments provides color fastness.
Gallery
Advertisement
Ad Space728 × 90
