1. Hydrophobic product for thickening and reinforcement of RTV-1K one-component silicone sealant
2. Improve the storage performance of silicone sealants
3. Waterproof and hydrophobic for liquid system
4. Rheological control of complex liquid systems
5. Anti-settling for coatings to improve the stability of pigments and strengthen the anti-settling effect
6. Improving hydrophobicity and rheology of offset printing inks
7. Promote and maintain the flow of powder and anti-caking
The average distance moved by the pigment particles during Brownian motion along the x-direction within t time is represented by x.
(2-8) where R——gas constant;
T thermodynamic temperature;
NA Ye Avogadro constant.
The above analysis shows that under certain viscosity and temperature conditions, the particle size of the pigment particles has a great influence on the stability of the dispersion system.
2. Surface free energy and Austenite maturation
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When pigment particles with a larger particle size are crushed into tiny particles, the specific surface area increases. If the large cube particles with a side length of 5um are crushed into small cubes with a side length of 0.5 pm, the number of particles, total area, sides, and corners will increase.
A large cubic particle 0.5um is composed of 1000 small cubic particles. From formula (2-7), it can be calculated that the sedimentation speed of large particles is 100 times that of small particles. In the absence of wetting, problems are unavoidable. Edges and corners are the most active and accessible positions of pigment particles. Large particles have only 8 angles, while small particles have 8,000 angles, which is 1,000 times larger, and the side length has also increased by 1,000 times. Their adsorption in the dispersion is unstable.
Assuming that the interfacial tension between the pigment particles and the dispersion medium is y. In thermodynamics, the interfacial tension and the specific surface free energy are equal, the smaller the particle size, the greater the specific surface area (S) increases, and the total interface free energy G.=yS . Assuming that the internal free energy does not change, the free energy of the dispersed system is dominated by G. Therefore, the smaller the particle size becomes, the more unstable it is in thermodynamics. Particles aggregate to reduce the specific surface area, reduce free energy, and stabilize the dispersion. If the dispersion medium contains a wetting and dispersing agent, it will be adsorbed on the surface of the particles, reducing the interfacial tension y, improving the lyophilicity of the particles, and keeping the dispersion system in a stable state.
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