Several methods of aluminum hydroxide dispersion-Flame retardant Masterbatches
The dispersion of aluminum hydroxide is actually particle dispersion. Particle dispersion refers to the process of separating and dispersing powder particles in a liquid medium and evenly distributing them in the entire liquid phase. It mainly includes three stages: wetting, de-agglomeration and stabilization of dispersed particles. Wetting refers to the process of adding powder to the vortex formed in the mixing system so that the air or other impurities adsorbed on the surface of the powder are replaced by liquid. De-agglomeration refers to dispersing aggregates of larger particle size into smaller particles by mechanical or ultrasonic methods. Stabilization refers to ensuring that the powder particles maintain a long-term uniform dispersion in the liquid.Flame retardant Masterbatches
1, mechanical dispersion method, etc.
Mechanical dispersion is a method of fully dispersing nanoparticles in a medium by mechanical energy such as external shearing force or impact force. Mechanical dispersion methods include grinding, ordinary ball milling, vibrating ball milling, colloidal milling, air milling, and mechanical stirring. This method is a commonly used method to disperse ultrafine powder, but it is easy to introduce impurities and may change the physical and chemical properties of the powder.
2, ultrasonic method
Ultrasonic dispersion is to directly place the particle suspension to be processed in the sound field and treat it with ultrasonic waves of appropriate frequency and power. It is a high-intensity dispersion method. The mechanism of ultrasonic dispersion is cavitation, which can generate local high temperature and high pressure, and generate huge impact force and micro jet. Under its action, the surface energy of nano powder is weakened, which can effectively prevent the agglomeration of particles to make it full dispersion.
3, chemical dispersion method
"Chemical dispersion" means selecting one or more suitable dispersants to improve the dispersion of the suspension and improve its stability and rheology. Commonly used dispersants are:
① Small molecular weight inorganic electrolytes or inorganic polymers, such as sodium silicate, sodium aluminate, potassium tripolyphosphate, etc. This type of dispersant can be dissociated and charged. Adsorption on the surface of the powder can increase the surface potential of the particles, increase the electrostatic repulsion, and improve the stability of the slurry. The mechanism of action is electrostatic repulsion and stability.
②Surfactant, this type of dispersant is composed of two parts: lipophilic group and hydrophilic group. It is an amphiphilic molecule, including long-chain fat, CTAB, etc. It is mainly due to steric hindrance. The hydrophilic group is adsorbed on the surface of the powder and the hydrophobic chain extends into the solvent, which has a good effect on improving the rheology of the slurry.