The polymer is dispersed in the form of emulsion particles in water to form an emulsion, and the size of the emulsion particle diameter in the emulsion is the emulsion particle size. The emulsion particle size obeys Gaussian distribution, and its inhomogeneity is expressed by polydispersity, which is a unitless value less than 1. The larger the value, the wider the emulsion particle size distribution.
Emulsion particle size and particle size distribution is an important technical index of polymer emulsions, the size of its value, the performance of the emulsion, such as the color of the emulsion, the gloss of the coating film, the adhesion of the polymer, etc. It has a direct impact on the performance of the emulsion, such as the color of the emulsion, the gloss of the coating film and the adhesion of the polymer.
Polymer emulsions are water-based and are usually blue-white or milky white. When the emulsion is very fine emulsion particles, the emulsion is translucent, and may even be transparent; when the emulsion particles are coarse, the emulsion will no longer be transparent and become milky white.
2, Factors affecting the particle size of emulsions
The size of emulsion particle size is related to the emulsion polymerization process. In the process of emulsion polymerization reaction, small molecules of monomer with the help of emulsifier in the form of droplets dispersed in water, in the role of initiator in the emulsion particles polymerized into large molecules. Polymerization system mainly consists of monomer, emulsifier, water and water-soluble initiator. Many factors will have an impact on the emulsion particle size, such as the choice of monomer type and water solubility, emulsifier type and concentration, initiator type and concentration, reaction temperature, compared to, stirring strength, polymerization process.
Emulsion particle size range is generally within 4000 nanometers, the size of the emulsion particle is directly related to the use of emulsion. Film formation and bonding are the main application areas of copolymer wax dispersion, different applications require different emulsion particle sizes.
When used as a film-forming agent, the emulsion particle size will affect the fluidity and film-forming properties of polymer emulsions, so it is appropriate to use emulsions with small particle size for film-forming agents, such as glossy topcoats. To a certain extent, the finer the particle size, the better the emulsion film gloss, and the higher the critical pigment volume concentration of emulsion paints. Emulsion particle size distribution is wide, and its film density is high. The average particle size of the finer emulsion has a stronger bonding ability to the color filler. Sealer generally requires emulsion particle size greater than 1000nm to be used as a sealing layer on the surface of porous building materials, or as a base layer before coating.
When used as a binder, the average particle diameter of latex particles is about 1000nm to achieve the maximum bonding strength. The reason is that the emulsion particle diameter is too small, it is easy to penetrate too much into the voids within the loose substrate, and the large particles have a sealing effect, which can prevent too much paint from penetrating into the pores being bonded and lost.
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