What are the properties of emulsion polymers?

Generally speaking, emulsion polymers have the following properties:

(1) The appearance ranges from milky white (often with a blue hue) to a translucent, uniform fluid with a certain viscosity.

(2) The viscosity has nothing to do with the molecular weight of the polymer, and is generally low. Emulsion is a non-Newtonian fluid, and its stress-strain relationship is not linear. The viscosity must be measured with a rotary viscometer. The measured values ​​are expressed in P (poise) and cP (centipoise).

(3) A small amount of agglomerated particles is allowed in the process of agglomerate emulsion polymerization, but it cannot exceed a certain limit value.

(4) The minimum MFT film-forming temperature value is related to the glass transition temperature of the polymer. When the temperature drops below the MFT, the emulsion cannot form a film and a film-forming aid must be used.

(5) There are several types of emulsifiers used in ionic emulsion polymerization: anionic emulsifiers are used alone; nonionic emulsifiers are used alone; cationic emulsifiers are used alone; anionic and nonionic emulsifiers are used in combination. Ionic properties are important for the ingredients to be used in the formulation.

(6) Particle size and particle size distribution The polymer emulsion is a heterogeneous system, and the polymer is in a particle-like irregular dispersion state in the emulsion. Due to the different emulsifiers and polymerization processes used in the emulsion polymerization process, the resulting emulsion particles and their distribution are quite different. The particle size and distribution of the emulsion are directly related to the appearance of the emulsion. Therefore, different emulsions have different appearances, which are mainly manifested in the hue.

(7) Residual monomer content The emulsion polymerization reaction can generally reach a relatively complete level, but there are often a small amount of incompletely reacted monomers, resulting in high VOC content, which is not conducive to environmental protection. Therefore, the content of residual monomers in the emulsion is limited, usually less than 0.1%.

(8) Stability Since the emulsion is a heterogeneous system, there must be stability problems, including chemical stability, mechanical stability, storage stability, freeze-thaw stability, dilution stability, etc.