During the emulsion polymerization process, an important role of stirring is to disperse the monomers into droplets and facilitate heat transfer. However, the stirring intensity should not be too high. When the stirring intensity is too high, the number of latex particles will decrease, the diameter of latex particles will increase, and the polymerization reaction rate will decrease. Meanwhile, the emulsion will produce gel and even demulsify. Therefore, moderate stirring should be adopted.

• The Influence of Stirring Intensity on the Diameter of Latex Particles: In emulsion polymerization, the higher the stirring speed, the larger the diameter of latex particles and the fewer the number of latex particles. This is because in the dispersion stage of emulsion polymerization, when the rotation speed is high, the monomers are dispersed into smaller monomer droplets, and the surface area of monomer droplets per 1 cm³ of water is larger. The amount of emulsifier adsorbed on the surface of monomer droplets increases, resulting in a decrease in the number of micelles per 1 cm³ of water and a decrease in the nucleation probability. Therefore, the number of latex particles Np (per 1 cm³ of water) formed decreases. When the initial amount of monomers is constant, the diameter of latex particles will increase.
• The Influence of Stirring Intensity on the Polymerization Reaction Rate: As mentioned above, when the stirring intensity is high, the number of latex particles per 1 cm³ of water decreases, and the number of reaction centers decreases, resulting in a lower polymerization reaction rate. On the other hand, when the stirring intensity is high, more air is mixed into the system, and oxygen in the air is an inhibitor of free radical reactions, which also reduces the reaction rate.
• The Influence of Stirring on the Stability of Emulsion: Excessive mechanical action will reduce the stability of the emulsion, and even cause gelation and demulsification. This is because: ① The stirring action imparts kinetic energy to the latex particles. When the kinetic energy of the latex particles exceeds the repulsive force or steric hindrance between the latex particles, the latex particles will coalesce and form a gel. ② The emulsifier has a certain binding fastness on the surface of the latex particles. When the stirring intensity increases, due to the enhanced friction between the surface of the latex particles and the water medium, the emulsifier on the latex particles will be instantaneously pulled away, reducing the coverage of the emulsifier on the surface of the latex particles, thus the stability decreases. When a large number of bubbles are excited (mainly due to the emulsifier), the impact on stability is even greater. ③ The stabilization of the emulsion by non-ionic emulsifiers depends on hydration. When the stirring intensity increases, the friction between the latex particles and water increases, resulting in a thinner hydration layer, so the stability decreases.

In conclusion, to ensure a stable production process and uniform product quality, it is advisable to install a variable frequency speed regulator on vertical motor reaction kettles. For horizontal motor reaction kettles, it is advisable to determine the appropriate wheel diameter ratio according to the shape of the stirring rod and the stirring efficiency to ensure the optimal stirring intensity.