Definition
The stirring and dispersion multi-purpose machine is a general laboratory equipment that integrates the functions of stirring, dispersion and homogenization. It applies mechanical shear force to the liquid or solid-liquid mixture through a high-speed rotating agitator or dispersion disc to achieve the mixing, dispersion, emulsification, or dissolution of materials. This equipment is widely used in sample preparation and process simulation in various fields such as chemical industry, coatings, food, and material science.
Principle
The working principle of the stirring and dispersion multi-purpose machine is based on the shear and turbulence effects in fluid dynamics. The motor rotates at high speed by a spindle that drives the agitator (e.g. paddles, serrated dispersion discs, etc.). When the agitator is immersed in the material, its rotational motion creates a strong radial and tangential flow, forming a vortex. At the edge of the agitator, especially at the serrated structure, the high linear velocity generates a strong local shear force that breaks up particle aggregates or droplets and disperses them evenly in the continuous phase. The relationship between basic power and shear rate can be described in the following simplified model:
P ∝ μ · γ̇²
where P is the power, μ is the viscosity of the material, and γ̇ is the shear rate. In actual work, the shear rate is closely related to the diameter, rotation speed and rheological characteristics of the agitator.
Measurement and evaluation methods
Equipment performance is often evaluated by combining process parameters with final sample characteristics. Key operating parameters such as speed, torque, and power consumption can be read or calculated directly from the device sensors. The evaluation of sample dispersion relies on offline analysis, such as measuring particle size distribution using a particle size analyzer, observing the morphological uniformity of the dispersed phase through a microscope, or measuring physical and chemical indicators such as slurry viscosity and stability. In standard operations, dispersion procedures are often standardized with reference to relevant industry standards such as ASTM D6580 for the coatings industry to ensure comparability of results.
Influencing factors
The stirring and dispersion effect is affected by multiple factors. The equipment parameters include the agitator geometry, diameter, number and angle of serrations, as well as the speed and lifting stroke of the spindle. The process parameters involve dispersion duration, material temperature control, and dosing sequence. The characteristics of the material itself, such as the viscosity of the continuous phase, the concentration of the dispersed phase, the initial particle size and surface properties of the particles, also play a decisive role. Additionally, if the shape and size of the container do not match the agitator, it may cause flow dead spots or air entrainment, affecting the dispersion efficiency and consistency.
Applications
In the chemical sector, the equipment is used to prepare nanomaterial suspensions, catalyst slurries, or polymer solutions. The coatings and inks industry is mainly used for the dispersion of pigments in resin bases to achieve the desired coloring power and stability. In the food industry, it can be used to prepare emulsified sauces, sauces or homogenization pretreatment for functional beverages. In the research and development of battery materials, it is used for the stirring and dispersion of electrode slurries (mixtures of active substances, conductive agents and binders). Its versatility makes it the foundation for formulation research, process optimization, and quality control in various laboratories.
Selection considerations
Systematic matching is required during selection. First of all, the properties of the main materials to be processed should be clarified, especially the viscosity range and the required dispersion fineness, and the required power and torque range of the equipment should be determined accordingly. Secondly, according to the conventional experiment, the appropriate host lifting stroke and adaptable container size are selected. Agitators and dispersion discs need to be equipped with a variety of types to suit different tasks, from low-viscosity mixing to high-viscosity strong shearing. The equipment should have stable speed control, overload protection, and possibly consider the need for additional modules such as vacuum or heating. Finally, the ease of operation, safety protection design, and compliance with relevant safety standards are also aspects that cannot be ignored.