Definition
A laboratory stir disperser is a type of equipment used to mix, disperse, homogenize, or emulsify liquids, semi-fluids, or suspensions in a laboratory setting. It realizes full contact and distribution between materials through mechanical action, and is widely used in the sample preparation and process research stages in the fields of chemicals, coatings, food, cosmetics, materials science and environmental monitoring.
Principle
Laboratory stirrer dispersers typically work on high-speed rotating agitators or dispersion discs. The motor drives the rotating shaft so that the stirring paddle or dispersion pan mounted at the end rotates at high speed in the sample container. During rotation, the paddle or platter exerts shear, impact, and turbulence on the material, thereby breaking the agglomeration of particles and promoting the uniform dispersion of different components. For high-viscosity systems, the equipment may combine a stator-rotor structure to create a stronger shear effect through a narrow gap and achieve fine dispersion. Its basic force can be described as the relationship between shear rate and viscosity, and the relevant formula can be expressed as:τ = η × γ, among themτfor shear stress,ηis the viscosity of the fluid,γis the shear rate.
Measurement and evaluation methods
The stirring dispersion effect can be evaluated in a variety of ways. The particle size distribution is often measured by a particle size analyzer, and the degree of dispersion is characterized by parameters such as D50 and D90. The stability can be observed by standing and the stratification can be observed, or the suspension stability can be analyzed by centrifugal sedimentation method and zeta potentiometer. Viscometers can be used to monitor changes in the rheological properties of the system during dispersion. In addition, visual observation and microscopy are also practical methods to assist in judging the dispersion state. During operation, process parameters such as speed, time, and temperature should be recorded to ensure that the process is reproducible.
Influencing factors
The stirring and dispersion effect is affected by multiple factors. Equipment parameters include agitator type (e.g., paddle, turbine, toothed dispersion disc), speed range, power and processing capacity. Process conditions such as dispersion time, temperature control, dosing sequence, and speed can also affect the results. In terms of material characteristics, base viscosity, solids content, particle hardness and wettability are all key factors. The relative position of the vessel geometry to the agitator can affect the flow field distribution, which in turn changes the mixing efficiency. In actual operation, the combination of parameters needs to be adjusted according to the characteristics of the system.
Applications
Laboratory mixer dispersers play a role in research and quality inspection in multiple industries. In the coatings and inks industry, it is used for dispersion and stability testing of pigments in resins. It is often used in the preparation and homogenization of emulsions and pastes in the field of cosmetics. Mixed process development for sauces and beverages in the food industry. The research and development of new materials such as nanomaterials, battery slurries, and ceramic pastes also rely on them for precursor dispersion. It can be used in environmental analysis for the preparation of water samples or soil suspensions. It provides a basic means for small-batch recipe optimization and process simulation.
Key points to consider when selecting
When choosing a laboratory mixer and disperser, it is necessary to comprehensively consider the technical requirements and usage conditions. The viscosity range and rheological characteristics of the material are used to determine the required torque and power. Sample capacity should match the throughput of the equipment to avoid over-design or under-capacity. The speed range and control accuracy should meet the needs of process exploration, and some applications require stepless speed regulation or program control. The agitator and dispersion head should be made of materials that are compatible with the sample chemistry to prevent contamination or corrosion. In terms of safety, attention should be paid to equipment overheating protection, mechanical stability and ease of cleaning. Extended functions such as vacuum defoaming and temperature monitoring can be considered as appropriate for research needs. It is recommended to compare the technical parameters and operating experience of different models in combination with specific application scenarios.