Definition
An emulsifying mixer is a type of laboratory equipment used to form a stable or semi-stable emulsion by mechanical shearing of two or more immiscible liquids, usually oil and water, so that one phase is uniformly dispersed in the form of tiny droplets in the other phase. It plays a key role in R&D and quality control in many industries, including food, cosmetics, chemicals, materials science, and petroleum.
Principle
The core working principle of emulsifying mixer is based on mechanical fluid shear and turbulence. The equipment usually consists of a drive motor, a drive shaft and a stirring head (or rotor-stator structure). The motor provides power and drives the mixing head to rotate at high speed. When the mixing head is immersed in the mixture, the high-speed rotating rotor sucks the material from the axial direction and is forcefully sheared, squeezed and torn between the rotor and the precisely matched stator. At the same time, the resulting strong turbulence and hole effect further break the dispersed phase droplets into micron or even nano levels, resulting in uniform emulsification. Its shear rate is a key parameter to measure the emulsification capacity, and the calculation formula can be expressed as: γ = (π * D * N) / δ, where γ represents the shear rate, D is the rotor diameter, N is the rotor speed, and δ is the gap between the rotor and the stator.
Measurement and evaluation methods
The measurement and evaluation of the emulsification effect is usually not done directly by the mixer itself, but with the help of other analytical instruments to characterize the prepared emulsion. The main methods include: using a laser particle size analyzer to measure the particle size and distribution of emulsion droplets, which is the core index for evaluating emulsification uniformity; Evaluate the physical stability of the emulsion by observing the stratification, sedimentation or flocculation of the emulsion using a stability analyzer or by centrifugation acceleration experiments; The rheological properties of emulsion such as viscosity and thixotropy were measured by rheometer. and direct observation of the shape and dispersion of droplets through a microscope (such as light or electron microscope).
Influencing factors
The emulsification process and the quality of the final product are affected by multiple factors. In terms of equipment parameters, the structure of the mixing head (e.g., tooth shape, slotted design), rotor speed, shearing time, and the depth of the mixing head in the vessel are crucial. The process conditions include the order of addition of the two-phase liquid, the control of the mixing temperature, and the duration of the entire emulsification process. In addition, the properties of the material itself have significant effects, such as the volume ratio of the dispersed phase to the continuous phase, the interfacial tension between the two phases, and the presence of emulsifiers and their types and concentrations. These factors collectively determine the particle size, distribution, and long-term stability of the system of the emulsion droplets.
Applications
Emulsifying mixers have a wide range of applications. In the food industry, it is used to prepare salad dressings, creams, ice cream mixes, and beverage emulsions. In the field of cosmetics and personal care products, it is a key equipment in the manufacture of creams, lotions, shampoos, and toothpastes. In the chemical industry, it is used in the production of paints, coatings, inks, adhesives and various pesticides and emulsions. In materials science, it can be used to prepare nanocomposites or functional emulsions. In addition, in the petroleum industry, it also involves the research and testing of crude oil emulsification and fuel oil blending processes.
Selection considerations
Selecting the right emulsifying mixer for a specific application requires a comprehensive evaluation of several technical indicators. The volume and viscosity range of the material being processed should be considered first, which determines the motor power and mixing head size of the required equipment. Secondly, the requirements for the particle size of the target emulsion are directly related to the maximum shear rate that the equipment can produce and the precision of the stirring head structure. Material compatibility cannot be overlooked, and all components that come into contact with the material, such as shafts and mixing heads, should be made of stainless steel or special coatings depending on the chemical properties of the material. The operating characteristics of the equipment, such as the speed control range (whether it is stepless speed regulation), timing function, lifting mechanism, and easy-to-clean design, also affect the convenience and repeatability of the experiment. Finally, it is also necessary to consider the noise level and safety protection measures during the operation of the equipment.