Definition
A laboratory pneumatic disperser is a type of laboratory equipment powered by compressed gas, which is mainly used to evenly disperse solid particles in a liquid medium to form a stable suspension or slurry. This equipment realizes the wetting, deagglomeration and dispersion of particles through the synergy of mechanical force and fluid shear force, and is one of the key instruments for sample preparation and preparation in materials science, coating research and development, nanotechnology and many industrial research fields.
Principle
The core working principle of laboratory pneumatic dispersion machine is based on the mechanical design of pneumatic motor drive and dispersion structure. Compressed air drives a pneumatic motor to generate high-speed rotation, driving the rotor (or dispersion disc) to move at high speed in the stator (or container). The precise gap between the rotor and the stator forms a high-shear area, in which the material is subjected to strong shear, impact and turbulence. The shear rate and dispersion effect can be roughly described by the formula: τ = μ · γ, where τ is the shear stress, μ is the fluid viscosity, and γ is the shear rate. By adjusting the inlet pressure and flow rate, the equipment can realize the continuous control of rotor speed and output power, so as to adapt to the material system with different viscosity and dispersion difficulty.
Measurement and evaluation methods
Evaluation of dispersion effects usually requires a combination of multiple analytical methods. Particle size distribution can be measured by laser diffraction or dynamic light scattering to characterize the degree of dispersion and agglomeration of particles. Dispersion stability can be quantified by observing the settling rate of the suspension, determining the zeta potential, or using multiple light scatterometers. In addition, rheological tests of the final slurry, such as viscosity-shear rate curves, can also indirectly reflect the dispersion quality. In practice, the control variable method is often used to compare the dispersion results under different equipment parameters under the conditions of fixed dispersion time, medium and formula.
Influencing factors
The dispersion effect is affected by multiple factors. In terms of equipment parameters, rotor line speed, rotor and stator geometry and clearance size, dispersion time and energy input are the key to determining the shear strength. The process parameters include the stability of the inlet pressure and flow, the temperature control of the processed materials, etc. The material characteristics cover the initial particle size, surface properties, and hardness of the particles, as well as the viscosity, polarity, and additive type and concentration of the dispersion medium. These factors are interrelated and need to be optimized and matched through system experiments.
Applications
Laboratory pneumatic dispersers are widely used in scientific research and quality control processes that require efficient and safe sample preparation. In the coatings and inks industry, it is used for pre-dispersion and stability studies of pigments and fillers. In battery material development, it is used for the uniform preparation of electrode slurries. In the field of ceramics and refractories, it is used for mixing and dispersing powders and adhesives. In the study of nanocomposites, it is used for the deagglomeration and distribution of nanoparticles in the matrix. Its pneumatic drive avoids the risk of electrical sparks, making it suitable for flammable and explosive environments or places where explosion-proof is required.
Selection considerations
Technical requirements and operating conditions should be comprehensively considered when selecting. First, the required shear strength and equipment power should be determined based on the characteristics of the material being processed (such as viscosity range, particle hardness, sensitivity) and the target dispersion fineness. Secondly, it is necessary to pay attention to the equipment material (such as whether the contact parts are corrosion-resistant and wear-resistant) and the seal design to adapt to different chemical properties. In terms of safety, pneumatic models with explosion-proof certification should be preferred in potentially explosive atmospheres. In addition, the ease of cleaning, noise level, air consumption, and ease of connection to existing laboratory air systems are also important practical considerations. It is recommended to use a sample trial to verify the suitability of the equipment for a particular process.