Agglomeration and dispersion are the behavior of particles (especially fine particles, ultrafine particles) in opposite directions in the medium. In the gas phase or the liquid phase, the state in which the particles form a polymerization state due to the interaction force is called agglomeration; the particles are mutually incoherent, and the state in which they can move freely is called dispersion. Particle dispersion technology applications increasingly widespread throughout the chemical industry, metallurgy, food, medicine, paint, paper, construction and materials. In the chemical industry, such as coatings, dyes, inks and cosmetics, dispersion and dispersion stability directly affect the quality and performance of products; in the field of materials science, the success of composite materials and nanomaterial preparation and the dispersion of ultrafine powders Sex is closely linked. Dispersion technology is the most critical technology in the preparation, classification and processing of ultrafine powders. In short, dispersion has become an indispensable technical means to improve the quality and performance of products (materials) and to improve process efficiency. 1. Agglomeration state of particles The agglomeration of particles can be divided into three states according to their mechanism of action: Condensate Refers to the primary particles that meet face to face, whose surface area is much smaller than the sum of their individual particle compositions. This state is very difficult to redisperse. Agglomerate Refers to the attachment of primary particle clusters or small particles that are connected by dots and angles on large particles. The total surface area is larger than that of aggregates, but smaller than the sum of individual particle compositions, and redispersion is easier. Aggregates and agglomerates are also called secondary particles. Flocculation Refers to a looser structure created to reduce surface energy due to increased surface area of ​​the system and increased surface energy. Generally, due to the bridging action of the macromolecular surfactant or the water-soluble polymer, the particles are connected in series to form a lump which is loosely structured like a batt. In this configuration, the distance between ions is much larger than that of aggregates or agglomerates. 2. Agglomeration and dispersion of particles in the air 01 Causes of particle agglomeration in the air Force between particles Van der Waals forces, electrostatic forces and liquid bridge forces are the main causes of particle agglomeration in the air. Among these three forces, the electrostatic force is much smaller than the liquid bridge force and van der Waals force. In air, the agglomeration of particles is mainly caused by liquid bridge forces, and in very dry conditions is caused by van der Waals forces. Therefore, keeping the ultrafine powder dry in an air state is an important measure to prevent agglomeration. In addition, the use of grinding aids and surface modifiers is also an extremely effective method. Air humidity When the relative humidity of the air exceeds 65%, the water vapor begins to aggregate on the surface of the particles and between the particles, and the agglomeration is greatly enhanced by the formation of a liquid bridge between the particles. 02 Ways to disperse particles in the air Mechanical dispersion Mechanical dispersion refers to the mechanical agglomeration of particle agglomeration. The necessary condition is that the mechanical force (referring to the shear force and compressive stress of the fluid) should be greater than the adhesion between the particles. Usually, the mechanical force is caused by the strong turbulent motion of the airflow caused by the high-speed rotating impeller disk or the jetting and impact of the high-speed airflow. Mechanical dispersion is easier to achieve, but since this is a mandatory dispersion method, although the particles that are bonded to each other can be broken up in the disperser, the force between them does not change, and when the particles are discharged from the disperser, there is It is possible to re-agglomerate. In addition, mechanical dispersion may cause brittle particles to be pulverized, and the dispersion effect is reduced when the mechanical equipment is worn. Dry dispersion The liquid bridge force is often ten or ten times that of the intermolecular force. In humid air, the liquid bridge formed between the particles is the main cause of particle agglomeration. Therefore, the elimination of the liquid bridge or the destruction of the formed liquid bridge is one of the main means to ensure particle dispersion. Surface modification Surface modification refers to the physical or chemical treatment of particles, purposefully changing the physicochemical properties of the surface, so that the particles have new functions and improve their dispersion. It can be seen from the table that the CaCO3 powder is treated with different modifiers and different dosages, and the dispersion effect is also different. Electrostatic dispersion For homogenous particles, the electrostatic force acts as a repulsive force due to the same surface charging. Therefore, electrostatic force can be used to perform particle dispersion, and the key to the problem is how to fully charge the particle group. The particles can be charged by contact charging, inductive charging, etc., but the most effective method is corona charging, so that the continuously supplied particles group form an ion curtain through corona discharge to charge the particles. 3. Agglomeration and dispersion of particles in liquid 01 Wetting of solid particles The wettability of the surface of the particles is of great significance to the dispersion of the powder, and is the theoretical basis for the processes of powder dispersion, solid-liquid separation, surface modification and granulation. The process by which solid particles are wetted by the liquid is primarily based on the wettability of the surface of the particles. (To understand the wettability of the powder, please poke the link: ask every Monday | Do you know what is the wetting of the powder?) According to the size of the surface contact angle, the solid particles can be divided into two categories: hydrophilic and hydrophobic. The specific classification is shown in Table 2. 02 Ways to disperse particles in a liquid Medium regulation A well-dispersed suspension can be obtained by selecting an appropriate medium depending on the surface properties of the particles. The basic principle for selecting a dispersion medium is that non-polar particles are easily dispersed in a non-polar liquid; polar particles are easily dispersed in a polar liquid, the so-called principle of the same polarity. In addition, the principle of the same polarity requires the combination of the physical and chemical conditions determined in the same series to ensure the realization of good dispersion. Dispersant regulation The physicochemical conditions required for the good dispersion of the particles in the liquid are mainly achieved by the addition of an appropriate amount of dispersing machine, and the addition of the dispersing machine enhances the mutual repulsion between the particles. Commonly used dispersants are: inorganic electrolytes, surfactants and polymeric dispersants. Ultrasound regulation Ultrasonic regulation is to directly place the industrial suspension to be treated in the ultrasonic field, and control the appropriate ultrasonic frequency and action time to fully disperse the particles. Ultrasonic is more effective for the dispersion of nanoparticles. Ultrasonic dispersion is the use of local high temperature, high pressure, strong shock wave and micro jet generated during ultrasonic cavitation, which greatly weakens the nano-effect energy between nanoparticles and effectively prevents the agglomeration of nanoparticles. And make it fully dispersed. However, superheated ultrasonic agitation should be avoided because as the thermal and mechanical energy increases, the probability of particle collision increases, which in turn leads to further agglomeration. Mechanical agitation regulation Mechanical agitation and dispersion means that the particles are agglomerated and disintegrated by strong mechanical turbulence, causing strong turbulent flow of the liquid to generate mechanical forces such as impact, shearing force and stretching. The main problem with mechanical agitation is that once the particles leave the turbulent flow field generated by mechanical agitation and the external environment recovers, they are likely to re-form agglomerates. Therefore, the dual effect of mechanical agitation plus chemical dispersant tends to result in better dispersion. 1.The punching piece is passed between the pressure roller and the abrasive belt, and the deburring process can be completed at one time. Silicon Steel Deburring Machine Sheet Metal Deburring Machine,Silicon Steel Deburring Machine,Motor Silicon Steel,Silicon Steel Deburring Xinxiang Sunrise CNC Bearing Equipment Co., Ltd. , https://www.cncsunrise.com
2.The back surface of the abrasive belt is provided with a precision elastic pad and a wear-resistant pad, which forms the pressure difference and the abrasion reducing effect, thereby ensuring the deburring precision (2M53130 is a precision slotted rubber roller).
3.The workpiece feeding use variable frequency speed regulation, and the apply speed range is large for punching piece passed.
4.The axial direction is equipped with the anti deviation device controlled by the photoelectric switch, so that when the belt is rotated at high speed, the belt can not be off tracking, and the abrasive belt grinding and abrasion are uniform, thereby improving the service life and the durability of the abrasive belt.
5.The machine is equipped with a large capacity vacuum cleaner, which can remove the burr and dust in time, so as to ensure the operator's physical health and the cleanliness of the machine.
6.Both ends of the machine punching piece inlet and outlet are equipped with hydraulic lifting platform, convenient operation, reduce the labor intensity of workers.
7.The machine can also add delivery, unloading and conveying device at the front and back end, can be composed by punching →deburring→automatic painting line.