月: 2022年11月

What Is an IC Package?

An IC package is a case component attached to semiconductor chips. It serves multiple functions, including supplying power, protecting the chip from external environmental factors, transmitting signals to and from the chip, and enhancing chip performance.

Applications of IC Packages

These packages are integral to a wide range of devices, from smartphones and tablets to various sophisticated electronic devices in homes. As technology evolves, there is a growing demand for smaller, lighter, and more functional packages. They are also adapting to incorporate multiple mechanisms in a single package, especially in sensor devices that operate on multiple wavelengths.

Principle of IC Package

IC packages consist of structures for electrical connection and protection. Electrical connections often use gold plating for high-specification applications. The protective part, known as the sealing material, has traditionally used metal but is now increasingly using resin-based materials for weight and cost efficiency. Ceramics are also gaining popularity due to their superior properties.

Types of IC Packages

Package types vary based on the terminal extension method and the material used for the package body. They range from plastic packages to ceramic packages and include:

1. System In Package (SIP)

Encapsulates multiple chips in one package, suitable for cost reduction and insertion mounting, with excellent heat dissipation performance.

2. Small Outline Package (SOP)

Features terminals extending in two directions, often used for small semiconductor chips.

3. Quad Flat Package (QFP)

Has terminals extending in four directions, suitable for various applications.

4. Land Grid Array (LGA)

Includes terminals at the package bottom, allowing for grid-pattern socket mounting.

Other Information on IC Packages

Advantages of Ceramics

Ceramics offer high thermal resistance and maintain shape after heat treatment. They are in high demand due to their thermal conductivity and workability, leading to advancements in recycling technology for sustainable material sourcing.

What Is Packaging Machinery?

Packaging machinery is used to pack and package foodstuffs and pharmaceuticals automatically.

There are various types and names of packaging machinery, such as filling machines, pillow wrapping machines, shrink wrapping machines, sealing machines, and tying machines. There is also packaging machinery with automatic weighing functions to keep products at a certain weight and quantity, as well as vacuum packaging machinery that creates a vacuum inside packages. There are many other types of packaging machinery to create appropriate packaging for food or pharmaceutical products.

Uses of Packaging Machinery

Packaging machinery is used to package products in food and pharmaceutical plants.

Bottle filling machines are used to fill bottles with liquids. Pillow packaging machinery is used to wrap powders in sticks, frozen foods, and snacks. Container forming and filling machines are used when a box-shaped container, such as a milk carton, is to be made and the product is to be placed inside.

Sealing machines are used to seal food products to keep them from outside air for a long time. Gas-filled packaging machines and vacuum packaging machines are used to vacuum or inject gas.

Closure machines are used to close the mouth of the bag with tape or vinyl tape after the bread, etc., is packed in the bag. Boxing machinery is used for packing finished products into cardboard boxes. Shrink packaging machinery is used when trays containing side dishes are to be wrapped in film.

Shrink-wrapping machines are used to wrap trays of side dishes, etc. in film.

Principle of Packaging Machinery

Packaging machinery named “filling machines” includes liquid level regulating types, piston types, weight types, and meter types. The level control types use a level sensor to check the volume inside a bottle. The weight type has the function of a weight scale, and the meter type has the function of weighing liquid levels. The piston type uses the same method as a syringe and is used to fill bottles with highly viscous liquids, such as shampoo. Both types stop when the product weight or liquid level reaches a set value.

Pillow packaging machinery and sealing machinery use heaters to crimp the ends and dorsal fins of the product as it is being packaged. The film is cut by a cutter as it is crimped, resulting in a product of a predetermined length. In the case of a sealing machine, the entire bag is lightly crushed with a sponge or other soft material to prevent air from entering the bag just before crimping.

In the case of a tying machine, pre-bagged products such as bread are conveyed by a conveyor belt, and the mouth of the bag is squeezed while being pulled in with a roll, and then tied with a bag closure or vinyl ties.

The box-packing machine uses a robot arm to fill the product into a box. It has a sensor that detects the product to be filled and the presence or absence of a small box. The robot arm fills the box in accordance with the signals emitted by the sensor.

Shrink packaging machinery packs products by wrapping them in film that shrinks when heated. When the shrink-wrapped product is passed through a tunnel, the film is heated by hot air or steam in the tunnel and the product is shrink-wrapped.

Gas-filled packaging machinery inserts nozzles through the entrance of the bag containing the product. Air is drawn from one side of the two inserted nozzles, and gas is filled from the other side. This method is also called the nozzle method, and vacuum packaging machinery works similarly.

What Is an Accelerometer?

An accelerometer is a device that measures acceleration, the rate of change of speed per unit of time.

Accelerometers can measure the acceleration of a vehicle or the vibration of a machine. They can also collect and store information on vibration and tilt.

Accelerometers are divided into four main types: piezoelectric, servo, strain gauge, and semiconductor.

Uses of Accelerometers

Accelerometers are used in a wide range of fields, including the automotive, processing, and electronics industries. In the automotive industry, they are used for engine testing. In addition to this, they are often installed for automobile research and development and abnormality detection.

When used as vibration meters, they are installed to monitor abnormal vibrations in rotating equipment. Sudden failure of rotating equipment directly leads to increased costs, so vibration monitoring prevents equipment failure before it occurs.

Accelerometers are also used in large industrial equipment for quality control of products in transit.

Accelerometers have long been used as vibration meters for vibration measurement and testing. In recent years, accelerometers have been built into smartphones and used in pedometers and health care applications.

Principle of Accelerometers

The principles of how accelerometers can measure vibration and acceleration vary depending on the type of accelerometer.

1. Piezoelectric Accelerometer

The piezoelectric element inside the sensor expands and contracts under the pressure caused by acceleration and releases an electric charge to detect acceleration.

2. Servo Type Accelerometer

Consists of a coil, magnet, and pendulum. The movement of the pendulum caused by acceleration generates electricity in the coil, and the amount of electricity generated is measured and converted to acceleration.

3. Strain Gauge Type Accelerometer

Strain is generated by the inertial force on the internal weight due to acceleration, and the amount of strain is detected by the gauge to measure acceleration.

4. Semiconductor Type Accelerometer

A capacitor consisting of movable electrodes is incorporated inside a semiconductor. Acceleration is measured when the capacitance of the capacitor changes due to the bending of the movable electrodes caused by acceleration.

How to Fix Accelerometers

The method of mounting an accelerometer has a significant impact on the accuracy of the measurement. There are five major methods of securing acceleration sensors.

1. Screw Fixation

This is the most ideal method. To increase rigidity, a thin layer of grease is applied to the object to be measured and then tightened to the specified torque.

2. Cementing Agent Clamping

Apply the cementing agent to the object to be measured and fix it.

3. Insulating Washer Fixing

Used to insulate the object to be measured from the sensor.

4. Fixing Magnet

Used as a simple fixing method when the object to be measured is magnetic.

5. Hand Probe Fixing

This is used when it is not possible to fix the probe with screws, or when a quick inspection is required. Fix the cable so that no excessive force is applied to the connection part of the accelerometer.

Other Information on Accelerometers

Measuring Vibration With Accelerometers

Vibration is measured from three parameters: displacement, velocity, and acceleration. Accelerometers are used as one of the sensors for measurement. Among vibration sensors, piezoelectric accelerometers are characterized by their ability to cover a wide frequency range.

The definition of mechanical vibration is defined as “a temporal change in the magnitude of a quantity representing the motion or displacement of a mechanical system that alternately repeats a state in which it is greater than or less than a certain average or reference value.”

Frequency analysis is widely used to analyze vibration. It is a method to determine what frequencies and how much intensity each of the measured waveforms contains.

What Is a Heating Coil?

A heating coil is a coil utilized in induction heating.

Heating is achieved by placing the object to be heated inside the coil. The shape, number of windings, and diameter of the heating coil vary depending on the heating requirements, such as the characteristics and shape of the object to be heated and the area to be heated. It is important to optimize the heat distribution by designing a coil that meets the requirements.

A coil design that meets requirements is also necessary to maximize work efficiency by making it easy to insert and remove the object into and from the coil. Furthermore, during heating, the heating coil itself is indirectly heated by the heat emitted from the object. Therefore, it is common to have a structure that can be constantly cooled.

Uses of Heating Coils

Heating coils are used in induction heating, and they are used in situations where precise and controllable heat treatment is required without direct contact with the object. Specific examples of industrial applications are as follows:

• Preheating for welding
• Quenching
• Tempering
• Annealing
• Brazing
• Hardfacing
• Soldering
• Metal melting and forging
• Getter heating
• Floating Melting
• Material Testing
• Cap sealing
• Material hardening
• Metal-to-glass bonding
• Crimping
• Susceptor Heating

Heating coils are flameless, which not only reduces carbon dioxide and environmental impact but also ensures clean and waste-free heat treatment. A well-known induction cooktop is a cooking appliance that applies this characteristic to ordinary households.

Principle of Heating Coils

The principle of a heating coil is that a coil is connected to an AC power source, which generates magnetic field lines around the coil to heat the object. This method of heating by electromagnetic induction is called “induction heating.” There are two types of induction heating methods:

1. Direct Heating Method

In induction heating, a conductive object is placed inside a heating coil and an electric current is applied to the object, which itself generates heat. This is the “direct heating method.”

This heating method uses a mechanism in which eddy currents flow in the object in a direction that prevents the magnetic flux from changing, and Joule heat is generated due to electrical resistance. The eddy currents are larger near the surface and smaller toward the interior. This is called the “proximity effect,” and the direct heating method is suitable for surface heating.

2. Indirect Heating Method

When heating insulators such as ceramics with a heating coil, the object is placed in a conductive container, and the container is heated directly, causing heat transfer and heating the object. This is the “indirect heating method.”

In this heating method, the heating element and the object are in contact with each other, or the heating element and the object are separated. The latter is called far-infrared heating because infrared rays heat the object.

Structure of Heating Coils

The shape of the heating coil is not simple, as the optimum one is selected according to the dimensions and shape of the object. A wide variety of coils exist, such as an outer surface coil in which the product is inserted inside the coil when heating the outer surface of a shaft, or an inner surface coil in which the coil is inserted when heating the inside of a steel pipe or other object.

For example, the high-frequency quenching method using induction heating includes the “stationary one-shot quenching method,” in which the object is heated without moving, and the “moving quenching method,” in which the object is sequentially quenched while moving. The heating coils used are different for each method.

1. Heating Coil Structure of the High-Frequency Quenching Method

In the “in-situ one-shot quenching method,” heating coils are manufactured according to the shape of the object, so they must be prepared according to the type of product. The shape of the heating coil is important, and experience and know-how are required for design and fabrication.

However, the advantage of this method is that even complex shapes can be heated uniformly, and the time required for heating can be shortened compared to the moving quenching method. The moving quenching method, on the other hand, uses single or multiple coils. The shape is simpler than that of the stationary one-shot quenching method and is selected in consideration of the shaft diameter and length of the object.

2. Heating Coil Structure with Coolant Injection

When used for quenching, the structure is provided with a quenching water jet. This is because the heated object needs to be cooled rapidly.

There are two types of water jets:

• A type that injects hardening water from inside the heating coil toward the object.
• A separate cooling jacket is installed near the heating coil.

The type that injects cooling water from inside the heating coil has a structure that allows both the cooling of the heating coil and the object with the quenching water. The object can be cooled efficiently since it can be cooled directly from the heating point, but in most cases, the shape is complicated.

What Is a Vibrator?

A vibrator is a device designed to test the strength and reliability of products by applying vibration, typically used in mechanical engineering, civil engineering, and architecture to simulate the effects of shaking structures, including earthquake simulations.

Applications of Vibrators

Vibrators play a crucial role in the development and quality assurance of industrial products, as well as in evaluating the durability of structures in civil engineering and construction. They help in testing how components, like those in automobiles or entire buildings, withstand vibrations to ensure no functional breakdown or abnormal noise occurs, mimicking conditions such as vehicle motion or seismic activity.

Principle of Vibrators

The operation of vibrators is based on the principle of electrokinetic vibration, similar to how speakers produce sound through air vibrations. Utilizing Fleming’s left-hand rule, vibrators control the force generated by magnetic fields and electric currents to create precise vibrations. Feedback circuits are employed to monitor and adjust the vibrations to achieve the desired outcome.

Types of Vibrators

Vibrators come in various forms, including mechanical, hydraulic, electrodynamic, and piezoelectric, each suitable for different testing requirements and object sizes:

1. Mechanical Vibrators

Mechanical shakers are preferred for large-scale strength and durability tests, capable of generating significant vibratory forces at low frequencies.

2. Hydraulic Vibrators

Hydraulic vibrators, known for their compact size yet large excitation force, are versatile, supporting a wide frequency range and the generation of arbitrary waveforms, making them ideal for comprehensive vehicle testing.

3. Electrodynamic Type Vibrators

Electrodynamic shakers, while less powerful than hydraulic types, can operate at higher frequencies, suitable for small to medium-sized test objects.

4. Piezoelectric Vibrators

Piezoelectric shakers excel in high-frequency applications but offer lower vibratory force, typically used when testing requires frequencies in the tens of kilohertz range.

Other Information on Vibrators

Types of Vibration Testing

Vibration testing with vibrators can be categorized into several types, each designed to simulate different environmental conditions and responses:

1. Sweep Test: The frequency varies continuously to simulate scenarios like a car’s accelerating engine.
2. Spot Test: Applies a continuous sine wave at a specific frequency, used when the environmental vibration is known.
3. Random Wave Vibration Test: Applies vibrations randomly to identify resonance phenomena within the product.
4. Shock Wave Vibration Test: Simulates short-duration, large-amplitude vibrations to mimic impacts or collisions.

What Is a Control Cabinet?

A control cabinet is a box that stores components and electrical equipment used to control industrial machinery and equipment.

It is made of metal or synthetic resin and is installed to protect the control equipment from the surrounding environment. The control equipment and control cabinet together are called a control cabinet.

Examples of equipment housed inside include wiring circuit breakers or ground-fault circuit breakers, electromagnetic switches, and sequencers. Generally, there is a door for opening and closing, and it is coated with powder or baking paint to prevent rust, corrosion, and salt damage. They are classified into unit type and collective type according to the storage method.

Uses of Control Cabinets

A control cabinet is mainly used in industry.

The following are examples of control cabinet applications:

• Protection of elevator control equipment
• Protection of control equipment for air-conditioning systems
• To protect the drive units of fire pumps
• For storing control equipment of automatic conveyor systems

Since electronic components and precision devices are used in control and drive equipment, they must be protected from dust and debris. Control cabinets are used to isolate control and drive equipment from these harmful factors. Since they are often installed outdoors, outdoor control cabinet with excellent waterproofing and dustproofing are also available.

Principle of Control Cabinets

Control cabinet materials are synthetic resin or metal. Generally, metal products are used in most cases, and synthetic resin products are considered when control panels need to be manufactured inexpensively. Most of the metal control cabinet lineup is made of steel. However, products made of stainless steel are also available to enhance weather resistance.

Steel control cabinets are often sold coated. The purpose of the coating is to prevent rusting or corrosion, and products are generally primed with epoxy resin and then coated with polyester resin. The standard coating color is light beige (Munsell code: 5Y7/1) or cream (Munsell code: 2.5Y9/1).

However, the paint color can be changed if specified. It is also possible to select and purchase glossy, semigloss, or non-glossy paint. Control cabinets are often sold with a board inside. The board is the board to which the controls are attached and can be made of wood or steel. On the board, drive devices such as inverters and electromagnetic switches, and control devices such as sequencers and relays are mounted.

Since drives and control devices are electrical and electronic components, most of them generate heat. Heat buildup in the control cabinet can cause equipment failure, so coolers or fans may be installed as a thermal countermeasure. By opening apertures in the control cabinet panel surface, display and operating components, such as indicator lights, meters, and switches, can be installed.

Other Information on Control Cabinets

1. Double-Sided Cabinet

Control cabinet front doors can be either double or single-sided. Depending on the manufacturer, double-folding doors are generally used when the size is 600 mm x 600 mm or larger. Due to their size, double-fronted control cabinets are mainly used for freestanding cabinets.

2. Free-Standing Control Cabinet

Cabinets specifically designed for freestanding control cabinets are available from various manufacturers. They are characterized by the presence of a base for installing anchor bolts to secure the cabinet. Another feature is that the cabinet has bars on the sides for installing wiring ducts and other equipment.

What Is a Control box?

A control box is a box that contains circuits and devices used to control electrical and mechanical equipment. It is also sometimes called a control panel or cabinet. However, a cabinet that does not contain control equipment, such as one that only contains instruments and breakers, is often not called a control box.

By housing the electrical and electronic devices that make up the control system inside a control box, these elements are protected from the outside environment and the risk of electric shock from accidental human contact is reduced.

Control boxes vary in shape and size depending on the system in which they are to be housed, but they are sold by various manufacturers with standardized dimensions to some extent.

Uses of Control Boxes

Control boxes contain electronic devices, such as sensors, motors, and other devices that control the operation of machines. They are used to control various types of equipment in factories, elevators, trains, and many other facilities around us.

Basically, electronic devices such as controllers are susceptible to external influences such as shocks and dust, so electronic devices that cannot be housed inside machinery and equipment are stored in control boxes outside the equipment.

Control boxes equipped with buttons, touch panels, and other input devices may be installed outside the machine, even in the case of small control devices, if the operator wants to control the device.

Features of Control Boxes

In addition to protecting the stored equipment from the outside environment and reducing the risk of electric shock from human contact, a control box may be required to perform a variety of other functions.

When installed outdoors without a roof or near a heat source, a control box with a cooling fan or cooler is used because the heat buildup may cause the electronic equipment inside to malfunction. Dustproof and waterproof control boxes are also used in food factories, etc., where they are easily exposed to dust and splashes of water. Control boxes with a structure that does not allow electromagnetic waves to penetrate the interior and stainless steel control boxes with excellent corrosion resistance are also used, depending on the site environment.

In addition, most control boxes are equipped with DIN rails, which are standardized rails that are arranged in a tiered configuration. This is so that the devices to be stored are placed at appropriate intervals and are easy to see. Programmable logic controllers (PLCs) and electromagnetic relays, which are often used in factories, are also compatible with DIN rails, making it easy to construct a system with a layout as designed by mounting each piece of equipment on the rail.

What Is Cutting Oil?

Cutting Oil is used in metalworking processes such as turning and milling to “lubricate metals to reduce friction,” “cool heat generated during machining,” “control the scattering of cutting dust and cleaning,” and “prevent rusting.

Cutting Oil contributes to preventing seizures, improving dimensional accuracy, and extending tool life. Cutting Oil is applied to the point of contact between the cutting tool and the workpiece during machining, as shown in the photo above.

Uses of Cutting Oil

Cutting Oil is used to lubricate, cool, clean, and prevent rust during cutting, grinding, rolling, drawing, pressing, and other processes of metal materials. Cutting oil generally comes out of a nozzle installed in a machine tool, and is applied (poured) onto the tip of the cutting tool.

Cutting oil remains on the part after machining, so if cutting oil needs to be removed as a delivery item, clear instructions must be given at the time of the machining request. On the other hand, packing and transporting the parts with cutting oil remaining may provide advantages such as “prevention of rust, etc.” and “resistance to deterioration even if stored for a long period of time,” etc. Therefore, judgment must be made according to the characteristics of the parts.

In addition, cutting oil generally comes out of a nozzle that is mounted as part of the machine tool, but some types have a hole in the tool itself through which cutting oil comes out. The nozzle type can be used for various sizes of workpieces because the direction of the cutting oil can be adjusted by changing the position and direction of the nozzle.

The type with holes in the tool itself has stronger pressure to inject Cutting Oil, which makes it easier to pour off cutting dust.

Types of Cutting Oil

There are two main types of Cutting Oil: Insoluble Cutting Oil, which is used as lubricating oil, and Water Soluble Cutting Oil, which is a mixture of lubricating oil and additives in water. Water-soluble Cutting Oil is diluted 10~50 times during processing.

1. Insoluble Cutting Oil

Figure 1. Types and properties of insoluble cutting oils

Insoluble Cutting Oil is mainly composed of base oil such as mineral oil to which extreme pressure additives and friction reducers are added, and has superior lubricity compared to water-soluble cutting oil. Cutting oils are classified into four types, N1 to N4, according to the JIS standard, depending on the combination of extreme pressure additives, kinematic viscosity, and sulfur content.

• N1
  Does not contain extreme pressure additives and is used for machining nonferrous metals such as copper and castings, which are prone to corrosion.
• N2
  Contains extreme pressure additives and is suitable for various types of steel.
• N3 and N4
  In addition to extreme pressure additives, they contain sulfur content and are used when machining difficult metals or when severe machining surface accuracy is required.

2. Water-Soluble Cutting Oil

Figure 2. Types and properties of water-soluble cutting oils

Water-soluble Cutting Oil is mainly composed of a lubricating oil base and water, to which surfactants and rust inhibitors are added to impart dispersibility and solubility in water, and is also used when diluted with water at the time of use. Since water is the main ingredient, it has excellent cooling properties and can be classified into three types according to JIS standards.

• A1 (Emulsion Type)
  A1 is a water-soluble Cutting Oil with good lubricity and a cloudy white color when diluted.
• A2 (soluble Type)
  It has good cooling and penetrating properties and becomes slightly cloudy when diluted.
• A3 (Solution Type)
  Cooling and rancidity resistance, also easily separates from other oils. Appearance remains almost the same even after dilution.

It is important to distinguish between insoluble and water-soluble Cutting Oils depending on the machining method. Insoluble Cutting Oils have better lubricity and are suitable for precision machining at low speeds, while water-soluble Cutting Oils have better cooling and chip cleaning properties and are suitable for continuous machining at high speeds.

Other Information on Cutting Oil

Additives for Cutting Oil

Figure 3. Types of cutting oil additives

Cutting Oil additives include lubricant base materials, extreme pressure agents, emulsifiers, dispersants, and rust inhibitors. In recent years, the need for water-soluble Cutting Oil has been increasing due to the need for improved working environment, safety, and processing speed.

The disadvantage of water-soluble Cutting Oil, besides its inferiority in lubricating performance, is that it is prone to problems such as bacterial growth, rust formation, and foaming. For this reason, in addition to the additives listed in Table 3, preservatives and cationic dispersants with high antimicrobial properties are used.

What Is a Separating Tank?

Separating tanks are primarily used to separate oil and water. It is also called a grease trap or a gasoline trap. Oil and water are separated using the difference in specific gravity. Due to the difference in specific gravity, oil floats against water, and the floating oil is adsorbed using adsorption mats. In addition, by separating the tanks with shielding plates and passing them through in sequence, the amount of oil can be gradually reduced while also removing foreign matter, etc.

As dirt inevitably accumulates with use, regular maintenance is important.

Uses of Separating Tanks

Separating tanks are used to separate oil and water contained in wastewater. In recent years, as awareness of environmental destruction and legislation has increased, oil-water separating tanks have been introduced in various locations where oil may spill. In particular, they are widely used in automobile factories, maintenance shops, gas stations, car washes, and other places where automobile-related work is performed.

In addition, some laws require the installation of separate tanks in the kitchens of restaurants and other places where oil may spill into the sewerage system.

Principle of Separating Tanks

The following is an explanation of the principle of separating tanks, which separate oil and water. Separating tanks use the sinking property of water, which has a higher specific gravity than oil, to separate oil and water.

The inside of the separating tank is divided into about four sections by shielding. The first step is to pass through the dust trap and move to the next tank. The dust trap removes debris and foreign matter to prevent excess debris from accumulating in the tank.

The upper part of the separated tanks is designed to pass through an adsorption mat, which absorbs any oil floating on top. In addition, the flow between the tanks is through a shielding plate and tubes, which are arranged in alternating directions for efficient separating tanks. Many products place an oil checker in the last tank to check for oil residue before draining.

If the separating tank is not cleaned regularly, mud and debris may accumulate, preventing the separation function from working properly and preventing purification.

Products with FRP (Fiberglass Reinforced Plastic) inside the separating tank are particularly easy to install because they are corrosion resistant and easy to machine.

What Is a Dispersant?

A dispersant is an agent used to uniformly disperse particles in a medium and maintain a stable dispersion state without re-agglomeration.

Dispersants can be broadly classified into two types: surfactant-type dispersants and polymer-type dispersants. Surfactant-type dispersants consist of hydrophilic and hydrophobic groups and are categorized as anionic, cationic, or nonionic based on the component of the hydrophilic group.

Principle of Dispersants

Figure 1. Interaction between the electric double layer and particles

Dispersants achieve dispersion by two mechanisms: electrostatic repulsion and steric hindrance repulsion. These mechanisms prevent particles from agglomerating in a liquid. The balance between electrostatic repulsion and cohesive forces, such as Van der Waals forces, determines whether particles will aggregate or disperse. When Van der Waals forces dominate, particles tend to aggregate and settle.

1. Electrostatic Repulsion

Particles in a dispersant carry charges and ions with opposite charges surround the particles, forming an electric double layer. Thickening this electric double layer with the help of dispersants increases the repulsive force between particles, preventing agglomeration.

2. Steric Hindrance Repulsion

Figure 2. Protective colloidal effect of polymeric dispersants

Polymeric dispersants with large molecular weights adsorb to particle surfaces, creating a protective colloidal layer that hinders particle aggregation. Increasing the number of molecules in this layer leads to a bulkier structure, making it difficult for particles to come into close contact and promoting dispersion stabilization.

When organic solvents are used as dispersing solvents, electrostatic repulsion is weaker than in aqueous systems. Therefore, dispersion via steric hindrance repulsion is employed. When selecting a polymer-based dispersant, both the molecular structure and molecular weight are crucial. Higher molecular weights offer stronger protective colloidal effects, but if the molecular weight exceeds a certain point, the dispersant molecules can absorb two or more particles, leading to increased agglomeration. Thus, selecting an appropriate molecular weight is essential.

Types of Dispersants

Figure 3. Types and characteristics of dispersants

Dispersant types include surfactant-type dispersants, polymer-type dispersants, and inorganic-type dispersants. Among them, surfactant-type dispersants can be further classified as anionic, cationic, or nonionic.

How to Select Dispersants

The choice of dispersant depends on the quality of the dispersant, the dispersant medium, and the dispersant concentration. However, when dispersing in water, the following three points are crucial:

• Select a dispersant that dissolves well in water and can be easily absorbed.
• For smaller particle sizes, use a surfactant-type dispersant with excellent wetting properties to reduce interfacial energy and minimize cohesive forces.
• For high dispersion concentrations, polymer-type dispersants that provide steric hindrance repulsion are effective.

Other Information on Dispersants

Functions of Dispersants Beyond Dispersion

Dispersants also serve functions beyond dispersion, such as improving the wettability of base materials. In applications like paints and other coatings, poor wettability can lead to paint flaking. This issue is caused by surface tension, which minimizes contact between the liquid and the coated object. Adding dispersants reduces surface tension, facilitating paint spreading on the coated surface.