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What Is Polyurea?

Polyurea is a resin with a urea (urea) structure in its main chain and is obtained by polymerizing isocyanate and polyamine. Polyurea is mainly used as a lining material. Polyurea coats an object by mixing isocyanate and polyamine in a spray, discharging it, and causing a quick chemical reaction after coating. Polyurea has excellent chemical resistance, water resistance, and abrasion resistance, making it suitable for lining chemical plants and chemical tanks.

Polyurethane is a resin with a structure similar to polyurea. The structure of the main chains of both resins is different, and the C-N bonds of polyurea are easily hydrolyzed, whereas the C-O bonds of polyurethane are more easily degraded.

On the other hand, polyurethanes are more flexible than polyureas because the main chains of polyurethanes are more rotatable than those of polyureas.

Polyurea Applications

Polyurea is a resin with a urea (urea) structure in the main chain and is obtained by polymerizing aromatic or aliphatic amines and isocyanates.

The main application method is by spray, in which a spray mixture of the two aforementioned components is applied, and a coating is applied by causing a chemical reaction to proceed on the object.

The main application of polyurea is as a lining material. Due to its excellent waterproofing, chemical resistance, abrasion resistance, and various other physical properties, polyurea is used to protect surfaces such as chemical tanks, chemical plant equipment, liquid-proof dikes, pits, and waterways. In addition, polyurea coatings are also used on cars to improve texture and durability.

Formation Reaction of Polyurea

Polyurea is a polymer of isocyanate and amine. By changing the structure of the raw material monomer, it is possible to obtain polyurea resins with different physical properties. Typical isocyanate is 4,4′-diphenylmethane diisocyanate (MDI), and amine is polyetheramine.

In the spray application, isocyanate and amine are compressed, heated, and sprayed from the sprayer in a mixed state. Immediately after the heated mixture adheres to the object, it reacts, and polyurea is immediately formed and coated. The spray also has the advantage of having a low environmental impact because it does not contain volatile organic solvents (VOCs) such as toluene or ethyl acetate.

Polyurea and Polyurethane

Polyurethane is a resin similar to polyurea. Polyurethanes have urethane bonds obtained from the reaction of isocyanate and polyol. Urethane resins are used in a variety of industries, including textiles, paints, adhesives, and synthetic leather, because their properties, such as hydrophilicity and chemical resistance, can be changed by changing formulations and molding conditions.

However, polyurethanes are susceptible to degradation due to hydrolysis at the C-O site, and they are also degraded by oxidative reactions caused by light and heat.

The C-N bond of polyurea does not undergo hydrolysis, so polyurea is less susceptible to degradation than polyurethane. Also, polyurethanes tend to rotate their main chains more easily than polyureas in terms of molecular structure, so polyureas tend to be rigid and excellent at blocking substances, while polyureas tend to be more flexible.

What Is a Ball Valve?

A Ball Valve is a valve with a ball-shaped plug. They are operated either fully open or fully closed. It is not suitable for flow adjustment by opening.

However, since the internal flow path is the same as the pipe diameter, there is almost no pressure loss. For this reason, the ball valve is often used in locations where there is no problem with only fully open or fully closed control.

Corrosion resistance can also be ensured by changing the material.

Uses of Ball Valves

Ball valves are used in a wide range of applications, from consumer products to industrial applications.

For consumer products, ball valves are used for gas stove valves. They are also used in water supply valves.

In industrial applications, they are used in many situations due to their extremely low pressure drop and high shut-off performance. They are especially used in water and gas lines.

They are also used in lines conveying food solids and drainage lines containing sludge, since there are no obstructions in the flow path when fully open.

By applying a PFA coating to the inside or manufacturing with PVC or PTFE, it can also be used in chemical lines such as hydrochloric acid.

Principle of Ball Valve

The structure of a ball valve is very simple. A ball-shaped valve piece with a cylindrical hole is contained inside, and the valve is opened and closed by rotating the valve ball 90°.

In general, the direction of the handle is fully closed when it is perpendicular to the flow path and fully open when it is parallel to the flow path. Since the direction of the handle is easy to distinguish, there is no need to worry about mishandling.

However, due to its structure, it is not suitable for flow control. PTFE is often used to seal the valve plug.

It is self-lubricating and can be used for many fluids, but cannot be used under high temperatures such as steam lines. Under high temperature and high pressure, heat-resistant materials or metal gaskets should be used.

Since the contact area between the gasket and the ball is large, the larger the bore size of the valve ball, the greater the opening and closing torque. 100 A or more will require a considerably large torque, making it difficult to open by hand.

Other Information on Ball Valves

1. Flow Direction of Valve Balls

There are several types of valves, such as Gate Valves, Check Valves, Globe Valves, and Ball Valves. Each type has different characteristics.

Gate valves and ball valves do not control flow rate. Globe valves can control the flow rate, but the pressure loss is higher. Each valve also has its own restrictions regarding the direction of flow.

Check valves are installed to prevent backflow, so they flow in one direction and not in the opposite direction. Globe valves are also basically one-directional. Depending on the structure, they may also be used in the reverse direction. Gate valves and ball valves basically have no restrictions on flow direction.

Valve ball valves operate by turning the handle 90° to stop the fluid. Because of its simple operation, it can open and close more rapidly than a gate valve. However, care must be taken to avoid water hammer.

In general, the handle is considered open when it is parallel to the piping. 

2. Full Bore of Ball Valves

There are two types of valve ball valves: reduced bore and full bore. Reduced bore valves have a valve plug opening smaller in diameter than the inside diameter of the piping. In the full bore, the valve plug opening is the same diameter as the pipe bore.

The pressure loss of a full bore is smaller than that of a reduced bore. Therefore, when designing piping, pressure loss calculations are performed to determine whether to use a reduced bore or a full bore. If there is a pressure drop problem due to a large pressure drop, a full bore will be used.

What Is a Homogenizer?

A homogenizer is a device used to disperse and break up substances in liquids to homogenize them. In a broader sense, it can also involve stirring powders with devices like propellers. The methods of particle crushing include grinding (high-pressure type), high-frequency crushing (ultrasonic type), and chopping (stirring type).

The high-pressure type is often used in factories for processing large amounts of samples under pressure. Ultrasonic homogenizers are compact and suitable for small samples, widely used in scientific experiments and increasingly in manufacturing. Agitating homogenizers can homogenize hard materials quickly due to their high-speed pulverization capability.

Homogenizers are utilized in manufacturing, research, and medical fields.

Uses of Homogenizers

Homogenizers are employed for crushing, dispersing, and mixing fine particles, as well as for emulsifying water and oil. They find applications in:

1. Food Production

Used in the manufacture of dairy products, beverages, sauces, dressings, and other food items.

2. Research Fields

Utilized for extracting proteins, DNA, RNA, and other cellular components, and in materials research.

3. Medical Care

Involved in the production of pharmaceuticals, dyes, cosmetics, and the homogenization of sludge.

Principle of Homogenizers

1. High-Pressure Homogenizer

Works by applying pressure, pressurizing fluid through a homovalve, and homogenizing by particle collisions and shear force. This method allows for processing larger quantities and finer homogenization but requires cooling due to frictional heat.

2. Ultrasonic Homogenizer

Applies ultrasonic waves to liquids, causing cavitation and breaking up particles. This method results in spherical particle shapes and is excellent for emulsification, although it has a low processing volume.

3. Stirring Homogenizer

Uses a fixed outer blade and a rotating inner blade powered by a generator. The flow of liquid generated crushes particles, with ultrasonic waves from the inner blade enhancing the homogenization process.

What Is a Hot Melt Adhesive?

Hot melt adhesives, commonly known as hot glue, are used in a method called hot melt. This process involves melting the resin by heating it and causing it to adhere as it cools and solidifies. These adhesives are safe as they do not contain solvents, making them popular in DIY projects.

Hot melt adhesives are available in various forms, such as pillow, stick, block, and container types, wrapped in non-adhesive release paper. They are melted using a heating device called an applicator.

Uses of Hot Melt Adhesives

Hot melt adhesives are widely used due to their safety and versatility. They are used in “hot glue” guns in discount stores for DIY projects, for sealing cardboard boxes in packaging, and even in food-related applications due to their safety. Additionally, their easy peelability makes them ideal for attaching labels in logistics.

Principle of Hot Melt Adhesives

To use, hot melt adhesives are heated to about 120°C, becoming liquid. They spread between bonding surfaces, form a resin film, and then cool and solidify, creating physical adsorption at the molecular level. This process does not alter the physical properties of the resins and does not affect the adherend, making them suitable for bonding a variety of materials like polypropylene, polystyrene, wood, glass, iron, stainless steel, and aluminum.

Features of Hot Melt Adhesives

Hot melt adhesives are environmentally friendly, as they do not use solvents and bond quickly. They adhere through a “heating-melting-cooling-solidifying” cycle, which is faster than the chemical reaction of general adhesives.

Types of Hot Melt Adhesives

Common types of hot melt adhesives include olefin-based and rubber-based adhesives. Olefin-based adhesives are effective for materials hard to bond with general adhesives, while rubber-based adhesives are used when liquid adhesives penetrate the adherend.

Other Information on Hot Melt Adhesives

Advantages and Disadvantages of Hot Melt Adhesives

Hot melt adhesives have several advantages, such as quick bonding, applicability to various materials, high safety, reusability, easy storage, and automation compatibility. However, they have limited heat resistance, lower adhesive strength compared to curable adhesives, and are not suitable for heat-sensitive materials. Their adhesion also varies with temperature and requires a special applicator.

What Is Beryllium Copper?

Beryllium Copper (BeCu) is a copper-based alloy to which 0.5-3.0% beryllium is added.

While maintaining the high electrical and thermal conductivity of copper, BeCu has high strength and durability comparable to those of special steels, as well as heat and corrosion resistance.

Specialty steels are iron alloys that have unique properties compared to ordinary iron alloys. They are synthesized by adding nickel, chromium, and other elements. Therefore, Beryllium Copper is said to have the best balance of properties of all copper alloys. Beryllium Copper’s superior properties make it a highly reliable component in a wide variety of industries.

Uses of Beryllium Copper

The following are the four main applications of Beryllium Copper.

1. Conductive Spring Materials

Conductive spring materials are materials that can conduct electricity and can be coiled and used as springs. Beryllium Copper in plate or wire form is highly conductive, strong, and durable. This property is used as a conductive spring material for electronic components in automobiles, industrial equipment, cell phones, and home appliances.

2. Sliding Parts

Sliding parts are materials used for parts in contact with each other. Beryllium Copper has high strength and durability, as well as excellent abrasion and galling resistance against steel materials. Therefore, it is used for sliding parts such as landing gears of aircraft.

3. Electrode Member for Resistance Welding

Resistance welding is a welding method that uses the resistance heat generated when electricity is applied to the metal to be welded. Electrode materials for resistance welding are materials used for the electrodes that conduct electricity used in resistance welding.

In addition to high electrical conductivity, resistance welding electrode materials must also be durable because of the pressure applied to them. Beryllium Copper is used in the automotive and other industries as an electrode material for resistance welding because of its high conductivity, high strength, and high durability.

4. Safety Tools

Beryllium Copper has high strength comparable to that of special steel, yet is non-igniting, non-magnetic, and corrosion resistant. Therefore, it is used in pliers and wrenches as safety tools to prevent explosions at work sites.

Strengthening Mechanism of Beryllium Copper

The interior of metals contains many atomic arrangement defects called “dislocations. As these dislocations move through the crystal, the metal crystal is deformed. Therefore, in order to increase the strength of a material, it is necessary to suppress the migration of “dislocations” to prevent them from moving as much as possible.

Figure 1. Dislocation movement

Generally, alloys such as iron, titanium, and aluminum are heat treated to increase their strength. This is done using solid solution strengthening and precipitation strengthening, two of the most common methods of metal strengthening.

1. Solid Solution Strengthening

Solid solution strengthening is a method of strengthening a material by dissolving alloying additive elements into the metallic elements of the base metal phase and dispersing the additive elements uniformly in the base metal phase. When elements of different sizes are mixed, strain occurs around the mixture. As a result, dislocation migration is inhibited and the metal is strengthened. In the case of beryllium copper, the base metal is copper and the additive element is beryllium.

Figure 2. Solid solution strengthening

2. Precipitation Strengthening

Precipitation strengthening is a technique to strengthen a metal by precipitating nano-level fine and hard crystals within the crystals, thereby inhibiting the movement of dislocations. To precipitate fine crystals, a heat treatment called aging is used. Fine crystals precipitate as the aging heat treatment time progresses. However, care must be taken because if the aging time is too long, the fine crystals coarsen and the metal crystals soften.

Figure 3. Precipitation strengthening

Beryllium Copper is also heat treated at appropriate temperatures and times to obtain strength and properties comparable to those of specialty steels.

Other Information on Beryllium Copper

Regulations and Handling of Beryllium Copper
Because Beryllium Copper contains beryllium, there are sometimes concerns about restrictions on its use due to environmental and health concerns. However, there are currently no laws or regulations that restrict the use of Beryllium Copper, and the EU RoHS Directive, ELV Directive, and REACH Regulation are not applicable to Beryllium Copper. However, since beryllium itself is highly hazardous, Japan’s PRTR system obliges companies to report to the government the amount of emissions and transfers depending on the size of their business and the amount handled.

In terms of occupational health, Beryllium Copper is exempt from the Ordinance on Prevention of Hazards due to Specified Chemical Substances because its beryllium content is less than 3%, and there is no health risk during normal use. However, protective measures such as local exhaust ventilation and dust masks are recommended for welding, dry grinding, polishing, and other processes that generate fumes and fine dust.

What Is a Plastic Pallet?

In warehouses, you’ve likely seen forklifts carrying loads on platforms known as pallets. These pallets come in two primary varieties: wooden pallets and plastic pallets. Plastic pallets are utilized for transportation, logistics, and storage, serving the dual purpose of supporting cargo and safeguarding it during storage. They are characterized by their distinctive sawtooth design.

Plastic Pallet Sizes

The most common size for plastic pallets is Type 11, featuring 1100 mm x 1100 mm squares. Other variations include Type 14, with 1400 mm x 1100 mm rectangles, smaller pallets under 1000 mm, and larger pallets exceeding 2000 mm in size.

Advantages and Disadvantages of Plastic Pallets

1. Durability:

Compared to wooden pallets, plastic pallets excel in durability. Unlike wooden counterparts that are susceptible to moisture absorption and subsequent corrosion, plastic pallets remain impervious to moisture. This resilience extends to protection against pests and bacteria, which can affect wooden pallets. However, it’s important to note that plastic pallets cannot be repaired by replacing damaged sections since the pallet’s surface is molded as a single piece.

2. Impact on Cargo:

Plastic pallets offer an advantage by preventing surface cracks and wood “scuffing” on the underlying surface, a common occurrence with wooden pallets. As a result, the bottom of loaded plastic pallets is less prone to scratching. Additionally, unlike wooden pallets that can absorb odors, plastic pallets are odor-resistant and won’t transfer unwanted smells to the cargo they carry. This makes them suitable for transporting goods where odor contamination is a concern.

Other Advantages of Plastic Pallets

Due to their lightweight nature, plastic pallets reduce labor and physical strain during transportation, thus improving workplace conditions. Unlike wooden pallets, which cannot be recycled and must be disposed of as waste, plastic pallets can be crushed and processed into pellets for recycling, aligning with ecological and SDGs (Sustainable Development Goals) considerations.

Conclusion

While plastic pallets may have a higher initial cost compared to wooden pallets, their superior durability, ability to maintain product quality, lightweight design for enhanced work environments, and recyclability make them a compelling choice. Consider incorporating plastic pallets into your company’s operations to reap these benefits.

What Is Brake Lining?

Brake Lining is a friction material that is a component of the brake system. Brakes convert kinetic energy into thermal energy through friction. Brake lining is the friction material that provides that friction.

However, brake lining is not used in regenerative braking where there is no physical contact. Generally, those attached to disc brakes are called pads, while those attached to drum brakes are called shoes.

Uses of Brake Lining

Brake Lining is used for equipment in which a braking system is incorporated. They are used in a wide range of applications, from industrial to consumer products, and the main examples of their use are as follows:

• Inside a disc brake used on the front wheels of an automobile
• Inside a drum brake used on large vehicles
• Inside a band brake used on a bicycle or washing machine
• Inside a disc brake used on an elevator hoist

Principles of Brake Lining

Brake devices that use brake lining include Disc Brakes, Drum Brakes, and Band Brakes.

The principle of each is as follows:

• Disk brake
  In a disc brake, friction is generated by sandwiching the rotor, which rotates with the shaft, between the brake lining.
• Drum Brakes
  In a drum brake, the brake lining is pressed against a drum that rotates with the shaft to create friction.
• Band Brake
  A band brake generates friction by tightening the drum, which rotates with the shaft, with a band with Brake Lining.

All brakes convert kinetic energy into thermal energy. When selecting brake lining, there are conditions such as operating temperature and coefficient of friction.

In addition, factors such as discomfort noise and vibration during braking also exist, so the types and blends of friction material materials vary widely, with more than 10 different raw materials blended together to make the product.

Other Information on Brake Lining

1. Brake Lining and Pads

Brake Lining and Brake Pads are both wear parts used in brakes. For drum brakes, they are called “Brake Lining” and for disc brakes, they are called “Brake Pads”.

Both are abrasion materials, which wear during braking to slow down the object. In the case of automobiles, materials are used that function reliably even when affected by snow and mud.

In the case of a vehicle that repeatedly drives at high speed and stops abruptly, such as a racing car, the brake linings generate a lot of heat and turn bright red. A material that does not impair braking performance under these conditions should be used. In order to use brake linings that are appropriate for the vehicle, it is preferable to use the manufacturer’s original brake linings when replacing them.

2. Replacement of Brake Lining

Brake Lining is designated as a periodic replacement part because it wears out with use. Replacement timing is determined by checking the mileage and measuring the amount of wear. Longer mileage increases the frequency of braking, and thus the wear of brake lining is more likely to progress.

Even when the mileage is short, premature wear may occur due to frequent emergency braking or overloading. The amount of wear should be measured during periodic inspections, and if it is close to the replacement threshold, replacement of brake lining is recommended. In many cases, brake lining wear can be detected by a change in brake sound.

As the brake lining wears down, a high-pitched “squealing” sound is heard when the brakes are applied. This is because the metal parts of the brake linings begin to contact each other due to wear. If you hear this unpleasant sound when braking, you should replace the brake lining as soon as possible. Continued driving under this condition may result in a serious accident due to reduced braking force.

What Is a Flexible Printed Circuit Board (PCB)?

A Flexible Printed Circuit Board (PCB) is a substrate with a wiring pattern made of bendable copper on a base film. The base film is composed of an insulating and bendable resin.

Flexible Printed Circuit Board (PCB) can be made thinner and can be bent freely while maintaining its electrical characteristics.

Uses of Flexible Printed Circuit Board (PCB)

Flexible Printed Circuit Boards can be used as a circuit board by mounting components, etc., and can also be used as a connecting member like a cable by forming only wiring patterns.

Due to its thin and soft characteristics, it is often used for moving parts that require bending and folding, and for connecting parts, and together with flexible rigid substrates, it is also used for three-dimensional circuits.

Flexible Printed Circuit Boards are often used not only in the space exploration and military fields where it was originally intended, but also in familiar fields such as smartphones, cell phones, typing keyboards, and calculators that require thinness and lightness.

Principle of Flexible Printed Circuit Board (PCB)

Flexible Printed Circuit Boards consist of a wiring pattern formed by bendable copper on a base film made of a bendable resin such as polyimide.

There are also rigid printed circuit boards with wiring patterns on a rigid, non-flexible insulating base

board. Flexible Printed Circuit Boards differs from rigid PCB in that the base is a thin film and the base is bendable. As with rigid substrates, components can be mounted on the wiring pattern.

Types of Flexible Printed Circuit Board (PCB)

Flexible Printed Circuit Boards have a single-sided structure in which only one layer of the wiring pattern is formed on one side of the base film, and a double-sided structure in which one layer is formed on both sides of the base film. There is also a multi-layered Flexible Printed Circuit Board with two or more layers of wiring patterns on each side of the base film.

1. Single-Sided Structure

The single-sided structure of Flexible Printed Circuit Boards is one in which a single-layer wiring pattern is formed on only one side of the base film. Single-sided structure is often used in moving parts because of its light weight, flexibility, and durability against movement.

2. Double-Sided Structure

Flexible Printed Circuit Boards with a double-sided structure have a single-layer wiring pattern formed on both sides of the base film. The double-sided structure is superior in that it is compact and allows high-density wiring patterns to be formed, and more functions can be mounted. However, compared to the single-sided structure, it is inferior in flexibility and durability, making it unsuitable for use in moving parts.

3. Multilayered Flexible Printed Circuit Board (PCB)

Multilayered Flexible Printed Circuit Boards are multilayered flexible printed circuit board. Flexible Printed Circuit Boards, like rigid PCB, can have two or more layers of wiring patterns on the surface of the base film.

In this case, in order to efficiently multilayer, two or more wiring patterns are stacked on both sides of the base film with an insulating layer in between. This multilayered Flexible Printed Circuit Board with a protective layer is called a Flex Rigid Board.

This multilayered Flexible Printed Circuit Board is lightweight, but has the same high mechanical strength and circuit formation capabilities as rigid substrates, making it suitable for use in three-dimensional circuits. It is an indispensable component for reducing the size of electronic devices to a compact size.

Other Information on Flexible Printed Circuit Board (PCB)

1. Manufacturing Method of Flexible Printed Circuit Board (PCB)

The manufacturing method of Flexible Printed Circuit Board is explained using a single-sided flexible printed circuit board as an example.

• Application of photoresist
  Photoresist is applied to CCL, which is an insulating base film such as polyimide film with copper foil laminated to it.
• Formation of photomask
  A photomask with a predetermined wiring pattern shape is placed over the CCL. At this time, the photomask is shaped in the same way as in printing and photographic techniques, with the wiring pattern portion removed.
• UV curing of the photomask
  UV light is irradiated from the top of the photomask, and only the portion corresponding to the wiring pattern is UV cured.
• Photoresist removal
  The photomask is removed, and uncured photoresist is removed using a chemical solution.
• Copper foil removal
  The next process is called etching. In the etching process, a chemical solution is used to remove the copper foil, leaving only the copper foil in the area protected by the photoresist, i.e., the wiring pattern area, where the wiring pattern is formed.
• Removal of cured photoresist
  The cured photoresist covering the wiring pattern is removed with a chemical solution.
• Formation of coverlay
  An insulating layer called a coverlay is formed to protect the wiring pattern.

The production of such Flexible Printed Circuit Board requires a great deal of chemical knowledge. Knowledge of inorganic chemistry is required for the etching process, which leaves only the wiring pattern, and the coverlay formation process, which protects the wiring pattern.

The wastewater from the rinsing process contains a wide variety of hazardous substances, so advanced wastewater treatment technology based on chemical knowledge is required.

2.Global Trends in Flexible Printed Circuit Board (PCB)

Flexible Printed Circuit Boards are manufactured worldwide by about 2,500 companies, with Taiwanese manufacturers topping the list in 2018, followed by Japan, Korea, China, and some other leading manufacturers in East Asia.

Flexible Printed Circuit Board demand is expected to continue to grow in a variety of sectors, including public and private military and industrial machinery, the space industry, and the automotive and telecommunications sectors.

Some observers predict that China will have the most momentum due to its investment in improving its technological capabilities and its abundant rare metal resources. Taiwan, Japan, and South Korea, the top group, are moving toward higher unit price niche fields, while China is currently increasing sales centered on low-priced PCBs, but the gap in technological capabilities is shrinking, and it is only a matter of time before China will join the top group in the future.

What Is a Phenolic Resin?

Phenolic resins have excellent heat resistance, chemical resistance, and insulation properties and are used in a wide range of applications, such as automobiles, electronic components, and insulation materials. Phenolic resins are obtained through polymerization reactions using phenols and aldehydes as raw materials. Their physical properties can be changed by changing the chemical structures of the phenols and aldehydes used as raw materials and additives added to the resin and other factors.

Phenolic resins are classified into two types with different chemical structures: the novolac type obtained by acid catalyst reaction and the resol type obtained by base catalyst reaction. In the former, a curing reaction occurs when mixed with a curing agent such as epoxy resin and heated, while in the latter, a curing reaction occurs only by heating without a curing agent. Other differences include thermoplasticity in the novolac type and thermosetting in the resol type.

Uses of Phenolic Resins

Phenolic resin is the world’s first man-made plastic, invented by Bakelite in 1907. It has excellent heat resistance, chemical resistance, insulation, and mechanical strength and is still used in many industries. For example, phenolic resins are used in high-temperature process parts, such as resins for automobile brakes and the steel and glass industries. They are also used in insulation materials for housing and resins for photoresists.

Phenolic resins can change their physical properties by changing the chemical structure of the resins by changing the structure of phenols and aldehydes used as raw materials and by changing additives such as fillers. Therefore, selecting the optimal phenolic resin according to the required properties is necessary.

Types of Phenolic Resins

Phenolic resins obtained by reacting phenols with aldehydes include “novolac type” and “resol type”. Novolac-type resins are obtained by reaction under an acid catalyst and are reusable thermoplastic resins. On the other hand, the result type is a non-reusable thermosetting resin obtained by using a base catalyst.

Novolac resins are cured by heating with a curing agent such as epoxy resin, resulting in a high molecular weight resin. On the other hand, in the case of the resol type, the curing reaction proceeds by heating or acid even in the absence of a curing agent. Therefore, resol resins may also change over time during storage, resulting in higher molecular weight.

Synthesis of Phenolic Resins

Phenolic resins are obtained by the addition-condensation of phenols and aldehydes. The reaction of phenol and formaldehyde is introduced here as a typical example.

As mentioned above, the compounds obtained differ between acid and base catalysts. With an acid catalyst, an electrophilic substitution reaction occurs at the ortho or para position of the OH group of phenol, which reacts with formaldehyde. After the reaction, a condensation reaction occurs with another phenol to obtain a novolac resin.

On the other hand, when a base catalyst is used, multiple formaldehyde reacts with the benzene ring of phenol to produce an oily mixture called resol. When this is heated, the resolves react with each other to form a thermosetting resin called resin.

In this way, when acid and base catalysts are used, the bonding sites and amounts of phenols and aldehydes that react are different, and the structure and physical properties of the phenolic resin obtained are also different.

Disadvantages and Cautions of Phenolic Resins

While phenolic resins have various advantages, they also have some disadvantages. For example, phenolic resins undergo hydrolysis when in contact with a strong base such as sodium hydroxide in the presence of water, resulting in the degradation of the resin.

In addition, the phenolic resin itself is colored yellow or reddish brown and turns black when oxidized, so there is a limit to the range of coloring possible. Phenolic resins are also hard but brittle.

What Is a Pipette Tip?

Figure 1. Image of pipette tip

A Pipette Tip is a plastic conical tube attached to a micropipette.

Pipette tips are used for measuring solutions in the order of μL to mL in research, development, and quality control in the chemical, biological, and other fields. This operation of measuring solutions by aspiration and ejection of a pipette is called pipetting.

Different sizes of pipettes are available, and the color of the pipette may vary depending on the size. To prevent contamination, pipettes should be stored in dedicated racks and discarded once used.

Uses of Pipette Tip

Pipette Tips are attached to micropipettes and used in all fields related to chemistry and biology.

Specific uses include laboratory experiments in the field of biochemistry, quality control at pharmaceutical manufacturers, and specimen collection in clinical testing. Micropipettes are used for handling minute amounts of liquids ranging from µL to several mL.

Although it is possible to quickly collect a fixed amount of liquid by simply pressing a button, it requires more care in operation than a glass volumetric analyzer because the volume tends to change more easily than a glass volumetric analyzer.

Principle of Pipette Tip

Figure 2. How to use pipette tips

The Pipette Tip is attached by filling the special rack for the pipette tip and directly inserting the tip of the micropipette.

Aspirate the liquid by slowly pushing the push button of the micropipette to the first stage, and when dispensing, push the button to the second stage to dispense the entire amount. To dispose of the pipette tip after use, simply push the ejector button.

Since there is no need to touch the pipette tip by hand, contamination of the sample and chemicals on the operator can be prevented.

Types of Pipette Tip

Figure 3. Various pipette tips

The capacities of pipette tip mainly used are 10 µL, 200 µL, and 1000 µL. Other types include 250 µL and 30 µL, and larger 5 mL and 10 mL pipette tips are also available.

Pipette Tips are available in several sizes, so it is important to select the appropriate size micropipette and pipette tip according to the volume of liquid to be measured. Specifically, the maximum volume that can be weighed out by the micropipette should be close to the volume of the liquid to be weighed out. This is important to minimize the error of the liquid volume.

Other Information on Pipette Tips

Points to Keep In Mind When Using Pipette Tips

For accurate measurement with pipette tips, the following points should be noted:

1. Pre-rinsing
Pipette Tips are made of a material that may absorb solution components on its inner wall. It is effective to aspirate and dispense the liquid to be weighed at least twice and pre-rinse the pipette before use. 

2. Tip angle of penetration
The angle of entry of the tip should be as close to 90 degrees to the liquid surface as possible. It is appropriate to maintain within 20 degrees of vertical. If the pipette is held at an angle close to horizontal, an excessive amount of liquid may be aspirated. 

3. Tip immersion depth
It is known that if the tip is immersed too deeply, the gas inside the tip is compressed and too much liquid is aspirated. It is appropriate to immerse the tip at a depth of 1 to 2 mm for a micro volume pipette tip and at a maximum of 3 to 6 mm for a normal volume pipette tip.

4. Proper pipetting motion
First of all, when aspirating liquid, care should be taken to raise the finger slowly without abruptly releasing it from the button. The purpose is to minimize the difference in aspiration speed due to the difference in viscosity of the liquid, and also to prevent the pipette from being broken when the rapidly aspirated liquid enters the mechanical part of the pipettor.

When dispensing, even the last remaining droplet should be dispensed completely, so that it does not adhere to the tip of the tip. In particular, it is recommended that the tip tip be dispensed along the wall of the container.

When weighing liquids with low surface tension, such as organic solvents, it should be noted that the liquid may remain adhered to the outer wall. In some cases, it may be more appropriate to use a microneedle with a needle-like tip.