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What is Material Dielectric? Types, Application & Selection Guide

Dielectric

A dielectric is an insulator, such as air, mica, ceramics, cellophane, plastic, oil, etc are all dielectrics. Its function is to separate conductors with different potentials to maintain different potentials and prevent current from flowing to unwanted places. There are hot spots where polarization occurs in the electric field and polarized charges appear on the faces perpendicular to the direction of the electric field. Next we will introduce the definition, classification and how to choose the dielectric in this article

What is Dielectric

Insulating materials, also known as dielectrics, refer to materials with high resistivity and difficult for current to pass through. They are mainly used for wrapping, gaskets, sheaths, etc in electronic products. The function of the dielectric is to isolate the charged parts with different potentials in the electrical equipment. Therefore, dielectric should have high insulation resistance and withstand voltage strength, which can avoid accidents such as leakage, creepage or electrical breakdown; heat resistance should be good (especially the performance change due to long-term heating is the most important) ; It should also have the characteristics of good thermal conductivity, moisture resistance, high mechanical strength and convenient processing.

Dielectric
Dielectric

Dielectrics not only have the characteristics of high compressive strength, good heat resistance, moisture resistance and convenient processing, but also can be classified according to their use, chemical properties and material form.

Types of Dielectric Material

Insulating materials can be divided into dielectric materials (such as ceramics, glass, plastic film, mica, capacitor paper, etc.), device materials (such as device ceramics, phenolic resin, etc.), impregnating materials and coating materials according to their uses.

Insulation materials can be divided into:

Inorganic insulating materials:such as mica, asbestos, ceramics, etc.,are mainly used for winding insulation of motors and electrical appliances, as well as manufacturing materials for switch plates, skeletons and insulators.

Organic insulating materials:such as shellac, resin, rubber, cotton silk, paper, hemp, rayon, etc., are characterized by low density, easy processing, and softness, but low heat resistance, poor chemical stability, and easy aging. It is mainly used in the manufacture of electronic components and composite insulating materials.

Composite insulating material: Various shaped insulating materials made of the above two materials after processing, often used as electrical bases, casings, etc., such as glass cloth laminated boards.

Insulation materials can be divided into gas insulation materials (such as air, nitrogen, hydrogen, etc.), liquid insulation materials (such as capacitor oil, transformer oil, switch oil, etc.) and solid insulation materials (such as capacitor paper, polystyrene, mica, ceramics, glass, etc.) three types.

Types of Dielectric
Types of Dielectric

Different types of dielectrics have their own characteristics and scope of application. Thin insulating materials are usually used for wrapping, liners, sheaths, etc, and thermoplastic insulating materials are used for various sheaths, instrument covers, etc. These are the contents to be discussed below commonly used dielectrics and their main uses.

Common Dielectrics & Applications

Thin insulating material: mainly used for wrapping, padding, sheathing, etc.

Insulating paper: Commonly used are capacitor paper, green shell paper, copper paper, etc, mainly used for low-voltage coil insulation with low requirements.

Insulation cloth: commonly used are yellow wax cloth, yellow wax silk, glass varnished cloth. This material can also be made into various sleeves for the wire sheathing.

Organic films: Polyester, polyimide, polyvinyl chloride, and polytetrafluoroethylene films are commonly used. Generally, it can replace insulating paper or insulating cloth.

Adhesive tape: The organic film is coated with adhesive to become various insulating adhesive tapes.

Plastic sleeves: Plastic sleeves are sleeves of various colors and specifications made of polyvinyl chloride as the main material, and are widely used in electronic assembly. There is also a heat-shrinkable plastic sleeve that is often used as a sheath for the end of the wire.

Insulating varnish: mainly used for impregnation of electrical coils and the surface covering.

Thermoplastic insulating material: It can be processed by thermoplastic, used for various sheaths, instrument covers, etc.

Thermoset Laminates: Often used as insulating substrates.

Rubber products: Rubber has excellent elasticity in a large temperature range, electrical insulation, heat resistance, cold resistance and corrosion resistance. It is a traditional insulating material and has a wide range of uses.

Mica products: Mica is a brittle material with good heat resistance,the heat transfer, and insulation properties. It is mainly used on occasions that can withstand high voltage and conduct heat, such as insulating gaskets between metal-encapsulated high-power transistors and heat sinks.

Common Dielectrics
Common Dielectrics

If you know the commonly used dielectrics and their main uses, but still don’t know how to choose the right dielectric, the following chart can help you.

Selection of Commonly Used Dielectrics

Please refer to the chart below for the main purposes of commonly used dielectrics. When using, the dielectric should be selected reasonably according to the electrical performance of the product and the environmental conditions.

Name & Standard Number

Model

Features & Uses

Cable Paper
QB131-61

K-08,K-12,K-17

Used as 35kV power cable, control cable, communication cable and other cable insulation paper

Capacitor Paper
QB603-72

DR-II

Used as interlayer insulation for transformers in electronic equipment

Yellow Paint Cloth And Yellow Paint Silk
JB879-66

2010(lay flat)
2210

Applicable to general motor electrical gasket or coil insulation

Yellow Paint Tube
JB883-66

2710

Has a certain degree of elasticity, suitable for wire connection protection and insulation of electrical instruments, radio devices and other electrical devices

Epoxy Glass
Varnished Cloth

 

Special electrical coils suitable for wrapping epoxy resin casting

Soft Polyvinyl Chloride (Belt) HG2-64-65

 

Electrical insulation and protection. The colors are gray, white, sky blue, purple, red, orange, brown, yellow, green, etc.

PTFE Capacitor Film, PTFE Capacitor Insulating Film

SFM-1
SFM-3

Used for insulation in capacitors and electrical instruments, applicable temperature -60°C- +25°C

Phenolic Laminated Cardboard
JB885-66

3021
3023

3023 has low dielectric loss and is suitable for radio communication

Phenolic Laminated Cloth Board
JB886-66

3025

It has high mechanical properties and certain dielectric properties, and is suitable for use as insulating structural parts in electrical equipment

Epoxy Phenolic Glass Cloth Board
JB887-66

3240

It has high mechanical properties, dielectric properties and water resistance, and is suitable for use as structural parts of electrical equipment in humid environments

Reference Chart of Common Dielectric & Applications

Conclusion

The dielectric is a non-conductive material under the allowable voltage, but it is not absolutely non-conductive. Although it has properties such as heat resistance and moisture resistance, it will age after long-term use. If you want to know more related content, you can pay attention to other follow-up articles.

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