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Basic knowledge of insulating materials
Jun 28, 2018

Basic knowledge of insulating materials

A material that isolates the charged body from other parts of the electrical equipment. Commonly

 used solid materials are insulating paper, leather, rubber, plastic, paint, glass, ceramics, mica

 and so on. Commonly used liquid materials are transformer oil. Gaseous materials in the air, 

nitrogen, sulfur hexafluoride and other use more.

Insulation material: the resistivity of 109 ~ 1022 Ω? Cm material composition of the material in

 the electrical technology known as insulating materials, also known as electrolytes. Simply means

 that the charged body and other parts of the material isolation. Insulation material on the DC 

current has a very large resistance, under the action of DC voltage, in addition to a very small

 surface leakage current, in fact, almost non-conductive, and for the AC current capacitor current

 through, but also that is not Conductive. The greater the resistivity of the insulating material,

 the better the insulation performance.

Insulation Materials

A material for isolating the conductive portions of different potentials. Its conductivity is

 about 10-10 West / m below. Different electrical products, according to the need for insulation

 materials often play a role in energy storage, cooling, cooling, arc, moisture, mildew,

 anti-corrosion, radiation protection, mechanical support and fixed, protective conductor and so


Classification and performance of many types of insulating materials, can be divided into gas, 

liquid, solid three categories. Commonly used gas insulation materials are air, nitrogen, sulfur

 hexafluoride and so on. Liquid insulation materials are mainly mineral insulating oil, synthetic

 insulating oil (silicone oil, dodecyl benzene, polyisobutylene, isopropyl biphenyl, diaryl ethane

 etc.) two categories. Solid insulation materials can be divided into organic, inorganic two 

categories. Organic solid insulation materials include insulating varnishes, insulating glue, 

insulating paper, insulating fiber products, plastic, rubber, lacquered lacquers and insulating 

impregnated fiber products, electrical thin films, composite products and adhesive tape,

 electrical laminates and so on. Inorganic solid insulation materials are mainly mica, glass,

 ceramics and their products. In contrast, solid insulation material variety, but also the most


Different electrical equipment requirements for the performance of insulating materials are 

focused. High-voltage electrical equipment such as high-voltage motors, high-voltage cables and 

other insulation materials require high breakdown strength and low dielectric loss. Low-voltage

 electrical appliances, such as mechanical strength, elongation at break, heat-resistant grade as

 the main requirements.

The macroscopic properties of insulating materials such as electrical properties, thermal 

properties, mechanical properties, chemical resistance, weather resistance, corrosion resistance

 and other properties are closely related to its chemical composition and molecular structure.

 Inorganic solid insulation material is mainly composed of silicon, boron and a variety of metal

 oxides to ion-based structure Mainly characterized by high heat resistance, the working

 temperature is generally greater than 180 ℃ Good stability, resistance to atmospheric aging, 

chemical resistance And long-term under the action of the electric field aging performance; but

 high brittleness, low impact strength, high pressure and low tensile strength; poor process.

 Organic materials are generally polymers with an average molecular weight between 104 and 106, 

and their heat resistance is generally lower than that of inorganic materials. Contains aromatic

 rings, heterocycles and silicon, titanium, fluorine and other elements of the material heat 

resistance is higher than the general line of chain polymer materials.

An important factor affecting the dielectric properties of insulating materials is the strength 

of the polar and the content of polar components. The dielectric constant and dielectric loss of

 the polar material are higher than those of the non-polar material, and the impurity ions are 

easily adsorbed to increase the conductivity and reduce the dielectric properties. Therefore, in 

the insulation material manufacturing process should pay attention to clean, to prevent pollution.

 Capacitor dielectrics require high dielectric constants to increase their specificity.

Development Overview The earliest use of insulating materials for cotton, silk, mica, rubber and

 other natural products. At the beginning of the 20th century, industrial synthetic plastic 

phenolic resin first came out, its electrical properties, and high heat resistance. And later 

appeared in the performance of better urea-formaldehyde resin, alkyd resin. The appearance of the

 insulating oil of trichlorobiphenyl has led to a leap in the specificity of the power capacitor

 (but since it is harmful to human health and has ceased to be used). Sulfur hexafluoride was also

 synthesized in the same period.

Since the 30's synthetic insulation materials have been rapid development, mainly acetal resin,

 chloroprene rubber, polyvinyl chloride, styrene butadiene rubber, polyamide, melamine, 

polyethylene and excellent performance known as the king of plastic polytetrafluoroethylene Wait

. The emergence of these synthetic materials, the development of electrical technology played a 

significant role. Such as acetal enameled wire for the motor, so that the working temperature and

 reliability to improve, while the motor volume and weight greatly reduced. Glass fiber and its 

woven belt successfully developed and the synthesis of silicone resin insulation for the increase

 in the H-class heat-resistant grade.

40 years after the unsaturated polyester, epoxy resin come out. The emergence of powder mica paper

 so that people get rid of the plight of the lack of mica resources.

Since the 1950s, synthetic resin-based new materials have been widely used, such as unsaturated

 polyester and epoxy and other insulating rubber for high-voltage motor coil impregnation.

 Polyester series products in the motor slot insulation, enameled wire and impregnated paint used

 to develop the E-class and B-class low-voltage motor insulation, the motor volume and weight to

 further decline. Sulfur hexafluoride began to be used for high-voltage electrical appliances, 

and to large-scale development of large-capacity. The air insulation of the circuit breaker and 

the oil and paper insulation of the transformer are partially replaced by sulfur hexafluoride.

60 years with heterocyclic and aromatic ring of heat-resistant resin has been a great development,

 such as polyimide, polyaromatic amide, poly aryl sulfone, polyphenylene sulfide and other H-class

 and higher heat-resistant grade of the material. The synthesis of these heat-resistant materials

 for the future development of F-class, H-class motor to create favorable conditions.

 Polypropylene film was also successfully used in power capacitors during this period.

Since the 1970s, the development of new materials is relatively small, this period is mainly on 

the existing materials to modify and expand the scope of application. The use of new methods of

 mineral insulating oil to reduce its wear and tear; epoxy mica insulation to improve its

 mechanical properties and to achieve no air gap to improve its electrical performance has done 

a lot of improvements. Power capacitors from the paper composite structure to the full film 

structure transition. 1000 kV high voltage power cable began to use synthetic paper insulation 

to replace the traditional natural fiber paper. Pollution-free insulation materials since the

 1970s has developed rapidly, such as non-toxic media isopropyl biphenyl, ester oil to replace 

toxic media chlorinated biphenyl, solvent-free paint to expand the application. With the 

popularity of household appliances, the insulation material caused by fire and major fire 

accidents have occurred, so the research on the flame retardant material attracted attention.

Development trend Insulation material development and development level is one of the key factors

 affecting the development of electrical technology. From the future trend, the requirements of

 the development of high pressure, heat insulation solvent-free pollution-free insulation 

composite insulation corrosion, water, oil, cryogenic, radiation and flame retardant materials,

 the development of energy-saving materials. Focusing on the development of high-pressure 

large-capacity generators for the epoxy mica insulation system; small and medium-sized motor with

 the F, H-class insulation series; high-voltage power transmission equipment with sulfur

 hexafluoride gaseous medium; Non-toxic synthetic media; high-performance insulating oil;

 synthetic paper composite insulation; flame-retardant rubber and plastic materials and surface

 protection materials, while actively accelerating the traditional electrical equipment with the

 replacement of insulating materials.

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