Insulating materials Inorganic-Organic-Mixed insulating materials are divided into three categories.
(1) Inorganic insulating materials: mica, porcelain, asbestos, marble, glass, sulfur, etc. Used for winding insulation of motors and electrical appliances, insulating materials switch base plates and insulators, etc.
(2) Organic insulating materials: rubber, resin, insect glue, cotton yarn paper, hemp, silk, rayon tube, etc. Used in the manufacture of insulating paint, the outer layer of winding wire insulation, etc.
(3) Mixed insulating materials: molding insulating materials processed by two kinds of insulating materials. Used for the base of electrical appliances, shells, etc.
Organic insulating materials can be divided into the following categories.
1. Resin Resin is divided into natural resin and synthetic resin, and synthetic resin includes thermoplastic resin and thermosetting resin.
(1) Thermoplastic synthetic resins. Thermoplastic synthetic resins are synthesized artificially by chemical methods through polymerization reactions, and their polymers are linear in structure and have thermoplasticity.
Thermoplastic synthetic resins are widely used. Polyethylene has considerable elasticity and flexibility, can be made into a film, commonly used to do high-frequency cable insulation, high-frequency skeleton and capacitor film medium; polystyrene high resistivity, commonly used to do high-frequency and ultra-high-frequency low-loss insulation: polytetrafluoroethylene high chemical stability, will not burn, for high-temperature capacitors; polyvinyl chloride is widely used in the manufacture of a variety of plastic, wire insulation and cable protection layer, as well as for the manufacture of insulating paint; polymethyl methacrylate, also known as organic glass, can be used for decoration, making general structural parts, reading lenses, insulating parts and shells, covers, terminal blocks, etc.
(2) thermosetting synthetic resins. Thermosetting synthetic resin is produced by chemical condensation reaction, the polymer is mostly space structure, with thermosetting properties. Commonly used thermosetting synthetic resins are: Phenolic resin: most of the phenolic resin is thermosetting, is obtained from the condensation of phenol and formaldehyde thermosetting phenolic, also known as gum wood (Bakelite), inexpensive, quite common in the electronics industry. Such as for the manufacture of synthetic resistors and synthetic potentiometer resistance body, phenolic plastic, phenolic laminate, electricians in all kinds of switches, sockets, plugs, etc.. But its high-frequency loss is large, only for low-frequency occasions such as industrial frequency and audio.
Epoxy resin: epoxy resin is originally thermoplastic, under the action of various curing agents, it will become thermosetting. Epoxy resin has good electrical insulation, heat resistance, climate change resistance, high stability, small moisture permeability, good lofty junction, and can be closely bonded with a variety of materials such as metals and ceramics. In the electronics industry, it is mainly used in braiding, casting, encapsulation, coating and laminates. Silicone resin: also known as organic resin, a new type of polymer compound with the advantages of organic and inorganic substances. It has good mechanical properties and heat resistance, good dielectric properties, water proof, moisture proof, cold proof, chemical corrosion resistant, and arc high voltage corona resistant. Widely used in the manufacture of silicone paints, silicone molding compounds for impregnation, coating and encapsulation of electronic components. Transparent silicone glass resin, electrical properties and high-frequency performance, suitable for high temperature, high humidity conditions, commonly used to do a variety of materials surface coating 2. Plastic Plastic is a synthetic resin as the main raw material, adding fillers and a variety of additives, etc. formulated from powder, granular or fibrous, at a certain temperature, pressure conditions can be plastic polymer materials. Plastic is light, excellent electrical properties, sufficient hardness and mechanical strength, easy to mold processing molding, so it is widely used in electrical equipment.
(The basic components of U plastics. The basic components of plastics are gumming agent and filler. Gumming agent will be all components of the glue fusion, it determines the basic characteristics of plastic products, commonly used gumming agent is a synthetic resin. The addition of fillers can improve the mechanical strength of plastics and reduce costs. In order to make the plastic obtain some different properties, sometimes also add different kinds of additives, such as plasticizers, coloring agents, stabilizers, lubricants, curing agents, etc.
(2) Classification of plastics. Plastics can be classified into two categories: thermosetting and thermoplastic according to the type of resin that is their main component.
Thermosetting plastics become insoluble and non-melting curing after hot pressing, commonly used phenolic resin as the main component of phenolic plastic, and high temperature resistant 4250 plastic, polyimide plastic, polyenergy plastic, etc.. Although thermoplastics are cured after hot extrusion molding, their physical and chemical properties do not change significantly, they are still soluble and meltable and can be repeatedly molded. The following thermoplastics are commonly used.
ABS engineering plastics: ivory-colored opaque body, good mechanical and electrical properties, dimensional stability within a certain temperature range, high surface hardness, easy machining and molding, the surface can be metalized. But heat resistance, cold resistance is poor, contact with certain chemicals (such as glacial acetic acid and acids) and certain vegetable oils, easy to produce cracks. Engineering plastics are suitable for making various instrument housings, brackets, small motor housings, power tool housings, structural parts and decorative parts, etc.
Polyamide (nylon) 1010: white translucent body, high mechanical strength at room temperature, good electrical properties, impact toughness, wear resistance, self-lubricating, stable structure, good oil resistance, resistance to organic solvents, available for coil skeleton, socket, terminal block, carbon brush frame and instrument gear, etc., commonly used in the cable industry to do aviation wire and cable sheathing.
Polyethylene (Yang): white translucent solid, density is smaller than water, has good electrical properties, its relative dielectric constant and dielectric loss is almost independent of frequency, and small coefficient of friction, high chemical stability, moisture resistance, excellent cold resistance, but the softening temperature is low, long-term working temperature should not be higher than 70 ℃. The film made of polyethylene is widely used as conductor insulation layer for communication cables, high frequency cables and underwater cables, etc.
Polyvinyl chloride (PVC): There are two types of insulation and sheathing grades, of which the insulation grade is 65℃, 80℃, 90℃ and 105℃ respectively according to the temperature resistance conditions, and the sheathing grade is 65℃. Polyvinyl chloride has good mechanical and electrical properties, stable structure, moisture resistance, corona resistance, non-flammable, low cost, easy processing and other advantages.
Polytetrafluoroethylene: known as the plastic king, its film has high heat and cold resistance, excellent electrical properties, small dielectric loss, and almost unaffected by changes in temperature and frequency, not charred under the action of electric arc, chemically stable, not dissolved in any organic solvent, not burning, not hygroscopic, only alkali metals and fluorine elements at high temperatures have a significant corrosive effect on it, high temperature (such as more than 300 ℃) Tensile strength decreases more, elongation increases, the opposite situation at low temperature, the temperature exceeds 500 ℃, will decompose the highly toxic, chemically active gaseous fluorine. PTFE film is often used in high temperature or corrosive environment of the motor, cable or other equipment winding insulation and inter-slot insulation, as well as capacitor manufacturing, instrumentation insulation, etc.
Poly: colorless transparent film, with high tensile strength, electrical insulation strength, heat resistance and humidity resistance, stable to most chemicals and solvents, and will not mold, but the arc resistance, alkali resistance is poor, the working temperature is -60 ℃ 120 ℃, suitable for low-voltage motor in the slot insulation, phase insulation and molding coil wrapping with insulation tape, often and Green shell paper composite use.
(3) the main use of plastic. Plastic in the electronics industry is mainly used for insulation parts, structural parts, appearance parts, the use of different requirements for its performance is also different.
Insulation parts: according to its application, the operating frequency range of the dielectric properties of the requirements, and taking into account the environmental conditions and process performance, such as wire and cable insulation, sheathing, etc..
Structural parts: require high mechanical properties, for high-temperature environment and friction operation of the structural parts require good heat resistance, low coefficient of friction, wear resistance, in some cases can use reinforced plastics or composite plastics, such as some electronic clocks, recorders, such as the movement of plastic parts.
Appearance parts: in addition to certain mechanical properties, require a smooth surface, good coloring, easy plating, as well as light transmission, heat resistance, such as the plastic case of the instrument.
3. Insulating adhesive Insulating adhesive is a class of substances with easy junction properties, can partially replace welding, riveting and screws and other mechanical connections. According to its nature, the adhesive is broadly divided into thermosetting resin teaching agent, thermoplastic resin teaching agent, rubber adhesive torture, special adhesive easy agent. Commonly used adhesives are the following two kinds: (1) 502 glue. It is a colorless or slightly yellow transparent liquid. In a very short time at room temperature will produce polymerization and hardening, short storage period, there is a strong fusion effect. 502 glue on a variety of metals, glass, plastics (except polyethylene and polytetrafluoroethylene) and rubber and other materials have strong fusion, suitable for large area fusion.
Insulating materials Inorganic-Organic-Mixed insulating materials are divided into three categories.