The performance of insulating materials directly affects the quality, processing efficiency and application scope of wires and cables. The performance of insulating materials directly affects the quality, processing efficiency and application scope of wires and cables.
1.PVC polyvinyl chloride wires and cables
Polyvinyl chloride (hereinafter referred to as PVC) insulating materials are mixtures in which stabilizers, plasticizers, flame retardants, lubricants and other additives are added to PVC powder. According to the different applications and characteristic requirements of wires and cables, the formula is adjusted accordingly. After decades of production and application, the manufacturing and processing technology of PVC has now become very mature. PVC insulating material has very wide applications in the field of wires and cables and has distinct characteristics of its own:
A. The manufacturing technology is mature, easy to form and process. Compared with other types of cable insulation materials, it not only has a low cost, but also can effectively control the color difference, gloss, printing, processing efficiency, softness and hardness of the wire surface, the adhesion of the conductor, as well as the mechanical and physical properties and electrical properties of the wire itself.
B. It has excellent flame retardant performance, so PVC insulated wires can easily meet the flame retardant grades stipulated by various standards.
C. In terms of temperature resistance, through the optimization and improvement of material formulas, the currently commonly used types of PVC insulation mainly include the following three categories:
In terms of rated voltage, it is generally used in voltage levels rated at 1000V AC and below, and can be widely applied in industries such as household appliances, instruments and meters, lighting, and network communication.
PVC also has some inherent drawbacks that limit its application:
A. Due to its high chlorine content, it will emit A large amount of thick smoke when burning, which can cause suffocation, affect visibility, and produce some carcinogens and HCl gas, causing serious harm to the environment. With the development of low smoke zero halogen insulation material manufacturing technology, gradually replacing PVC insulation has become an inevitable trend in the development of cables.
B. Ordinary PVC insulation has poor resistance to acids and alkalis, heat oil, and organic solvents. According to the chemical principle of like dissolves like, PVC wires are highly prone to damage and cracking in the specific environment mentioned. However, with its excellent processing performance and low cost. PVC cables are still widely used in household appliances, lighting fixtures, mechanical equipment, instruments and meters, network communication, building wiring and other fields.
2. Cross-linked polyethylene wires and cables
Cross-linked PE (hereinafter referred to as XLPE) is a type of polyethylene that can transform from a linear molecular structure to a three-dimensional three-dimensional structure under certain conditions under the action of high-energy rays or cross-linking agents. At the same time, it transforms from thermoplastic to insoluble thermosetting plastic.
At present, in the application of wire and cable insulation, there are mainly three cross-linking methods:
A. Peroxide cross-linking: It involves first using polyethylene resin in combination with appropriate cross-linking agents and antioxidants, and then adding other components as needed to produce cross-linkable polyethylene mixture particles. During the extrusion process, cross-linking occurs through hot steam cross-linking pipes.
B. Silane cross-linking (warm water cross-linking) : This is also a method of chemical cross-linking. Its main mechanism is to cross-link organosiloxane and polyethylene under specific conditions, a
nd the degree of cross-linking can generally reach about 60%.
C. Irradiation cross-linking: It utilizes high-energy rays such as R-rays, alpha rays, and electron rays to activate the carbon atoms in polyethylene macromolecules and cause cross-linking. The high-energy rays commonly used in wires and cables are electron rays generated by electron accelerators. Since this cross-linking relies on physical energy, it belongs to physical cross-linking.
The above three different crosslinking methods have distinct characteristics and applications:
Compared with thermoplastic polyethylene (PVC), XLPE insulation has the following advantages:
A. It has enhanced the heat deformation resistance, improved the mechanical properties at high temperatures, and improved the resistance to environmental stress cracking and heat aging.
B. It has enhanced chemical stability and solvent resistance, reduced cold flow, and basically maintained the original electrical performance. The long-term working temperature can reach 125℃ and 150℃. The cross-linked polyethylene insulated wire and cable also improves the short-circuit resistance, and its short-term temperature resistance can reach At 250℃, for wires and cables of the same thickness, the current-carrying capacity of cross-linked polyethylene is much greater.
C. It has excellent mechanical, waterproof and radiation-resistant properties, so it is widely used in various fields. Such as: internal connection wires for electrical appliances, motor leads, lighting leads, low-voltage signal control wires for automobiles, locomotive wires, wires and cables for subways, environmental protection cables for mines, Marine cables, cables for nuclear power laying, high-voltage wires for TV, high-voltage wires for X-RAY firing, and power transmission wires and cables, etc.
XLPE insulated wires and cables have significant advantages, but they also have some inherent disadvantages that limit their application:
A. Poor heat-resistant adhesion performance. When processing and using wires beyond their rated temperature, it is easy for the wires to stick to each other. In severe cases, it can lead to insulation damage and short circuits.
B. Poor heat conduction resistance. At temperatures exceeding 200℃, the insulation of wires becomes extremely soft. When subjected to external force squeezing or collision, it is prone to cause the wires to cut through and short circuit.
C. It is difficult to control the color difference between batches. Problems such as scratches, whitening and printed characters peeling off are prone to occur during the processing
D. The XLPE insulation with a temperature resistance grade of 150℃ is completely halogen-free and can pass the VW-1 combustion test in accordance with UL1581 standards, while maintaining excellent mechanical and electrical properties. However, there are still certain bottlenecks in manufacturing technology and the cost is high.
3. Silicone rubber wires and cables
The polymer molecules of silicone rubber are chain structures formed by SI-O (silicon-oxygen) bonds. The SI-O bond is 443.5KJ/MOL, which is much higher than the C-C bond energy (355KJ/MOL). Most silicone rubber wires and cables are produced through cold extrusion and high-temperature vulcanization processes. Among various synthetic rubber wires and cables, due to its unique molecular structure, silicone rubber has superior performance compared to other ordinary rubbers.
A. It is extremely soft, has good elasticity, is odorless and non-toxic, and is not afraid of high temperatures and can withstand severe cold. The operating temperature range is from -90 to 300℃. Silicone rubber has much better heat resistance than ordinary rubber. It can be used continuously at 200℃ and for a period of time at 350 ℃.
B. Excellent weather resistance. Even after long-term exposure to ultraviolet rays and other climatic conditions, its physical properties have only undergone minor changes.
C. Silicone rubber has a very high resistivity and its resistance remains stable over a wide range of temperatures and frequencies.
Meanwhile, silicone rubber has excellent resistance to high-voltage corona discharge and arc discharge. Silicone rubber insulated wires and cables have the above series of advantages and are widely used in high-voltage device wires for televisions, high-temperature resistant wires for microwave ovens, wires for induction cookers, wires for coffee POTS, leads for lamps, UV equipment, halogen lamps, internal connection wires for ovens and fans, especially in the field of small household appliances.
However, some of its own shortcomings also limit its wider application. For example:
A. Poor tear resistance. During processing or use, it is prone to damage due to external force squeezing, scratching and grinding, which may cause a short circuit. The current protective measure is to add a layer of glass fiber or high-temperature polyester fiber braided outside the silicone insulation. However, during the processing, it is still necessary to avoid injuries caused by external force squeezing as much as possible.
B. The vulcanizing agent currently mainly used in vulcanization molding is double, two, four. This vulcanizing agent contains chlorine. Completely halogen-free vulcanizing agents (such as platinum vulcanizing) have strict requirements for the production environment temperature and are costly. Therefore, when processing wire harnesses, the following points should be noted: the pressure of the pressure wheel should not be too high. It is best to use rubber material to prevent fracturing during the production process, which may lead to poor pressure resistance.
4. Cross-linked ethylene propylene diene monomer (EPDM) rubber (XLEPDM) wire
Cross-linked ethylene propylene diene monomer (EPDM) rubber is a terpolymer of ethylene, propylene and a non-conjugated diene, which is cross-linked through chemical or irradiation methods. Cross-linked EPDM rubber insulated wire combines the advantages of both polyolefin insulated wire and ordinary rubber insulated wire:
A. Soft, flexible, elastic, non-stick at high temperatures, long-term aging resistance, and resistant to harsh weather conditions (-60 to 125℃).
B. Ozone resistance, UV resistance, electrical insulation resistance, and chemical corrosion resistance.
C. The oil and solvent resistance is comparable to that of general-purpose chloroprene rubber insulation. It is processed by ordinary hot extrusion equipment and irradiation cross-linking is adopted, which is simple to process and low in cost. Cross-linked ethylene propylene diene monomer (EPDM) rubber insulated wires have the above-mentioned numerous advantages and are widely used in fields such as refrigeration compressor leads, waterproof motor leads, transformer leads, mobile cables in mines, drilling, automobiles, medical devices, ships, and general internal wiring of electrical appliances.
The main disadvantages of XLEPDM wires are:
A. Like XLPE and PVC wires, it has relatively poor tear resistance.
B. Poor adhesion and self-adhesiveness affect subsequent processability.
5. Fluoroplastic wires and cables
Compared with common polyethylene and polyvinyl chloride cables, fluoroplastic cables have the following prominent features:
A. High-temperature resistant fluoroplastics have extraordinary thermal stability, enabling fluoroplastic cables to adapt to high-temperature environments ranging from 150 to 250 degrees Celsius. Under the condition of conductors with the same cross-sectional area, fluoroplastic cables can transmit a larger allowable current, thereby greatly expanding the application range of this type of insulated wire. Due to this unique property, fluoroplastic cables are often used for internal wiring and lead wires in aircraft, ships, high-temperature furnaces, and electronic equipment.
B. Good flame retardancy: Fluoroplastics have a high oxygen index, and when burning, the flame spread range is small, generating less smoke. The wire made from it is suitable for tools and places with strict requirements for flame retardancy. For example: computer networks, subways, vehicles, high-rise buildings and other public places, etc. Once a fire breaks out, people can have some time to evacuate without being knocked down by thick smoke, thus gaining precious rescue time.
C. Excellent electrical performance: Compared with polyethylene, fluoroplastics have a lower dielectric constant. Therefore, compared with coaxial cables of similar structures, fluoroplastic cables have less attenuation and are more suitable for high-frequency signal transmission. Nowadays, the increasing frequency of cable usage has become a trend. Meanwhile, due to the high-temperature resistance of fluoroplastics, they are commonly used as internal wiring for transmission and communication equipment, jumpers between wireless transmission feeders and transmitters, and video and audio cables. In addition, fluoroplastic cables have good dielectric strength and insulation resistance, making them suitable for use as control cables for important instruments and meters.
D. Perfect mechanical and chemical properties: Fluoroplastics have high chemical bond energy, high stability, are almost unaffected by temperature changes, and possess excellent weather aging resistance and mechanical strength. And it is not affected by various acids, alkalis and organic solvents. Therefore, it is suitable for environments with significant climate changes and corrosive conditions, such as petrochemicals, oil refining, and oil well instrument control.
E. Facilitates welding connections In electronic instruments, many connections are made by welding. Due to the low melting point of general plastics, they tend to melt easily at high temperatures, requiring proficient welding skills. Moreover, some weld points need a certain amount of welding time, which is also the reason why fluoroplastic cables are popular. Such as the internal wiring of communication equipment and electronic instruments.
Of course, fluoroplastics still have some disadvantages that limit their use:
A. The price of raw materials is high. Currently, domestic production still mainly relies on imports (Daikin of Japan and DuPont of the United States). Although domestic fluoroplastics have developed rapidly in recent years, the production varieties are still single. Compared with imported materials, there is still A certain gap in thermal stability and other comprehensive properties of the materials.
B. Compared with other insulating materials, the production process is more difficult, the production efficiency is low, the printed characters are prone to fall off, and the loss is large, which makes the production cost relatively high.
In conclusion, the application of all the above-mentioned types of insulating materials, especially high-temperature special insulating materials with a temperature resistance of over 105℃, is still in a transitional period in China. Whether it is wire production or wire harness processing, there is not only a mature process, but also a process of rationally understanding the advantages and disadvantages of this type of wire.
Post time: May-27-2025