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What are the advantages and disadvantages of commonly used wire and cable insulation materials?

2021-04-29
What are the advantages and disadvantages of commonly used wire and cable insulation materials?

1. PVC material


PVC polyvinyl chloride (hereinafter referred to as PVC) insulation material is a mixture of stabilizers, plasticizers, flame retardants, lubricants and other additives added to PVC powder. According to the different application and different characteristics of the wire and cable, the formula is adjusted accordingly. After decades of production and use, the current PVC manufacturing and processing technology has been very mature. PVC insulation material has a very wide range of applications in the field of wire and cable, and has significant own characteristics:
    1) The manufacturing technology is mature, easy to shape and process and manufacture. Compared with other types of cable insulation materials, it is not only low-cost, but also can be used in terms of color difference, mattness, printing, processing efficiency, softness, adhesion of the conductor, and the mechanical and physical properties and electrical properties of the wire itself. Effective control.
   2) It has very good flame-retardant properties, so PVC insulated wires can easily reach the flame-retardant levels required by various standards.
   3) In terms of rated voltage, it is generally used in the rated voltage of 1000V AC and below, which can be widely used in household appliances, instrumentation, lighting, network communications and other industries.
   4) Non-toxic and tasteless PVC insulated wire can also be widely used in air conditioners, refrigerators and other electrical wiring.

PVC also has some shortcomings of its own, which limit its use:
    1) Because it contains a large amount of chlorine, a large amount of dense smoke will suffocate when burning, affect visibility, and produce some carcinogens and HCl gas, which cause serious harm to the environment. With the development of low-smoke halogen-free insulation material manufacturing technology, gradually replacing PVC insulation has become an inevitable trend in cable development. At present, some influential and socially responsible enterprises have clearly put forward the timetable for replacing PVC materials in the company's technical standards.
    2) Ordinary PVC insulation has poor resistance to acids and alkalis, heat-resistant oils, and organic solvents. According to similar chemical principles of compatibility, PVC wires are easily damaged and cracked in the specified environment.
    However, with its excellent processing performance and low cost. PVC cables are still widely used in household appliances, lighting, mechanical equipment, instrumentation, network communications, building wiring and other fields.

2. XLPE wire and cable insulation


Cross-linked polyethylene (Cross-linke PE, hereinafter referred to as XLPE) is a polyethylene that is subjected to high-energy rays or cross-linking agents, and under certain conditions, it can transform from a linear molecular structure to a three-dimensional structure. At the same time, it is transformed from thermoplastic into insoluble thermosetting plastic. At present, in the application of wire and cable insulation, there are three main cross-linking methods:
   (1) Peroxide crosslinking. Firstly, polyethylene resin is mixed with appropriate cross-linking agent and antioxidant, and other ingredients are added as needed to make cross-linkable polyethylene mixture particles. During the extrusion process, cross-linking occurs through the hot steam cross-linking pipe.
   (2)Silane crosslinking (warm water crosslinking). It is also a chemical cross-linking method. The main mechanism is to cross-link organosiloxane and polyethylene under specific conditions. The degree of cross-linking can generally reach about 60%.
   (3) Irradiation crosslinking is the use of high-energy rays such as r-rays, alpha rays, electron rays and other energies to activate carbon atoms in polyethylene macromolecules. The high-energy rays commonly used in wires and cables are electron rays generated by electron accelerators. The cross-linking relies on physical energy, so it is a physical cross-linking.
The above three different cross-linking methods have different characteristics and applications:
Cross-linking category characteristics application

   In the cross-linking process, it is suitable for the production of high electro-melt, long-length, peroxide cross-linking temperature, through the hot steam cross-linking of large cross-section cables, the production of small-size wave pipes, and cross-linking. Fedo. Silane cross-linking General-purpose cables suitable for small size, small specification, low equipment, and extruder subject to temperature limitation and power consumption can be used. The cross-linking anti-enthalpy is in the silane cross-linking system, and the linking will be completed under the conditions of water or moisture when it is exposed to moisture. The higher the temperature, the cross-linking speed is suitable for the production of low-melt cables. The relationship between the energy of the radiation source and the , Suitable for insulation thickness is not too thick, resistant to not too thick insulation, insulation high temperature flame retardant cables. When the radiation cross-linking is too thick, there will be uneven irradiation.

Compared with thermoplastic polyethylene, XLPE insulation has the following advantages:

   (1)Improved heat deformation resistance, improved mechanical properties at high temperatures, and improved resistance to environmental stress cracking and heat aging.
   (2)Enhanced chemical stability and solvent resistance, reduced cold flow, basically maintained the original electrical performance, long-term working temperature can reach 125 ℃ and 150 ℃, cross-linked polyethylene insulated wire and cable, also improved short circuit The bearing capacity of XLPE can reach 250℃ in a short time, and the current carrying capacity of cross-linked polyethylene is much larger for wires and cables of the same thickness.
   (3) XLPE insulated wires and cables have excellent mechanical, waterproof and radiation resistance properties, so they have a wide range of applications. Such as: electrical internal connection wires, motor leads, lighting leads, automotive low-voltage signal control wires, locomotive wires, subway wires and cables, mining environmental protection cables, marine cables, nuclear power laying cables, TV high-voltage cables, X-RAY firing high-voltage cables, and power Transmission wire and cable industries. XLPE insulated wires and cables have significant advantages, but they also have some shortcomings of their own, which limit their use:
   1) Poor heat blocking performance. When the wire is processed and used at a temperature exceeding the rated temperature of the wire,
It is easy to cause adhesion between the wires, which can seriously cause the insulation to break and form a short circuit.
   2) Poor heat-resistant cut-through performance. At temperatures exceeding 200°C, the wire insulation becomes extremely soft, and squeezing and collision by external forces may easily cause the wire to cut through and short-circuit.
   3) The color difference between batches is difficult to control. The processing process is easy to scratch and whitish, printing off and other problems
   4) XLPE insulation at 150°C temperature resistance level, completely halogen-free and able to pass the UL1581 VW-1 combustion test, and maintain excellent mechanical and electrical properties, there are still certain bottlenecks in the manufacturing technology, and the cost is high.
   5) There is no relevant national standard for the insulated wire of this kind of material in the connection of electronic and electrical appliances.

3. Silicone rubber wire and cable insulation


   Silicone rubber is also a polymer molecule is a chain structure 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 of the silicone rubber wires and cables use cold extrusion and high temperature vulcanization processes. Among many synthetic rubber wires and cables, due to its unique molecular structure, silicone rubber has better performance than other ordinary rubbers:
   1) Very soft, good elasticity, odorless and non-toxic, not afraid of high temperature and resistant to severe cold.
The operating temperature range is -90~300℃. Silicone rubber has much better heat resistance than ordinary rubber. It can be used continuously at 200°C, and it can also be used for a period of time at 350°C.
   2) Excellent weather resistance. Under ultraviolet light and other climatic conditions for a long time, its physical properties have only slight changes.
   3) Silicone rubber has a high resistivity and its resistance remains stable in a wide range of temperature and frequency. At the same time, silicone rubber has good resistance to high-voltage corona discharge and arc discharge. Silicone rubber insulated wires and cables have the above series of advantages. They are used in TV high-voltage device wires, microwave ovens high temperature resistant wires, induction cooker wires, coffee pot wires, lamp leads, UV equipment, halogen lamps, ovens and fan internal connection wires, etc. Especially in the field of small household appliances, it has a wide range of applications, but some of its own shortcomings also restrict wider applications. Such as
   1) Poor tear resistance. Extruded by external force during processing or use, it is easy to be damaged by scraping and causing short circuit. The current protective measure is to add a glass fiber or high-temperature polyester fiber woven layer to the silicone insulation, but it is still necessary to avoid damage caused by external force extrusion as much as possible during the processing.
   2) The vulcanizing agent added for vulcanization molding currently mainly uses double 24. The vulcanizing agent contains chlorine element,
Completely halogen-free vulcanizing agents (such as platinum vulcanization) have strict requirements on the production environment temperature and are costly.
Therefore, attention should be paid to the processing of the wire harness: the pressure of the pressure roller should not be too high, and it is best to use rubber material to prevent poor pressure resistance caused by fracturing during the production process. At the same time, please note: the glass fiber yarn needs to take necessary protective measures during the production process to prevent inhalation of the lungs and affect the health of employees