Views: 0 Author: Site Editor Publish Time: 2021-12-02 Origin: Site
Heat-resistant cables generally refer to cables with a temperature of (90～155)℃ and below, while high-temperature cables are cables with a temperature of 180℃ and above. To solve the problem of ordinary cables that are not resistant to high temperatures, it is necessary to improve the materials or use insulating materials that can withstand high temperatures.
Main features of heat-resistant and high-temperature wire and cable
Heat-resistant and high-temperature wires and cables are generally determined by two requirements. The first is the high ambient temperature of the wire and cable, and the cable can normally transmit signals or electric energy under high temperature for a long time; the other is the power transmission cable, which is mainly for increasing the interception capacity.
Cable working in high temperature environment. Ordinary cables are prone to insulation aging and scorching at high temperatures, and the use of cables loses performance, is damaged and cannot be used. The high temperature cable can work normally and stably under the rated high temperature, the signal or power transmission performance is not affected, and the cable has a long service life. This type of functional cable is the most common and most common type of high-temperature cable, and its use characteristics are also the easiest to understand.
Load-increasing high-temperature cables are mainly designed to reduce the outer diameter and weight of the cable under the prerequisite of current-carrying, and develop towards lighter weight. Generally speaking, the higher the working temperature of the cable, the greater the current carrying capacity of the cable of the same cross-section. For occasions like airplanes and automobiles, weight reduction is of great significance, and the use of high-temperature cables greatly reduces the cross-section. When the operating temperature rises from 90°C to 155°C, the current-carrying capacity increases by 50%. Under the same current-carrying capacity, the weight of the cable is reduced by half and the cost is also reduced. Of course, at the same time as high current interception, the power loss of most insulating materials will also increase.
Heat-resistant wire and cable
Heat-resistant wires and cables are divided into two types: heat-resistant materials and heat-resistant modification of common materials.
(1) Wire and cable made of heat-resistant materials
Heat-resistant wire and cable are insulated and sheathed materials. The body resin has heat-resistant properties. The main varieties are: polyurethane (up to 155°C), polyester (up to 135°C), polyvinylidene fluoride (150°C) ) And nylon (up to 115℃) insulation or sheath material. Commonly used in industries such as communications, automobiles, motors, and construction.
(2) Common cable materials are modified in various ways to achieve heat resistance:
1. Heat-resistant modification of rubber materials
Because of its poor heat resistance, rubber materials have a small margin for increasing the working temperature. Ordinary rubber can only reach 90°C with more heat stabilizers and cross-linking treatment, so it cannot be called heat-resistant cables, such as styrene butadiene rubber, Neoprene rubber, chlorosulfonated polyethylene, etc. Mainly used in rubber-insulated mobile flexible wires, rubber-insulated flexible power cables and control cables, etc.
However, EPDM rubber can be modified to increase the temperature resistance level to 135°C. In addition, it has better insulation properties, so it has a better development prospect in rubber.
2. Modification of PVC cable
The working temperature of ordinary PVC cable is 70℃. The high miscibility of PVC cable material makes it possible to modify it. The use of a large amount of heat stabilizer can facilitate the heat resistance of PVC to rise from 70℃ to 90℃. ℃ or 105℃, which greatly expands the applicability of PVC, an old-fashioned material. Perhaps this is one of the reasons why PVC cables will last forever? 90℃ PVC cable materials are often used in cross-linked polyethylene cable sheaths. For power, control and electrical equipment cables, due to the modification of PVC, the use of PVC cable materials that could be obsolete will continue for a long time in the use of sheaths. The main component of polyvinyl chloride butyronitrile compound is PVC, so it has the same modification properties as polyvinyl chloride butyronitrile compound cables and PVC insulated cables.
3. Modification of polyethylene cable
The plasticity of polyethylene material is better, but the fillability is poor, so it is impossible to fill the heating stabilizer method to increase the heat-resistant temperature. Polyethylene cables can be used for DCP dry chemical crosslinking and silane warm water crosslinking to increase the working temperature to 90°C. The former is used for medium and high voltage power cables, and the latter is used for low voltage cables. But another cross-linking method—irradiation cross-linking modification can greatly increase the working temperature of polyolefins (mainly polyethylene). The irradiated insulating material can be irradiated according to different conditions, and the temperature resistance can reach 105 ℃, 125℃, 135℃, 150℃, and it can be increased to 180℃ in foreign countries. It is mainly through the conversion of high-energy electrons into stable bond energy to strengthen the thermal stability of its molecular structure. At the same time, it is equipped with an appropriate thermal stabilizer. According to the energy level and the performance of the thermal stabilizer, it is divided into different heat resistance levels.
The commonly used processing equipment in the radiation cross-linking industry is an electron accelerator, which increases the energy of the electron beam at high pressure to achieve the purpose of cross-linking polyolefin materials. The energy level of the accelerator commonly used in electricity processing is 1.0 ~ 3MeV. Radiation crosslinking can also crosslink materials such as rubber, PVC and fluoroplastics. Irradiation cross-linked polyolefin wires and cables are mainly used for heat-resistant building wires, automotive wires, aviation wires, locomotive wires and electrical and electrical lead wires.