Brief introduction of the hottest heat-resistant a

Brief introduction of heat-resistant and high-temperature wires and cables

Abstract: the content of this paper mainly introduces some varieties of wires and cables with higher working temperature than the conventional ones, and briefly describes the heat-resistant and high-temperature materials used in cables, combined with the varieties and heat-resistant properties of products, so that we can open the oil delivery valve to understand the special field of high-temperature wires and cables more

key words: wire and cable; Fluoroplastics; Irradiation crosslinking; Polyurethane; Silicone rubber

I. Introduction

general wires and cables are insulated and sheathed with plastic and rubber. These materials are conventional engineering materials with rich sources, which can meet mass production, and the cost is relatively low. However, for some special industries such as petrochemical industry, steel, aerospace, shipbuilding, military industry, pharmaceutical industry, food, plastic machinery, boiler and other industries related to heat and high temperature, wires and cables that can withstand a certain high temperature are required. Ordinary wires and cables obviously cannot be used. Wires and cables that can withstand high temperature are required to ensure the safe operation of power and signals

with the rapid development of China's economy, the demand for high-temperature cables in special industries has increased at a high speed. Heat resistant and high-temperature cables are growing at a rate of 20% every year. As an important part of special cables, high-temperature cables have strong vitality, and supply exceeds demand. China imports about 2 billion yuan from abroad every year for domestic construction

now let's know what kind of working temperature is called heat-resistant and high-temperature cable. The International Electrotechnical Commission (IEC) generally divides the heat-resistant grade of insulation into the following according to the provisions of Table 1: the provisions of Table 1 heat-resistant grade

the insulation and sheath of ordinary wires and cables are ordinary engineering rubber and plastic, which are basic resins, but the requirements are insulation grade. Common rubber materials for cables include: butadiene rubber, ethylene propylene rubber, natural rubber, chlorosulfonated polyethylene, etc., and the working temperature is (60 ~ 75) ℃; Common plastic materials for cables include polyvinyl chloride, polyethylene (including cross-linked polyethylene) and polypropylene, and the working temperature is (70 ~ 90) ℃. It can be seen that these cables are not strictly heat-resistant or high-temperature cables

heat resistant cables generally refer to cables at or below (90 ~ 155) ℃, while high-temperature cables are cables at or above 180 ℃. To solve the problem that ordinary cables are not resistant to high temperature, it is necessary to improve the materials or use insulation grade materials that can withstand high temperature

II. Main characteristics of heat-resistant and high-temperature wires and cables

heat-resistant and high-temperature wires and cables are generally determined by two kinds of needs. The first is that the ambient temperature of wires and cables is high, and the cables can normally transmit signals or electric energy under high temperature for a long time; The other is the power transmission cable, which mainly aims to increase the interception capacity

cables working in high temperature environment. Ordinary cables are prone to insulation aging and scorching at high temperature, so the cable loses its performance and cannot be used due to damage. The high-temperature cable can work normally and stably under the rated high temperature, and the signal or power transmission performance will not be affected, which can also ensure that the cable has a long service life. This kind of functional cable is the most common type of high-temperature cable, and its use characteristics are also the easiest to understand

load increasing high-temperature cable is mainly to reduce the outer diameter and weight of the cable under the premise of current carrying and develop towards lightweight. Generally speaking, the maximum number of experimental channels of the system is 10. The higher the working temperature of the cable, the greater the ampacity of the cable with the same section. In places such as airplanes and automobiles, it is of great significance to reduce weight. The use of high-temperature cables greatly reduces the cross-section. If the working temperature rises from 90 ℃ to 155 ℃, the current carrying capacity will increase by 50%. Under the same current carrying capacity, the cable weight will be reduced by half, and the cost will also be reduced. Of course, at the same time of high current cut-off, the power loss of most insulating materials will also increase

III. heat resistant wires and cables

heat resistant wires and cables are divided into two types: heat-resistant materials and heat-resistant modification of ordinary materials

(I) wires and cables made of heat-resistant materials

wires and cables made of heat-resistant materials are insulation and sheathing materials. The body resin has heat-resistant properties, and the main varieties are: polyurethane (up to 155 ℃), polyester (up to 135 ℃), polyvinylidene fluoride (150 ℃) and nylon (up to 115 ℃) insulation or sheathing materials. It is commonly used in communication, automobile, motor, construction and other industries

(II) ordinary cable materials achieve heat resistance through modification in various ways:

1. Heat resistance modification of rubber materials

rubber materials have less margin to improve the working temperature because of their poor heat resistance. Ordinary rubber can reach 90 ℃ only after adding more heat stabilizers and cross-linking treatment, so it cannot be called heat-resistant cables, such as styrene butadiene rubber, neoprene, chlorosulfonated polyethylene, etc. It is mainly used in rubber insulated mobile flexible wires, rubber insulated flexible power cables and control cables

however, EPDM can be modified to improve the temperature resistance grade to 135 ℃, and it has good insulation performance, so it has a good development prospect in rubber

2. Modification of PVC cable

the working temperature of ordinary PVC cable is 70 ℃, and the high miscibility of PVC cable material makes its modification possible. The use of a large amount of heat stabilizer can make the heat resistance of PVC rise from 70 ℃ to 90 ℃ or 105 ℃, which greatly expands the applicability of PVC, an old-fashioned material. Maybe this is one of the reasons why PVC cable is prosperous

90 ℃ PVC cable material is often used in cross-linked polyethylene cable sheath, mainly used in power, control and electrical equipment cables. Due to the modification of PVC, the obsolete PVC cable material will continue to be used in the sheath for a long time

the main component of PVC NBR composite is PVC, so the complex (2) harmonics with PVC NBR can be electrically transmitted to other electrical consumers. The composite cable has the same modification performance as PVC insulated cable

3. Modification of polyethylene cable

polyethylene material has good plasticity, but poor fillability, so it cannot be filled with heating stabilizer to improve the heat-resistant temperature. The working temperature of polyethylene cable can be increased to 90 ℃ through DCP dry chemical crosslinking and silane warm water crosslinking. The former is used for medium and high voltage power cables, and the latter is used for low-voltage cables

however, the working temperature of polyolefin (mainly polyethylene) can be greatly increased by irradiation crosslinking modification, and the temperature resistance of irradiated insulating materials can reach 105 ℃, 125 ℃, 135 ℃ and 150 ℃ according to different conditions, while it can be increased to 180 ℃ abroad. 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 appropriate heat stabilizers, which are divided into different heat-resistant grades according to the energy level and the efficiency of heat stabilizers

the common processing equipment in the irradiation crosslinking industry is the electron accelerator, which is to increase the energy of the electron beam under high pressure to achieve the purpose of crosslinking polyolefin materials. The energy level of the common accelerator for electricity processing is 1.0 ~ 3MeV. Irradiation crosslinking can also crosslink rubber, PVC, fluoroplastics and other materials

irradiated cross-linked polyolefin wires and cables are mainly used for heat-resistant construction lines, automobile lines, aviation wires, locomotive lines, electrical and electrical leads, etc

heat resistant cable is a cable with medium temperature, which has certain heat resistance and can adapt to a certain temperature environment. The most widely used is that in power transmission cables, it is of great significance to increase the cable current carrying capacity and reduce the cable weight and section while ensuring the insulation performance

IV. high temperature and ultra-high temperature wires and cables

high temperature cables are divided into screw organic polymer high temperature cables and inorganic high temperature cables

(I) high temperature cables made of organic polymer materials are mainly fluoroplastic and silicone rubber cables

1. Fluoroplastics insulated wires and cables

fluoroplastics is an important category of plastics. Generally, people know fluoroplastics from contacting polytetrafluoroethylene (PTFE), the king of plastics. In fact, polytetrafluoroethylene is only the fluoroplastic variety with the largest output and consumption. The commonly used fluoroplastics for wires and cables are: FEP (commonly known as F46), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene copolymer (ETFE, commonly known as F40), polyvinylidene fluoride (PVDF), etc. Table 2. Various fluoroplastic properties

fluoroplastic cables mainly include: high temperature communication cables, high temperature resistant guide wires and installation wires, high temperature compensation wires and industrial high temperature resistant power and control signal cables, radiation resistant cables for atomic reactors and wires for locomotives and rolling stock

(2) silicone rubber insulated wire and cable

silicone rubber is mainly a polymer material formed by replacing carbon with silicon, and silicone rubber has good heat resistance. The common silicone rubber for wires and cables is methyl vinyl silicone rubber, and the working temperature range is -60 ℃ ~ 180 ℃. Silicone rubber has good bending properties and low-temperature properties, which are not easy to damage and crack. These properties are not available in general high-temperature cables. Therefore, silicone rubber cables have a wide range of applications, and have become a highlight of high-temperature cables

silicone rubber cable is used in high-temperature mobile cable, soft power cable, motor lead wire, low-temperature environment and high-temperature operation place

(II) inorganic materials high temperature cable

inorganic materials do not have excellent processing properties such as extrusion, so it is difficult to process and form cable insulation, with poor adhesion and uniformity, and the insulation performance is lower than that of polymer materials, but the excellent high temperature performance can meet the needs of special high temperature industries

1. Mineral insulated fireproof cable

the product structure is copper core copper sheathed magnesium oxide insulated cable, mainly including power cable, control cable, heating cable and cloth wire. The conventional working temperature is 250 ℃, but the actual working temperature can be higher, because the melting point of magnesium oxide is 2800 ℃, which is much higher than the melting point of copper. The cable can still be reused safely after a fire

the production of this cable is that the magnesium oxide shaped porcelain column is threaded outside the copper conductor, and the copper conductor and the outer copper tube are formed by pulling and annealing at the same time. The magnesium oxide porcelain column is crushed evenly to form cable insulation. The production length of mineral insulated fireproof cable is limited to a certain extent, and the large specification is shorter

mineral insulated fire-proof cable has the characteristics of high temperature resistance, fire prevention, explosion-proof, waterproof, radiation resistance, strong corrosion resistance, high mechanical strength, good grounding performance, small volume, long service life, large carrying capacity, strong overload capacity, etc

2. Inorganic insulated ultra-high temperature cable

inorganic insulated insulated cable generally adopts inorganic tape and wire, and the cable is processed by technology. As a high-temperature resistant material, the fire-resistant tape can still maintain the insulation performance at 800 ℃, so it is one of the main materials of high-temperature resistant cables; Alkali free glass fiber is made of inorganic silicon material, which has certain insulation, and the melting temperature is above 600 ℃. It is processed by weaving process and also used as a reinforcement; The above two materials cannot form sealing and tight insulation, so the insulator can be formed by coating inorganic curing paint, silicon powder and borax

among inorganic materials, there are many high-temperature resistant materials, but the machinability and formability are poor. The cable insulation formed by the above method is also easy to be damaged. According to the selected materials, cables with working temperatures of 500 ℃, 800 ℃ or even 1000 ℃ can be made. In addition, nickel plated copper conductors or matching high-temperature alloy conductors should be selected as conductors

UHT cables are often used in aviation