How to choose heat-resistant high temperature wire and cable

2022-09-08

Ordinary wires and cables use plastic and rubber as insulating covers. These materials are common engineering materials, and there are abundant sources to meet large-scale production, and the cost is relatively low. However, for some special industries related to heat and high temperature, such as petrochemical, steel, aerospace, shipbuilding, military industry, pharmaceuticals, food, plastic machinery, boilers, etc.

 

How to choose heat-resistant high temperature wire and cable

 

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

 

The International Electrotechnical Commission (IEC) Insulation Heat Ratings - General regulations are as follows:

 

Heat resistance grade YAEBFHC

 

Maximum allowable operating temperature/C 90105120130155180180

 

Our commonly used wire and cable insulation and sheathing use ordinary engineering rubber and plastic as the basic resin, but the requirements are insulation grade. Typical rubber materials for cables are: stub rubber, ethylene, natural rubber, chlorosulfonated polyethylene, etc. The working temperature is (60 ~ 75). Typical plastic materials for cables include polyvinyl chloride, polyethylene (including cross-linked polyethylene), polypropylene, etc., 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 below (90~155), and high-temperature cables are cables above 180. To solve the high temperature resistance of ordinary cables, it is necessary to improve materials or use insulation grade materials that can withstand high temperatures. How to choose heat-resistant high temperature wire and cable?

 

foreword

 

Ordinary wires and cables use plastic and rubber as insulating covers. These materials are conventional materials, and there are abundant sources that can meet mass production, and the cost is relatively low. However, for some special industries related to heat and high temperature, such as petrochemical, steel, aerospace, shipbuilding, military industry, pharmaceuticals, food, plastic machinery, boilers, etc.

 

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

 

Let's take a look at what operating temperatures are called heat-resistant and high-temperature cables.

 

Our commonly used wire and cable insulation and sheathing use ordinary engineering rubber and plastic as the basic resin, but the requirements are insulation grade. Typical rubber materials for cables are: stub rubber, ethylene, natural rubber, chlorosulfonated polyethylene, etc. The working temperature is (60 ~ 75). Typical plastic materials for cables include polyvinyl chloride, polyethylene (including cross-linked polyethylene), polypropylene, etc., and the working temperature is (70 ~ 90C). Therefore, these cables are not strictly heat resistant or high temperature cables.

 

Heat-resistant cables generally refer to cables below (90~155), and high-temperature cables are cables above 180. To solve the high temperature resistance of ordinary cables, it is necessary to improve materials or use insulation grade materials that can withstand high temperatures.

 

A. 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 that the ambient temperature of the wire and cable is high, and the cable can transmit signals or power normally under high temperature for a long time. The other is the power transmission cable, whose main purpose is to increase the shutdown capability.

 

Cables that work in high temperature environments. Ordinary cables are prone to insulation aging and scorching at high temperatures, and the cable performance is lost, damaged, and cannot be used. The high temperature cable works normally at the rated high temperature, the signal or power transmission performance is not affected, and there is a guarantee of long cable life. This kind of functional cable is the most common in high temperature cables, and the use characteristics are also the easiest to understand.

 

The increased load type high temperature cable is mainly to reduce the outer diameter and weight of the cable under the heading of oil, so as to develop to light weight. Generally speaking, the higher the operating temperature of the cable, the greater the current-carrying capacity of the same part of the cable. In the case of airplanes, automobiles, etc., the significance of reducing weight is considerable, and the use of high-temperature cables greatly reduces the cross-section. If the operating temperature rises from 90C to 155, oil flow will occur, and of course, with high containment, the power loss of most insulation materials will also increase.

 

B. Heat-resistant wires and cables

 

Heat-resistant wires and cables are divided into two types: heat-resistant materials and heat-resistant modification of general materials.

 

(a) Wire and cable of heat-resistant material

 

The wire and cable of heat-resistant material is insulation and external material body resin, which has heat resistance. The main varieties are: polyurethane (up to 155), polylipid (up to 135), polyvinyl fluoride (150), nylon (up to 115) insulation or external materials. Often used in communications, automobiles, motors, construction and other fields.

 

(b) General cable materials are modified in various ways to achieve heat resistance.

 

1. Modify the PVC cable

 

The working temperature of ordinary PVC cable is 70, the high mixing of PVC cable material, a large amount of heat stabilizer can be used, and the heat resistance rises from 70 to 90 or 105, which greatly expands the applicability of PVC, an old-fashioned material. . This may be one of the reasons why PVC cables don't wilt. The main component of polyvinyl chloride nitrile composite material is polyvinyl chloride, so it has the same modification properties as polyvinyl chloride nitrile composite cable and polyvinyl chloride insulated cable.

 

2. Heat-resistant modification of rubber materials

 

The rubber material has poor heat resistance, so the margin for increasing the working temperature is small. Generally, rubber needs more heat stabilizer and cross-linking treatment to reach 90, so it cannot be called a heat-resistant cable (such as styrene-butadiene rubber, neoprene, chlorine, etc.). Sulfonated polyethylene, etc.). Mainly used for rubber-insulated flexible wires for mobile use, rubber-insulated flexible power cords, control cables, etc.

 

However, the room temperature grade of ternary ethylene rubber has been increased to 135, which has good insulation and good development prospects in rubber.

 

3. Modification of polyethylene cable

 

Polyethylene material has good plasticity, but poor filling, and cannot be filled with heating stabilizer to increase the heat-resistant temperature. Polyethylene cables can increase the working temperature to 90 by DCP dry chemical crosslinking and silicon hot water crosslinking, the latter is used for medium and low voltage power cables. But another way of crossing -- radiation cross-linking deformation -- can make polyethylene mirrors (mostly polyethylene). Mainly through the conversion of high-energy electrons into stable bond energy, the molecular structure can enhance thermal stability, and at the same time, appropriate thermal stabilizers are prepared.

 

The processing equipment commonly used in the radiation cross-linking industry is to increase the energy of electron beams at high pressure to achieve vertical cross-polyolefin materials. Generally, the energy level of the accelerator is 1.0~3 MeV for electricity processing. Radiation crossing will also cross materials such as rubber, fluoroplastics, etc. Radiation crossed polyester brand wire and cable is mainly used for heat-resistant construction wire, automobile wire, aviation wire, locomotive wire, motor electrical lead wiring, etc. Heat-resistant cables are medium-temperature cables that are heat-resistant and can adapt to temperature environments. The most widely used is that it is very important to improve the carrying capacity of the cable and reduce the weight and section of the cable while ensuring the insulation performance in the power transmission cable.