1. development of crosslinking technology
In 1952, Charles by invented crosslinked polyethylene insulation by using radiation energy to trade polyethylene into polyethylene in a nuclear reactor test;
In 1957, Ge first made cross-linked ACSR Cable in cable industry by using peroxide (DCP) as chemical crosslinking reagent on the basis of the above principles;
In the late 1960s, Dow Corning invented silane crosslinking technology, and has developed to date
2. radiation crosslinking process of cable
There are three kinds of production processes: two-step one-step copolymerization and ethylene silane copolymerization.
The two-step technology is the first developed technology. The secondary method has less investment and low cost, but it is easy to bring impurities, so it can only be used in the manufacture of low-voltage cable. It has little requirements for equipment and can be completed on conventional extrusion equipment;
The one-step process of grafting reaction and adding condensation catalyst was combined to extrude the cable in one step to reduce the pollution opportunity of impurities, which is suitable for the manufacture of medium and low voltage power cables. But the technology is difficult, and it needs special extruder, and the investment is bigger than one-step;
In the copolymerization, silane copolymers are reacted in PE reactor, which improves the electrical insulation performance of crosslinked PE significantly, and is more suitable for medium and low voltage AAAC Cables besides the manufacture of low voltage cables. Reply to “cable”, and check for more related articles
3. requirements for materials of irradiation cable
Irradiation cable shall be processed three times
a) Material modification to get cable material
b) Cable sheath plastic
c) To withstand the attack of high energy particles
The environment of irradiation cable
High temperature, possibly oil pollution, other harsh environment
4. irradiation crosslinking of polymer materials
5. Application of irradiation crosslinking cable
Various connecting wires and installation wires commonly used in buildings are copper wires wrapped in insulation layer, which are used for low voltage electrical equipment and lighting devices. This wire is commonly known as “laying wires”.
Electrical installation line, but the application field of electrical installation line is more extensive, and the requirements for cables are different in different application occasions. In some cases, the diameter of the line is relatively thin, which belongs to the commonly known “electronic line”.
Radiation crosslinking cable is also needed in the lead-up flexible wire of motor winding
Car and locomotive lines
Marine and petroleum platform cables
Overhead insulated cable
Locomotive navigation aids light cable
New energy cable (photovoltaic, wind, charging pile)
Other special occasions (aerospace, nuclear)
6. Standard and quality control of irradiation crosslinking cable and materials
1. gel content
Gel content is an important index of cross-linking degree of surface materials. Generally, linear polymer materials can be dissolved in some solvents under certain conditions, but the crosslinked network structure is not soluble in any solvent. Based on this principle, gel content can be obtained. It is the most direct and simple method to characterize the degree of crosslinking of polymers. The cross linked polymer with known weight was put into Soxhlet extractor and refluxing with suitable solvent for a certain time. After being removed, the gel content was obtained by vacuum drying and weighing.
2. thermal extension
Although the gel indicates that the degree of crosslinking of polymers is more accurate, but the operation is rather cumbersome, it is often tested in the cable industry to determine the degree of cross-linking after the thermal elongation of the material coated by the radiation. After applying 0.2MPa tensile force at 200 ℃ for 15min, the elongation is less than 175%. After the sample is taken out of the heat aging box and cooled, the permanent thermal deformation is less than 15%, which means the cross-linking is qualified.
3. thermal aging
The temperature grades of crosslinked cable materials in JB / t10436-2004 are 90 ℃, 105 ℃, 125 ℃, 150 ℃, and the aging time is 168 hours, but the aging temperature is 121 ℃, 136 ℃, 158 ℃, 180 ℃ respectively
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