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Three Causes of Blackening Copper Wires in Rubber Jackets
March 06, 2023
The rubber sheathed cable is a kind of soft and movable cable variety with multiple strands of fine copper wire as the conductor, outsourcing rubber insulation and rubber sheath. In general, it includes general rubber sheathed flexible cables, welding machine cables, submersible motor cables, radio equipment cables, and photographic light cables.
The reason for the blackening of the rubber cable copper wire is caused by a variety of factors, not only the rubber formula problem, but also the state of the copper wire itself, the rubber processing technology, the rubber vulcanization process, the structure of the cable, the rubber sheathing formula , production environment and many other factors.
1. Analysis of the reasons for the blackening of rubber hair and copper wire
1.1 Causes of copper wire itself In the 1950s and 1960s, most domestic manufacturers used ordinary copper rods with a copper content of 99.99%, all of which were aerobic copper rods. The production method was based on multi-channel heating of copper ingots. After the rolling, a black copper rod was produced, and the copper rod was made into a relatively thin copper wire through the large, medium, and small pulls. Because copper itself is not oxygen-free copper, oxidation of the surface of the copper wire is inevitable during processing. In the 1980s, domestic advanced oxygen-free copper rod production technology and domestically developed oxygen-free copper rod production technology made the entire wire and cable industry use oxygen-free copper rods, which is undoubtedly improved. Black wire problem. However, due to the processing of copper rods, in particular the mastery of the toughening process and the poor storage conditions of the processed copper cores, the copper core itself has been slightly oxidized, which is one of the reasons for the blackening of copper wires.
1.2 The reason for the rubber formula In the 1950s, rubber insulation was formulated using natural rubber and styrene-butadiene rubber. Since the insulating rubber is in direct contact with the copper wire, it is not possible to use sulfur directly as a vulcanizing agent, that is, using less sulfur also makes the copper wire black. Some compounds that can decompose free sulfur must be used, such as the accelerator TMTD mentioned above and the vulcanizing agent VA-7, and some vulcanization accelerators must be added to increase the vulcanization speed and vulcanization degree to ensure the physical and mechanical properties of the insulating rubber. And electrical performance. However, from the perspective of the elasticity, strength, and permanent deformation of the insulating rubber, it is not as good as a rubber with sulfur added (if the copper wire is not considered black). Decades of practice have confirmed that TMTD cannot solve the blackening problem of copper wire. In addition, the insulating rubber must have a variety of colors. Red, blue, yellow, green, and black are the basic colors. The appearance of these colors also promotes the stickiness of the rubber and blackening of the copper wire. The main fillers in the formulation are light calcium carbonate and talcum powder. Due to the price, some manufacturers use calcium carbonate and talcum powder, which are particularly inexpensive, in order to reduce costs. These fillers have large particles, large content of free base, and impurities. Many, so the physical and mechanical properties are relatively poor, poor electrical properties, but also easily cause black copper wire. Other factories use active ultra-fine calcium carbonate to improve the physical and mechanical properties of the insulating rubber. Most of the active calcium is treated with stearic acid, which is also responsible for the blackening of the copper wire. The use of vulcanizing agent VA-7 can improve the blackening of the copper wire, but due to the insufficient degree of vulcanization, the permanent deformation of the rubber may cause the rubber to become sticky. In particular, after adding the accelerator ZDC, the vulcanization speed is increased. In order to prevent scorch, an accelerator DM is added to retard the scorch time. From the perspective of the structure of the accelerator ZDC, it is an indirect metal zinc in the two connected sulfurs in the TETD structure. The structural formula is: SSH5C2‖‖H5C2>NCS-Zn-SCN NCSSCN
2, from the wire and cable structure analysis
2.1 Catalytic aging of copper is an important cause of rubber stickiness. The former Soviet Union’s Institute of Cable Science has proved that copper penetrates from the contact with rubber into the insulating rubber during the vulcanization process. The insulated rubber of 1.0-2.0mm thickness contains 0.009-0.0027% of copper. . As we all know, trace copper has a great destructive effect on rubber, which is what we commonly call the aging of heavy metals on rubber. In the insulating vulcanization process, thiuram precipitates a number of free sulfur and reacts with copper to form an active copper-containing group: CH3│CH2-CH-C-CH2-|│SS││CuCu During aging, weak-SS- The bond is broken to form an active copper-containing group: Cu-S-, which acts on the rubber and acts simultaneously with oxygen to destroy the rubber's long-chain molecules, making the rubber soft and viscous. This is a combination of low-molecular chains. The French Rubber Research Institute also pointed out that if the rubber contains harmful metals, such as copper, manganese and other heavy metal salts, then rubber stickiness will occur regardless of the type of accelerator.
2.2 Migration of sulphur in rubber sheath cables to the surface of insulating rubber and copper wire Soviet scientists applied radioactive isotopes to confirm the possibility of sulfur diffusion in cable jacket rubber. In natural rubber-based vulcanizates, the diffusion coefficient of free sulfur is about 10-6 cm2/s at a temperature of 130-150°C. In a continuously vulcanized production plant, when the vulcanized sheath rubber is used, the temperature is between 185-200°C, and the coefficient of diffusion is even greater. Due to the diffusion of free sulfur in the rubber sheath, the structure of Qiulam rubber is changed, and polysulfide bonds may be formed. These polysulfides are chemically decomposed and combined to achieve migration, ie "chemical diffusion." As a result of the migration, not only the structure of the insulating rubber can be changed, the heat resistance thereof is reduced, but also sulfur reacts with the copper surface to form copper sulfide and cuprous sulfide, resulting in blackening of the copper wire. In turn, copper sulfide and cuprous sulfide accelerate the aging of the rubber, which in turn leads to stickiness.
3, the processing process
3.1 Reasons for the processing of rubber materials In the insulation formula based on the combination of natural rubber and styrene-butadiene rubber, natural rubber needs to be plasticized to improve the plasticity of the rubber. Some large plants use plastic mixers for plastics production, but also add a small amount of chemical plasticizer-accelerator M to increase plasticity. If the plasticizing temperature and the temperature of the raw rubber filter are not well controlled, a high temperature of 140°C or more occurs. When the raw rubber is put on the open mill and slowly passes through the drum, the upper glue is subjected to the hot oxygen and the accelerator M at the same time. The effect is that the rubber surface appears to be coated with a layer of oil. In fact, the rubber molecules are severely broken under the promotion of chemical plasticizers, resulting in a relatively soft and viscous smaller molecular weight rubber. Although they were later mixed with styrene-butadiene rubber to insulate the rubber, these small-molecular-weight natural rubbers were evenly dispersed in the rubber. After the rubber was squeezed on the copper wire for continuous vulcanization, there might not be any problems at that time. , but has buried a hidden danger for rubber sticky copper wire, that is to say, these small-molecular-weight natural rubber will first appear partial sticky copper wire phenomenon. The process of insulating rubber plus vulcanizing agents and accelerators is also very important. Some small plants add vulcanizing agents to the open mills, which means that the tank containing the vulcanizing agent is poured in the middle of the drum, with many in the middle and less on both sides. When the vulcanizing agent is eaten into the rubber, the number of turning over the triangle will be less, and the vulcanizing agent will be unevenly distributed in the rubber material. In the case of continuous vulcanization in extrusion, the phenomenon of blackening of the copper wire is likely to occur in a place containing a relatively large amount of a vulcanizing agent, and a phenomenon of a sticky copper wire occurs in a dark place for a long time.
3.2 Insulation rubber vulcanization reasons Some companies in order to pursue production, continuous vulcanization tube is only 60 meters long, steam pressure is 1.3Mpa, and vulcanization speed to 120 meters/minute, so that the residence time of the insulating rubber in the tube is only 30 seconds . The eraser itself is a poor conductor of heat, and the surface temperature of the insulated wire core is greater than 190°C. When the temperature is transferred to the inner layer rubber that is in contact with the copper wire, it is absorbed by the copper wire again, and the copper wire is heated to a temperature close to that of the inner layer rubber. The vulcanized rubber wire core has been vulcanized. This inner layer rubber temperature is relatively low, about 170 °C, only a few seconds to stay out of the vulcanization tube, into the cooling and take-off, insulation rubber will be insufficient vulcanization. In order to achieve sufficient vulcanization. The amount of accelerator TMTD (used as vulcanizing agent) is as high as 3.4%. Excess vulcanizing agent also releases more free sulfur in the vulcanization process. Except for cross-linked rubber molecules, there is excess free sulfur. This is the reason for the darkening of the surface of the copper wire.
In short, it is still more difficult to solve the problem of blackening of copper wires. Every process from copper wire to eraser must be taken seriously in order to achieve better results. The selection of rubber species and the use of vulcanization systems remain the key to the problem. The solution to this problem needs to pass the test of time.
The reason for the blackening of the rubber cable copper wire is caused by a variety of factors, not only the rubber formula problem, but also the state of the copper wire itself, the rubber processing technology, the rubber vulcanization process, the structure of the cable, the rubber sheathing formula , production environment and many other factors.
1. Analysis of the reasons for the blackening of rubber hair and copper wire
1.1 Causes of copper wire itself In the 1950s and 1960s, most domestic manufacturers used ordinary copper rods with a copper content of 99.99%, all of which were aerobic copper rods. The production method was based on multi-channel heating of copper ingots. After the rolling, a black copper rod was produced, and the copper rod was made into a relatively thin copper wire through the large, medium, and small pulls. Because copper itself is not oxygen-free copper, oxidation of the surface of the copper wire is inevitable during processing. In the 1980s, domestic advanced oxygen-free copper rod production technology and domestically developed oxygen-free copper rod production technology made the entire wire and cable industry use oxygen-free copper rods, which is undoubtedly improved. Black wire problem. However, due to the processing of copper rods, in particular the mastery of the toughening process and the poor storage conditions of the processed copper cores, the copper core itself has been slightly oxidized, which is one of the reasons for the blackening of copper wires.
1.2 The reason for the rubber formula In the 1950s, rubber insulation was formulated using natural rubber and styrene-butadiene rubber. Since the insulating rubber is in direct contact with the copper wire, it is not possible to use sulfur directly as a vulcanizing agent, that is, using less sulfur also makes the copper wire black. Some compounds that can decompose free sulfur must be used, such as the accelerator TMTD mentioned above and the vulcanizing agent VA-7, and some vulcanization accelerators must be added to increase the vulcanization speed and vulcanization degree to ensure the physical and mechanical properties of the insulating rubber. And electrical performance. However, from the perspective of the elasticity, strength, and permanent deformation of the insulating rubber, it is not as good as a rubber with sulfur added (if the copper wire is not considered black). Decades of practice have confirmed that TMTD cannot solve the blackening problem of copper wire. In addition, the insulating rubber must have a variety of colors. Red, blue, yellow, green, and black are the basic colors. The appearance of these colors also promotes the stickiness of the rubber and blackening of the copper wire. The main fillers in the formulation are light calcium carbonate and talcum powder. Due to the price, some manufacturers use calcium carbonate and talcum powder, which are particularly inexpensive, in order to reduce costs. These fillers have large particles, large content of free base, and impurities. Many, so the physical and mechanical properties are relatively poor, poor electrical properties, but also easily cause black copper wire. Other factories use active ultra-fine calcium carbonate to improve the physical and mechanical properties of the insulating rubber. Most of the active calcium is treated with stearic acid, which is also responsible for the blackening of the copper wire. The use of vulcanizing agent VA-7 can improve the blackening of the copper wire, but due to the insufficient degree of vulcanization, the permanent deformation of the rubber may cause the rubber to become sticky. In particular, after adding the accelerator ZDC, the vulcanization speed is increased. In order to prevent scorch, an accelerator DM is added to retard the scorch time. From the perspective of the structure of the accelerator ZDC, it is an indirect metal zinc in the two connected sulfurs in the TETD structure. The structural formula is: SSH5C2‖‖H5C2>NCS-Zn-SCN
2, from the wire and cable structure analysis
2.1 Catalytic aging of copper is an important cause of rubber stickiness. The former Soviet Union’s Institute of Cable Science has proved that copper penetrates from the contact with rubber into the insulating rubber during the vulcanization process. The insulated rubber of 1.0-2.0mm thickness contains 0.009-0.0027% of copper. . As we all know, trace copper has a great destructive effect on rubber, which is what we commonly call the aging of heavy metals on rubber. In the insulating vulcanization process, thiuram precipitates a number of free sulfur and reacts with copper to form an active copper-containing group: CH3│CH2-CH-C-CH2-|│SS││CuCu During aging, weak-SS- The bond is broken to form an active copper-containing group: Cu-S-, which acts on the rubber and acts simultaneously with oxygen to destroy the rubber's long-chain molecules, making the rubber soft and viscous. This is a combination of low-molecular chains. The French Rubber Research Institute also pointed out that if the rubber contains harmful metals, such as copper, manganese and other heavy metal salts, then rubber stickiness will occur regardless of the type of accelerator.
2.2 Migration of sulphur in rubber sheath cables to the surface of insulating rubber and copper wire Soviet scientists applied radioactive isotopes to confirm the possibility of sulfur diffusion in cable jacket rubber. In natural rubber-based vulcanizates, the diffusion coefficient of free sulfur is about 10-6 cm2/s at a temperature of 130-150°C. In a continuously vulcanized production plant, when the vulcanized sheath rubber is used, the temperature is between 185-200°C, and the coefficient of diffusion is even greater. Due to the diffusion of free sulfur in the rubber sheath, the structure of Qiulam rubber is changed, and polysulfide bonds may be formed. These polysulfides are chemically decomposed and combined to achieve migration, ie "chemical diffusion." As a result of the migration, not only the structure of the insulating rubber can be changed, the heat resistance thereof is reduced, but also sulfur reacts with the copper surface to form copper sulfide and cuprous sulfide, resulting in blackening of the copper wire. In turn, copper sulfide and cuprous sulfide accelerate the aging of the rubber, which in turn leads to stickiness.
3, the processing process
3.1 Reasons for the processing of rubber materials In the insulation formula based on the combination of natural rubber and styrene-butadiene rubber, natural rubber needs to be plasticized to improve the plasticity of the rubber. Some large plants use plastic mixers for plastics production, but also add a small amount of chemical plasticizer-accelerator M to increase plasticity. If the plasticizing temperature and the temperature of the raw rubber filter are not well controlled, a high temperature of 140°C or more occurs. When the raw rubber is put on the open mill and slowly passes through the drum, the upper glue is subjected to the hot oxygen and the accelerator M at the same time. The effect is that the rubber surface appears to be coated with a layer of oil. In fact, the rubber molecules are severely broken under the promotion of chemical plasticizers, resulting in a relatively soft and viscous smaller molecular weight rubber. Although they were later mixed with styrene-butadiene rubber to insulate the rubber, these small-molecular-weight natural rubbers were evenly dispersed in the rubber. After the rubber was squeezed on the copper wire for continuous vulcanization, there might not be any problems at that time. , but has buried a hidden danger for rubber sticky copper wire, that is to say, these small-molecular-weight natural rubber will first appear partial sticky copper wire phenomenon. The process of insulating rubber plus vulcanizing agents and accelerators is also very important. Some small plants add vulcanizing agents to the open mills, which means that the tank containing the vulcanizing agent is poured in the middle of the drum, with many in the middle and less on both sides. When the vulcanizing agent is eaten into the rubber, the number of turning over the triangle will be less, and the vulcanizing agent will be unevenly distributed in the rubber material. In the case of continuous vulcanization in extrusion, the phenomenon of blackening of the copper wire is likely to occur in a place containing a relatively large amount of a vulcanizing agent, and a phenomenon of a sticky copper wire occurs in a dark place for a long time.
3.2 Insulation rubber vulcanization reasons Some companies in order to pursue production, continuous vulcanization tube is only 60 meters long, steam pressure is 1.3Mpa, and vulcanization speed to 120 meters/minute, so that the residence time of the insulating rubber in the tube is only 30 seconds . The eraser itself is a poor conductor of heat, and the surface temperature of the insulated wire core is greater than 190°C. When the temperature is transferred to the inner layer rubber that is in contact with the copper wire, it is absorbed by the copper wire again, and the copper wire is heated to a temperature close to that of the inner layer rubber. The vulcanized rubber wire core has been vulcanized. This inner layer rubber temperature is relatively low, about 170 °C, only a few seconds to stay out of the vulcanization tube, into the cooling and take-off, insulation rubber will be insufficient vulcanization. In order to achieve sufficient vulcanization. The amount of accelerator TMTD (used as vulcanizing agent) is as high as 3.4%. Excess vulcanizing agent also releases more free sulfur in the vulcanization process. Except for cross-linked rubber molecules, there is excess free sulfur. This is the reason for the darkening of the surface of the copper wire.
In short, it is still more difficult to solve the problem of blackening of copper wires. Every process from copper wire to eraser must be taken seriously in order to achieve better results. The selection of rubber species and the use of vulcanization systems remain the key to the problem. The solution to this problem needs to pass the test of time.
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Ucoax Thunderbolt 3 и 4 Массовое производство
March 24, 2024
Ucoax 2024 Новый 8K HDMI Cable
January 04, 2024
Новости промышленности
Что такое DisplayPort 2.0?
December 20, 2022
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November 23, 2022
Blog News
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Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.