Wires and cables are indispensable infrastructure in modern industry and daily life. They are widely used in power transmission, communication, construction, transportation and other fields. As an important part of wires and cables, the selection of insulation and sheath materials directly affects the performance, life and safety of cables. Plastic resin has become a key material in the manufacture of wires and cables due to its excellent electrical properties, mechanical properties and chemical stability.
Although there are many types of wires and cables, the structures of most products are similar, and the raw materials used are basically the same. Common raw materials include conductive materials, insulating materials, sheath materials, shielding materials, filling materials, etc. And they can be roughly divided into two categories according to their properties. Metal raw materials, such as copper, aluminum, aluminum alloy, and plastic raw materials (common ones are PVC, PE, PP, etc.)
The specific role of plastic resin in wires and cables
Insulation role. Plastic resins such as PVC and FEP have good insulation properties, which can effectively isolate the conductor inside the wire, prevent current leakage, and ensure the safe operation of the equipment. PVC cable material has excellent insulation properties, which can prevent current conduction, avoid current leakage and electromagnetic interference, and ensure the normal operation of the cable.
Protective role. As the sheath material of the cable, plastic resin can protect the wires from the external environment. PVC cable material has good wear resistance and weather resistance, can resist mechanical wear, chemical corrosion and ultraviolet radiation, and extend the service life of the cable. FEP resin is widely used in the insulation layer and sheath of special cables due to its excellent corrosion resistance and high and low temperature resistance, ensuring the stable performance of the cable in extreme environments.
Weather resistance and chemical resistance. Plastic resin has good weather resistance and chemical resistance, and can maintain stable performance in harsh environments (such as high temperature, low temperature, humidity, acid and alkali environment) and extend the service life of the cable.
Flame retardant properties. Some plastic resins (such as flame retardant PVC and low smoke halogen-free materials) have flame retardant properties, which can delay the spread of flames in fires, reduce the generation of toxic smoke, and improve safety.
Transmission function. Plastic resin has excellent processing performance and is easy to form. Its hardness, elasticity, heat resistance and other properties can be adjusted as needed to meet the needs of different engineering projects. PVC materials can be formed by various processing methods such as hot pressing, extrusion, injection molding to produce cable material products that meet the requirements.
Commonly used plastic resin in wires and cables
Polyvinyl chloride PVC. It is a common plastic raw material for wires and cables. PVC is generally used for insulation and sheath materials of wires and cables. This is because PVC has many good protective properties that can well protect the inside of wires and cables. For example, PVC is not easy to burn, aging-resistant, oil-resistant, chemical-resistant, and impact-resistant. These characteristics make it have good isolation and protection. Therefore, the insulation material of general wires and cables mostly uses PVC materials.
Polyethylene PE. The physical properties are white translucent waxy structure, with excellent flexibility, can be stretched to a certain length, lighter than water, and non-toxic. However, compared with polyvinyl chloride, polyethylene has the characteristics of being easy to burn, and it will remain burning even if it leaves the fire source. There are many extended varieties of polyethylene, including LDPE, MDPE, and HDPE. LDPE is a kind of low-density one, called low-pressure polyethylene, with very good flexibility. MDPE is medium-density polyethylene, also known as medium-pressure polyethylene, and its performance is basically similar to that of high-density polyethylene. HDPE is high-density polyethylene, also known as high-pressure polyethylene. Its comprehensive performance is very superior, especially its heat resistance and mechanical strength have been optimized. Polyethylene has excellent electrical insulation properties and is widely used in the insulation of communication cables.
EVA. It is a kind ofthermoplastic similar to rubber. Its performance is closely related to the content of vinyl acetate (VA). The lower the VA content, the more it resembles polyethylene, and the higher the content, the more it resembles rubber. EVA has good elasticity, low temperature resistance, and chemical resistance. When mixed with LDPE, it can improve the problem of LDPE’s easy cracking, and the impact resistance, hardness, and adhesion between the conductor and the insulation can be well coordinated and strengthened.
Polypropylene. It is one of the most commonly used plastics with a relatively small specific gravity. It has high mechanical strength, low temperature resistance, and aging resistance. In addition, with high breakdown strength and low water absorption, PP materials can be competent for the position of high-frequency insulation materials.
Polyester material. This type of material is characterized by high tear resistance, high wear resistance, high elasticity and low hysteresis. The upper limit of the applicable temperature is 1500℃, which is much higher than other thermoplastic rubbers. In addition, it has excellent oil and solvent resistance.
Fluoroplastic resin FEP. It has excellent corrosion resistance, low friction coefficient and non-stickiness, and can remain stable in the temperature range of -80℃ to +200℃. FEP is commonly used in the manufacture of insulation layers, sheaths and special cables in wires and cables, and is favored for its chemical stability and high and low temperature resistance.
Polytetrafluoroethylene (PTFE). It is known for its excellent chemical corrosion resistance, low dielectric constant and high temperature stability, and can remain stable at temperatures up to 260℃. PTFE is mainly used in the manufacture of insulation layers, battery separators and printed circuit boards in wires and cables. It is widely used in the electronic and electrical industry.