Other Raw materials for wire cable

Wire cable materials can be divided into conductive materials, insulating materials, sheath materials, shielding materials, filling materials, etc. according to their use parts and functions. According to material properties, it can be divided into metal (copper, aluminum, aluminum alloy, steel), plastic (PVC, PE, PP, XLPE/XL-PVC, PU, TPE/PO), rubber, etc. But some of these materials are common to several structural parts. Especially thermoplastic materials, such as polyvinyl chloride, polyethylene, etc., can be used on insulation or sheathing as long as part of the formula is changed.
Next, we will introduce other commonly used non-metallic wire and cable raw materials

1. Polyvinyl chloride (PVC)
   PVC is generally used as insulation and sheath material. The performance of PVC as wire and cable insulation: non-combustible, aging resistance, oil resistance, chemical resistance, impact resistance, easy coloring; but due to the large dielectric constant, it is generally only used as an insulating material for low-voltage cables and control cables.
   The performance of PVC as a wire and cable sheath: it has good wear resistance, can resist oil, acid, alkali, bacteria, moisture and sunlight, etc., and has self-extinguishing performance against the flame; the PVC sheath The lowest working temperature is -40 degrees, and the high temperature resistance can reach 105 degrees.
2. Polyethylene (PE)
   General physical properties of PE: white wax, translucent, flexible and tough, slightly elongated, lighter than water, non-toxic; burning characteristics: flammable, continue to burn after leaving the fire, the upper end of the flame is yellow and the lower end is blue , melts and drips when burning, and emits the smell of paraffin burning; the melting point range of polyethylene processing is 132~1350C, the ignition temperature is 3400C, and the spontaneous combustion temperature is 3900C.
   Polyethylene (PE) is generally divided into several categories: LDPE, MDPE, HDPE, and FMPE.
3. LDPE: Low-density polyethylene is the lightest one in the polyethylene series, also known as low-pressure polyethylene. Its structural characteristics are nonlinear. It has low crystallinity and softening point, and has good flexibility. Elongation, electrical insulation, transparency, and high impact strength. Low-density polyethylene has poor mechanical strength and low heat resistance. In addition, an obvious weakness is poor environmental stress cracking resistance.
4. MDPE: Medium-density polyethylene is also known as medium-pressure polyethylene and Philips polyethylene. Its performance is similar to that of high-density polyethylene. It is no longer used in our factory and will not be described in detail here.
5. HDPE: Compared with low-density polyethylene, high-density polyethylene, also known as high-pressure polyethylene, has excellent comprehensive properties, such as improved heat resistance and mechanical strength (such as tensile length, bending strength, compressive strength, shear strength, etc.) shear strength), and improve the barrier performance of water vapor and gas, excellent resistance to environmental stress cracking.
6. FMPE: Foamed PE is the most widely used foam material. It uses chemically foamed foamed polyethylene, and its dielectric constant can be reduced to about 1.55. If the new process of physical foaming is adopted, that is, inert gas (nitrogen or air) is injected into the molten polyethylene to foam during extrusion, foamed polyethylene with smaller bubble size can be obtained, and the foaming degree can be controlled at 35. Between -40% and 40% or more, the dielectric constant can be reduced to about 1.20, and because no chemical foaming agent is used, the insulation does not contain foaming agent residue, the dielectric loss can also be greatly reduced, and the loss has been reduced. To the level of air insulation.
   Polyethylene has excellent electrical insulation properties and is widely used in the insulation of communication cables; in order to improve the technical-economic indicators of communication cables, foamed polyethylene is generally used. In order to improve the resistance to environmental stress cracking, in addition to cross polyethylene, PE with a small melt index can also be selected. In general, the lower the molecular weight (higher melt index), the poorer the environmental stress cracking resistance. Those with a melt index below 0.4 can basically avoid environmental stress cracking. The density is around 0.950, the smaller the melt index, the most resistant to environmental stress cracking. If the density is greater than 0.95, the environmental stress cracking resistance will also be poor, but the lower density and the same melt index are much better. However, internal stress often remains when HDPE is formed, which should be paid attention to during use.
   PE and EVA mixed in a certain proportion can improve environmental stress cracking; mixed with PP can increase hardness; mixed with PE of different densities can adjust its softness and hardness.
7. Ethylene-vinyl acetate copolymer (EVA)
   EVA is a kind of thermoplastic with rubber-like elasticity. Its performance has a great relationship with the content of vinyl acetate (VA): the smaller the VA, the more it looks like high-pressure polyethylene, and the more VA, the more it looks like rubber. EVA high-pressure polyethylene with low VA content is soft and has good impact strength, so it is suitable for making composite materials.
   EVA has good elasticity and low-temperature flexibility, chemical resistance, and weather resistance. It can be used for copolymerization with LDPE to improve the environmental cracking resistance, impact resistance, softness and hardness of LDPE and the adhesion between conductors and insulation.
   Four polypropylene (PP)
   The proportion of polypropylene is 0.89-0.91, which is the smallest proportion of commonly used plastics. It has excellent mechanical strength, the highest softening temperature among thermoplastic resins, good low temperature resistance and aging resistance; only slightly poor optical resistance. But it can be improved by adding a stabilizer through copolymerization.
   General properties of polypropylene: The appearance of PP is very similar to HDPE. It is a white waxy solid, more transparent than PE, non-toxic, flammable and will continue to burn after leaving the fire, and emits the smell of petroleum.
   Compared with polyethylene, polypropylene has the following different characteristics:
8. The surface hardness of PP is higher than that of PE, and the wear resistance and bending deformation ability are very good, so PP is called “low-density high-strength plastic”.
9. Another advantage of PP over PE is that there is almost no environmental stress cracking phenomenon, and PP has excellent environmental stress cracking resistance. However, due to the high regularity of the molecular structure of PP itself, its impact performance at room temperature and low temperature is very poor.
10. Electrical insulation properties of PP: PP is a non-polar material, so it has good electrical insulation.
    Its electrical insulation is basically similar to that of LDPE, and it does not change in a wide frequency range. Due to its extremely low density, the dielectric constant is smaller than that of LDPE (ε=2.0 ~ 2.5), the dielectric loss tangent is 0.0005 ~ 0.001, the volume resistivity is above 1014Ω.m, and the breakdown field strength is also very high, which is 30MV /m; In addition, the water absorption is very small, so PP can be used as a high-frequency insulating material.
    5 Polyester
    This kind of material is characterized by high modulus, high tear resistance, high wear resistance, high elasticity and low hysteresis. The upper limit of applicable temperature is 1500C, which is much higher than other thermoplastic rubbers. In addition, it has excellent oil resistance and solvent resistance.