YIHETAI founded in december 2001,mainly specializes in the production of hook-up wires and wire-processing. It integrates research with production and marketing and has been possessed of the privilege of import and export at its own. Our company is a professional manufacturer of wiring of the interiors of various kinds of electronic appliance and their exterior hook-up wires. Its products mostly are applied to the products of telecommunication, photo-electricity and for consumers’uses.
Main plastic raw materials of wires and cables
Materials for wires and cables can be divided into conductive materials, insulating materials, protective layer 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. However, 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 sheath as long as some formula components are changed.
Now let's introduce our common non-metallic wire and cable raw materials
1、 Polyvinyl chloride (PVC)
PVC is generally used as insulation and protective layer material. The properties of PVC as wire and cable insulation: not easy to burn, aging resistance, oil resistance, chemical resistance, impact resistance and easy coloring; However, due to the large dielectric constant, it is generally only used as the insulating material of low-voltage cables and control cables.
Performance of PVC as wire and cable sheath: it has good wear resistance, can resist oil, acid, alkali, bacteria, moisture and sunlight, and has self extinguishing performance for the action of flame; The minimum working temperature of PVC sheath is - 40 ℃, and the high temperature resistance can reach 105 ℃.
2、 Polyethylene (PE)
General physical properties of PE: white wax, translucent, soft and tough, slightly elongated, lighter than water and non-toxic; Combustion characteristics: it is flammable and continues to burn after leaving the fire. The upper end of the flame is yellow and the lower end is blue. It melts and drips during combustion and gives off the smell of paraffin combustion; 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 LDPE, MDPE, HDPE and FMPE.
1. LDPE: low density polyethylene is the lightest kind of polyethylene series, also known as low-pressure polyethylene. Its structural characteristics are nonlinear. It has low crystallinity and softening point, 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 its poor resistance to environmental stress cracking.
2. MDPE: medium density polyethylene, also known as medium pressure polyethylene and Philips polyethylene, its performance is similar to that of high density polyethylene, which is no longer used by our factory, and will not be detailed here.
3. HDPE: compared with low-density polyethylene, also known as high-pressure polyethylene, high-density polyethylene has excellent comprehensive properties, such as improved heat resistance and mechanical strength (such as tensile length, bending strength, compressive strength and shear strength), improved barrier performance to water vapor and gas, and superior environmental stress cracking resistance.
4, FMPE: foamed PE is the most widely used foam material. The dielectric constant of chemically foamed polyethylene can be reduced to about 1.55. If the new process of physical foaming is used, that is, when the inert gas (nitrogen or air) is injected into molten polyethylene for foaming in the extrusion process, the foamed polyethylene with smaller bubble size can be prepared. The foaming degree can be controlled between 35-40%, and the dielectric constant can be reduced to about 1.20, and the dielectric constant can be reduced to about 1.20. Moreover, the foaming agent residue is not included in the insulation because no chemical foaming agent is used. The dielectric loss can also be greatly reduced, and the loss has reached 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 and economic indexes of communication cables, foamed polyethylene is generally used. In order to improve the environmental stress cracking resistance, in addition to cross polyethylene, PE with low melt index can also be selected. Generally, the smaller the molecular weight (the higher the melt index), the worse the environmental stress cracking resistance. If the melt index is less than 0.4, environmental stress cracking can be basically avoided. The varieties with a density of about 0.950 and a smaller melt index are the most resistant to environmental stress cracking. If the density is greater than 0.95, the environmental stress cracking resistance becomes worse, but the one with lower density and the same melt index is much better. However, HDPE molding often has residual internal stress, which should be paid attention to in the process of use.
The mixed use of PE and EVA in a certain proportion can improve the environmental stress cracking; Mixing with PP can improve the hardness; Mixed with PE of different density, its softness and hardness can be adjusted.
3、 Ethylene vinyl acetate copolymer (EVA)
EVA is a kind of thermoplastic with rubber like elasticity. Its performance is closely related to the content of vinyl acetate (VA): the smaller VA is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more it is, the more. EVA Nuo high pressure polyethylene with low VA content is soft and has good impact strength. It is suitable to make composite materials.
EVA has good elasticity, low temperature flexibility, chemical resistance and weather resistance. When copolymerized with LDPE, it can improve the environmental cracking resistance, impact resistance, soft hardness and adhesion between conductor and insulation of LDPE.
4、 Polypropylene (PP)
The specific gravity of polypropylene is 0.89-0.91, which is the smallest of commonly used plastics. It has excellent mechanical strength, the highest softening temperature in thermoplastic resin, and good low temperature resistance and aging resistance; The optical rotation resistance is only slightly poor, but it can be improved by copolymerization and adding stabilizer.
General properties of polypropylene: PP looks like HDPE. It is a white waxy solid. It is more transparent than PE, non-toxic, combustible, and will continue to burn after leaving the fire, giving off the smell of oil Nuo.
Compared with polyethylene, polypropylene has the following different characteristics:
1. The surface hardness of PP is higher than that of PE, and its wear resistance and bending deformation ability are very good. Therefore, PP is known as "low density and high strength plastic".
2. Another advantage of PP over PE is that there is almost no environmental stress cracking, and PP has excellent resistance to environmental stress cracking. However, due to the high regularity of PP molecular structure, its impact properties at room temperature and low temperature are very poor.
3. Electrical insulation performance of PP: PP is a non-polar material, so it has good electrical insulation.
Its electrical insulation is basically similar to LDPE, and does not change in a wide frequency range. Because of its very low density, its dielectric constant is smaller than that of LDPE（ ε＝ 2.0 ~ 2.5), the dielectric loss tangent is 0.0005 ~ 0.001, and the volume resistance coefficient is 1014 Ω M above, the breakdown field strength is also very high, 30mV / M; In addition, the water absorption is very small, so PP can be used as high-frequency insulating material.
5、 Polyester material
These materials are characterized by high modulus, high tear resistance, high wear resistance, high elasticity and low hysteresis. The upper limit of applicable temperature is up to 1500C, which is much higher than other thermoplastic rubbers. In addition, they also have excellent oil resistance and solvent resistance.