Wire and cable materials can be divided into conductive materials, insulating materials, protective materials, shielding materials, filling materials and so on according to their use parts and functions. According to the 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 structures. Especially thermoplastic materials, such as polyvinyl chloride, polyethylene, as long as the change of part of the formula can be used in insulation or sheath.

Next, we introduce the common non-metallic wire and cable raw materials

One, polyvinyl chloride (PVC)

PVC is generally used as insulation and protective material. PVC as wire and cable insulation performance: not easy to burn, aging resistance, oil resistance, chemical resistance, impact resistance, easy coloring; However, due to the large dielectric constant, it is generally only used as the insulation material of low-voltage cable and control cable.

PVC as wire and cable sheath performance: with good wear resistance, resistance to oil, acid, alkali, bacteria, moisture and sunlight, and flame action has self-extinguishing performance; PVC sheath has a minimum operating temperature of -40 ° C and a high temperature resistance of 105 ° C.

Two, polyethylene (PE)

PE general physical properties: white waxy, translucent, soft and tough, slightly able to stretch, light than water, non-toxic; Combustion characteristics: flammable, from the fire to continue burning, the upper end of the flame is yellow and the lower end is blue, melting dripping when burning, give out the smell of paraffin burning; Polyethylene processing melting point range is 132~1350C, ignition temperature is 3400C, spontaneous combustion temperature is 3900C.

Polyethylene (PE) is generally divided into LDPE, MDPE, HDPE, FMPE several categories.

1, LDPE: low density polyethylene is one of the lightest series of polyethylene, also known as low-pressure polyethylene, the structure characteristics are nonlinear, it has low crystallinity and softening point, has better flexibility, elongation, electrical insulation, transparency, and high impact strength. Low density polyethylene has poor mechanical strength, low heat resistance and, in addition, an obvious weakness is poor resistance to environmental stress cracking.

2, MDPE: medium density polyethylene, also known as medium pressure polyethylene and Philip polyethylene, its performance and high density polyethylene phase nuo, the factory is no longer used, not detailed here.

3, HDPE, high density polyethylene with low density polyethylene, also known as high pressure polyethylene, it has excellent comprehensive performance, such as improved heat resistance and mechanical strength, such as tensile length, bending strength, compression strength and shear strength), and improved the water vapour and gas barrier properties, environmental stress cracking resistance is superior.

4, FMPE: foamed PE is the most widely used foam material, using chemical foamed polyethylene, its dielectric constant can be reduced to about 1.55. If the new technology of adopting physical foaming, that is, when extrusion to inert gas (nitrogen or air) into the molten polyethylene foam, the small size of the bubbles can be obtained from polyethylene foam, foaming degree can be controlled between 35-40%, more than 40% Zhui, its dielectric constant can be reduced to 1.20 or so, and because the do not use chemical foaming agent, The insulation does not contain foaming agent residue, and the dielectric loss can be greatly reduced, which has reached the level of air insulation.

Polyethylene has excellent electrical insulation performance and is widely used in communication cable insulation. In order to improve the technical and economic indicators of communication cables, foam polyethylene is generally used. In order to improve the environmental stress cracking performance, in addition to the use of XPE, can also choose the melting index of small PE. Generally, the smaller the molecular weight (the higher the melting index), the worse the environmental stress cracking resistance. The melting index below 0.4 can basically avoid environmental stress cracking. The density of 0.950, the melting index of the smaller variety, the most resistant to environmental stress cracking. If the density is greater than 0.95, the environmental stress cracking resistance is also worse, but the lower density with the same melting index is much better. However, HDPE molding often has residual internal stress, which should be paid attention to in the process of use.

Mixing PE and EVA in a certain proportion can improve the environmental stress cracking; Mixed with PP can improve hardness; Mixed with PE of different density, can adjust its softness and hardness.

Ethylene – vinyl acetate copolymer (EVA)

EVA is a kind of thermoplastic with elastic like nuo rubber, its performance and the content of vinyl acetate (VA) has a great relationship: the smaller the VA is more like high pressure polyethylene, and the more the VA is more like rubber. EVA nuo high pressure polyethylene with low VA content, soft and good impact strength, suitable for manufacturing composite materials.

EVA has good elasticity and low temperature flexibility, chemical resistance, weather resistance, and LDPE copolymerization, can improve the environmental cracking resistance of LDPE, impact resistance, hardness and adhesion between conductor and insulation.

Tetrapolypropylene (PP)

The specific gravity of polypropylene is 0.89 to 0.91, which is the smallest one in common plastics. It has excellent mechanical strength, the highest softening temperature in thermoplastic resin, and good low temperature resistance and aging resistance. Only the optical rotation resistance is slightly poor, but can be improved by copolymerization with stabilizers.

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, combustible and will continue to burn after fire, and release the smell of petroleum nuo.

Compared with polyethylene, polypropylene has the following different characteristics:

1, PP surface hardness is higher than PE, wear resistance and bending deformation ability are very good, so PP is known as “low density high strength plastic”.

2, PP is better than PE another advantage is almost no environmental stress cracking phenomenon, PP has excellent resistance to environmental stress cracking. However, due to the high regularity of PP molecular structure, its impact performance at room temperature and low temperature is very poor.

3, THE electrical insulation performance of PP: PP is a non-polar material, so there is a good electrical insulation.

Its electrical insulation is basically similar to LDPE, and does not change in a broad frequency range. Due to its very low density, dielectric constant is smaller than LDPE (ε = 2.0 ~ 2.5), dielectric loss Angle tangent is 0.0005 ~0.001, volume resistivity of 1014 ω. M, 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 insulation material.

Five polyester material

This kind of material is characterized by high modulus, high tear resistance, high wear resistance, high elasticity and low lag, the upper limit of the applicable temperature is 1500C, much more than other thermoplastic rubber, but also has excellent oil resistance, solvent resistance characteristics.