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Types and characteristics of commonly used plastics
Plastic is famous for its light weight, and its density is roughly between 83 and 2, and in most cases it is between 1 and 5. Rubber and plastic are commonly used materials in wire production, and their specific gravity has an important influence on different types of wire and extra temperature. In addition, the elongation and tensile strength of insulation materials will also be different due to different wire types and CLASS grades. Therefore, when selecting and using these materials, we must refer to the corresponding safety specifications such as UL and IEC to ensure the safety and compliance of products.
PVC (Poly Vinyl Chloride)
(1) PVC has excellent hardness adjustment ability, so it can be transparent or translucent, and even can be made into soft PVC by adding plasticizer.
(2) The advantages of PVC include excellent performance in concave-convex temperature environment, excellent flame resistance, high flexibility and affordable price.
(3) However, the heat resistance of PVC is not good, and its dielectric coefficient will change with the change of temperature and frequency, which makes the electrical characteristics difficult to control. In addition, when heated, PVC will release hydrochloric acid and turn black, and when burned, it will produce black smoke and toxic gas.
(4) PVC is widely used in AWM and computer cables with a voltage below 600V as wire insulation or covering materials. Its specific gravity scale is 2050, that of soft PVC is 2, and that of hard PVC is 4. Usually, the specific gravity is 5 as the benchmark to calculate the dosage. In addition, the elongation of PVC can reach 150,400% and the tensile strength is 2~5kg/mm2.
Sr-PVC (semi-rigid polyvinyl chloride) semi-rigid PVC
(1) Semi-rigid PVC has higher strength than ordinary PVC.
(2) However, due to its high hardness, the elongation will decrease after high temperature aging.
(3) Semi-rigid PVC is often used for core insulation data of computer cables. Its density scale is 35~50, and the dosage is usually calculated based on 5. In addition, according to the requirements of UL444 safety regulations, its elongation should reach more than 100% and its tensile strength should be at least 3000PSI.
Polypropylene (PP)
(1) Polypropylene is a rapidly developing and widely used thermoplastic.
(2) Compared with other general thermoplastics, polypropylene has the advantages of small specific gravity, good rigidity, high strength, buckling resistance, heat resistance above 100℃ and excellent chemical resistance. Together, its price is relatively low.
(3) Even so, polypropylene has poor impact resistance at low temperature, simple aging and large molding shrinkage. Incineration will produce droplets, which are not easy to burn quickly and completely, and there is a risk of delayed combustion.
(4) Application: The composition of PP and EVA is often used for core insulation data of electric wires, especially in communication cables and telephone lines. Its specific gravity is 9091, and it has an elongation of 200700% and a tensile strength of 0~0kg/mm2. In addition, the composition must meet the requirements of UL1581 safety regulations, that is, the elongation is at least 150% and the tensile strength is at least 3000PSI.
EVA (ethylene-vinyl acetate copolymer)
It is formed by copolymerization of ethylene and vinyl acetate, and has rubber-like elasticity. Its compatibility with other materials is outstanding, and it can be combined with PP, PE, PVC and other materials. However, excessive use may damage the appearance of the wire core and reduce the insulation and withstand voltage functions. In addition, EVA has poor oil resistance.
PE (polyethylene)
It is a light, soft and water-resistant material with excellent electrical characteristics. Although PE is not heat-resistant and simply ages at high temperature, it is widely used in communication cables, high-voltage cables and submarine cables.
High density polyethylene (HDPE) is produced by low pressure method, so it is also called low pressure polyethylene. It has excellent chemical resistance and electrical characteristics.
PVC (Poly Vinyl Chloride)
(1) PVC has excellent hardness adjustment ability, so it can be transparent or translucent, and even can be made into soft PVC by adding plasticizer.
(2) The advantages of PVC include excellent performance in concave-convex temperature environment, excellent flame resistance, high flexibility and affordable price.
(3) However, the heat resistance of PVC is not good, and its dielectric coefficient will change with the change of temperature and frequency, which makes the electrical characteristics difficult to control. In addition, when heated, PVC will release hydrochloric acid and turn black, and when burned, it will produce black smoke and toxic gas.
(4) PVC is widely used in AWM and computer cables with a voltage below 600V as wire insulation or covering materials. Its specific gravity scale is 2050, that of soft PVC is 2, and that of hard PVC is 4. Usually, the specific gravity is 5 as the benchmark to calculate the dosage. In addition, the elongation of PVC can reach 150,400% and the tensile strength is 2~5kg/mm2.
Sr-PVC (semi-rigid polyvinyl chloride) semi-rigid PVC
(1) Semi-rigid PVC has higher strength than ordinary PVC.
(2) However, due to its high hardness, the elongation will decrease after high temperature aging.
(3) Semi-rigid PVC is often used for core insulation data of computer cables. Its density scale is 35~50, and the dosage is usually calculated based on 5. In addition, according to the requirements of UL444 safety regulations, its elongation should reach more than 100% and its tensile strength should be at least 3000PSI.
Polypropylene (PP)
(1) Polypropylene is a rapidly developing and widely used thermoplastic.
(2) Compared with other general thermoplastics, polypropylene has the advantages of small specific gravity, good rigidity, high strength, buckling resistance, heat resistance above 100℃ and excellent chemical resistance. Together, its price is relatively low.
(3) Even so, polypropylene has poor impact resistance at low temperature, simple aging and large molding shrinkage. Incineration will produce droplets, which are not easy to burn quickly and completely, and there is a risk of delayed combustion.
(4) Application: The composition of PP and EVA is often used for core insulation data of electric wires, especially in communication cables and telephone lines. Its specific gravity is 9091, and it has an elongation of 200700% and a tensile strength of 0~0kg/mm2. In addition, the composition must meet the requirements of UL1581 safety regulations, that is, the elongation is at least 150% and the tensile strength is at least 3000PSI.
EVA (ethylene-vinyl acetate copolymer)
It is formed by copolymerization of ethylene and vinyl acetate, and has rubber-like elasticity. Its compatibility with other materials is outstanding, and it can be combined with PP, PE, PVC and other materials. However, excessive use may damage the appearance of the wire core and reduce the insulation and withstand voltage functions. In addition, EVA has poor oil resistance.
PE (polyethylene)
It is a light, soft and water-resistant material with excellent electrical characteristics. Although PE is not heat-resistant and simply ages at high temperature, it is widely used in communication cables, high-voltage cables and submarine cables.
High density polyethylene (HDPE) is produced by low pressure method, so it is also called low pressure polyethylene. It has excellent chemical resistance and electrical characteristics.
