7 Plastics For Commonly Used Wires And Cables
- May 05, 2019-
1) Polyvinyl chloride(PVC):
It is a highly polar thermoplastic(plastic thermoplastic and thermosetting) non-crystalline polymer electrolyte, so the mechanical properties are good and the dielectric constant is large. At 20C, 1MHz, the dielectric is often 40. ~ 4.6. It contains 47 % halogen, is difficult to ignite, and is flammable after being formulated into plastic. The density is 1.35 g/cm cubic hard and soft density is different. The insulation performance is good, the climate resistance is strong, the chemical resistance is very low, and the shrinkage rate is generally 0.2 ~ 0.6 %. The temperature resistance level is divided into 70C, 90C, 105C, CM, CMR, CMP. For PVC materials with a temperature resistance level of 105C and above, cross-linking should be performed, that is, the material is changed from a linear linear structure to a linear structure through the radiation of an electron accelerator. Network structure, Thus improving its heat resistance stability and mechanical properties.
Mainly used for insulation and sheath, because PVC's poor flow performance is less used for injection molding.
High density polyethylene(HDPE: suitable for high-speed extrusion), medium density polyethylene(MDPE, low density polyethylene(LDPE: long used in power cables), linear low density polyethylene(LLDPE), flammable, low water absorption, The medium loss angle and dielectric constant are small, and the non-foaming dielectric at 20C and 1MHz is often 2.28 ~ 2.35, and the insulation performance is better than that of PVC. Poor filling, usually used for communications cable insulation or power cable sheath. Density 0.917 ~ 0.975 g/cm3. In order to meet the needs, our country has already developed XLPE.
Mechanical and electrical properties are very similar to PE, but the environmental stress resistance is better than PE. The disadvantage is that copper has a corrosive effect on PP, and the use of tin plating is not very effective. The density is 0.895 g/cm3, and the dielectric constant is 2.55 at 20C and 1MHz.
Also known as nylon, it has wear resistance, oil resistance, high mechanical strength, heat resistance, high melting temperature, and usually a homogenized section temperature of 300 C. Strong water absorption, large dielectric constant, poor insulation performance, often at 20C, 1MHz, generally not used for insulation, combustion is to emit the smell of burning objects. Its models are nylon 6, 9, 11, 12, 66, 610, 612, and nylon 1010 developed by China. Nylon has three disadvantages in making wires: 1) Anti-white, which is determined by the nature of PA. 2) Poor adhesion, 3) large water absorption, easy to bubble during the push out process, so the material should be preheated before the push out, temperature 80 ~ 105C
The commonly used fluorinated plastics in industry are polytetrafluoroethylene(PTFE), but the most commonly used fluorinated plastics for online cables are polyfluoroethylpropene(FEP), whose density is between 2.08 and 2.20. In addition, commonly used fluorine plastics include ethylene tetrafluoroethylene copolymer(ETFE) and polyvinylidene fluoride(PVDF). The density is between 1.70 and 1.75. The heat resistance level is at least 200C or above. In addition, it also has very good cold resistance. Chemical corrosion resistance, low water absorption, dielectric constant 2.6 at 20C, 1MHz. It is currently one of the two best plastics in terms of high temperature resistance(the other is silicone cable). It is usually used in high-defense communication cables, aerospace, radar, radiation resistant cables for atomic reactors, vehicle cables, etc., Geological exploration cables, and logging cables.
However, the disadvantage is that the process is more difficult to process. When the wire is used, no mold is used to push out, the corona resistance is poor, and the plastic has a corrosive effect on copper. Tin must be Plated, followed by a higher price.
The main purpose of this material is not to make insulation or protective covers. Its main role in the manufacture of wires and cables is to be used as a package of wire cores. At the same time, it also uses Changhe aluminum foil and(coated on aluminum foil) to form an aluminum composite strip. It is fully demonstrated that polyester has good insulation properties.
7) Low-smoke halogen-free cable material(LSOH)
Low smoke refers to 65 % of the plastic produced by combustion, and some companies can even control more than 87 %. No halogen refers to the gas produced by 1 gLOSH material at a high temperature of 935C for 30 minutes when testing for corrosion gas release. The mass is within 2mg -5 mg. If it is in the range of 5mg-15mg, we call it low halogen.
Nowadays popular LOSH materials are mainly PP, PE, EVA, flame retardant Mg(OH) 2
, AL(OH) 3 is the main, supplemented by SbO2 flame retardant, mainly making it a synergistic effect, reducing the amount of MgOH2, Mg(OH) 2 is large, and the compatibility, dispersion, and impact resistance are poor, It is one of the main reasons for the poor mechanical performance of the LOSH material. Therefore, coupling agents must be added so that the mixture can be tightly combined to increase its elongation and resistance to long lengths. The commonly used coupling agents are silane coupling agents. At the same time, this plastic is not PVC as the main material, there is no need to add plasticizers, so LOSH is non-shifter, while LOSH material has good thermal stability, do not need to add stabilizer, in the formula of general PVC, Stabilizers and colorants are the two main enemies of environmental protection! Formula example PP + EVA(VA content 20-30 %) + Mg(OH) 2 + coupling agent + slider + elastomer + other special additive FRLOSH material we often call thermoplastic low-smoke halogen-free flame retardant polyolefin, Is an emerging environmental cable material, we firmly believe that after 10 years, PVC cable material will be forgotten by us!
Supplement: TPE is a thermoplastic elastomer. It is called different regions. It is a general term for certain plastics.