Cable material to achieve the flame retardant, low smoke and heat, the best choice is to have these characteristics of polymer materials. Such as: Fluoropolymer, but because of its high price and difficult to promote the use of. Polyethylene (PE), polypropylene (PP) with low smoke, but flammable, you must add a large number of flame retardants to achieve better flame retardant requirements, which in turn can lead to mechanical and electrical properties decline. For example: the German LSZH cable standard (VDE0207) and China's PVC (PVC) cable standard (GB8815-88) compared to the former tensile strength and the latter only 1/3 to 1/2, the fracture Elongation and the latter only 70% to 80%, the volume resistivity is less than the latter. In addition, PE and PP are less flexible and can be used for wire and cable wrapping applications only for less frequent motions.
PVC resin with high flame retardancy and high electrical insulation and low prices, is currently the largest amount of cable material raw materials. Overhead insulation grade PVC cable material processing steps and ordinary 70 ℃ insulation grade PVC cable material processing procedures are the same, except that the process conditions are slightly different. Processing process is divided into grinding, mixing, sieving, extrusion granulation and packaging.
Grinding a solid auxiliary such as Tribasic Lead Sulphate, Dibasic Lead Phosphite, lead stearate, photothermal stabilizer and a plasticizer are mixed and then ground on a three-roll mill; the carbon black is mixed with a plasticizer and ground on a three-roll mill . Adjust the roller distance, the three grinding, the solid material fineness of 25μm or less. Then fine ground the material transported to the mixing process.
PVC mixture powder into the extruder hopper, heating, shearing, plasticizing, the head flange again at a filter, the filter is 60 mesh, the molten material through the machine head, under the action of a rotating cutter cut Into a cylindrical pellet, the fan sent to the hopper, cooling after packaging. Production of overhead insulated PVC cable material when the extruder temperature control and production of ordinary 70 ℃ insulation grade PVC cable material when the extruder temperature control of the average high about 10 ℃.