1、Common PVC flame-retardant cable material contains a lot of halogen, which will produce a lot of smoke and poisonous corrosive hydrogen halide gas when burning. Halogen-free flame-retardant is mainly realized in polyolefin, so low-smoke halogen-free cable will be the main trend of future development. So the following two aspects are simple for extrusion of low-smoke halogen-free cable material and colleagues and experts in cable industry. Discussion.
A 、The main component of wire and cable extrusion equipment is screw, which relates to the application scope and production efficiency of extruder. In order to meet the needs of different plastic extrusion, there are many types of screw. Low smoke halogen-free flame retardant cable material contains high filling flame retardants such as magnesium hydroxide or aluminium hydroxide, so special halogen-free screw is generally used for screw selection, and its compression ratio can not be too large, generally between 1:1 to 1:2.5 is more appropriate. Compression ratio: the ratio of effective volume in feed section to that in homogenization section.
B 、In the extrusion process, there is also an important factor affecting the extrusion of low smoke halogen-free cable material, that is, the cooling device of the extruder. Because of the particularity of low smoke halogen-free material, in the extrusion process, there is a large amount of heat generated by friction, which requires that the extrusion equipment have a good cooling device, in order to accurately control the process temperature. If the temperature is too high, there will be air holes on the surface of the cable, and if the temperature is too low, the current of the extrusion equipment will be increased, and the load of the motor will be too large, which will easily damage the equipment.
3、Extrusion die: Because magnesium hydroxide or aluminium hydroxide and other flame retardant fillers account for a large proportion in the low smoke halogen-free cable material formula, which results in the melt strength, tensile ratio and viscosity of the melt are quite different from those of ordinary PVC cable material, so the selection of the die is also different.
A 、The first is the choice of extrusion mode. For the extrusion of low smoke halogen-free cable material, the extrusion mode of insulation extrusion should be selected, while the semi-extrusion mode should be selected in the process of sheath extrusion, so as to fully guarantee the tensile strength, elongation and surface finish of the material.
B 、Next is the choice of the die sleeve. When using the extrusion die, because of the high viscosity of the material, the pressure of the die is very high. When the extrusion leaves the die, the die sleeve will expand, so the die sleeve should be smaller than the actual size. The mechanical processing performance of low smoke halogen-free material is not superior to that of ordinary PVC cable material, and its drawing ratio is small, only about 2.5-3.2. Therefore, when choosing dies, the drawing performance of low smoke halogen-free material should be fully considered. This requires that the selection of dies should not be too large, otherwise the surface of cables is not compact and the extrusion package is loose.
A 、The main component of wire and cable extrusion equipment is screw, which relates to the application scope and production efficiency of extruder. In order to meet the needs of different plastic extrusion, there are many types of screw. Low smoke halogen-free flame retardant cable material contains high filling flame retardants such as magnesium hydroxide or aluminium hydroxide, so special halogen-free screw is generally used for screw selection, and its compression ratio can not be too large, generally between 1:1 to 1:2.5 is more appropriate. Compression ratio: the ratio of effective volume in feed section to that in homogenization section.
B 、In the extrusion process, there is also an important factor affecting the extrusion of low smoke halogen-free cable material, that is, the cooling device of the extruder. Because of the particularity of low smoke halogen-free material, in the extrusion process, there is a large amount of heat generated by friction, which requires that the extrusion equipment have a good cooling device, in order to accurately control the process temperature. If the temperature is too high, there will be air holes on the surface of the cable, and if the temperature is too low, the current of the extrusion equipment will be increased, and the load of the motor will be too large, which will easily damage the equipment.
3、Extrusion die: Because magnesium hydroxide or aluminium hydroxide and other flame retardant fillers account for a large proportion in the low smoke halogen-free cable material formula, which results in the melt strength, tensile ratio and viscosity of the melt are quite different from those of ordinary PVC cable material, so the selection of the die is also different.
A 、The first is the choice of extrusion mode. For the extrusion of low smoke halogen-free cable material, the extrusion mode of insulation extrusion should be selected, while the semi-extrusion mode should be selected in the process of sheath extrusion, so as to fully guarantee the tensile strength, elongation and surface finish of the material.
B 、Next is the choice of the die sleeve. When using the extrusion die, because of the high viscosity of the material, the pressure of the die is very high. When the extrusion leaves the die, the die sleeve will expand, so the die sleeve should be smaller than the actual size. The mechanical processing performance of low smoke halogen-free material is not superior to that of ordinary PVC cable material, and its drawing ratio is small, only about 2.5-3.2. Therefore, when choosing dies, the drawing performance of low smoke halogen-free material should be fully considered. This requires that the selection of dies should not be too large, otherwise the surface of cables is not compact and the extrusion package is loose.
