The last one is about the shielding layer of heat-shrinkable tube insulated cables, in which the defects of the shielding layer in the production process are analyzed. Next, in order to eliminate the defects of the heat-shrinkable tube shielding layer and make the interface highly smooth, the following points must be done:
(1) Semiconductor mixtures with good extrudability are used.
(2) Good mixing process of semiconductor materials, carbon black must be evenly dispersed, wet carbon black or other mixtures are strictly prohibited to use;
(3) Semiconductor and insulator are extruded at the same time. At present, the multilayer extrusion process (1 + 2 extrusion, 2 + 2 extrusion or 3-layer extrusion) is generally used in the mass production of XLPE (and other polymers) insulation. Close a-bonding and other defects at the interface are solved on the basis of the multilayer extrusion process (1 + 2 extrusion, 2 + 2 extrusion or 3-layer extrusion).
Sometimes the external semiconductor is wrapped by a semiconductor tape on the insulation. At this time, a layer of graphite suspension is coated on the insulation layer to ensure good contact with the semiconductor.