So how does the manufacturing process affect the insulation performance of heat-shrinkable tubes?
In the early production of insulated heat-shrinkable casing, due to production process limitations, insulated heat-shrinkable tube can only use wet crosslinking process, which brings a lot of moisture into the insulation. The practice shows that the insulation heat-shrinkable tube produced by this method is suitable for low-voltage products, but it should be cautious. For example: four times military standard heat-shrinkable tube, halogen-free non-flame retardant ultra-thin heat-shrinkable tube; When the voltage level exceeds the medium voltage, the safety of insulated heat-shrinkable tube decreases greatly. With the improvement of the process, the method of extruding three layers at the same time, including inner and outer semi-conductive layer and insulating layer, is now used. The advantages are:
(1) it can prevent the introduction of external impurities between the main insulation layer and conductor shielding, as well as between the main insulation layer and insulation shielding;
(2) in the manufacturing process, it can prevent accidental damage of conductor shielding and main insulation layer, so as to prevent spikes due to mechanical damage of semi-conductive layer;
(3) the internal and external shielding is tightly combined with the main insulation layer, so as to improve the initial free discharge voltage.
The relationship between ac breakdown voltage and insulation layer thickness of thermal shrinkable pipe manufactured by different technology. It can be seen that the manufacturing of ac breakdown strength by extrusion process is much better than that by wrapping semi-conductive band.
So in the choice of heat-shrinkable tube and insulation materials must choose the regular manufacturers.