The more common and troublesome quality problem of low smoke zero halogen flame-retardant cables is the environmental stress cracking of insulating materials. The main causes of environmental stress cracking of halogen-free low-smoke flame retardant materials are:
(1) caused by polymer properties;
(2) Extrusion process of materials;
(3) Factors in the use of the environment and storage conditions: Halogen-free low-smoke materials based on polyethylene are generally more sensitive to temperature. Under the environmental conditions with large temperature changes, the internal stress caused by thermal expansion and contraction often causes cracking of the interface region.
(4) The structural form of the extrusion die, the draw ratio and the tensile equilibration rate are also crucial for the elimination of the internal stress after extrusion.