It is well known that the sheath material plays an important protective role for the optical cable. The  type of optical cable also changes with the variety of the sheath  material. If the sheath material is low-smoke halogen-free fuel, the  optical cable is called a low-smoke halogen-free flame-retardant optical  cable. However,  some optical cable manufacturers do not have a comprehensive  understanding of the sheath material, sometimes unilaterally emphasize  certain indicators and ignore other indicators, resulting in the  purchase of the sheath material does not meet the required technical  indicators; more often, it will lead to some The  sheathing material manufacturing enterprise takes the opportunity of  the drilling and optical cable manufacturing enterprises to provide poor  quality sheathing materials. The following are some important indicators for low-smoke halogen-free flame retardant sheath materials, for your reference:
★ Oxygen index
In  almost everyone's eyes, it represents an indicator of the flame  retardant properties of halogen-free flame retardant materials. Most  people believe that the higher the oxygen index, the better the flame  retardant performance, or the oxygen index is up to standard. In  fact, high oxygen index may not pass the cable flame retardant test,  and the low oxygen index may not pass the cable flame retardant test. Reason:  Whether the amount of dripping and dripping of the material in the  combustion greatly determines whether the cable can pass the flame  retardant test and the flame retardant level of the cable.
★ Thermal deformation and high temperature pressure
This is an indicator that is easily overlooked but represents a temperature rating. When  it comes to temperature resistance, everyone will think of the  indicators of heat aging, and it is easy to ignore the indicators of  heat deformation and high temperature pressure. Then,  for thermoplastic low-smoke halogen-free fuels, poor thermal  deformation and high temperature pressure means that – 1 cable sheath  has a low melting point and is easily deformed, ie it can be changed  below the maximum temperature of the cable. Soft  or even melt, at the same time under the action of external force and  self-weight, the cable is deformed or even destroyed, so that the cable  loses normal protection; 2 The cable sheath is easy to crack, that is,  the cable is easily cracked in a soft area when it is partially heated  and stressed. For  example, when it is exposed to sunlight or baked, it will crack on the  exposed surface and the baking surface. 3 The cable made is poor in  flame retardancy, that is, the oxygen index of the material is not low,  but the cable is burned. The test can not pass. Cause: The material temperature index is low and the halogen-free material dripping when the cable is burning.
★ Extrusion performance
The  halogen-free extrusion performance is worse than other materials, so  everyone is focusing on the improvement of extrusion performance, but  the very good extrusion of halogen-free materials will inevitably have  the following problems. 1 The flame retardant may not be added enough to  cause insufficient flame retardancy. 2  The material is too soft and the temperature resistance is not enough,  resulting in unqualified high temperature pressure. At the same time,  due to the low temperature index and dripping of the material, the flame  retardancy of the cable is unqualified.