As we all know, jacket materials play an important role in protecting optical

 cables. The types of optical cables also vary with the variety of sheath materials,

 such as low smoke halogen free fuel, which is called low smoke halogen free

 flame retardant cable. However, some optical cable manufacturers are not fully

 aware of the sheathing materials. Sometimes, some indexes are ignored and 

other indicators are ignored, which leads to the lack of the required technical

 indicators. Sheathing material. In order to make the light cable manufacturing

 enterprises to have a more comprehensive understanding of the sheathing 

material, and to purchase the safe and high quality and cheap sheathing materials

, we have carefully investigated and studied several important indicators of the

 sheath and listed some problems existing in the market of the sheathing sheath

 at present for everyone to participate in the examination.

1, low smoke halogen free flame retardant cable material
oxygen index

It represents the flame retardant performance of halogen free flame retardants

 in almost all eyes. Most people believe that the higher the oxygen index is,

 the better the flame retardancy is, or if the oxygen index is up to standard, 

the flame retardancy of the material is up to standard. In fact, the high oxygen

 index may not necessarily pass the flame test of cables, and the low oxygen

 index may not necessarily pass the flame test of cables. Cause: whether the

 material drips and drops in combustion determines the degree of flame

 retardancy and flame retardancy of cables.

Thermal deformation and high temperature pressure

This is an easy to be ignored, but it represents the index of temperature

 tolerance. When it comes to temperature resistance, we all think of the

 index of thermal aging, which is easy to ignore the index of thermal 

deformation and high temperature pressure. So, for the thermoplastic low

 smoke halogen free fuel, the thermal deformation and the poor performance

 of the high temperature pressure mean that the melting point of the 

cable sheath is low and easy to be deformed, that is, it can be softened 

and even melted when the cable is lower than the maximum use temperature.

 At the same time, the cable can be changed or even destroyed under 

the action of external force and self weight, so that the cable is lost and the 

cable loses its positive. It is often protected; 2 cable sheath is easy to crack,

 that is, when the cable is partially heated, it is easy to crack in the soft area. 

For example, when it is exposed or baked in the sun, it will crack on the blast 

and baking surface; the flame retardancy of the cable made in 3 is poor, that

 is, the oxygen index of the material is not low, but the cable made of the 

cable is passed through the combustion test. Reason: low temperature index

 of material and no halogen material dripping when cable burns.

Extrusion performance

The extrusion performance of the halogen free material is worse than other 

materials, so everyone is trying to improve the extrusion performance, but 

the very good extruded non halogen material will also have the following 

problems, which may result in the insufficient addition of the flame retardant,

 which results in insufficient flame retardancy and insufficient temperature

 resistance, resulting in the unqualified high temperature pressure. At the 

same time, the material temperature is not qualified. Low index and trickle 

flow, resulting in unqualified flame retardancy of cables.

2, PE sheath

Carbon black content, carbon black dispersion and carbon black absorption

 coefficient

These are proof of UV protection. The carbon black in the sheath is not only

 dyeing, but it is more important to use it to protect the ultraviolet light, 

so as to avoid the aging of the sheath material by ultraviolet radiation, but 

not any variety of carbon black has good anti ultraviolet performance when

 the content is 2.6 + 0.25% and the dispersion is more than 6. Only by 

choosing the appropriate carbon black to ensure the first two properties 

and make the absorption coefficient more than 400, will the sheath 

material have excellent UV protection capability.

Thermal aging and oxidation induction period are the embodiment of heat 

resistance and oxygen resistance.

In the production of sheath materials, in addition to the selection of the 

suitable molecular weight and molecular structure of the resin as the substrate,

 a full amount of antioxidant should be added to ensure the material has

 excellent heat resistance and antioxidant capacity. If the anti oxygen agent

 is not added or the anti oxygen dose is insufficient or improper coordination,

 it will cause a large number of molecular broken chain and oxidation cross

 linking phenomenon when the use time is not long, so that the material 

becomes brittle and begins to crack, so that the cable will lose its protection quickly.

Environmental stress cracking resistance

If the sheath material is cracked under the stress of natural environment,

 the sheath will be damaged and the cable will lose protection. This performance

 basically depends on the selected PE resin material itself. In general, only 

the copolymerized PE resin with a certain content of second monomers

 (which also contains third monomers) will have excellent environmental

 stress cracking resistance. When the same content, the second monomer

 species will also greatly affect the performance. When the second monomer

 species and content are the same, different molecular weight and molecular

 structure will also produce different environmental stress cracking properties.

 Therefore, this performance mainly depends on the PE resin matrix used. If

 the material is not properly selected, it is prone to produce bad environmental 

stress cracking performance. The combination of the above three indexes 

determines the service life of the PE sheath. The single item performance is

 good, which can not explain the long life of the sheath material, but the single

 performance is very poor, but it can show that the life of the sheath material is very short.

Low temperature impact embrittlement

It can explain whether it is easy to crack in cold area. The low temperature

 impact embrittlement protective sheath will become very brittle at low 

temperature. When it is applied to cold area cable, it will appear when 1

 cables are exposed to the external forces such as falling, bending, collision

 and collision in the construction. The cracking of 2 cables is easy to crack

 when the cable is used.

Tensile strength and elongation at break

The ability to bear external forces. Only when the test results of tensile

 strength and elongation at break are more parallel and meet the standard 

requirements, the ability to withstand external force will be good if the 

test results are in accordance with the standard.