Why should optical cable polyethylene sheath material test carbon black content?

Optical cable is the main transmission carrier of optical fiber communication, and its reliability and service life are of great significance to the reliability of communication network. During the long-term use of optical fiber cables, they will inevitably be affected by the external natural environment, resulting in the gradual deterioration of the performance of the outermost polyethylene sheath, which may eventually affect the transmission of information in the internal optical fiber. Therefore, the environmental resistance of the polyethylene sheath is one of the important indicators to evaluate the quality of the cable, and it is also one of the important factors to ensure the life of the cable (25 to 30 years).

Polyethylene sheath material is one of the main raw materials of optical cable products, because the polyethylene resin itself is very sensitive to the light in the natural environment (mainly ultraviolet light), in order to delay its photooxidation degradation by sunlight, industrial processing needs to add carbon black as a UV stabilizer of the resin. Carbon black is a light screen agent that can absorb ultraviolet light and prevent the breaking and cracking of polyethylene molecular chains, thereby improving the UV resistance of the jacket. In GB/T 15065-2009 "Black polyethylene plastic for wire and cable" and YD/T 1485-2006 "Medium density polyethylene sheath for optical cable", the range of carbon black content is stipulated to be 2.60%±0.25%, too little carbon black will lead to insufficient anti-ultraviolet ability of the material. Too much carbon black will sacrifice the physical and mechanical properties of polyethylene. Therefore, the carbon black content is a very important performance index of polyethylene material for optical cable jacket.