The advantages for MDPE to be used as cable sheath

MDPE has very high resistance to abrasion and it is extremely hard and has a low dielectric constant with superior oxidation resistance. The hardness of the MDPE cable sheathing protects the cable from sharp objects dropped or loaded onto the cable. This helps MDPE finds particular usage in transmission cables in the toughest of environments, notably those with the high ambient temperatures found in tropical and subtropical countries. But at these high ambient temperatures alternative sheathing materials such as PVC would be soft and prone to damage easily during laying of the cables. 

Compared with LDPE (low density polyethylene), MDPE has significantly more strength enabling it to be pulled under heavy load for cabling applications; while compared to HDPE (high density polyethylene), HDPE has improved resistance to cracking.

Besides, various additives can be applied to MDPE compounds to improve fire retardant properties, UV and weathering resistance and the chemical degradation.