The IEC 60287 does not list materials for filler but states: depending on the filler material and its compaction, the thermal resistivity is in the range 6 to 13 K.m/W for cables with extruded insulation, 10 K.m/W is suggested for fibrous polypropylene.
Following values are taken from IEC 60287-2-1 Ed.2.0 for insulation or jacket with following additions:
- The value for fibrous polyolefin copolymer (FPOC) is taken from the book 'Handbook of Polyolefins' by C. Vasile (2000)
- The value for fibrous polypropylene (FPP) is as suggested by the IEC 60287-2-1 Ed.2.0
- The value for the tapes is an approximative mean value based on different sources
- The value for air is valid for heat transfer through air by conduction without considering convection and radiation
- The value for other materials (Ot) is considered to be like FPP