Cableizer

Thermal emissivity cable

Thermal emissivity in the long-wave infrared band is governed primarily by the molecular structure and chemical composition of the surface material, not by its visible colour. This is a fundamentally different wavelength regime from solar (short-wave) radiation, where colour matters greatly because visible light is absorbed by pigments.

In the IR, almost all organic polymers and rubbers — whether black, white, grey, or red — behave as near-blackbody radiators with emissivity between 0.84 and 0.97. For cable ampacity calculations, the IEC 60287-2-1 default of 0.9 for all cable surfaces is well justified regardless of jacket colour, as the variation across the entire practical range is only about ±0.07. The only notable exception is metallic-pigmented paint (e.g. aluminium paint). For painted metal ducts or armour, the paint layer (being organic) also exhibits high emissivity (0.75–0.96) regardless of colour.

Symbol
$\epsilon_{e}$
Used in
$\eta_{e}$
Thermal reflectivity cable
$h_{rad,int}$
Heat transfer coefficient radiation cable—riser [W/(K.m$^2$)]
$K_{r}$
Radiation shape factor
$\zeta_{er}$
Radiation shape factor touching cables
Choices
CodeValueMaterialRangeNotes
Polymers
PE0.92Polyethylene (LD/MDPE, ST3)0.90-0.95black PE: 0.92, plastics general: 0.90-0.97
HDPE0.92High density polyethylene (HDPE, ST7)0.90-0.95same polymer family as PE
XLPE0.92Crosslinked polyethylene (XLPE)0.90-0.95same base polymer as PE
XLPEf0.92Crosslinked polyethylene (XLPE) filled0.90-0.95same as XLPE, mineral fillers do not significantly change IR emissivity
PVC0.92Polyvinyl chloride (PVC, ST1/2)0.91-0.93PVC: 0.91-0.93, typically carbon-black filled
POC0.92Polyolefin copolymer (POC)0.90-0.95polyolefin family, plastics general: 0.90-0.97
PP0.95Polypropylene (PP)0.92-0.97PP: 0.97 (natural), compounded jacket slightly lower
PPY0.95Polypropylene yarn (PP)0.92-0.97PP: 0.97 (natural), compounded jacket slightly lower
SiR0.9Silicone rubber (SiR)0.85-0.93silicone rubber ~0.90, black silicone paint: 0.93
FRNC0.9Flame-Retardant Non-Corrosive polyethylene (FRNC)0.88-0.95polyolefin base + high filler content (ATH/MH)
EPR0.92Ethylene-propylene rubber (EPR)0.90-0.95rubber family: natural hard 0.91, hard 0.94, hard glossy 0.94-0.97
IIR0.9Butyl rubber (IIR isobutylene isoprene rubber)0.86-0.95rubber soft/gray: 0.86, foam: 0.90, natural hard: 0.91
NR0.9Natural rubber (NR)0.86-0.95rubber soft/gray: 0.86, foam: 0.90, natural hard: 0.91
PPLP0.93Polypropylene laminated paper (PPLP)0.90-0.97paper: 0.93, PP: 0.97, roofing paper: 0.91
Mass0.92mass-impregnated paper0.90-0.95paper: 0.93, roofing paper: 0.91, tar paper: 0.93
OilP0.93oil-filled paper0.90-0.95paper: 0.93, oil transparent in IR, paper dominates
EVA0.92Ethylene vinyl acetate (EVA)0.90-0.95ethylene copolymer, plastics general: 0.90-0.97, PE: 0.92
XHF0.92X-HF-110 (AS/NZS 3808:2000 R2016)0.90-0.95halogen-free flame-retardant sheathing, plastics: 0.90-0.97
CR0.92Polychloroprene (CR, Neoprene)0.90-0.95natural hard rubber: 0.91, hard glossy rubber: 0.94
CSM0.92Chlorosulphonated polyethylene (Hypalon, synthetic rubber)0.90-0.95rubber/polyethylene copolymer, both high-ε
CJ0.9Compounded jute0.85-0.95organic fibre + bituminous compounds
RSP0.92Rubber sandwich protection0.90-0.95rubber-based, natural hard rubber: 0.91, glossy: 0.94
BIT0.92PVC/bitumen tapes0.90-0.96bitumen black/highly emissive, oil paints: 0.92-0.96
HFS0.92HFS-110-TP (AS/NZS 3808:2000 R2016)0.90-0.95halogen-free polyolefin sheathing, plastics: 0.90-0.97
Ot0.9OtherIEC 60287-2-1 default for all cable surfaces
Metals
Cu0.14Copper0.12-0.15polished: 0.023-0.052, oxidized: 0.78, dull: ~0.14
Al0.2Aluminium0.09-0.30commercial sheet: 0.09, heavily oxidized: 0.20-0.31, rough: 0.07
AL30.09Aldrey (EN 50183)0.07-0.20Al-Mg-Si alloy, polished: 0.09 (Alloy 24ST), A3003 polished: 0.1-0.2, roughened: 0.2-0.8, smooth extruded surface typical
Brz0.2Bronze (CuSn)0.06-0.55phosphor bronze polished: 0.06, polished: 0.10, porous rough: 0.55, powder: 0.76-0.80
CuZn0.4Brass (CuZn)0.22-0.56dull plate: 0.22, oxidized 600C: 0.61, rolled natural: 0.06, polished: 0.03
Ni0.07Nickel0.04-0.10polished: 0.072, electrolytic: 0.04-0.2, oxidized: 0.59-0.86 but cable-grade typically bright/electrolytic
S0.09Steel0.07-0.10polished: 0.07, mild steel: 0.20-0.32, oxidized: 0.79
SS0.6Stainless steel0.50-0.70type 301: 0.54-0.63, weathered: 0.85, polished: 0.075, galvanized new: 0.23