Ageing of flame retardant cables

Tests show that aging deterioration of PIN FR cable sheath depends on environmental conditions: heat, water, salt. LSZH (low smoke zero halogen) cable sheath material pellets were supplied by an electrical equipment company in China and were composed mainly of EVA*, polyolefin elastomer, polyethylene and EAMA* with the PIN FRs AlPi and melamine cyanurate. Ageing was tested for 360 hours: thermal (GB/T 2951.12–2008 @ 135°C), hygrothermal (GB/T 15,905–1995 = humidity plus heat cycles) and salt spray (GB/T10125–2021). Fire performance deteriorated compared to the unaged cable material, with up to +14% increase in total heat release and -16% in LOI. Hygrothermal ageing had the most effect on this cable material, followed by salt spray. The authors conclude that ageing should be more widely tested for fire performance of cables, but that impact of aging depends on complex environmental parameters.
EVA = ethylene-vinyl acetate copolymer, EAMA = ethylene acrylate maleic anhydride copolymer.

“Flammability degradation behavior and ageing mechanism of flame-retardant cable sheath under different ageing conditions”, H. Liu et al., Polymer Degradation and Stability 230 (2024) 111019 https://doi.org/10.1016/j.polymdegradstab.2024.111019