The effect of accelerated ageing of building wires

Abstract

SUMMARYThe fire performance of two electric cables (building wires) designed for indoor use has been tested, both as new products and after accelerated thermooxidative ageing. The cables were aged for a maximum time of 16.5 weeks at 80 • C. The cables are commercially available, and were constructed using a PVC material in one case and a non-halogenated polyolefin-based material, called Casico, in the other. The effects of ageing on the fire performance of the cables, and the chemical changes that have caused the observed fire behaviour, have been investigated and are discussed. Special attention is paid to the behaviour of the plasticizers that are used in the PVC cable, and how the fire behaviour is affected by the loss of plasticizers from the cable and by the migration of plasticizers between the parts of the cable (insulation, bedding and sheathing).

Effects of ageing on the fire behaviour of flame-retarded polymers: a review

“…For example, in cables, copper can catalyse degradation. Migration of low‐molecular‐weight additives from the inner part to sheathing in multilayer cables (containing insulation, bedding and sheathing parts) was already reported …”

“…Emanuelsson et al investigated two commercially available cables in terms of flammability (measured using a cone calorimeter) after accelerated thermo‐oxidative ageing at 80 °C in an oven for 1, 3, 8 and 16.5 weeks. The first cable was based on ethylene butylene acrylate copolymerized with ethylene with CaCO 3 and silicon gum.…”

Durability of the flame retardance of ethylene‐vinyl acetate copolymer cables: Comparing different flame retardants exposed to different weathering conditions

“…As the duration of artificial weathering exposure increased, ketones (1711 cm −1 ) were generated for all EVA samples (Scheme 1 (3)), a phenomenon that was not found after the other two kinds of conditions, where mostly aldehydes (1696 cm −1 , Scheme 1 (4)) and carboxylic acids (1685 cm −1 , Scheme 1 (5)) appeared. Furthermore, there were some similar reactions after the other two exposure conditions aside from artificial weathering, such as the formation of alkyne (3256 cm −1 , Scheme 1 (6)), linear or branched alkanes (2958 cm −1 , Scheme 1 (7), conjugated dienes (1603 cm −1 , Scheme 1 (8)), macromolecular alcohols (1435 cm −1 , Scheme 1 (9)), methyl ketones (1711 cm −1 , Scheme 1 (10)), and (CH 3 )CH groups (1165-1121 cm −1 , Scheme 1 (11)). However, slightly different for salt spray exposure, one special reaction was the generation of endocyclic alkenes (3167, 3053 cm −1 , Scheme 1 (12)), which can be obtained from the conjugated dienes.…”

“…Therefore, special considerations need to be taken into account when formulating additive systems to combine sufficient weathering resistance with flame retardant efficacy over the whole service lifetime of polymeric articles. 7,8 Regarding the modern fire retardancy of EVA cables, apart from cost and flame retardant efficiency, the environmental friendliness of flame retardants is an important issue that should be focused on. 4,5 During its long lifetime or applications in extreme surroundings, such as construction, shipbuilding, or in nuclear, automotive, or photovoltaic applications, 6 several service conditions (mainly the weathering exposures) are inevitable, including UV irradiation, temperature, and humidity, and sometimes even salt spray.…”

“…6 Accordingly, it is important and necessary to investigate the long-term durability of cables exposed under different weathering conditions, as well as the deterioration of flame retardancy. 7,8 Regarding the modern fire retardancy of EVA cables, apart from cost and flame retardant efficiency, the environmental friendliness of flame retardants is an important issue that should be focused on. 9,10 Metal hydroxides and intumescent flame retardants are two successful kinds of halogen-free flame retardants that have drawn much attention.…”