PVC materials

PVC materials have generally fine and stable mechanical performance. Fire propagation behavior may be fine, but smoke and acid generation during fire are main problems which must be considered in certain fire scenario. Environmental legislation will limit some types of compounds in certain countries.

PVC sheathings are significantly affecting temperature performance of attenuation, but only for unscreened cables. In most cases the degradation is well within the specified limit. However, this should always be verified, also in cases where the PVC compound is "just" changed in connection with regular production.

Halogen free materials

Halogen free materials are frequently based on EVA (ethylene vinylacetate copolymer), but also flame retardant PE (polyethylene) is applied. EVA compounds are containing magnesium or aluminium hydroxydes to facilitate flame or fire retardancy. These hydroxides are forming water when heated and thus creating flame or fire resistance.

EVA based materials may be applied in both flame and fire retardant cables. PE based materials are, as far as 3P knows, only applied in flame retardant cables.

Halogen free materials have improved significantly over the past many years, but still a general problem for the EVA based materials is the mechanical behavior. The elongation of the sheath is usually close, but safely over the specified limit (min. 125 % elongation at break). However, if production is not well controlled it may be reduced significantly. 3P estimates that performance is only affected in the very few cases where a very low elongation is found.

Plenum type materials

Plenum type materials are usually based on fluorocarbon (FEP) compounds, with or without mixing with other materials. Plenum type cables are commonly used in the US, while Europe has so far alternatively focused mainly on halogen free cables. PVC type cables are applied everywhere.

Plenum materials are having superior fire propagation resistance, but lower smoke and acidity performance than halogen free materials. Depending on the focus one could therefore rate the better fire propagation of plenum cables or the lower smoke and corrosivity of the halogen free cables for most valuable.

The costs of the plenum cables are significantly higher than the costs of the halogen free cables. This point must of course also be included in any decision making concerning application of plenum type cables.