Objectives and content:
In the field of electrical power distribution, fire behaviour of low voltage cables in public premises is a strong preoccupation, from both environmental and human safety concerns. Depending on the application, three classes of fire retardancy must be considered: flame retardant, fire retardant and fire safety cables. For this last category, not only the cables should not propagate the flame, or the fire, they must also continue to operate under fire conditions. This very strong requirement corresponds to an increasing world-wide vital market: public housing, hospitals, factories, large office buildings, off shore platforms, mass transit vehicles and marine vessels, etc. This market is highly competitive, within Europe, but also in Japan and in the US. Today, some products partly comply with standard requirements. However, present standards are considered non-realistic in most fire environments and are about to be modified: today, they involve testing at 750-900ÐC with mechanical shocks, and cables must keep operating during and after the tests. In future standards, testing will be performed at higher temperature (e.g. 1100ÐC), with mechanical shocks and under water spraying. There is no material/product available today which fulfils all these requirements. The objective is to develop new, low cost, halogen-free ignifugation processes, to guarantee cable operation up to 1100ÐC, for at least 90 minutes under water spraying. These properties will come in addition to standard non-toxicity, smoke emissivity and flame non-propagation requirements. Today, such cables include micaceous tape and/or 2 vulcanised silicone rubber layers.
They provide current carrying capabilities during a limited time, for temperatures up to 900ÐC. These solutions are expensive and electrical properties at higher temperature are not sufficient (especially the leakage current). Improved high temperature properties will require new combinations of polymers and ceramic-forming materials. One key, innovative action in the programme is the incorporation of fillers/additives, to promote in situ vitrification of the base material. This ceramisation will be initiated before the polymer is fully decomposed. The resulting target ceramic must be hard, compact without cracks, with electrical insulating properties, whatever the temperature. In addition the fillers will be optimised to maintain the thermomechanical properties of the base polymer and electrical properties of the cable at its operating temperature. The programme will be performed using a silicone elastomere in a first part. Partial substitution by a second polymer will later be experimented, to lower costs. The partnership includes partners from five european countries: an industrial partner (base polymer materials provider), a technical centre (ceramics technology provider), a leading cable manufacturer, research partners in the fields of fire resistance and polymer degradation (both academic and industrial research centres), and a certified body in the field of fire testing and standards. The primary target is the application to future low voltage safety cables, both in power distribution and remote control applications, with possible extension to medium voltage and power cables. This is a new market, for which no technical solution exists yet.
The solutions developed in the course of this programme could be extended to other electrical accessories and products, using the same base materials and manufacturing processes, whenever strict fire standards compliances are to be met. Beyond the direct economic impact of European products in that market (0.45 billions ecus worldwide; EU shares 33 %; 10% annual growth rate), there are many indirect benefits, connected with increased safety and decreased accident risks and consequences: this includes the reduction of human casualties and costly damage to machines, buildings, infrastructure and industrial plants. BE97-4962
Funding SchemeCSC - Cost-sharing contracts
501 15 Boraas
10125 Torino (Turin)