Posted on 19/03/2018 in Electric & Electronic News 32 2018

Camillo Cardelli, iPOOL Materials Design, Italy, explained that cables in Europe today must undergo the EN 59399 vertical fire test for CPR (Construction Products Regulation), with demanding parameters for flame spread, non-dripping, smoke density, smoke corrosivity and smoke toxicity. He presented results of testing of a range of non-halogenated FR cable compounds (tested as tapes) in the “Mini SBI” (see SUSPI, pinfa Newsletter n°76), a non-regulatory, experimental set-up suitable to compare fire behaviour of different compounds and different raw materials.

The formulations tested were based on polyethylene/EVA and POE (polyolefin elastomers) with stabilisers, hydrophobic and processing agents. Inorganic FRs tested were ATH, MDH, brucite, Böhmite, Calcium borate, and stearic acid or silane coated versions of these. Results showed many variations, but two possible conclusions were that all MDH containing recipes tends to give less flaming drips than does ATH (with collapse of char in fire), and that milled natural MDH gives good results comparable with fine synthetic MDH. Coatings applied on ATH or MDH could also positively or negatively affect the results of burning tests.

Thomas Fabian, Underwriters Laboratories, described different testing methods and possible correlations between results, noting the need for new testing methods to enable to rapidly fire test new materials under development and to ensure fire safety of new materials and new applications, for example in building and construction. He noted the difficulties of producing meaningful data on smoke emissions from testing, because smoke is mostly produced at the temperature of polymer degradation so emissions will depend on to what extent the material is near this temperature in the test. He also noted that when materials flow away from the heat source in testing this can result in a test pass despite a fire risk. Also, fire performance can deteriorate with ageing. He notes that today HFFR cables are available (non halogenated polymer, PIN FRs) which are “Plenum Rated by the Steiner Tunnel Test, that is the most demanding flame spread resistance rating.

Werner Tecker, LEONI, develops cables for performance applications, in particular automotive. Customer demand to move towards halogen free cable solutions in applications such as commercial buildings, domestic cables and automobile is challenged by cost restraints. Fire safety requirement in the car industry may become tighter. For example, at present, flame test requirements in the passenger compartment are lower than under the bonnet. Electric vehicles will also set new challenges: temperature resistance can maybe be lowered, but higher currents will pose safety issues in e.g. battery connection cables. High current loading combined with flexibility will favorise use of PIN additives such as silicones. New specifications will be needed for external charger cables (UV resistance, weathering). Increasing use of polyolefins in cable insulation will require new combinations of PIN flame retardants and synergists in order to meet fire performance, mechanical, water uptake and electrical requirements.
LEONI: see pinfa Newsletter n°s 45, 74. LEONI, with over 80 000 employees in 30 countries worldwide, is one of the world’s leading providers of wires, optical fibres, cables, cable systems, and related services to the automotive industry, electrical appliances and industrial applications.

Dmitriy Lyashenko and Valery Moroz, Prominvest Cable Compounds, Ukraine, noted that the market in both Russia and Europe is increasingly pushing for fire performance rated cables, in construction, transport and in specialised industries such as offshore and oil and gas. To combine this with mechanical and electrical requirements, and with cost constraints, new cable compounding solutions are being developed including new polymers, new flame retardants and PIN synergists. Challenges include flexibility at low temperatures, hydrocarbon resistance and low smoke toxicity, already today required in public buildings and in railway systems. Smoke opacity testing in Russia uses green light (coherent with emergency exit lighting) rather than red light in Europe. Prominvest is identifying opportunities to transfer to cable compounding innovative polymer / FR / synergist solutions developed in other applications.
Prominvest is a leading producer of cables in the CIS (Eastern Europe and Russia) region, producing some 70 grades and formulations of cable compounds with capacity of 45,000 tons per year.

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