Community Research and Development Information Service - CORDIS

Mineral filler polymer matrix materials for insulation and sheathing of electric cables

It has been shown that low cost halogen-free materials for wire and cable applications can be developed. Two flame retardant fillers can be selected. Several types of polymer have been tested. Ethylene vinyl acetate (EVA), linear low and very low density polyethylene (LLDPE, VLDPE) are the polymers which give the best results.

First industrial trials were produced with silane coupling agents; despite a good surface aspect and good initial mechanical characteristics, these compatibilizers are rejected because of decreasing of the elongation at break after ageing, and because of the price compared to the objective. Other industrial trials were produced with a commercial maleic anhydride grafted polymer as compatibilizer. Compounds are produced and fulfil the requirements with a price in accordance with the objective. Compatibilizers from the University of Liege are industrially produced and are tested in compounds. The extrusions give a very good aspect surface. We can notice the very high elongation at break, between 400 and 500% on cable. All the other characteristics are fulfilled except the tensile strength at break.

This lower tensile strength at break measured on cable is due to the evaporation during the extrusion of the remaining solvent contained in compatibilizer. This evaporation induces porosity in the cable and decreases the mechanical characteristics, especially the tensile strength at break. A better drying of the compatibilizer with stronger evaporation of the solvent during the synthesis should increase the tensile strength at break.

Contact

Jean-François MILLION-BRODAZ, (Development Engineer)
Tel.: +33-4-72722436
Fax: +33-1-78587901
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