Self-regulating heating element and a process for the production thereof
AssigneeElectricite de France (Service National)
InventorsBernard M. Dalle, Claude Caillot, Francois A. Legros
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Abstract
A self-regulating heating element (1) comprising a crosslinked copolymer based on ethylene and a comonomer of vinyl acetate in which the proportion of vinyl acetate is less than 10% and more than 2% by weight, more especially from 9 to 2% by weight and, in practice, from 9 to 5% by weight, said copolymer containing from 13 to 30% by weight carbon black and having a ratio ##EQU1## of greater than 10.sup.4.
Claims3
In a self-regulating heating element of the cable or band type of a crosslinked synthetic polymeric material based on ethylene and vinyl acetate to which a resistivity .sup..rho., increasing with the temperature from a value .sup..rho. amb at ambient temperature to a maximum value .sup..rho. max, is imparted by incorporating conductive charges consisting of carbon black, the improvement according to which the proportion of vinyl acetate is from 9 to 2% by weight, said carbon black which is present in a proportion from 13 to 30% by weight being selected from those of which
- the specific surface is from 40 to 270,
- the structure index is from 100 to 270,
- the volatile content is less than 2%,
- the mean particle size is from 10 to 40 nm.
Dependencies are inferred from the claim text.