Positive temperature coefficient of resistance compositions
AssigneeRaychem Corporation
InventorsDavid A. Horsma, Teddy J. Hammack
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Abstract
Disclosed is a positive temperature coefficient of resistance (PTC) crosslinked polymeric composition comprising a first polymeric material exhibiting high green strength prior to crosslinking and elastomeric behavior subsequent to cross-linking, and a second polymeric material comprising a thermoplastic, both said materials having dispersed therein conductive particles, e.g., carbon black, and further, said composition exhibiting a rise in resistance with increased temperature at temperatures above the melting point of either material.
Claims20
An electrically conductive crosslinked polymeric composition which (a) is suitable for use in a self-regulating heating article comprising at least two electrodes positioned so that that, when the electrodes are connected to a power source, current passes through the composition, (b) has a positive temperature coefficient of resistance and (c) comprises (1) a first polymeric material which prior to cross-linking exhibits significant green strength corresponding to a tensile stress of at least 10 p.s.i. at 20% elongation and which exhibits elastomeric properties at ambient temperatures in the crosslinked state (2) a second thermoplastic polymeric material, and (3) conductive particles which have been dispersed in said polymeric material such that the composition exhibits increased resistance with increased temperatures at temperatures substantially above the melting point of either material.
Dependencies are inferred from the claim text.