Raychem Limited

Alan J Gotcher

Paul B Germeraad

Andrew N Au

Lee M Middleman

Viktors Jansons

Larry J White

Burton E Miller

Robert W Fouts, Jr

Peter V Van Konynenburg

Chris Rauwendaal

Conductive polymer compositions comprises a polymeric material having dispersed therein (a) conductive particles composed of a highly conductive material and (b) a particulate filler. The compositions exhibit a positive temperature coefficient of resistivity and undergo a large increase in resistivity as the temperature increases above a certain value. The compositions are useful in preparing electrical devices such as current limiting devices, heaters, EMI shields and the like.

Conductive polymer compositions and devices

Melt-processable fluorocarbon polymer compositions requiring high temperature processing can be highly crosslinked by exposure to radiation after post-extrusion incorporation of at least one of certain crosslinking agents. These polymer compositions can be crosslinked to exceptionally high levels affording polymeric materials of improved mechanical properties at elevated temperatures, especially when utilized in wire constructions.

Shaped article from crosslinked fluorocarbon polymer

Electrical devices comprising PTC elements have improved electrical stability when they comprise an oxygen barrier which restricts access of air to the element so that the PTC element absorbs oxygen at a rate less than 10.sup.-6 cc/sec/gram. The devices are for example circuit control devices or self-limiting heaters. Preferred PTC elements comprise a polymer having dispersed therein carbon black and an additive which stabilizes the polymer against degradation, especially an organic antioxidant. The oxygen barrier may for example be a layer of a polymeric composition or a self-supporting container principally made of metal and filled with an inert gas.

PTC Devices comprising oxygen barrier layers

Compositions which exhibit PTC behavior with a switching temperature (T.sub.s) above 0.degree. C., which have a resistivity at a temperature below T.sub.s of less than 7 ohm. cm, and which comprise a crystalline polymer and a particulate filler component which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area S in m.sup.2 /gram such that S/D is not more than 10. The composition preferably has a peak resistivity of at least 1000 ohm. cm and is electrically stable when aged at elevated temperature. The quantity ##EQU1## is preferably less than 1, especially less than 0.5. Shaped articles of such compositions are prepared by a process in which the carbon black is dispersed in the molten polymer and the dispersion is then melt-shaped, the total energy used in preparing and melt-shaping the dispersion being 1 to 300 hp. hr. ft.sup.-3, preferably 1 to 100 hp. hr. ft.sup.-3, especially 1 to 50 hp. hr. ft.sup.-3. The compositions are particularly useful in circuit protection devices.

Low resistivity PTC compositions

Compounds useful as crosslinking agents have the formula: ##STR1## wherein R.sub.1, R.sub.2, and R.sub.3 and R.sub.4 are independently vinyl, allyl, methallyl, propargyl, crotyl, C.sub.1 to C.sub.18 alkyl, aryl or inert group substituted derivatives thereof and where X is a saturated or unsaturated alkylene moiety having up to 12 carbon atoms saturated or unsaturated C.sub.1 -C.sub.18 heteroaliphatic, C.sub.5 -C.sub.18 heteroaromatic, C.sub.5 -C.sub.18 alicyclic or C.sub.1 -C.sub.18 heterocyclic, where n and m are independently 0 or integers of from 1-12 inclusive. These compounds are particularly useful as crosslinking agents for high temperature processable (&gt;200.degree.) polymers, especially fluorocarbon polymers. Also described are polymer compositions comprising from about 0.1 weight percent to about 50 weight percent of said crosslinking agent or mixture of said crosslinking agents. The products resulting from melt fabrication and subsequent crosslinking of such compositions are useful as shaped articles, e.g., wire products. Most of said compounds are novel compositions of matter.

Shaped article of radiation crosslinked triazine-trione polymeric

Shaped article from crosslinked fluorocarbon polymer and process therefor

A composition comprising a polymer having a processing temperature of at least 200.degree. and from about 0.1 wt % up to about 30 wt % of crosslinking agent said crosslinking agent comprising a compound of the formula ##STR1## wherein X is hydrogen and Y is ##STR2## and X and Y are substituents on adjacent carbon atoms of A or wherein X and Y together form the imide ring system ##STR3## which is joined to A on adjacent carbons atoms, thereof, wherein A is an aromatic, heteroaromatic, alicyclic, or heterocyclic system or an open chain aliphatic moiety, where R is vinyl, allyl, methallyl or propargyl and wherein R' is hydrogen, C.sub.1 to C.sub.12 alkyl or R and mixtures thereof. Compounds per se and articles manufactured from the above-indicated polymer compositon are also taught.

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Sunnyvale, CA, United States of America

Alan J Gotcher