Abstract: Polymeric compositions comprising 7-28%, preferably 12 to 25%, of a thermoplastic olefin polymer, 1-10%, preferably 2 to 6%, of a siloxane polymer containing 2-70% of siloxane units and at least 20% by weight of carbonate, urethane or amide units, and 69 to 90%, preferably 72 to 83%, of an elastomer. The olefin polymer can for example be polyethylene, polypropylene, or a polar ethylene copolymer. The elastomer can be a thermoplastic elastomer, an ionomer, or a styrene/butadiene copolymer. The compositions are particularly useful in the medical field, for example in the form of tubing.

Abstract: Novel PTC conductive polymer compositions contain a mixture of two crystalline polymers of different melting points, the higher melting of the polymers having a melting point which is at least 160.degree. C. and at least 25.degree. C. higher than the melting point of the other polymer. The compositions do not increase in resistivity by a factor more than 2 when maintained at 150.degree. C. for 1000 hours, and are therefore particularly suitable for self-limiting heaters which can be used on apparatus which is periodically subjected to high temperatures, e.g. during steam-cleaning thereof.

Abstract: Elongate electrical devices, comprising two conductors with electrical elements connected in parallel between them, have improved performance if the power supply is connected to one conductor at the near end and to the other conductor at the far end. Particularly useful devices are heaters, e.g. PTC conductive polymer heaters. The power supply is connected to the far end of the device through a connection means whose electrical properties can be correlated with those of the device in order to obtain a wide range of useful results. For example the connection means can have PTC, NTC or ZTC character and can be a simple conductor or another elongate device. The power supply can be DC or single-phase, two-phase or three-phase AC.

Abstract: A heat-recoverable article which can be connected to a power supply and a switch unit which comprises a thermally-responsive member which can be thermally coupled to the article. The thermally-responsive member, when so coupled, regulates the passage of current through the article. The article heats and recovers and current through the article is regulated automatically.

Abstract: Elongate electrical devices, comprising two conductors with electrical elements connected in parallel between them, have improved performance if the power supply is connected to one conductor at the near end and to the other conductor at the far end. Particularly useful devices are heaters, e.g. PTC conductive polymer heaters. The power supply is connected to the far end of the device through a connection means whose electrical properties can be correlated with those of the device in order to obtain a wide range of useful results. For example the connection means can have PTC, NTC or ZTC character and can be a simple conductor or another elongate device. The power supply can be DC or single-phase, two-phase or three-phase AC.

Abstract: An electrical system which comprises (1) a temperature-sensitive device comprising a PTC or NTC element, (2) a load in series with the temperature-sensitive device and (3) a control device in parallel with the load and the temperature-sensitive device. The control device is a device whose resistance can be changed from a high value (which may be infinite) to a low value or vice versa, by a change in the electrical or physical environment thereof, e.g. a diode, triac, thyristor, PTC device or NTC device. The system is connected to a power supply so that, under normal conditions of operation, either (a) the temperature-sensitive device has a low resistance and the control device has a high resistance, whereby the load is activated, or (b) the temperature-sensitive device has a high resistance and the control device has a low resistance, whereby the load is isolated. By an appropriate change in the power source, e.g. its size or direction, or in the physical environment of the control device, e.g.

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.

Abstract: Circuit protection devices comprise a PTC conductive polymer element and means for minimizing the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped. An enclosure encloses, but is spaced apart from, the PTC element. In one embodiment at least part of the interior surface of the enclosure is composed of polytetrafluoroethylene, a ceramic or another material which discourages the formation of permanent low resistance paths through carbonaceous material lying on its surface. In another embodiment the enclosure has a large internal surface area compared to the volume of the PTC element. In further embodiments, electrical leads are connected to and pass through the enclosure, and at least one of the leads is insulated along its length and/or the leads pass through opposite ends of the enclosure.

Abstract: Laminar heaters comprise a laminar heating element sandwiched between two laminar electrodes having substantial electrical resistance along the thickness thereof. The heater has a heating area of irregular shape, and at least one of the electrodes extends over a connection area in which heat is not generated but which provides a shorter and/or more uniform current path to the heat-generating parts of the heater.

Abstract: Circuit protection devices comprise a PTC conductive polymer element and means for minimizing the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped. An enclosure encloses, but is spaced apart from, the PTC element. In one embodiment at least part of the interior surface of the enclosure is composed of polytetrafluoroethylene, a ceramic or another material which discourages the formation of permanent low resistance paths through carbonaceous material lying on its surface. In another embodiment the enclosure has a large internal surface area compared to the volume of the PTC element. In further embodiments, electrical leads are connected to and pass through the enclosure, and at least one of the leads is insulated along its length and/or the leads pass through opposite ends of the enclosure.

Abstract: A PTC heater assembly comprises at least one PTC heater surrounded by an envelope of high thermal conductivity, thus greatly increasing the power output of the heater under operating conditions. In a preferred assembly a strip heater, comprising (i) an elongate strip of a conductive polymer PTC composition, (ii) electrodes embedded in said strip, and (iii) an insulating jacket, is sandwiched between a pair of metal, e.g. aluminum, sheets.

Abstract: 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.

Abstract: A self-regulating heating article comprising a layer of material exhibiting a positive temperature coefficient of resistance (PTC) and said PTC layer having at least partially contiguous therewith at least one layer of constant wattage output material. The article operates such that when connected to an electric power source, the current flows through at least a portion of the thickness of the PTC layer and of the constant wattage layer. In a preferred embodiment, upon heating the article, a change in dimensions as well as activation of an adhesive occurs.

Abstract: Circuit protection devices comprise a PTC conductive polymer element and means for minimizing the adverse effects of carbonaceous dust evolved by the PTC element when it is tripped. An enclosure encloses, but is spaced apart from, the PTC element. In one embodiment at least part of the interior surface of the enclosure is composed of polytetrafluoroethylene, a ceramic or another material which discourages the formation of permanent low resistance paths through carbonaceous material lying on its surface. In another embodiment the enclosure has a large internal surface area compared to the volume of the PTC element. In further embodiments, electrical leads are connected to and pass through the enclosure, and at least one of the leads is insulated along its length and/or the leads pass through opposite ends of the enclosure.

Abstract: The high temperature aging of polyamides is substantially improved by incorporating therein an antioxidant and an oxide of a metal of Group II or III of the Periodic Table, preferably a crystalline aluminosilicate such as a synthetic zeolite. The amount of antioxidant is preferably 1 to 5% and the amount of metal oxide is preferably 0.5 to 5%. Polyamides which can be stabilized in this way include Nylon-6, Nylon-11 and Nylon-12.

Abstract: Termination apparatus for elongate heaters which have an outer metal sheath and which are designed for use in hazardous environments. The apparatus comprises a junction box within which the heater is terminated and which has an entry port through which the heater enters the junction box. Secured to the entry port is a connection member comprising first and second compression members which surround a heater passing through the entry port and which define between them a chamber. Within the chamber is a grommet which is composed of lead or another deformable metal. The compression members can be drawn together, thus reducing the size of the chamber between them and deforming the grommet into close conformity with the metal sheath of the heater. In this way, if flames are generated within the junction box, they cannot ignite explosive gases surrounding the junction box.

Abstract: A device for maintaining physical separation between electrical conductors of a cable passing through a connector and for facilitating encapsulation of the conductors in a connector body. The device comprises an insulating platform having a configuration for engaging the connector body, the platform having (1) at least one passageway for passage of a conductor; (2) at least one aperture through which an encapsulant can be dispensed; and (3) at least one opening for allowing air to be voided during an encapsulation process; the platform forming with the connector body a hollow chamber through which at least one conductor passes and into which encapsulant can be dispensed through the aperture. The device further comprises a spline that extends from the platform for locating the device within the connector body; the spline comprising a step portion for resting on the cable and for defining a predetermined separation distance between the cable and the platform.

Abstract: Novel conductive polymer compositions which exhibit useful PTC behavior are produced by cross-linking processes. By correlating the polymer, the conductive filler dispersed therein, and the cross-linking conditions, PTC compositions having desired resistance/temperature characteristics can be prepared. In particular the cross-linking can be carried out so as to provide compositions having a switching temperature around the cross-linking temperature. The invention is applicable to both elastomeric and thermoplastic polymers, and provides for the first time a method of making PTC compositions exhibiting useful PTC behavior from elastomers.

Abstract: Polymeric compositions comprising 5-60%, preferably 12 to 40%, of a thermoplastic olefin polymer, 1-10%, preferably 2 to 6%, of a siloxane polymer and 30-94%, preferably 58 to 86%, of an elastomer. The olefin polymer can be polyethylene or a polar ethylene copolymer. The siloxane polymer can contain polycarbonate blocks. The elastomer can be an amorphous polyamide of low crystallinity, a thermoplastic elastomer, an ionomer, or a styrene/butadiene copolymer. The compositions are particularly useful in the medical field, for example in the form of tubing.

Abstract: Electrical insulation comprises (1) an inner layer of a cross-linked polymer, e.g. polyethylene, an ethylene/tetrafluoroethylene copolymer, an ethylene/chlorotrifluoroethylene polymer or a vinylidene fluoride polymer, and (2) an outer layer of an aromatic polymer having a glass transition temperature of at least 100.degree. C., e.g. a polyether ether ketone, a polyether ketone or a polyether sulfone. Such insulation combines excellent properties under normal service conditions with low smoke evolution on burning, and is therefore particularly useful for aircraft wire and cable.