Abstract: A method of joining, repairing or reinforcing substrates, particularly polymeric pipes for transporting fluids, e.g. natural gas and water. The method makes use of an article, preferably a heat-recoverable article, which comprises a conductive polymer composition and which is heated to its recovery temperature by passing electrical current through the conductive polymer. Preferably the article is a heat-shrinkable coupler. The coupler may make direct contact with and fuse to the pipes, or there may be an insert between the coupler and the pipes. The article preferably comprises carbon blank dispersed in either a sintered polymer, particularly ultra high molecular weight polyethylene or a very high molecular weight polymer, particularly polyethylene having a molecular weight greater than 150,000.

Abstract: Conductive polymer compositions based on polyvinylidene fluoride have improved properties when the polyvinylidene fluoride has a very regular structure which can be characterized by a low head-to-head content in the repeating units. The improved properties include electrical stability when contacted by organic fluids and/or when maintained at elevated temperatures in air. Such compositions which exhibit PTC behavior are particularly useful in the form of self-limiting heaters which are immersed in organic fluids, especially flexible strip heaters for heating diesel fuel before it passes through a fuel filter.

Abstract: Detection of events, e.g. liquid leaks and other changes in varibles. The event causes two conductors to become electrically connected, and thus creating a system in which the connection point can be located by measuring the potential drop from one end of one of the conductors (called the locating member) to the connection point. Preferably a fixed current flows through the connection, so that the result is independent of the resistance of the connection. The locating member can be a continuous resistive wire, preferably coated with a conductive polymer; such a locating member can form part of a sensor cable in which the elongate components of the circuit are in a wrapped configuration, or part of a cable in which the conductors are separated by a member shaped to prevent capillary action of a liquid from connecting the conductors. Alternatively the locating member comprises a plurality of discrete resistors.

Abstract: A tubular heat recoverable article comprises electrically conductive polymeric material and can be recovered by passing an electric current therethrough. The article comprises two or more elongate electrodes extending at least part way along the article. One or more of the electrodes are interrupted so that separate lengths of the article can be connected to an electrical power source and heated and or recovered independently.

Abstract: An electrical connector for an electrical lead which has a first conductor and a second conductor. The connector has a first component, a conductor-receiving member, into which the conductors are inserted, and second component, a conductor-connecting member. The conductor-receiving member and the conductor-connecting member are movable relative to one another between a unique mated configuration and a plurality of demated configurations. The conductor-receiving member is preferably transparent in order to visually determine the correct positioning of the conductors.

Abstract: An electrical plug for connecting the first and second conductors of an electrical lead to an electrical power outlet. The plug is designed to contain a fuse. When the plug is connected to the power outlet and the fuse makes a proper electrical connection, a signal member provides a signal.

Abstract: A heat recoverable article comprising a conductive polymeric material with particular electrical properties. Preferably, when expanded from X% to Y% to render it recoverable the resistivity of the composition decreases on expansion in at least part of the X-Y expansion range. Preferably the composition exhibits a pseudo PTC ratio (peak resistivity/resistivity at 25.degree. C.) in the range 11/2-10. Preferably the composition has a resistivity which increases on recovery as measured in the direction of current flow, throughout the temperature range 20.degree. C. to T.sub.e (extrapolated end temperature). The article is preferably tubular, and the electrtical behaviour allows it to be conveniently electroded with elongate electrodes, while avoiding overheating during recovery.

Abstract: A blanket for covering a child in a car seat fitted with a harness for restraining the child in the seat. The blanket comprises a plurality of apertures through which restraining members of the harness can be passed, thus enabling the harness to be fastened tightly around the child, and the blanket then to be wrapped around the child and the harness.

Abstract: Methods of preventing corrosion in which current flows between the to-be-protected substrate and a distributed electrode whose electrochemically active surface is provided by an element which is composed of a conductive polymer and which is at least 500 microns thick. In one embodiment, the electrode is a flexible strip comprising a highly conductive core. e.g. of copper, and a conductive polymer element surrounding the core. In another embodiment, the electrode is a conductive polymer layer which conforms to the surface of the substrate but is separated from it by a layer of insulation.

Abstract: A device assembly in which a plurality of PTC circuit protection devices are connected in series. Assemblies of this type are useful in providing protection under voltage conditions which would be unsafe for an individual protection device. In a preferred system the device assembly is connected in series with a circuit breaker.

Abstract: Electrodes for electrochemical processes, especially anodes for the cathodic protection of metal substrates, e.g. reinforcing bars in concrete, comprise a conductive core which acts as a current-distributing member, an outer member which provides an electrochemically active outer surface, and an intermediate member composed of a material which is of higher resistivity, and/or which is less electrochemically active, than the material of the outer member. The higher the resistivity of the intermediate member, the more regular the current distribution along the length of the electrode. When the intermediate member is less electrochemically active, this protects the core from corrosion if the outer member is damaged by physical means or through electrochemical erosion. Preferably at least one of the intermediate member and the outer member is composed of a conductive polymer, especially one comprising carbon black or graphite as conductive filler.

Abstract: Self-regulating articles, particularly heaters, containing two spaced-apart elongate electrodes which are joined together by a melt-extruded element composed of a conductive polymer. The conductive polymer is a dispersion of carbon black in a crystalline polymer, has a resistivity at room temperature of R ohm-cm, and contains L % by weight of carbon black, L being not greater than about 15, and L and R being such that2L+5 log.sub.10 R.ltoreq.45.

Abstract: Conductive polymer PTC compositions have improved properties, especially at voltage of 200 volts or more, if they are very highly cross-linked by means of irradiation, for example to a dosage of at least 50 Mrads, preferably at least 80 Mrads, e.g. 120 to 600 Mrads. The cross-linked compositions are particularly useful in circuit protection devices and layered heaters.

Abstract: Conductive polymer PTC compositions have improved properties, especially at voltages of 200 volts or more, if they are very highly cross-linked by means of irradiation, for example to a dosage of at least 50 Mrads, preferably at least 80 Mrads, e.g. 120 to 600 Mrads. The cross-linked compositions are particularly useful in circuit protection device and layered heaters.

Abstract: A sealing strip, particularly for making a telecommunications splice case comprises a sintered ultra high molecular weight polyethylene strip that can weld together parts of, for example, a wrap-around sleeve.

Abstract: Conductive polymer compositions based on polyvinylidene fluoride have improved properties when the polyvinylidene fluoride has a very regular structure which can be characterized by a low head-to-head content in the repeating units. The improved properties include electrical stability when contacted by organic fluids and/or when maintained at elevated temperatures in air. Such compositions which exhibit PTC behavior are particularly useful in the form of self-limiting heaters which are immersed in organic fluids, especially flexible strip heaters for heating diesel fuel before it passes through a fuel filter.

Abstract: A coupler for joining polymeric pipes comprises a generally cylindrical radially heat-shrinkable member which is composed of a conductive polymer. To recover the coupler, current is passed axially through the coupler via electrodes. The coupler has a center portion of increased wall thickness and in this way, when there is a gap between the pipes, overheating of the center portion of the coupler is avoided.

Abstract: A detection and location system, e.g. for liquid leaks, comprising a trunk line sensor cable and a plurality of branch line cables at intermediate points of the trunk cable. Each of the cables comprises two insulated conductors and two non-insulated conductors, e.g. conductive polymer-coated wires, which become connected upon occurrence of a leak. In one embodiment, each of the insulated conductors in the trunk line is continuous and each of the non-insulated conductors is discontinuous at each intermediate point; the branch line conductors are respectively connected to the discontinuous ends of the non-insulated trunk line conductors, and are connected in pairs of one insulated and one non-insulated conductor at the end of each branch.

Abstract: A sensing assembly suitable for detecting both a first event which involves the presence of an electrolyte and a second event which does not involve the presence of an electrolyte, and for distinguishing between them. The assembly comprises a first conductor and a second conductor which is electrically insulated from the first conductor in the absence of both first and second events but becomes electrically connected to the first conductor by either an ionic connection in the presence of a first event or an electronic connection in the presence of a second event. The assembly also comprises a sensing apparatus of determining whether the connection is ionic or electronic. The assembly is useful for detecting leaks of hydrocarbons, e.g. gasoline, and water in storage tanks.

Abstract: Devices for detecting and obtaining information about an event, for example the presence of a liquid, which comprise (1) a swellable member which swells upon occurrence of the event and (2) a restraining member which, when the swellable member swells, restricts movement of the swellable member and thus causes the impedance of the device to change. In a preferred embodiment the device comprises two elongate conductors helically wrapped around a support core, a swellable, conductive polymer member surrounding the conductors. Occurrence of an event causes the swellable material to swell and form a conductive bridge between the conductors.