Abstract: Electrical devices which comprise at least one metal electrode and a conductive polymer element in contact therewith, wherein the metal surface which contacts the conductive polymer has a roughened or otherwise treated surface to improve its adhesion to the conductive polymer. The metal electrode is preferably an electrodeposited foil. The conductive polymer preferably exhibits PTC behavior. The devices include heaters and circuit protection devices. The improved adhesion results in improved physical and electrical stability, and broadens the range of conductive polymer compositions which can be used in a number of important applications.

Abstract: An assembly which comprises a heat-recoverable article which is adapted to join substrates together and a plug which is in a recess of the article. The plug comprises a first polymer, e.g. nylon, which is opaque at room temperature and transparent at an elevated temperature, and preferably comprises a colored portion beneath the first polymer. When the article is connected to a power supply, it heats and recovers. At the recovery temperature of the substrate, the nylon melts and the colored portion becomes visible, thus indicating to an operator that the article should be disconnected from the power supply.

Abstract: Circuit protection devices which contain PTC conductive polymer elements and which are used in situations in which the device is mounted onto, or itself comprises, a rigid wall which is spaced apart from the PTC element and through which the electrodes pass. The behavior of the device can be adversely affected if the electrodes, which are prevented from moving by the rigid wall, prevent the PTC element from expanding to the extent necessary to provide the desired PTC effect. The invention includes the use of specially designed electrodes which lessen the danger that the PTC element, when it is tripped, is prevented from expanding to the extent necessary for effective operation.

Abstract: Methods, apparatus and articles for systems comprising optical fibers, in particular for feeding an optical signal into an optical fiber through the buffer thereof and for withdrawing an optical signal from an optical fiber through the buffer thereof. Preferably this is achieved with the aid of an optical coupling means which contacts and conforms to the surface of the buffer at a bent portion of the fiber. The coupling means can for example be a resiliently deformable material such as a polysiloxane. In a preferred aspect, the invention provides an apparatus and method for axially aligning, and preferably joining, the ends of optical fibers. The apparatus comprises means for holding two fibers so that the fiber ends are approximately abutting and axially aligned, adjacent means for passing an optical signal into one of the fibers through the buffer thereof, and adjacent means for withdrawing that signal from the other fiber through the buffer thereof.

Abstract: Polymer compositions comprising a segmented urethane block polymer and an elastomer having a glass transition temperature between -40.degree. and +15.degree. C. possess a good combination of properties, including relatively high damping and modulus values. Radiation cross-linked tubing prepared from these compositions finds application in the jacketing of marine sonar detection arrays comprising hydrophones.

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.

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: A monitoring system that may be employed with elongate heater units to provide information about a measurable parameter, for example the temperature of a heated substrate. The monitoring system may include many heater units and associated transmitter-receiver assemblies. The heater units as well as the assemblies can all be of the same kind. The many heater units and assemblies can be connected to a common power supply and the monitoring system can correlate the information provided by a particular receiver with a particular heater unit.

Abstract: Apparatus and method for monitoring a self-regulating heater comprising a PTC conductive polymer while it is being powered by a power supply signal. The apparatus is connected to a power supply and to the heater, the heater then producing a heater signal which is fed to a comparator. The comparator deterines the phasal relationship between the power supply signal and the heater signal and indicates when the signals are out of phase by a predetermined magnitude.

Abstract: A method and apparatus for converting a fluid tracing system, e.g., a thermally insulated steam heat tracing system for a substrate, into an electrical heat tracing system for the substrate. A typical steam tracing system includes a substrate to be heated; an interconnecting system of steam tracing tubes adjacent to and in thermal contact with the substrate; and thermal insulation surrounding the substrate and steam tracing tubes. The conversion method includes the steps of removing the thermal insulation at spaced-apart locations and opening up the plurality of interconnected tubes so that elongate electrical heating elements can be inserted into the tubes, inserting elongate electrical heating elements into the tubes, and connecting the elongate electrical heating elements to a power supply in order to heat the substrate. Preferably, a gel-forming liquid is introduced into the elongate tubes and is converted into a gel within the tubes.

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: 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: 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.

Abstract: Apparatus for heating and filtering diesel fuel in which incoming diesel fuel is passed in a heat-exchange relationship with already heated and filtered diesel fuel, is further heated by either an electric heater or by other means, is passed through a filter, and then is passed in a regenerative heat-exchange relationship with the incoming diesel fuel.

Abstract: Circuit protection devices which have a PTC conductive polymer element and an enclosure which is spaced apart from the PTC element and at least a part of whose interior surface is composed of a material which has an oxygen index of at least 70 and has a thermoset polymer, preferably an alkyd resin, and a filler, such as alumina trihydrate, which, when heated in the absence of air, decomposes to give a gaseous by-product.

Abstract: Circuit protection devices which comprise a PTC conductive polymer element and an enclosure, and which are less likely to cause damage to other electrical components through release of carbonaceous dust. On the interior surface of the enclosure, there is a projection or other disconformity which is spaced apart from the electrodes and which provides a site for arc initiation. In this way, the danger of erosion creating a hole in the enclosure is reduced. Preferably each of the electrodes is surrounded by a projection.

Abstract: A heater comprising a pair of flexible elongate parallel conductors which are connectable to a power supply, and a plurality of rigid heating modules connected in parallel with each other between the conductors. Each of the heating modules comprises a resistive heating component which has been deposited on the substrate and which generates heat when the conductors are connected to a suitable power supply. The heating component may have a positive temperature coefficient of resistance or substantially zero temperature coefficient of resistance.

Abstract: An apparatus and method for protection of a substrate, e.g. an electrical contact. The apparatus comprises a support member and an encapsulant which has a cone penetration value of 100 to 350 (10.sup.-1 mm) and an ultimate elongation of at least 200%, and preferably an elastic modulus of less than 10.sup.7 dynes/cm.sup.2. The encapsulant and the substrate are pressed together so that the encapsulant is deformed into close and conforming contact with the substrate. Preferably at least part of the deformation is elastic deformation.

Abstract: An assembly comprising a flexible corrugated metal tube and an elongate resistive heating element that is within the tube and which can be connected to a power supply to provide an elongate electrical heater. The tube has a wall thickness less than 0.012 inch, a corrugation depth greater than 0.030 inches and a distance between corresponding points in adjacent corrugations from 0.02 inch to 0.75 inch. The corrugations extend around the entire periphery of the tube.

Abstract: Melt-shapeable polymeric compositions comprising a first fluoropolymer of relatively low crystallinity, e.g. a copolymer of tetrafluoroethylene and a perfluorinated comonomer, and a second fluoropolymer of relatively high crystallinity, especially a fluoropolymer obtained by irradiating PTFE or another fluoropolymer which cannot be melt-shaped in the absence of other polymers. The weight ratio of the first to the second polymer is preferably 0.3:1 to 2.5:1. The compositions have a wide variety of uses, for example as insulating materials or, if they contain carbon black or another conductive filler, as PTC conductive polymers.