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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 t

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.

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1. A self-regulating electrical device which comprises (a) at least one PTC layer composed of a PTC material which exhibit PTC behavior with an anomaly temperature T s ; (b) at least one CW layer composed of a CW material which exhibits substantially CW behavior at T s and below, at least a part

1. A self-regulating electrical device which comprises (a) at least one PTC layer composed of a PTC material which exhibit PTC behavior with an anomaly temperature T s ; (b) at least one CW layer composed of a CW material which exhibits substantially CW behavior at T s and below, at least a part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer; and (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device; said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state; the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion and more than 50% of the heat output of the device being generated in said at least one CW layer when the device is connected to a source of electrical power at ambient temperature; subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer. 2. A device according to claim 1 wherein the ratio of the resistivity at 25° C. of the PTC material to the resistivity at 25° C. of the CW material is from 0.1 to 20. 3. A device according to claim 2 wherein said ratio is from 1 to 10. 4. A device according to claim 1 which comprises at least one CW layer composed of a material having a resistivity of more than 1 ohm.cm. 5. A device according to claim 1 wherein at least one of the PTC and CW layers is of substantially annular cross-section and surrounds an electrode which is in the form of a strip or wire. 6. A device according to claim 1 wherein at least one of the electrodes is surrounded by a PTC layer and (b) said PTC layer and the electrodes are surrounded by a CW layer. 7. A device according to claim 1 wherein (a) the PTC and CW layers have coextensive substantially planar surfaces; and (b) each of the electrodes has a continuous or foraminous planar surface which is at least coextensive with the PTC and CW layers. 8. A device according to claim 1 which comprises first and second CW layers and a PTC layer between the CW layers, and at least at some stage during said conversion of the device from its ambient temperature state to its high temperature state, current flowing between the electrodes passes sequentially through the first CW layer, the PTC layer and the second CW layer. 9. A device according to claim 1 which comprises (a) a first substantially planar CW layer having a first electrode in electrical contact therewith; (b) a second substantially planar CW layer having a second electrode in electrical contact therewith; and (c) a PTC layer in electrical and physical contact with the first and second CW layers; at least one of said first and second electrodes physically extending over a part only of the CW layer which it contacts; whereby, at least at some stage in said conversion of the device from its ambient temperature state to its high temperature equilibrium state, current flows along at least one of the CW layers in the thickness thereof. 10. A device according to claim 1 wherein each PTC layer is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 11. A device according to claim 1 wherein each of the PTC and CW layers is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 12. A device according to claim 1 which has an effective T s which is higher than the T s of the PTC material. 13. A device according to claim 1 which comprises at least one heat-recoverable member which can be recovered by connecting the device to a suitable source of power. 14. A device according to claim 13 wherein at least one of the PTC and CW layers is composed of a heat-shrinkable conductive polymer composition. 15. A device according to claim 1 which comprises a heat-responsive material which undergoes a desired change when the device is connected to a suitable source of electrical power. 16. A self-regulating electrical device which comrises (a) at least one PTC layer composed of a PTC material which has a resistivity at 75° F. of e 1 ohm.cm and which exhibits PTC behavior with an anomaly temperature T s ; (b) at least one CW layer composed of a CW material which has a resistivity at 75° F. of e 2 ohm.cm, where e 1 /e 2 is from 0.1 to 20, and which exhibits substantially CW behavior at T s and below, at least part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer; and (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device; said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state; the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion; subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer. 17. A device according to claim 16 wherein e 1 /e 2 is from 1 to 10. 18. A device according to claim 17 which comprises at least one CW layer composed of a material having a resistivity of more than 1 ohm.cm. 19. A device according to claim 17 wherein at least one of the PTC and CW layers is of substantially annular cross-section and surrounds an electrode which is in the form of a strip or wire. 20. A device according to claim 17 wherein (a) at least one of the electrodes is surrounded by a PTC layer and (b) said PTC layer and the electrodes are surrounded by a CW layer. 21. A device according to claim 17 wherein (a) the PTC and CW layers have coextensive substantially planar surfaces; and (b) each of the electrodes has a continuous or foraminous planar surface which is at least coextensive with the PTC and CW layers. 22. A device according to claim 17 which comprises first and second CW layers and a PTC layer between the CW layers, and at least at some stage during said conversion of the device from its ambient temperature state to its high temperature state, current flowing between the electrodes passes sequentially through the first CW layer, the PTC layer and the second CW layer. 23. A device according to claim 17 which comprises (a) a first substantially planar CW layer having a first electrode in electrical contact therewith; (b) a second substantially planar CW layer having a second electrode in electrical contact therewith; and (c) a PTC layer in electrical and physical contact with the first and second CW layers; at least one of said first and second electrodes physically extending over a part only of the CW layer which it contacts; whereby, at least at some stage in said conversion of the device from its ambient temperature state to its high temperature equilibrium state, current flows along at least one of the CW layers in the thickness thereof. 24. A device according to claim 17 wherein each PTC layer is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 25. A device according to claim 17 wherein each of the PTC and CW layers is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 26. A device according to claim 17 which has an effective T s which is higher than the T s of the PTC material. 27. A device according to claim 17 which comprises at least one heat-recoverable member which can be recovered by connecting the device to a suitable source of power. 28. A device according to claim 27 wherein at least one of the PTC and CW layers is composed of a heat-shrinkable conductive polymer composition. 29. A device according to claim 17 which comprises a heat-responsive material which undergoes a desired change when the device is connected to a suitable source of electrical power. 30. A self-regulating electrical device which comprises (a) at least one PTC layer composed of a PTC material which exhibits PTC behavior with an anomaly temperature T s ; (b) at least one CW layer composed of a CW material which has a resistivity at 25° C. of more than 1 ohm.cm and which exhibits CW behavior at T s and below, at least a part of a surface of the CW layer being in direct electrical and physical contact with at least a part of a surface of the PTC layer; and (c) at least two electrodes which can be connected to a source of electrical power to cause electrical current to flow through the device; said device, when said electrodes are connected at ambient temperature to a suitable source of electrical power, undergoing conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in a high temperature high resistance state; the electrical current flowing across the interface between the PTC layer and the CW layer at least at some stage during said conversion; subject to the proviso that if there are electrodes of opposite polarity which are in direct physical and electrical contact with the same PTC layer, the electrodes are embedded in and surrounded by the PTC layer, and the CW layer substantially surrounds the PTC layer. 31. A device according to claim 30 wherein at least one of the PTC and CW layers is of substantially annular cross-section and surrounds an electrode which is in the form of a strip or wire. 32. A device according to claim 30 wherein (a) at least one of the electrodes is surrounded by a PTC layer and (b) said PTC layer and the electrodes are surrounded by a CW layer. 33. A device according to claim 30 wherein (a) the PTC and CW layers have coextensive substantially planar surfaces; and (b) each of the electrodes has a continuous or foraminous planar surface which is at least coextensive with the PTC and CW layers. 34. A device according to claim 30 which comprises first and second CW layers and a PTC layer between the CW layers and at least at some stage during said conversion of the device from its ambient temperature state to its high temperature state, current flowing between the electrodes passes sequentially through the first CW layer, the PTC layer and the second CW layer. 35. A device according to claim 30 which comprises (a) a first substantially planar CW layer having a first electrode in electrical contact therewith; (b) a second substantially planar CW layer having a second electrode in electrical contact therewith and (c) a PTC layer in electrical and physical contact with the first and second CW layers; at least one of said first and second electrodes physically extending over a part only of the CW layer which it contacts; whereby, at least at some stage in said conversion of the device from its ambient temperature state to its high temperature equilibrium state, current flows along at least one of the CW layers in the thickness thereof. 36. A device according to claim 30 wherein each PTC layer is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 37. A device according to claim 30 wherein each of the PTC and CW layers is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 38. A device according to claim 30 which has an effective T s which is higher than the T s of the PTC material. 39. A device according to claim 30 which comprises at least one heat-recoverable member which can be recovered by connecting the device to a suitable source of power. 40. A device according to claim 39 wherein at least one of the PTC and CW layers is composed of a heat-shrinkable conductive polymer composition. 41. A device according to claim 30 which comprises a heat-responsive material which undergoes a desired change when the device is connected to a suitable source of electrical power. 42. A self-regulating electrical device which comprises (a) a laminar PTC layer composed of a PTC material which exhibits PTC behavior with an anomaly temperature T s ; (b) a first laminar CW layer composed of a CW material which exhibits CW behavior at T s and below; (c) a first electrode in physical and electrical contact with the first CW layer; (d) a second laminar CW layer composed of a CW material which exhibits CW behavior at T s and below; and (e) a second electrode in physical and electrical contact with the second CW layer; each of said CW layers being in direct physical and electrical contact with said PTC layer; said electrodes being connectable to a source of electrical power to cause electrical current to flow through the device; and at least one of the electrodes physically extending over a part only of the CW layer which it contacts, whereby, when said device is connected at ambient temperature to a suitable source of electrical power, it undergoes conversion from an ambient temperature state to a high temperature equilibrium state in which (a) the device generates heat by resistive heating at the same rate as it dissipates heat to its surroundings and (b) the PTC element is in its high temperature high resistance state; the electrical current flowing across the interfaces between the PTC layer and the CW layers at least at some stage during said conversion; and at least at some stage in said conversion, current flows along at least one of the CW layers in the thickness thereof. 43. A device according to claim 42 wherein each PTC layer is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 44. A device according to claim 42 wherein each of the PTC and CW layers is composed of a conductive polymer composition comprising a particulate conductive filler dispersed in an organic polymer. 45. A device according to claim 42 which has an effective T s which is higher than the T s of the PTC material. 46. A device according to claim 42 which comprises at least one heat-recoverable member which can be recovered by connecting the device to a suitable source of power. 47. A device according to claim 42 which comprises a heat-responsive material which undergoes a desired change when the device is connected to a suitable source of electrical power.