A flexible sheet of positive temperature coefficient (PTC) material formed of a polymer resin and a conductive filler, the sheet of PTC material having a thickness in a range of 10 μm to 100 μm. A method for forming the flexible sheet of positive temperature coefficient material may include preparing a PTC ink from a polymer resin, a conductive filler, and a solvent, applying the PTC ink to a substrate, pulling a blade over the PTC ink to create a uniformly thick layer of the PTC ink on the substrate, and allowing the PTC ink to dry so that the solvent evaporates and leaves a solid layer of PTC material on the substrate.

A radial-leaded over-current protection device comprises a PTC element, a first electrode lead, a second electrode lead and an electrically insulating encapsulation layer. The PTC element comprises a first conductive layer, a second conductive layer and a PTC material layer laminated therebetween. The PTC material layer comprises crystalline polymer and conductive filler dispersed therein. The first electrode lead has an end connecting to the first conductive layer, whereas the second electrode lead has an end connecting to the second conductive layer. The electrically insulating encapsulation layer includes a fluorine-containing polymer, and wraps around an entire outer surface of the PTC element and the ends of the first and second electrodes connecting to the PTC element. The electrically insulating encapsulation layer has a thickness of 10.sup.2˜10.sup.5 nm, and the radial-leaded over-current protection device has an initial resistance R.sub.bf of 0.0017˜0.0027Ω.

A radial-leaded over-current protection device comprises a PTC element, a first electrode lead, a second electrode lead and an electrically insulating encapsulation layer. The PTC element comprises a first conductive layer, a second conductive layer and a PTC material layer laminated therebetween. The PTC material layer comprises crystalline polymer and conductive filler dispersed therein. The first electrode lead has an end connecting to the first conductive layer, whereas the second electrode lead has an end connecting to the second conductive layer. The electrically insulating encapsulation layer includes a fluorine-containing polymer, and wraps around an entire outer surface of the PTC element and the ends of the first and second electrodes connecting to the PTC element. The electrically insulating encapsulation layer has a thickness of 10.sup.2˜10.sup.5 nm, and the radial-leaded over-current protection device has an initial resistance R.sub.bf of 0.0017˜0.0027Ω.

An over-current protection device comprises first and second electrode layers and a PTC material layer laminated therebetween. The PTC material layer comprises a polymer matrix and carbon black. The polymer matrix comprises a fluoropolymer having a melting point higher than 150° C. The carbon black is dispersed in the polymer matrix. A resistance jump R.sub.jump_1000@16V/50A of the over-current protection device at 16V/50 A by 1000 cycles is 0.80-1.20. A resistance jump R.sub.1000@16V/50A of the over-current protection device at 25V/50 A by 1000 cycles is 0.90-1.30.

The invention relates to a PTC heating element (1). The PTC heating element (1) comprises a block-shaped PTC thermistor (2) having two contact surfaces (4a, 4b) and two electrically conductive contact plates (3a, 3b). The PTC thermistor (2) is arranged between the contact plates (3a, 3b) and facing the contact plates (3a, 3b) with the contact surfaces (4a, 4b). An adhesion-promoting electrically conductive bonding layer (6a, 6b) each is arranged between the contact surface (4a, 4b) and the contact plate (3a, 3b). The PTC thermistor (2) is firmly connected to the respective contact plates (3a, 3b) by means of the respective bonding layers (6a, 6b) and electrically conductively contacted.

The adhesion-promoting electrically conductive bonding layer (6a, 6b) according to the invention comprises silicone or consists thereof.

An over-current protection device comprises first and second electrode layers and a PTC material layer laminated therebetween. The PTC material layer comprises a polymer matrix and carbon black. The polymer matrix comprises a fluoropolymer having a melting point higher than 150° C. The carbon black is dispersed in the polymer matrix. A resistance jump R.sub.jump_1000@16V/50A of the over-current protection device at 16V/50 A by 1000 cycles is 0.80-1.20. A resistance jump R.sub.jump_1000@25V/50A of the over-current protection device at 25V/50 A by 1000 cycles is 0.90-1.30.

A method for manufacturing a sheet of positive temperature coefficient (PTC) material includes providing a PTC material, grinding the PTC material into a powder, and inserting the ground PTC material into a press. The ground PTC material is compressed within the press until the PTC material defines a planar shape. The PTC material is then removed from the press to thereby provide a PTC sheet.

A PTC circuit protection device includes a PTC element and two electrodes attached to the PTC element. The PTC element includes a polymer matrix and a particulate conductive filler dispersed in the polymer matrix. The polymer matrix is made from a hetero-phase rheological polymer composition that contains first, second and third polyolefin components, the first, second and third polyolefin components being co-melted together and then solidified to form the polymer matrix. The first polyolefin component has a melt flow rate ranging from 0.1 to 2.5 g/10 min, the second polyolefin component has a melt flow rate ranging from 20 to 30 g/10 min, and the third polyolefin component has a melt flow rate of less than 0.00001 g/10 min measured under a temperature of 190° C. and a load of 2.16 Kg.

The present invention relates to a positive temperature coefficient composition comprising a semi-crystalline material, at least one binder, from 0.5 to 9.5% by weight of an electronically conductive material and a solvent. Furthermore, the present invention relates to use of a positive temperature coefficient composition according to the present invention in heating elements and sensors. A positive temperature coefficient composition according to the present invention provides low and stable resistance till self-regulating temperature, which allows fast heating of the heating element. Furthermore, the positive temperature coefficient composition according to the present invention has high PTC ration and therefore, has higher safety and more power can be applied to the heating element.

There is provided a temperature sensor element including a pair of electrodes and a temperature-sensitive film disposed in contact with the pair of electrodes, in which the temperature-sensitive film includes a matrix resin and a plurality of conductive domains contained in the matrix resin, the conductive domains include a conjugated polymer and a dopant, and the number of structural units constituting the conjugated polymer is 65 or less.