Polymer positive temperature coefficient body

Abstract

To provide a polymer positive temperature coefficient (PPTC) material which is suitable for applications such as resettable fuses, and provides a PPTC body realizing stable electrical operation without an abnormal trip below a trip temperature.SOLUTION: A PPCT component 100 is of a polymer positive temperature coefficient (PPTC) material and comprises: a polymer matrix 104 defining a PPTC body; a graphene filler component dispersed and arranged as microscopic sheets in the polymer matrix, where the graphene filler component 106 comprises a plurality of graphene particles aligned along a predetermined plane of the PPTC body 102; and a pair of opposing electrodes 108.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments relate to a polymer positive temperature coefficient body.

Background Art

[0002] Polymer positive temperature coefficient (PPTC) elements can be used as overcurrent protection devices or overheat protection devices, and current sensors or temperature sensors in various applications. In the case of polymer positive temperature coefficient materials, due to the thermal expansion of the polymer matrix containing a dispersed conductive material (filler) such as a conductive metal particle phase, a conductive carbon particle phase, or a ceramic conductive phase, the electrical resistance increases with an increase in temperature. At a trip temperature where the polymer matrix may undergo a phase transition such as a melting transition, if the volume of the polymer increases significantly accordingly, the conductive filler particles are separated from each other and the conductive path is broken, so the resistance can increase rapidly. When cooled, since the volume of the polymer shrinks, the resistivity of the PPTC material may return to a relatively low value below the trip temperature. Due to such behavior, PPTC materials are suitable for applications such as resettable fuses. Generally, the overall conductivity of PPTC materials and the increase in resistance with temperature depend on the content of the conductive filler. Here, in PPTC materials with a high resistivity (10 - 10000 Ω·cm), due to the low content of the conductive filler, the electrical resistance tends to increase significantly with an increase in temperature even below the trip temperature. When the resistance increases below the trip temperature, the I - R heating of the PPTC material increases, which may lead to abnormal trips of the PPTC element. Therefore, in useful applications where stable electrical operation below the trip temperature is required, known PPTC materials may not be very useful.

[0003] In view of this consideration and other considerations, the present disclosure is provided.

Summary of the Invention

[0004] In one embodiment, a polymer positive temperature coefficient (PPTC) material comprises a PPTC component including a polymer matrix defining a PPTC body and a graphene filler component disposed in the polymer matrix and including a plurality of graphene particles aligned along a predetermined plane of the PPTC body.

[0005] In another embodiment, a resistance heater can comprise a polymer positive temperature coefficient (PPTC) material disposed in a ring shape defining a heater body and an electrode assembly including two or more electrodes disposed to contact the heater body at two or more locations, wherein the PPTC material is a polymer matrix defining a PPTC body and a graphene filler component disposed in the polymer matrix and including a plurality of graphene sheets aligned along a plane of the heater body.

[0006] In another embodiment, a method of manufacturing a resistance heater comprises providing a polymer powder, mixing a graphene sheet component and / or a carbon nanotube component with the polymer powder to form a PPTC material, heating the PPTC material to form a hot melt, wherein the graphene sheet component is uniformly dispersed in a polymer matrix formed from the polymer powder, extruding the hot melt to form a PPTC sheet, laminating the PPTC sheet between an upper foil and a lower foil to form a PPTC body, and unitizing the PPTC body to form a PPTC resistance heater component.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, the present embodiment will be described in more detail with reference to the accompanying drawings showing exemplary embodiments. These embodiments should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and the scope of the embodiments will be fully conveyed to those skilled in the art. In the drawings, like numerals refer to like elements throughout.

[0027] In the following description and / or claims, the terms "on," "overlying," "disposed on," and "over" may be used. "On," "overlying," "disposed on," and "over" may be used to indicate that two or more elements are in physical direct contact with each other. Also, the terms "on," "overlying," "disposed on," and "over" may mean that two or more elements are not in direct contact with each other. For example, "over" may mean that one element is over another element but not in contact with each other, and there may be one or more other elements between these two elements. Further, the term "and / or" may mean "and," may mean "or," may mean "exclusive 'or,'" may mean "either," may mean "some but not all," may mean "neither," and / or may mean "both," but the scope of the claimed subject matter is not limited in this regard.

[0028] In various embodiments, a novel PPTC material is provided that includes a conductive filler having a nano-sized carbon filler material such as single-walled carbon nanotubes, multi-walled carbon nanotubes, or graphene. The PPTC material can include a polymer matrix such as polyethylene, a polyethylene copolymer, polyester, polyurethane, polyamide, a fluoropolymer resin, or a mixture of a fluoropolymer and another polymer. The PPTC material can include, in various non-limiting embodiments, antioxidants, dispersants, crosslinking agents, and arc suppressors, among others. As will be described in detail below, the advantages provided by the PPTC material of this embodiment are stable power over a temperature range from room temperature to the maximum use temperature, where the power variation can be less than 60%, for example, 50% - 60%, or, in some embodiments, less than 30%, for example, less than 20% - 30%.

[0029] Certain embodiments are based on a polymer positive temperature coefficient (PPTC) material formed from a graphene filler and a semi-crystalline polymer matrix. The stable resistance behavior provided by such PPTC materials enables new applications such as resistance heaters employing PPTC components. When the resistance behavior is stable, the heater power behavior, which is generally related to the trip temperature of the PPTC component, stabilizes according to the temperature below the melting point of the polymer matrix. Another advantage is uniform and effective heat transfer. Furthermore, since the resistivity and trip temperature can be adjusted by adjusting the type of polymer, the conductive filler, and the volume fraction of the conductive filler, the power consumption and the power limit temperature can be customized according to the application of the resistance heater.

[0030] In certain embodiments, the PPTC material can be arranged as a polymer matrix having a shape and size that define a PPTC body, according to the desired application. By way of example, the PPTC heater can be arranged as a planar heater including a ring-shaped heater or other suitable shape. The PPTC material also includes a graphene filler component disposed in the polymer matrix, where the graphene filler component is formed from a plurality of graphene sheets aligned along a predetermined plane of the PPTC body, such as the major plane of a ring-shaped PPTC component.

[0031] In some embodiments, the PPTC material can include a conductive filler formed of only the graphene filler, but in other embodiments, in addition to the graphene filler, a second conductive filler, such as a known carbon filler, can be added. FIG. 1 shows a PPTC component according to multiple embodiments of the present disclosure. The PPCT component 100 includes a PPTC body 102, which includes a polymer matrix 104 and a graphene filler 106 dispersed as micro-sheets within the polymer matrix 104. The PPTC component 100 further includes a pair of opposing electrodes shown as electrodes 108, and an external voltage can be applied to drive a current through the PPTC body 104 between these opposing electrodes. Non-limiting examples of polymers suitable for the polymer matrix 104 include semi-crystalline polymers such as polyethylene, polyvinylidene fluoride, ethylene tetrafluoroethylene, ethylene vinyl acetate, ethylene and acrylic acid copolymer, ethylene butyl acrylate copolymer, poly-perfluoroalkoxy.

[0032] The volume percentage of the polymer matrix in the PPTC body 102 can be in the range of 50 - 99% in some embodiments, and can be in the range of 60 - 95% in certain embodiments. In various non-limiting embodiments, the volume fraction of graphene can be in the range of 1% - 50%, and in certain embodiments, can be in the range of 4% - 30%. The graphene for the graphene filler 106 can be prepared by mechanical or chemical means, and the graphene particles are formed from graphene sheets where the number of graphene sheets in the particle is in the range of 1 to several hundreds according to various embodiments, and in certain embodiments, is in the range of 1 to about 30 layers. Thus, the graphene particles formed from several graphene sheets can also have a two-dimensional sheet-like shape. According to some embodiments, the size of the resulting graphene particles can be in the range of 0.1 μm - 100 μm, particularly in the range of 1 μm - 30 μm.

[0033] As background, graphene is a crystalline allotrope of carbon with two-dimensional properties. These carbon atoms are densely packed within graphene in a regular atomic-scale hexagonal pattern. Graphene has a high thermal conductivity in the range of 1500 - 2500 W / (m·K). In the embodiment of FIG. 1, the graphene filler is arranged as sheet-like particles, where the particles (meaning the plane of the sheet) are generally aligned along a predetermined plane of the PPTC body 104 (such as along the X-Y plane of the shown Cartesian coordinate system). The high thermal conductivity of the graphene filler 106 not only effectively enables heat transfer to the environment along the Z direction, but also enables uniform heat transfer in the X-Y plane. These thermal properties are particularly useful for heater applications. In addition, the graphene sheet has a low bulk electrical resistivity of 10 -6 Ω cm, and the most conductive metals have a bulk resistance close to 2×10 -6 Ω cm or more. Furthermore, due to the 2D structure of graphene, the semi-crystalline polymer in the polymer matrix 104 can contact both sides of the graphene particles, and as a result, when the polymer matrix 104 reaches its melting point, the PPTC material can respond to temperature in a synchronized manner.

[0034] Figure 2 shows another PPTC component 120 according to multiple embodiments of the present disclosure. In this example, the PPTC component 120 may be arranged generally in the same manner as the above-described PPTC component 100, and like components are labeled with the same reference numerals. The PPTC component 120 differs from the PPTC component 100 in that the PPTC body 112 further includes a conductive component 110, and the conductive component 110 may be a carbon filler and / or a ceramic conductive component arranged as a plurality of carbon particles or ceramic conductive particles (such as TiC or WC) in the polymer matrix 106. Therefore, the conductive component 110 can change the electrical characteristics of the PPTC component 120 with respect to the electrical characteristics of the PPTC component 100.

[0035] Figure 3 shows the resistance according to temperature for an exemplary PPTC material according to multiple embodiments of the present disclosure. In this case, these two different curves generally represent the behavior of two different PPTC materials as arranged in FIGS. 1 and 2, respectively. The lower curve corresponds to the PPTC component 100, and the upper curve corresponds to the PPTC component 120. In both examples, the resistance from room temperature to about 140°C - 150°C is relatively low and stable, but increases rapidly at the trip temperature of 170°C. In the case of a pure graphene component, the resistance increases to above 900 Ohm, and in the case of a PPTC component having graphene and a carbon filler, the resistance increases to above 24,000 Ohm. Note that in both examples, the low temperature resistance below the trip temperature is very stable.

[0036] FIG. 4 shows a schematic diagram of the processing of a PPTC component according to multiple embodiments of the present disclosure. To form a PPTC component suitable for applications such as heater applications, a PPTC material can be extruded by an extrusion device to form a layer or sheet of PPTC. Generally, a PPTC material 220, such as a mixture of a polymer material and graphene particles, may be added to a receptacle 202 coupled to an extrusion chamber 204, and the PPTC material 220 is mixed and heated by an extrusion component 206 and drawn to form a PPTC body 210 in the form of a sheet or layer.

[0037] FIG. 5 shows an exemplary process flow 302. In block 302, a polymer material, conductive powder, and optional additives are mixed. The polymer material can be a powder of a semi-crystalline polymer, while the conductive filler includes graphene particles and optionally may further include carbon particles and / or conductive ceramic particles. In block 304, a hot melt process is performed, and the mixed components such as the polymer and the conductive filler are heated to a temperature that melts the polymer and accordingly disperses the conductive filler particles more uniformly in the polymer matrix. In block 306, sheet extrusion is performed to form a sheet of the PPTC material, and the molten mixture of the polymer and the conductive filler is extruded to form a PPTC sheet or layer. In block 308, a conductive metal layer (foil) can be applied to the upper and lower surfaces of the extruded PPTC sheet to form a laminate. In block 310, one or more PPTC components are formed by singulating the laminate to form individual components including a PPTC body sandwiched between opposing electrodes. In some examples, the singulated PPTC body can have a ring shape such as a circular ring, rectangular ring, oval-shaped ring, elliptical ring, or polygonal ring. In block 312, the singulated PPTC body is assembled into a device such as a heater. For example, the singulated PPTC body can be attached to leads (wires) that are connected to these opposing electrodes to form a PPTC heater. Optionally, the heater can be incorporated into another structure such as a camera or another structure to be heated. In block 314, an insulating coating can be applied to encapsulate the components of the PPTC heater. For example, an insulating coating can be formed by electrophoretic deposition in a chemical solution bath, a parylene coating can be formed by CVD, or another insulating coating can be formed.

[0038] Referring now to FIGS. 6A and 6B, there are shown exemplary resistance and power curves as a function of temperature for an exemplary resistive heater according to embodiments of the present disclosure. The exemplary heater is formed from a PPTC material having a polymer matrix and a graphene filler. As shown in FIG. 6A, the resistance remains substantially unchanged from 25° C. to about 150° C., and then increases rapidly above 170° C. Conversely, the power consumption remains at 3.3 watts to 3 watts up to 100° C., gradually decreases to 1.8 W at 150° C., decreases more rapidly above 150° C., and is about 0.2 watts at 175° C., limiting the power near the melting point of the polymer.

[0039] FIGS. 7A and 7B show exemplary resistance and power curves as a function of temperature for another exemplary resistive heater according to embodiments of the present disclosure. The exemplary heater is formed from a PPTC material having a carbon filler and a polymer matrix in addition to a graphene filler. As shown in FIG. 7A, the resistance remains substantially unchanged from 25° C. to about 150° C., and then increases rapidly above 170° C. Conversely, the power consumption decreases from 3.3 watts to about 2.6 watts up to 100° C., and then decreases rapidly to near 0 watts at 170° C. The above results show how the heater characteristics can be adjusted by adding carbon to a graphene-based PPTC body.

[0040] In other embodiments of the present disclosure, the PPTC heater can be formed from a PPTC material having a filler formed from a carbon nanotube material such as a single-layer or multi-layer carbon nanotube material. FIGS. 7C and 7D show exemplary resistance and power curves as a function of temperature for another exemplary resistive heater according to embodiments of the present disclosure. The exemplary heater is formed from a PPTC material having a polymer matrix and a carbon nanotube filler. As shown in FIG. 7D, below 150° C., the power level is relatively stable compared to a carbon filler-based PTC heater as described below with respect to FIG. 9.

[0041] FIG. 8 shows exemplary power curves versus temperature for another exemplary resistive heater according to embodiments of the present disclosure. FIG. 8A shows an exemplary test circuit for measuring the electrical behavior of a PPTC device. In FIG. 8, two power curves are shown, one for when 16V is applied to the heater and the other for when 13.5V is applied to the heater. It is shown that when the voltage is higher, a higher power (3.4 watts compared to 2.4 watts) is driven. However, in both cases, the power is kept substantially constant between 20° C. and 140° C., and then decreases rapidly when exceeding 150° C., and reaches a power level of less than 1 watt when exceeding 170° C. The decrease in power after exceeding 150° C. reflects the trip of the PPTC heater, and since the resistance increases rapidly, the current and total power for a given applied voltage are limited. Thus, the heater element of the PPTC material in FIG. 8 functions to provide uniform power over a wide temperature range before decreasing to a limited power above the trip temperature.

[0042] For comparison, FIG. 9 shows power curves versus temperature for a reference heater based on a PPTC without graphene filler. FIG. 9 also shows two power curves, one for when 16V is applied to the heater and the other for when 13.5V is applied to the heater. It is shown that when the voltage is higher, a higher power (2.1 watts compared to 1.5 watts) is driven. However, in both cases, the power decreases continuously and substantially between 20° C. and 140° C., and reaches a power of almost zero watts when exceeding 150° C. Thus, such a resistive heater does not exhibit a stable power output over a useful temperature range, such as between room temperature and 150° C., below the trip temperature.

[0043] According to various embodiments of the present disclosure, a PPTC heater can be adapted for use in components such as cameras. In the following embodiments with reference to FIGS. 10A to 15B, a novel configuration of a PPTC resistive heater including the incorporation of the PPTC resistive heater into a camera is shown. According to various embodiments, the PPTC resistive heater may be based on a known PPTC material such as a carbon-filled polymer, as generally described in the foregoing embodiments, or may be based on a graphene-filled polymer. A PPTC heater based on a graphene-filled polymer may be particularly suitable for applications where stable current operation is required over a wide temperature range.

[0044] FIG. 10A shows a side view of an exemplary PPTC resistive heater 350 according to multiple embodiments of the present disclosure. The resistive heater 350 includes a PPTC resistive heater component 360 and an external wire 370. The resistive heater component can generally be arranged as described above with respect to the embodiments of FIGS. 1 and 2. The resistive heater component 360 can have a ring shape when viewed in plan view so as to be adjacent to the periphery of a component to be heated such as a camera. The arrows indicate the current path regarding the current flowing from the S-twisted wire 370 through the PPTC resistive heater component 360 and flowing out from the Z-twisted wire 370. FIGS. 10B and 10C show alternative variations of the resistive heater component 360 in plan view. The resistive heater component 360 includes a PPTC body 362 arranged as a circular ring body and opposing electrodes shown as electrodes 364. As shown in FIG. 10B, for example, a resistive heater component 360A is arranged with these opposing electrodes as two ring segments shown as segments 364A and 364B, and a part of the circular ring body is exposed at exposed regions 362A and 362B as shown. The configurations of FIGS. 10A and 10B differ from each other in the relative arrangement of segments 364A and 364B from each other and in the shape and size of exposed regions 362A and 362B. Due to this configuration, as shown in FIG. 10A, the current flowing through the path with the smallest resistance can flow vertically from the S-twisted wire 370 to the lower side of the electrodes 364, and then can flow horizontally along the lower surface of the PPTC body along the electrodes 364. Next, due to the break of the electrodes 364, the current can flow vertically to the upper surface, then horizontally along the upper surface, vertically from the upper surface of the PPTC body to the lower surface, and horizontally along the lower electrodes and flow out vertically from the Z-twisted wire 370.

[0045] FIG. 11 provides a circuit diagram of an exemplary PPTC-based resistive heater of FIGS. 10A - 10C. Elements R0 and R7 represent resistance from wire 370. Elements R1, R4, and R6 represent resistance from foil, and elements R2, R3, and R5 represent resistance from the PTC ring body. As shown, the resistance of element R3 may be greater than the resistance of R2 and R5 that occur on the left and right sides of the PTC ring.

[0046] FIG. 12 shows an exemplary PPTC-based resistive heater component shown as PPTC heater component 400 according to multiple embodiments of the present disclosure. In this example, the PPTC heater component 400 has a flat ring shape as shown in side views (top and bottom) and a plan view (center). The PPTC heater component 400 may generally be arranged as shown in the embodiments of FIGS. 1 and 2, with the PPTC body sandwiched between opposing electrodes. In this case, these opposing electrodes can cover most of the upper and lower ring surfaces.

[0047] FIG. 13 provides a circuit diagram of the exemplary PPTC-based resistive heater of FIG. 12. Elements R0 and R7 represent resistance from external wires connected to the PPTC heater 400. Elements R1, R2, R5, and R6 represent resistance from solder pads, and elements R3, R4 represent resistance from the PTC body.

[0048] FIG. 14 shows a side view of an exemplary PPTC resistive heater 450 according to multiple embodiments of the present disclosure. The resistive heater 450 includes the PPTC resistive heater component 400 and external wires 410. The arrows indicate the current path regarding the current flowing from the S-twisted wire 410 through the PPTC resistive heater component 400 and flowing out from the Z-twisted wire 410. As shown, the current can flow vertically from the S-twisted wire 410 from the lower surface to the upper surface of the PPTC body, then horizontally along the upper electrode, vertically from the upper surface to the lower surface of the PPTC body, and horizontally along the lower electrode and flow out from the Z-twisted wire 410.

[0049] In various embodiments, the PPTC heater can be incorporated into a printed circuit board (PCB). For example, the resistive heater component 400 can be incorporated into a resistive heater that uses a PCB to support a surface mount PTC resistive heater configuration.

[0050] As mentioned, the PPTC resistive heater according to this embodiment can be incorporated into a camera. FIG. 15A shows a novel camera 450 that includes a PPTC heater component 400A arranged as a ring incorporated into a camera lens assembly. The PPTC heater component 400A may be in thermal contact with the camera lens 430 so as to heat the camera lens by a resistive heating method. Due to the ring shape, the outer periphery of the camera lens 430 can be directly heated. In this way, the camera lens can be heated to a predetermined amount to, for example, drive away moisture or deposits.

[0051] In a particular embodiment of FIG. 15A, the heater component 400A can conduct a current as shown for the heater component 400 above. The heater component 400A includes a PTC body 412, a metal foil layer 414, a conductive metal portion 418, and an insulating layer 416. The heater component 400A can be joined to the wire 410 via a contact metal 419. FIG. 15B shows a plan view of the heater component 400A, and the upper part of FIG. 15A corresponds to a cross-section A-A along the semi-circular path shown in FIG. 15B. Thus, the heater component 400A can be arranged according to surface mount technology. In particular, the heater component 400A may be supported on a PCB ring 420, and the heater component 400A and the PCB ring 420 have a ring shape as shown in FIG. 15B. The heater component 400A can be divided into two segments as shown in order to generally generate a current path as shown in FIG. 14. In particular, the current between the wires 410 can move along two semi-circular parallel paths. In various non-limiting embodiments, the total thickness of the heater component 400A may be about 2 mm, and the thickness of the PCB ring 420 is less than 1 mm. Non-limiting examples of materials suitable for the PCB ring 420 include FR4, copper inlay PCB, or ceramic PCBs such as Al2O3 or AlN.

[0052] When the PPTC resistive heater according to this embodiment is incorporated into a camera or other device to be heated, the following advantages can be realized. 1) Self-balancing power distribution design, 2) Components that are thin but completely insulated from the camera housing, 3) A specially shaped heater that can fit into a very narrow area, 4) A component in which the power-versus-temperature performance of the resistive heater can be adjusted by adjusting the filler recipe, such as optional carbon particles added to the polymer matrix and the volume fraction of graphene particles (in the case of graphene-based PPTC materials), 5) A resistive heater (in the case of graphene-based PPTC materials) in which the power-generation-versus-temperature operation is stable over a wide temperature range, for example, up to the maximum operating temperature, 6) Higher power generation in colder environments, 7) Lower power generation in warmer environments, 8) A resistive heater with self-limiting power.

[0053] Although this embodiment has been disclosed with reference to specific embodiments, numerous modifications, alterations, and changes can be made to the described embodiments without departing from the scope and range of the present disclosure as defined in the appended claims. Accordingly, this embodiment should not be limited to the described embodiments, but may have the full scope defined by the language of the following claims and their equivalents.

Claims

1. 1. A polymeric positive temperature coefficient body (PPTC body) for use in a heater, comprising: a polymer matrix including a polymeric positive temperature coefficient material (PPTC material), the polymer matrix being arranged in a flattened ring shape lying in a plane, the PPTC body having upper and lower surfaces extending parallel to the plane; a graphene filler component disposed within the polymer matrix, the graphene filler component comprising a plurality of graphene particles comprised of graphene sheets, the graphene sheets being aligned parallel to the plane; and Equipped with a polymer positive temperature coefficient body.

2. 10. The polymeric positive temperature coefficient body of claim 1, further comprising at least one electrode disposed on the upper surface of the PPTC body and at least one additional electrode disposed on the lower surface of the PPTC body.

3. 3. The polymeric positive temperature coefficient body of claim 1 or 2, wherein the flattened ring shape comprises a circular ring, a rectangular ring, an elliptical ring, an oval ring, or a polygonal ring.

4. 4. The polymeric positive temperature coefficient body of claim 1, further comprising a carbon filler component disposed as a plurality of carbon particles within the polymer matrix.

5. The polymeric positive temperature coefficient body of any one of claims 1 to 4, wherein the volume percentage of the polymer matrix is ​​50 to 99%.

6. The polymeric positive temperature coefficient body of any one of claims 1 to 5, wherein the volume percentage of the graphene filler component is between 1% and 50%.

7. The polymeric positive temperature coefficient body of claim 1 further comprising a carbon nanotube filler component.

8. 1. A polymeric positive temperature coefficient body (PPTC body) for use in a heater, comprising: a polymer matrix including a polymeric positive temperature coefficient material (PPTC material), the polymer matrix being arranged in a flattened ring shape lying in a plane, the PPTC body having upper and lower surfaces extending parallel to the plane; a carbon nanotube filler component disposed within the polymer matrix, the carbon nanotube filler component comprising single-walled or multi-walled carbon nanotube material; a graphene filler component disposed within the polymer matrix, the graphene filler component comprising a plurality of graphene particles comprised of graphene sheets, the graphene sheets being aligned parallel to the plane; and Equipped with a polymer positive temperature coefficient body.

9. 9. The polymeric positive temperature coefficient body of claim 8, further comprising at least one electrode disposed on the upper surface of the PPTC body and at least one additional electrode disposed on the lower surface of the PPTC body.

10. 10. The polymeric positive temperature coefficient body of claim 8 or 9, wherein the flattened ring shape comprises a circular ring, a rectangular ring, an elliptical ring, an oval ring, or a polygonal ring.

11. The polymeric positive temperature coefficient body of any one of claims 8 to 10, wherein the volume percentage of the polymer matrix is ​​50 to 99%.

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