A high voltage resistant PPTC polymer composition and a method for preparing the same

Abstract

The application relates to the technical field of overcurrent protection sheets, and discloses a high-voltage-resistant PPTC high-molecular composition and a preparation method thereof. The high-voltage-resistant PPTC high-molecular composition comprises, by mass, 33-43 parts of a polymer, 22-28 parts of carbon black, 6-12 parts of conductive mica and 1-5 parts of porphyrin. The polymer is a fusion body of polyethylene terephthalate: polysulfone: polyether ether ketone = 1: (0.2-0.8): (0.05-0.4) by mass. The polymer has a narrow crystalline-to-amorphous transition interval, so that a uniform conductive network formed by the carbon black and the conductive mica can be disconnected or reconnected along with the transition of the polymer. The porphyrin helps to improve the carbon black and the conductive mica to form a uniform and densely connected conductive network in the polymer. The combination of the conductive mica and the carbon black can keep a low resistance when the polymer is in a crystalline phase state, and has good high-voltage resistance under high current. The PPTC high-molecular composition is installed in a circuit, so that the equipment in the circuit can be protected in the case of overcurrent of the circuit.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of overcurrent protection sheets, in particular to a high-voltage-resistant PPTC high-molecular composition and a preparation method thereof. BACKGROUND

[0002] PPTC is a high-molecular polymer positive coefficient thermistor, also known as a self-recovery fuse, a recoverable fuse or a polymer fuse, and is also called an overcurrent protection sheet when applied in a circuit.

[0003] The PPTC generally comprises two metal wires and a polymer body connecting the two metal wires. The polymer body is generally a high-molecular composition composed of a polymer, a conductive substance and an additive. The polymer body is bonded with metal foils at two end faces, and the two metal wires are welded on the metal foils at the two end faces. The two metal wires are connected to a circuit.

[0004] The PPTC has the characteristics of presenting a low resistance under a normal current and a sharp increase in resistance under an overcurrent fault, so as to protect a rear-end circuit. Due to the excellent recoverable characteristics of the polymer body, the conductive substance in the polymer body is reconnected after the fault is eliminated, and the circuit can automatically recover to a conducting state.

[0005] Some related PPTC high-molecular compositions have poor voltage resistance under a high current, such as 50-100 A, for example, weak 24V voltage resistance, and are easily damaged after use. SUMMARY

[0006] In view of the poor voltage resistance of some related PPTC high-molecular compositions under a high current (such as 50-100 A), for example, weak 24V voltage resistance, and the easily damaged condition after use, the application provides a PPTC high-molecular composition with good voltage resistance under a high current, and a preparation method of the composition.

[0007] In a first aspect, the application provides a high-voltage-resistant PPTC high-molecular composition, and adopts the following technical scheme.

[0008] The high-voltage-resistant PPTC high-molecular composition comprises, by mass, 33-43 parts of a polymer, 22-28 parts of carbon black, 6-12 parts of conductive mica and 1-5 parts of porphyrin. The polymer is a melt of polyethylene terephthalate, polysulfone and polyether ether ketone, and the polyethylene terephthalate: polysulfone: polyether ether ketone = 1: (0.2-0.8): (0.05-0.4) by mass.

[0009] By adopting the above technical scheme, the melt of polyethylene terephthalate, polysulfone and polyether ether ketone is a fused uniform polymer, has the same and narrow crystalline to amorphous transition interval, and has fast back-and-forth transition speed between the crystalline and amorphous states and good recovery performance, so that the uniform conductive network formed by the carbon black and the conductive mica can be disconnected or reconnected with the polymer transition, that is, the PPTC high polymer composition can have a sudden change in resistance value in the crystalline to amorphous transition interval. When passing through the narrow interval, the resistance value can change by several orders of magnitude. In the crystalline state, the PPTC high polymer composition has a very small resistance; in the amorphous state, the PPTC high polymer composition has a very large resistance. The PPTC high polymer composition is installed in a circuit, in the case of overcurrent in the circuit, the work of the current on the PPTC high polymer composition increases significantly, the temperature of the PPTC high polymer composition rises, and the PPTC high polymer composition changes from a crystalline state to an amorphous state in a very short time in a narrow temperature interval, the resistance value of the PPTC high polymer composition changes by several orders of magnitude, and the circuit is disconnected, thereby protecting the equipment in the circuit.

[0010] The surface of the carbon black particles has a large number of carbon nanotube structures, forming a large number of conductive channels, making carbon black a good conductive material. Using only carbon black as a conductive medium, carbon black is easy to agglomerate, and carbon black has weak flame retardancy and high voltage resistance, and the material is easy to burn under high current and high voltage. The conductive mica is in the form of a flake, which is a new type of electronic conductive functional material prepared by using mica as a substrate and forming a conductive layer on the surface through surface treatment and doping. The conductive mica has strong flame retardancy, and the use of conductive mica and carbon black together significantly improves the flame retardancy compared to using only carbon black as a conductive medium, and improves the agglomeration of pure carbon black. However, when carbon black and conductive mica are added to the polymer at the same time to form a composite conductive network, the electron transfer efficiency is reduced compared to a single conductive material, and the porphyrin has a large ring conjugated structure, which has good bonding force with the particle carbon black and the flaky conductive mica at room temperature, and good electron transfer effect, which significantly improves the electron transfer efficiency between carbon black and conductive mica, and improves the conductivity of the PPTC high polymer composition. At high temperatures, the porphyrin ring and the particle carbon black and the flaky conductive mica are easy to disconnect, so that the PPTC high polymer composition can maintain a low resistance at room temperature and a high resistance at high temperatures.

[0011] As an improvement of the high-voltage-resistant PPTC high polymer composition, the high polymer composition includes, by mass, 37-39 parts of polymer, 24-26 parts of carbon black, 8-10 parts of conductive mica and 2-4 parts of porphyrin.

[0012] By adopting the above technical solution and using the above ratio, porphyrin promotes more uniform dispersion of carbon black and conductive mica in the polymer, narrows the polymer phase transition temperature range, and enables the dendritic conductive structure formed by carbon black and conductive mica in the polymer to achieve simultaneous network disconnection or connection, with good response synchronization. This makes the PPTC polymer composition have strong overcurrent blocking ability and good protection effect on circuit devices.

[0013] As an improvement to the high-voltage resistant PPTC polymer composition, the poly(ethylene terephthalate):polysulfone:polyetheretherketone = 1:(0.4-0.6):(0.2-0.3) by mass.

[0014] By adopting the above technical solution, the melt of poly(ethylene terephthalate), polysulfone, and polyetheretherketone in this formulation is a uniformly fused crystalline polymer with good compatibility with carbon black, conductive mica, and porphyrin. Carbon black and conductive mica can be uniformly dispersed in the polymer and form a cross-linked conductive network. This polymer can achieve a crystalline-to-amorphous phase transition within a narrow temperature range, thus exhibiting fast response to overcurrent and strong protection for circuit devices.

[0015] As an improvement to the high-voltage resistant PPTC polymer composition, the polymer composition further includes additives, which, by mass, include 0.5 to 1 part diatomaceous earth and 0.2 to 0.6 parts calcium phosphate.

[0016] By adopting the above technical solution, diatomaceous earth possesses a porous structure with a porosity exceeding 80%, exhibiting a fine and smooth texture and good thermal insulation properties. It promotes the heat absorption and insulation of PPTC polymer compositions and induces a crystal phase transformation upon heating, thereby enhancing responsiveness. Calcium phosphate has excellent anti-caking properties; when combined with diatomaceous earth, it improves the electrical conductivity of PPTC polymer compositions and reduces impedance at room temperature.

[0017] As an improvement to the high-voltage resistant PPTC polymer composition, the additives, by mass, include 0.7-0.8 parts of diatomaceous earth and 0.35-0.45 parts of calcium phosphate.

[0018] By adopting the above technical solution, the added ratio of diatomaceous earth and calcium phosphate has a good effect on improving the temperature response sensitivity of the PPTC polymer composition and has a good effect on reducing the room temperature resistance of the PPTC polymer composition.

[0019] Secondly, this application also proposes a method for preparing a high-voltage resistant PPTC polymer composition, and adopts the following technical solution.

[0020] A method for preparing the high-voltage resistant PPTC polymer composition as described above, comprising:

[0021] The polyethylene terephthalate, the polysulfone and the polyether ether ketone are heated and melted to obtain the polymer, and in the molten state, carbon black, conductive mica and porphyrin are added and uniformly dispersed to obtain the polymer composition.

[0022] By using the above technical solution, the polyethylene terephthalate, the polysulfone and the polyether ether ketone form a uniform and stable crystalline polymer, and the porphyrin can promote the uniformity of the dispersion of the carbon black and the conductive mica in the molten polymer, and after cooling, a uniform branched conductive network can be formed, and the conductive network can be uniformly disconnected with the transformation of the polymer from the crystalline phase to the amorphous phase, so that the resistance of the PPTC polymer composition increases by several orders of magnitude instantaneously. When installed in a circuit, the PPTC polymer composition can achieve rapid circuit breaking when an overcurrent occurs, thereby effectively protecting the circuit device.

[0023] As an optional solution of the preparation method of the high-voltage-resistant PPTC polymer composition, the polyethylene terephthalate, the polysulfone and the polyether ether ketone are heated to 350-400℃ to melt, stirred for 0.5-2h to mix and melt into a uniform fluid to obtain the polymer, cooled to 230-260℃, and then the carbon black, the conductive mica and the porphyrin are added and uniformly stirred to obtain the polymer composition.

[0024] By using the above technical solution, heating to 350-400℃ can make the polyethylene terephthalate, the polysulfone and the polyether ether ketone all melt, and after stirring for 0.5-2h, the three polymer components are mixed and melted into a uniform fluid to obtain a polymer with a reduced melting point, which can be cooled to 230-260℃ and still be in a molten state. The carbon black, the conductive mica and the porphyrin are added and easily stirred and uniformly dispersed in the polymer to obtain the polymer composition. The fluid-state polymer composition can be molded by casting or pressure casting process to obtain a polymer body, and the two ends of the polymer body can be attached to metal electrodes to become a PPTC, which can be used in a circuit for overcurrent protection.

[0025] As an optional solution of the preparation method of the high-voltage-resistant PPTC polymer composition, (E)-1,2-bis(4-bromophenyl)ethylene is added at the same time as the carbon black, the conductive mica and the porphyrin, and the mass ratio of the (E)-1,2-bis(4-bromophenyl)ethylene to the polymer is 1:(33-43).

[0026] By using the above technical solution, the external bromine groups on the multiple aromatic rings of (E)-1,2-bis(4-bromophenyl)ethylene have a flame-retardant effect, and the alkenyl groups between the aromatic rings have an antioxidant effect of absorbing free radicals. (E)-1,2-bis(4-bromophenyl)ethylene is incorporated into the polymer chain to improve the flame retardance and antioxidant properties of the polymer.

[0027] In summary, the high-voltage resistant PPTC polymer composition and the preparation method thereof have the following beneficial effects: the melt of poly(cyclohexyl terephthalate), polysulfone and poly(ether ether ketone) is a fused uniform polymer, has the same and narrow crystalline to amorphous transition interval, and the speed of back and forth transition between the crystalline and amorphous states is fast and the recovery performance is good, so that the uniform conductive network formed by the carbon black and the conductive mica can be disconnected or reconnected with the polymer transition. The PPTC polymer composition is installed in the circuit, in the case of overcurrent in the circuit, the temperature of the PPTC polymer composition rises, and the resistance value changes by several orders of magnitude in a very short time, realizing the circuit breaking, thereby protecting the equipment in the circuit.

[0028] The porphyrin helps to improve the dispersity and compatibility of the carbon black and the conductive mica in the polymer, and promotes the carbon black and the conductive mica to form a uniform and densely connected conductive network in the polymer. The use of the conductive mica and the carbon black together significantly improves the conductivity of the conductive network compared with using only the carbon black as the conductive medium, can maintain low resistance in the crystalline state of the polymer, and has good high-voltage resistance under high current. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The resistance-temperature change curve of the polymer further prepared from the polymer composition prepared in Example 1, Comparative Example 1 and Comparative Example 7 is shown in the following figure. DETAILED DESCRIPTION

[0030] The following specifically describes some embodiments of the high-voltage resistant PPTC polymer composition and the preparation method thereof.

[0031] Example 1

[0032] According to the mass fraction, 22 parts of poly(cyclohexyl terephthalate), 11 parts of polysulfone and 5 parts of poly(ether ether ketone) are heated and melted to 350℃, stirred for 1h to be mixed and melted into a uniform fluid to obtain a polymer. When cooled to a molten state of 230℃, 25 parts of carbon black, 9 parts of conductive mica and 3 parts of porphyrin are added and stirred uniformly to obtain a polymer composition.

[0033] Example 2

[0034] According to the mass fraction, 23 parts of poly(cyclohexyl terephthalate), 10 parts of polysulfone and 6 parts of poly(ether ether ketone) are heated and melted to 350℃, stirred for 1h to be mixed and melted into a uniform fluid to obtain a polymer. When cooled to a molten state of 230℃, 24 parts of carbon black, 10 parts of conductive mica and 2 parts of porphyrin are added and stirred uniformly to obtain a polymer composition.

[0035] Example 3

[0036] Polymer was obtained by heating and melting polyethylene terephthalate 21 parts, polysulfone 11 parts and polyether ether ketone 5 parts to 350°C, stirring for 1 hour to mix and melt into a uniform fluid. Carbon black 26 parts, conductive mica 8 parts and porphyrin 4 parts were added under the molten state of 230°C, and the mixture was stirred uniformly to obtain the polymer composition.

[0037] Example 4

[0038] Polymer was obtained by heating and melting polyethylene terephthalate 20 parts, polysulfone 5 parts and polyether ether ketone 8 parts to 400°C, stirring for 2 hours to mix and melt into a uniform fluid. Carbon black 22 parts, conductive mica 12 parts and porphyrin 5 parts were added under the molten state of 246°C, and the mixture was stirred uniformly to obtain the polymer composition.

[0039] Example 5

[0040] Polymer was obtained by heating and melting polyethylene terephthalate 23 parts, polysulfone 18 parts and polyether ether ketone 1.3 parts to 383°C, stirring for 0.5 hour to mix and melt into a uniform fluid. Carbon black 28 parts, conductive mica 6 parts and porphyrin 1 part were added under the molten state of 260°C, and the mixture was stirred uniformly to obtain the polymer composition.

[0041] The difference between the above examples 1-5 is that the raw material ratio is different, the heating, cooling temperature of examples 4-5 and examples 1-3 is different, and the stirring time is different.

[0042] Example 6

[0043] Compared with example 1, 0.5 parts of diatomite and 0.6 parts of calcium phosphate were added in the preparation of the polymer composition of example 6, as follows.

[0044] Polymer was obtained by heating and melting polyethylene terephthalate 22 parts, polysulfone 11 parts and polyether ether ketone 5 parts to 350°C, stirring for 1 hour to mix and melt into a uniform fluid. Carbon black 25 parts, conductive mica 9 parts, porphyrin 3 parts, diatomite 0.5 parts and calcium phosphate 0.6 parts were added under the molten state of 230°C, and the mixture was stirred uniformly to obtain the polymer composition.

[0045] Example 7

[0046] Compared with example 1, 1 part of diatomite and 0.2 parts of calcium phosphate were added in the preparation of the polymer composition of example 7, as follows.

[0047] By mass fraction, take polyethylene terephthalate 22 parts, polysulfone 11 parts and polyether ether ketone 5 parts heated to melt at 350 °C, stirring 1 h mixed melt into a homogeneous fluid, to obtain the polymer, cooled to 230 °C melt state, add carbon black 25 parts, conductive mica 9 parts, porphyrin 3 parts, diatomite 1 part and calcium phosphate 0.2 parts, stirring uniform, to obtain the polymer composition.

[0048] Example 8

[0049] Compared with Example 1, the polymer composition of this embodiment 8 is prepared by adding diatomite 0.7 parts and calcium phosphate 0.35 parts, as follows.

[0050] By mass fraction, take polyethylene terephthalate 22 parts, polysulfone 11 parts and polyether ether ketone 5 parts heated to melt at 350 °C, stirring 1 h mixed melt into a homogeneous fluid, to obtain the polymer, cooled to 230 °C melt state, add carbon black 25 parts, conductive mica 9 parts, porphyrin 3 parts, diatomite 0.7 parts and calcium phosphate 0.35 parts, stirring uniform, to obtain the polymer composition.

[0051] Example 9

[0052] Compared with Example 1, the polymer composition of this embodiment 9 is prepared by adding diatomite 0.8 parts and calcium phosphate 0.45 parts, as follows.

[0053] By mass fraction, take polyethylene terephthalate 22 parts, polysulfone 11 parts and polyether ether ketone 5 parts heated to melt at 350 °C, stirring 1 h mixed melt into a homogeneous fluid, to obtain the polymer, cooled to 230 °C melt state, add carbon black 25 parts, conductive mica 9 parts, porphyrin 3 parts, diatomite 0.8 parts and calcium phosphate 0.45 parts, stirring uniform, to obtain the polymer composition.

[0054] Example 10

[0055] Compared with Example 1, the polymer composition of this embodiment 10 is prepared by adding (E)-1,2-bis(4-bromophenyl)ethene while adding carbon black, conductive mica and porphyrin, and the mass ratio of (E)-1,2-bis(4-bromophenyl)ethene and polymer is 1:38, as follows.

[0056] By mass fraction, take polyethylene terephthalate 22 parts, polysulfone 11 parts and polyether ether ketone 5 parts heated to melt at 350 °C, stirring 1 h mixed melt into a homogeneous fluid, to obtain the polymer, cooled to 230 °C melt state, add carbon black 25 parts, conductive mica 9 parts, porphyrin 3 parts and (E)-1,2-bis(4-bromophenyl)ethene 1 part, stirring uniform, to obtain the polymer composition.

[0057] Example 11

[0058] Example 11 is compared with Example 4, in the preparation of the high molecular composition, carbon black, conductive mica and porphyrin are added at the same time, (E)-1,2-bis(4-bromophenyl) ethylene is also added, the mass ratio of (E)-1,2-bis(4-bromophenyl) ethylene and polymer is 1:33, and the details are as follows.

[0059] According to the mass fraction, 20 parts of polyethylene terephthalate, 5 parts of polysulfone and 8 parts of polyether ether ketone are heated and melted to 400°C, and stirred for 2h to mix and melt into a uniform fluid to obtain a polymer. Under the molten state of cooling to 246°C, 22 parts of carbon black, 12 parts of conductive mica, 5 parts of porphyrin and 1 part of (E)-1,2-bis(4-bromophenyl) ethylene are added and stirred uniformly to obtain a high molecular composition.

[0060] Example 12

[0061] Example 12 is compared with Example 5, in the preparation of the high molecular composition, carbon black, conductive mica and porphyrin are added at the same time, (E)-1,2-bis(4-bromophenyl) ethylene is also added, the mass ratio of (E)-1,2-bis(4-bromophenyl) ethylene and polymer is 1:42.3, and the details are as follows.

[0062] According to the mass fraction, 23 parts of polyethylene terephthalate, 18 parts of polysulfone and 1.3 parts of polyether ether ketone are heated and melted to 383°C, and stirred for 0.5h to mix and melt into a uniform fluid to obtain a polymer. Under the molten state of cooling to 260°C, 28 parts of carbon black, 6 parts of conductive mica, 1 part of porphyrin and 1 part of (E)-1,2-bis(4-bromophenyl) ethylene are added and stirred uniformly to obtain a high molecular composition.

[0063] Example 13

[0064] Example 13 is compared with Example 1, in the preparation of the high molecular composition, carbon black, conductive mica and porphyrin are added at the same time, 0.75 parts of diatomite and 0.40 parts of calcium phosphate are also added, and (E)-1,2-bis(4-bromophenyl) ethylene is also added, the mass ratio of (E)-1,2-bis(4-bromophenyl) ethylene and polymer is 1:38, and the details are as follows.

[0065] According to the mass fraction, 22 parts of polyethylene terephthalate, 11 parts of polysulfone and 5 parts of polyether ether ketone are heated and melted to 350°C, and stirred for 1h to mix and melt into a uniform fluid to obtain a polymer. Under the molten state of cooling to 230°C, 25 parts of carbon black, 9 parts of conductive mica, 3 parts of porphyrin, 0.75 parts of diatomite, 0.40 parts of calcium phosphate and 1 part of (E)-1,2-bis(4-bromophenyl) ethylene are added and stirred uniformly to obtain a high molecular composition.

[0066] Comparative Example 1

[0067] The raw materials for preparing the polymer of Comparative Example 1 are different from those of Example 1, and are as follows.

[0068] The polyethylene terephthalate 2 parts, the polysulfone 20 parts and the polyether ether ketone 10 parts were heated and melted to 350°C, and stirred for 1 hour to form a uniform fluid, thereby obtaining a polymer. The polymer was cooled to a molten state at 230°C, and the carbon black 25 parts, the conductive mica 9 parts and the porphyrin 3 parts were added thereto and stirred uniformly, thereby obtaining the polymer composition.

[0069] Comparative Example 2

[0070] The raw materials for preparing the polymer composition of Comparative Example 2 are different from those of Example 1, and are as follows.

[0071] The polyethylene terephthalate 2 parts, the polysulfone 20 parts and the polyether ether ketone 10 parts were heated and melted to 350°C, and stirred for 1 hour to form a uniform fluid, thereby obtaining a polymer. The polymer was cooled to a molten state at 230°C, and the carbon black 25 parts, the conductive mica 9 parts and the porphyrin 3 parts were added thereto and stirred uniformly, thereby obtaining the polymer composition.

[0072] Comparative Example 3

[0073] The raw materials for preparing the polymer composition of Comparative Example 3 are different from those of Example 1, and the conductive mica is not added in Comparative Example 2, and are as follows.

[0074] The polyethylene terephthalate 2 parts, the polysulfone 20 parts and the polyether ether ketone 10 parts were heated and melted to 350°C, and stirred for 1 hour to form a uniform fluid, thereby obtaining a polymer. The polymer was cooled to a molten state at 230°C, and the carbon black 25 parts, the conductive mica 9 parts and the porphyrin 3 parts were added thereto and stirred uniformly, thereby obtaining the polymer composition.

[0075] Comparative Example 4

[0076] The raw materials for preparing the polymer composition of Comparative Example 4 are different from those of Example 1, and the polyethylene terephthalate is removed, and are as follows.

[0077] The polyethylene terephthalate 2 parts, the polysulfone 20 parts and the polyether ether ketone 10 parts were heated and melted to 350°C, and stirred for 1 hour to form a uniform fluid, thereby obtaining a polymer. The polymer was cooled to a molten state at 230°C, and the carbon black 25 parts, the conductive mica 9 parts and the porphyrin 3 parts were added thereto and stirred uniformly, thereby obtaining the polymer composition.

[0078] Comparative Example 5

[0079] The raw materials for preparing the polymer composition of Comparative Example 5 are different from those of Example 1, and the polysulfone is removed, and are as follows.

[0080] Polymer was obtained by heating and melting 22 parts of polyethylene terephthalate cyclohexane ester and 5 parts of polyether ether ketone to 350°C and stirring for 1 hour to form a uniform fluid. Carbon black 25 parts, conductive mica 9 parts and porphyrin 3 parts were added to the molten polymer at 230°C and stirred to form a uniform mixture to obtain the polymer composition.

[0081] Comparative Example 6

[0082] Comparative Example 6 was prepared by removing polyether ether ketone from the raw materials used in Example 1 as follows.

[0083] Polymer was obtained by heating and melting 22 parts of polyethylene terephthalate cyclohexane ester and 11 parts of polysulfone to 350°C and stirring for 1 hour to form a uniform fluid. Carbon black 25 parts, conductive mica 9 parts and porphyrin 3 parts were added to the molten polymer at 230°C and stirred to form a uniform mixture to obtain the polymer composition.

[0084] Comparative Example 7

[0085] Comparative Example 7 was prepared by removing porphyrin from the raw materials used in Example 1 as follows.

[0086] Polymer was obtained by heating and melting 22 parts of polyethylene terephthalate cyclohexane ester, 11 parts of polysulfone and 5 parts of polyether ether ketone to 350°C and stirring for 1 hour to form a uniform fluid. Carbon black 25 parts and conductive mica 9 parts were added to the molten polymer at 230°C and stirred to form a uniform mixture to obtain the polymer composition.

[0087] Test Example 1

[0088] The polymer compositions prepared in Example 1, Comparative Example 1 and Comparative Example 7 were cast into the same cylindrical shape and cooled to room temperature to obtain molded polymer compositions, which were called polymer bodies. The same nickel plates were attached to both end faces of each polymer body by hot pressing, and the nickel plates and the end faces of the cylindrical polymer body were the same in shape and size. The same nickel leads were welded to the outside of the nickel plates at each end to obtain PPTC (self-recovery fuse). The relationship between the resistance of the polymer bodies prepared in Example 1, Comparative Example 1 and Comparative Example 7 and temperature was tested as shown in Figure 1 The resistance of the PPTC was tested, and the resistance of the nickel plates and the nickel leads was 1% or less of the resistance of the polymer body at room temperature and at high temperature, and thus could be ignored. Therefore, the resistance of the PPTC was regarded as the resistance of the polymer body.

[0089] As shown in Figure 1, the ordinate represents the order of magnitude of resistance, lg value. The resistance of the polymer of Example 1 is almost constant in the temperature range of 20-122°C, and the resistance increases by several orders of magnitude in the temperature range of 122-128°C. When it is used in a circuit, it can protect the circuit device when a certain overcurrent occurs. The resistance of the polymer of Comparative Example 1 is in a process of obvious increase from 60 to 130°C. When it is installed in a circuit, it has a large resistance at a lower temperature, which affects the normal operation of other circuit devices, and is not suitable as an overcurrent protection device. This is because the ratio of polyethylene terephthalate, polysulfone and polyether ether ketone is not good, and the obtained polymer does not have a clear resistance jump temperature range. The polymer of Comparative Example 7 has a large resistance at a lower temperature of 20°C. When it is installed in a circuit, it has a large resistance at a lower temperature of 20°C, which affects the normal operation of other circuit devices, and is not suitable as an overcurrent protection device. This is because it lacks the conductive effect of porphyrin promoted carbon black and conductive mica, resulting in a large resistance.

[0090] Test Example 2

[0091] The polymer compositions prepared in Examples 1-13 and Comparative Examples 1-7 were poured into the same cylindrical shape, cooled to room temperature to obtain a molded polymer composition, which is called a polymer. The same nickel sheet was attached to the two end faces of each polymer by hot pressing, and the nickel sheet and the end face of the cylindrical polymer had the same shape and size. The same nickel lead was also welded to the outside of the nickel sheet at each end to obtain a PPTC (self-recovery fuse). More than 20 PPTC samples were prepared for each example and comparative example.

[0092] The resistivity of the polymer is p = R * S / l, R is the resistance of the PPTC obtained by testing, and the resistance of the nickel sheet and the nickel lead at room temperature and high temperature is less than 1% of the resistance of the polymer, which can be ignored. Therefore, R can be regarded as the resistance of the polymer. S is the area of the end face of the cylindrical polymer, 12.56 mm 2 , and l is the length of the cylindrical polymer, 2 mm.

[0093] The PPTC was tested by applying a back-and-forth cycle voltage of 18-24V, with a current of about 50-100A, simulating an overcurrent phenomenon, so that the PPTC cycles back and forth on both sides of the jump temperature. The voltage was increased from 18V to 24V at a rate of 1V / min, and then decreased from 24V to 18V at a rate of 1V / min, with a 5min stop. This was taken as one cycle, and 50 cycles were tested. The first abnormal phenomenon and the total number of abnormalities were recorded.

[0094] Each example and comparative example was tested for 20 PPTC samples, and the average resistance, average resistivity and cycle voltage test results are shown in Table 1.

[0095] Table 1 Resistance, resistivity and cycle voltage test

[0096]

[0097]

[0098]

[0099]

[0100] As shown in Table 1, the polymer of Examples 6-9 and 13 has relatively small resistance, which is due to the porous structure of the added diatomite, the porosity of which is more than 80%, and the diatomite is fine and lubricating, and has good heat preservation effect, which can promote the heat absorption and heat preservation of the PPTC polymer composition, and the crystal phase transition occurs during the heating, thereby improving the response sensitivity. The calcium phosphate has excellent anti-caking effect, and cooperates with the diatomite to improve the conductivity of the PPTC polymer composition and reduce the impedance at room temperature.

[0101] As shown in Table 1, the polymer of Examples 10-13 is not deformed, does not burn, and has no smoke phenomenon in the overcurrent cycle test, which is due to the fact that the added (E)-1,2-bis(4-bromophenyl) ethylene contains multiple aromatic ring outer bromine groups which have flame retardant effect, and the alkene groups between the aromatic rings have the effect of absorbing free radicals and resisting oxidation, and the (E)-1,2-bis(4-bromophenyl) ethylene is fused into the polymer chain, thereby improving the flame retardance and oxidation resistance of the polymer.

[0102] The comparative example 1 uses improper raw material ratio of the polymer, and the high voltage resistance is weaker than that of the product of the examples.

[0103] The comparative example 2 uses improper ratio of carbon black, conductive mica and porphyrin, and the conductive performance is weak, and the high voltage resistance is weaker than that of the product of the examples.

[0104] The comparative example 3 does not add conductive mica, and the flame retardance is weakened, and the high voltage resistance is weak.

[0105] The comparative example 4 removes polyethylene terephthalate from the raw materials for preparing the polymer composition, the comparative example 5 removes polysulfone from the raw materials for preparing the polymer composition, and the comparative example 6 removes polyether ether ketone from the raw materials for preparing the polymer composition, which cannot be fused into a uniform polymer, does not have the same and narrow crystal to amorphous transition interval, and makes the uniform conductive network formed by the carbon black and the conductive mica unable to be disconnected or reconnected in time with the transition of the polymer, and the high voltage cycle resistance is weak.

[0106] The comparative example 7 removes porphyrin from the raw materials for preparing the polymer composition, and the energy required for the charge transfer between the carbon black and the conductive mica is large, the conductivity of the PPTC polymer composition is poor, and the high voltage cycle resistance is weak.

[0107] In summary, in the embodiment, the melt of polyethylene terephthalate, polysulfone and polyether ether ketone is a fused homogeneous polymer, has the same and narrow crystalline to amorphous transition interval, and the speed of back and forth transition between the crystalline and amorphous states is fast and the recovery performance is good, so that the uniform conductive network formed by the carbon black and the conductive mica can be disconnected or reconnected with the transition of the polymer. The porphyrin helps to improve the dispersity and compatibility of the carbon black and the conductive mica in the polymer, and promotes the carbon black and the conductive mica to form a uniform and densely connected conductive network in the polymer. The PPTC polymer composition is installed in the circuit, in the case of overcurrent in the circuit, the temperature of the PPTC polymer composition rises, and it changes from the crystalline state to the amorphous state in a very short time, the resistance value changes by several orders of magnitude, and the circuit is disconnected, thereby protecting the equipment in the circuit. The use of conductive mica and carbon black together significantly improves the conductivity of the conductive network compared to using only carbon black as the conductive medium, and can maintain low resistance in the crystalline state of the polymer, and has good high voltage resistance under high current.

[0108] The above is only the preferred embodiment of the present application, and the optional cases of the present application are not limited to the above-mentioned embodiments. Any technical solution falling within the core concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also fall within the protection scope of the present application.

Claims

1. A high-voltage resistant PPTC polymer composition, characterized in that, By weight, it includes 33-43 parts polymer, 22-28 parts carbon black, 6-12 parts conductive mica, and 1-5 parts porphyrin; The polymer is a melt of poly(cyclohexyl terephthalate), polysulfone, and polyetheretherketone, wherein, by mass, the ratio of poly(cyclohexyl terephthalate):polysulfone:polyetheretherketone is 1:(0.2~0.8):(0.05~0.4).

2. The high-voltage resistant PPTC polymer composition according to claim 1, characterized in that, The polymer composition comprises, by mass, 37-39 parts of polymer, 24-26 parts of carbon black, 8-10 parts of conductive mica, and 2-4 parts of porphyrin.

3. The high-voltage resistant PPTC polymer composition according to claim 1 or 2, characterized in that, The ratio of poly(ethylene terephthalate):polysulfone:polyetheretherketone is 1:(0.4~0.6):(0.2~0.3) by mass.

4. The high-voltage resistant PPTC polymer composition according to claim 1, characterized in that, The polymer composition also includes additives, which, by mass, include 0.5 to 1 part diatomaceous earth and 0.2 to 0.6 parts calcium phosphate.

5. The high-voltage resistant PPTC polymer composition according to claim 4, characterized in that, The additives, by weight, comprise 0.7-0.8 parts diatomaceous earth and 0.35-0.45 parts calcium phosphate.

6. A method for preparing a high-voltage resistant PPTC polymer composition as described in any one of claims 1-5, characterized in that, include: The poly(ethylene terephthalate), polysulfone, and polyether ether ketone are heated and melted to obtain the polymer. Carbon black, conductive mica, and porphyrin are added in the molten state and dispersed evenly to obtain the polymer composition.

7. The method for preparing the high-voltage resistant PPTC polymer composition according to claim 6, characterized in that, The poly(ethylene terephthalate), polysulfone, and polyetheretherketone are heated to 350-400°C to melt, and stirred for 0.5-2 hours to form a homogeneous fluid to obtain the polymer. The polymer is then cooled to 230-260°C, and carbon black, conductive mica, and porphyrin are added and stirred until homogeneous to obtain the polymer composition.

8. The method for preparing the high-voltage resistant PPTC polymer composition according to claim 7, characterized in that, In addition to carbon black, conductive mica and porphyrin, (E)-1,2-bis(4-bromophenyl)ethylene is also added; the mass ratio of (E)-1,2-bis(4-bromophenyl)ethylene to the polymer is 1:(33~43).

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