A polymer-based PTC composite material based on π-π interactions, its preparation method and applications

Abstract

This invention belongs to the field of polymer conductive composite materials, specifically relating to a polymer-based PTC composite material based on π-π interactions, its preparation method, and its applications. A method for preparing a polymer-based PTC composite material based on π-π interactions includes the following steps: melt blending a polymer matrix, a carbon-based conductive filler, and an aromatic-containing supramolecular filler; hot pressing; and cold pressing to obtain the polymer-based PTC composite material. This material exhibits higher PTC strength, better cycle stability, and lower cost. It can be continuously produced without any additional modification methods, providing a new and effective method for improving the overall performance of PTC materials in PTC research.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer conductive composite materials, and particularly relates to a polymer-based PTC composite material based on π-π interaction, a preparation method and application. BACKGROUND

[0002] Composite conductive polymer is prepared by using different processing technology to fill different conductive fillers with polymer as matrix. Common polymer matrix includes polyethylene (PE), polystyrene (PS), polypropylene (PP), epoxy resin, etc. Common conductive fillers include carbon fiber (CF), carbon nanofiber (CNF), carbon nanotube (CNTs), carbon black (CB), graphene (GP), metal and metal oxide, etc. Among them, polymer-based PTC material has become an important application in the field of composite conductive polymer material, which mainly consists of two parts: polymer matrix and conductive filler. Its working mechanism is that when the working environment temperature rises to the characteristic temperature of the polymer matrix (melting temperature or glass transition temperature), the thermal expansion effect caused by the melting of the crystal region or the movement of the molecular chain segment makes the conductive network be diluted and destroyed, so that the resistivity of the material sharply increases (usually 3-9 orders of magnitude) in the temperature range, which is also called PTC effect, and the temperature at which PTC effect occurs is also called switching temperature. When the temperature continues to rise, the conductive filler will be rearranged with the molten matrix, so that the destroyed conductive network is rebuilt, and the resistivity decreases, that is, the negative temperature coefficient (NTC) effect occurs.

[0003] At present, there are a large number of research works devoted to the development of excellent PTC materials with low percolation threshold, high PTC strength (the ratio of the highest resistivity of the composite material in the process of temperature rise to the room temperature resistivity is logarithmic), weak NTC effect and good cycle stability. The main methods are: ① matrix and filler modification: achieve good distribution of conductive filler in the matrix, and then reduce the percolation threshold of conductive filler in the polymer matrix, so that the conductive network will be more easily broken when PTC effect occurs, and the PTC strength is improved. In addition, the modification of conductive filler can also improve the bonding strength with the matrix, thereby limiting the migration of conductive filler in the matrix and weakening the NTC effect; ② binary polymer matrix: when the temperature of single polymer matrix rises to the thermal deformation temperature of the material, the material will often deform and flow, and the matrix with strong flowability will also bring significant NTC effect. By introducing a second component polymer matrix, when the temperature rises to the melting temperature of the low melting point polymer, the low melting point polymer melts, but at this time the melting temperature of the high melting point polymer has not been reached, and at this time the overall viscosity of the matrix is still sufficient to limit the movement of conductive particles, so the NTC effect of the matrix is weakened with the support of the high melting point polymer; ③ composite filler: in order to reduce the content of filler, another filler with good conductive performance such as CNT (carbon nanotube) or CF (carbon fiber) can be added to the system to make the two fillers play a synergistic effect. This modified method can not only improve the room temperature conductivity of the composite PTC material, but also reduce the percolation threshold; ④ multi-component polymer matrix and filler work together.

[0004] At present, there are a large number of research works devoted to the development of excellent PTC materials with low percolation threshold, high PTC strength (the ratio of the highest resistivity of the composite material in the process of temperature rise to the room temperature resistivity is logarithmic), weak NTC effect and good cycle stability. The main methods are: ① matrix and filler modification: achieve good distribution of conductive filler in the matrix, and then reduce the percolation threshold of conductive filler in the polymer matrix, so that the conductive network will be more easily broken when PTC effect occurs, and the PTC strength is improved. In addition, the modification of conductive filler can also improve the bonding strength with the matrix, thereby limiting the migration of conductive filler in the matrix and weakening the NTC effect; ② binary polymer matrix: when the temperature of single polymer matrix rises to the thermal deformation temperature of the material, the material will often deform and flow, and the matrix with strong flowability will also bring significant NTC effect. By introducing a second component polymer matrix, when the temperature rises to the melting temperature of the low melting point polymer, the low melting point polymer melts, but at this time the melting temperature of the high melting point polymer has not been reached, and at this time the overall viscosity of the matrix is still sufficient to limit the movement of conductive particles, so the NTC effect of the matrix is weakened with the support of the high melting point polymer; ③ composite filler: in order to reduce the content of filler, another filler with good conductive performance such as CNT (carbon nanotube) or CF (carbon fiber) can be added to the system to make the two fillers play a synergistic effect. This modified method can not only improve the room temperature conductivity of the composite PTC material, but also reduce the percolation threshold; ④ multi-component polymer matrix and filler work together. SUMMARY

[0005] In view of the problems in the prior art, the application provides a preparation method of a polymer-based PTC composite material based on pi-pi interaction, which comprises the following steps:

[0006] The polymer matrix, the carbon-based conductive filler and the supermolecular filler containing an aromatic group are melt-blended, hot-pressed and cold-pressed to obtain the polymer-based PTC composite material.

[0007] Further, the polymer matrix is any one of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polymethyl methacrylate, epoxy resin, acetic acid-vinyl acetate copolymer, polystyrene, thermoplastic polyurethane elastomer, ethylene-propylene-diene rubber, polyethylene terephthalate, polyphenylene sulfide and cyclic olefin copolymer.

[0008] Further, the carbon-based conductive filler is any one of N,N'-dicyclohexyl terephthalamide, N1,N3,N5-tricyclopentyl benzene-1,3,5-triformamide, cyclohexyl phenyl ether, N2,N5-diphenyl pyrazine-2,5-diamide, diphenyl ether, N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide, N1,N3,N5-tricyclooctyl benzene-1,3,5-triformamide, biphenyl, N1,N4(dipyridyl-2 benzene) terephthalamide, terphenyl, N,N'-(1,4-benzene) dicyclohexane carboxamide, N,N'-(1,4-benzene) pyridine diamide, N-(4-octanoylaminophenyl) cyclohexanamide, N,N'-(1,4-benzene) bis(pyrzine-2-carboxamide), N1,N3,N5-tricyclohexyl benzene-1,3,5-triformamide, N-(4-tetradecanoylaminophenyl) cyclohexanamide, N,N'-diphenyl terephthalamide, N-(4-stearaminophenyl) cyclohexanamide, 1,3,5-tris(p-formylphenyl) benzene, N,N'-(1,4-benzene) benzamide, N1,N3,N5-tricycloheptyl benzene-1,3,5-triformamide, N,N'-(pyridine-2,5-benzene) benzamide, N2,N5-diphenyl pyridine-2,5-diamide, N1-(pyridine-2-benzene)-N4-(pyridine-3-benzene) terephthalamide, polycyclic aromatic hydrocarbon (anthracene, pyrene, phenanthrene, chrysene, perylene and triphenylene) and derivatives thereof.

[0009] Further, the carbon-based conductive filler is any one of graphite, carbon nanofiber, carbon nanotube, carbon fiber and carbon black.

[0010] Further, the melt-blending temperature is 160-180 DEG C, the blending time is 5-15 min and the rotating speed is 60-100 rpm.

[0011] Further, the pressure in the hot-pressing process is 10 MPa and the hot-pressing time is 5 min.

[0012] A polymer-based PTC composite based on pi-pi interaction, wherein the polymer-based PTC composite comprises 100 parts by weight of an aromatic polymer, 1-25 parts by weight of a conductive filler, and 0.05-10 parts by weight of an aromatic supermolecular filler.

[0013] Use of a polymer-based PTC composite based on pi-pi interaction, wherein the polymer-based PTC composite is used in the preparation of overcurrent protection materials.

[0014] Technical effects

[0015] (1) The polymer-based PTC composite based on pi-pi interaction provided by the present application has low cost and can be continuously produced without any additional modification auxiliary means. Compared with the polymer / conductive filler composite without the third component of the aromatic supermolecular filler, the composite with the aromatic supermolecular filler has higher PTC strength and better cycle stability, and can provide a new method for effectively improving the comprehensive performance of PTC materials for existing PTC material research work.

[0016] (2) The polymer-based PTC composite based on pi-pi interaction provided by the present application can provide a new method for improving PTC behavior. This method does not require any modification means or additional steps, but only uses the interaction between the aromatic small molecule and the conductive filler to improve the PTC strength, and the sample can be directly prepared in large quantities by a simple melt processing method, which undoubtedly provides a new method for improving the comprehensive performance of PTC materials.

[0017] (3) The use of the polymer-based PTC composite based on pi-pi interaction provided by the present application has a good application prospect in the preparation of overcurrent protection materials due to the improved strength of the polymer-based PTC composite. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the example embodiments of the present application, the drawings needed in the examples will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation on the scope. Other related drawings can also be obtained by those skilled in the art without creative labor. In the drawings

[0019] In the drawings:

[0020] Figure 1 The resistivity-temperature curve of the material obtained in Example 1 of the present application and the blank sample;

[0021] Figure 2Cycle curve of the material obtained in Example 1 of the present application;

[0022] Figure 3 Cycle curve of the blank sample of Example 1 of the present application;

[0023] Figure 4 Comparison of polymer crystallinity of the material obtained in Example 1 of the present application and the blank sample;

[0024] Figure 5 Resistivity-temperature curve of the material obtained in Example 2 of the present application and the blank sample;

[0025] Figure 6 Cycle curve of the material obtained in Example 2 of the present application;

[0026] Figure 7 Comparison of polymer crystallinity of the material obtained in Example 2 of the present application and the blank sample. DETAILED DESCRIPTION

[0027] The embodiments of the present application will be described below in conjunction with Examples 1-2 of the present application and the accompanying drawings. Figures 1 to 7 It should be apparent that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0028] Example 1

[0029] 34 g of polyethylene, 6 g of carbon nanofiber and 0.04 g of anthracene molecules were respectively blended by a banbury mixer; the blending temperature was 180°C, the rotating speed was 60 rpm, and the blending time was 10 minutes. Then the blended sample was hot-pressed into a sheet at 180°C by a flat vulcanization instrument to obtain a polymer-based PTC composite material based on π-π interaction.

[0030] The blank sample was a melt-blended product of 34 g of polyethylene and 6 g of carbon nanofiber, and its volume resistivity-temperature dependence curve is shown in Figure 1 The PTC strength of the blank sample was about 3.9, while the PTC strength of the sample obtained in Example 1 was about 5.5, indicating that the PTC strength of the composite material could be improved after adding 0.04 g of anthracene molecules.

[0031] It can be seen from Figure 2 that the cycle stability was also improved. After five temperature rising and falling cycles, the PTC strength and the room temperature resistance of the sample obtained in Example 1 were not found to change, while the blank sample showed that the PTC strength increased with the increase of the cycle number, indicating that the stability of the conductive network was gradually destroyed with the increase of the cycle number. Figure 3 Figure 4 ​It can be seen that the introduction of anthracene molecules can reduce the crystallinity of polyethylene, which eliminates the interference of crystallinity on the increase of PTC strength.

[0032] Example 2

[0033] 34 g of polyethylene, 6 g of carbon nanofiber and 0.04 g of pyrene molecules were respectively taken and blended by a banbury mixer; the blending temperature was 180 °C, the rotating speed was 60 rpm, and the blending time was 10 minutes. Then the blended sample was hot-pressed into a sheet at 180 °C by a flat vulcanizing instrument to obtain a polymer-based PTC composite material based on π-π interaction.

[0034] The volume resistivity-temperature dependence curve of the blank sample of Example 2, which was the melt-blended product of 34 g of polyethylene and 6 g of carbon nanofiber, is shown in Figure 5 The PTC strength of the blank sample of Example 2 was around 3.9, while the PTC strength of Example 2 was around 4.8, indicating that the PTC strength of the composite material could be improved after adding 0.04 g of pyrene molecules. From Figure 6 It can be seen that the cycle stability performance is also improved. From Figure 7 It can be seen that the introduction of pyrene molecules can reduce the crystallinity of polyethylene, which eliminates the interference of crystallinity on the increase of PTC strength.

[0035] According to the data in Table 1, the PTC strength of Example 1, Example 2 and the blank sample in the five heating processes can be known, and the data in Table 2 can know the crystallinity of Example 1, Example 2 and the blank sample.

[0036] The data in Table 1 is

[0037] The PTC strength of Example 1, Example 2 and the blank sample in the five heating processes in Table 1

[0038] Cycles Example 1 (2) blank Example 1 Example 2 1 3.84 5.45 4.81 2 3.97 5.57 5.06 3 4.51 5.45 5.13 4 5.06 5.75 4.83 5 4.79 5.96 4.72

[0039] The crystallinity of Example 1, Example 2 and the blank sample in Table 2

[0040] Sample Crystallinity (%) Example 1 (2) blank 77.65 Example 1 71.47 Example 2 73.11

[0041] The polymer-based PTC composite material based on pi-pi interaction provided by the application can improve the PTC intensity by adding aromatic super-molecular fillers, and when the temperature increases, the conductive network is destroyed, thereby increasing the gap between the conductive fillers, and because the aromatic fillers can interact with the carbon fillers with a conjugated structure through pi-pi interaction, the aromatic fillers tend to be around the conductive fillers during the blending process, so that when the gap between the conductive fillers increases with the increase of the temperature, the aromatic fillers can migrate into the gap through the polymer matrix, thereby improving the tunneling resistance, and thus increasing the PTC intensity, and the aromatic super-molecular fillers for improving the PTC intensity have not been reported in other documents, and other works only focus on the interaction between the conductive fillers and the matrix, and no work involves the interaction between the aromatic small-molecule fillers and the conductive fillers, therefore, by introducing the third component small molecules capable of interacting with the conductive fillers through a simple melt blending process, the work can improve the PTC intensity and the cycle stability to a certain extent, which is of guiding significance to the PTC work.

[0042] The preparation method of the polymer-based PTC composite material based on pi-pi interaction provided by the application does not need any other modification means or additional means, and the PTC intensity can be improved through the interaction between the aromatic small molecules and the conductive fillers in the simplest way, and the simple melt processing method can realize mass production, thereby providing a new method for improving the comprehensive performance of the PTC material.

[0043] The application of the preparation method of the polymer-based PTC composite material based on pi-pi interaction provided by the application can improve the intensity of the polymer-based PTC composite material through the improvement of the method and the material, and can be well applied to the preparation of overcurrent protection materials.

Claims

1. A method for preparing a polymer-based PTC composite material based on π-π interactions, characterized in that, The method comprises the following steps: The polymer matrix, carbon-based conductive filler and aromatic group-containing supramolecular filler are melt-blended, hot-pressed and cold-pressed The polymer matrix, carbon-based conductive filler and aromatic group-containing supramolecular filler are melt-blended, hot-pressed and cold-pressed The polymer matrix is any one of polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, ethylene-vinyl acetate copolymer and thermoplastic polyurethane elastomer; the aromatic group-containing supramolecular filler is any one of polycyclic aromatic hydrocarbons anthracene, pyrene, phenanthrene, chrysene, perylene and triphenylene and derivatives thereof; The melt-blending temperature is 160-180℃, the blending time is 5-15min, and the rotating speed is 60-100rpm; the pressure in the hot-pressing process is 10MPa, and the hot-pressing time is 5min; In the polymer-based PTC composite material, 100 parts by weight of polymer, 1-25 parts by weight of conductive filler and 0.05-10 parts by weight of aromatic group-containing supramolecular filler.

2. The method for preparing a polymer-based PTC composite material based on π-π interactions according to claim 1, characterized in that, The carbon-based conductive filler is any one of graphite, carbon nanofiber, carbon nanotube, carbon fiber and carbon black.

3. The polymer-based PTC composite material based on π-π interaction prepared by the method of claim 1 or 2 is applied to the preparation of overcurrent protection material.

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