TWI640570B - Polymer thermistor composite and polymer thermistor - Google Patents

Abstract

The polymer thermistor composite of the present invention comprises 5 wt% to 15 wt% of a crystalline polymer, 75 wt% to 90 wt% of a conductive filler, and 1 wt% to 7 wt% of an epoxy resin having at least three epoxy groups. 0.25 wt% to 0.5 wt% of a curing agent and 0.5 wt% to 3 wt% of an auxiliary agent. The polymer thermistor made of the polymer thermistor composite material has low electrical resistivity, good pressure resistance and good electrical resistance reproducibility at room temperature.

Description

Polymer thermistor composite and polymer thermistor

The invention relates to a polymer thermistor composite material and a polymer thermistor, in particular to a polymer thermistor composite material and a polymer thermistor comprising an epoxy resin having at least three epoxy groups.

The positive temperature coefficient thermistor (PTC thermistor) is a widely used electronic component for over-current protection applications. The positive temperature coefficient thermistor maintains its resistance at normal temperature. Low level, so that the circuit can operate normally; if the fault occurs, the current of the circuit is abnormally too large, so that the temperature of the circuit rises, the resistance of the positive temperature coefficient thermistor becomes larger as the temperature increases, thereby limiting the circuit Current to protect the circuit. When the fault condition is removed, the circuit temperature returns to normal as the current returns to normal, and the resistance of the positive temperature coefficient thermistor returns to a low level, so that the circuit can continue to operate normally.

Polymeric temperature coefficient thermistor (PPTC thermistor) is a kind of positive temperature coefficient thermistor, which is prepared by mixing a crystalline polymer with a conductive filler. The molecular thermistor composite material is then pressed onto both sides of the polymer thermistor composite material, and the polymer thermistor is obtained after cutting.

The crystalline polymer is generally a polyolefin or a copolymer thereof such as polyethylene, polypropylene or an ethylene/vinyl acetate copolymer. The conductive filler is generally carbon black powder, metal powder, metal Carbide or ceramic powder; wherein the carbon black powder has a good adhesion to the polymer due to the polar group on the surface, and has better stability, but the conductivity of the carbon black powder itself is limited, so the resistance The value is usually too high, which is not conducive to meeting the requirements of low resistance.

Alternatively, metal powder can be used as the conductive filler, which can effectively reduce the resistance value, but since the metal powder is easily oxidized, the composite material needs to be encapsulated to prevent the metal powder from being oxidized in the air to cause an increase in the resistance value, however, when After the composite material is encapsulated, its volume is difficult to shrink, so it cannot satisfy the demand for miniaturization of electronic components.

In order to satisfy both the low resistance and the miniaturization of electronic components, metal carbide ceramic powder can be used as a conductive filler, such as titanium carbide, but it is difficult to control because the combination of metal carbide and crystalline polymer is generally poor. The reproducibility of the resistor, therefore, there is still room for improvement in the existing polymer thermistor composite.

In view of the above problems, an object of the present invention is to provide a polymer thermistor composite material and a polymer thermistor having low electrical resistivity, good withstand voltage performance and good temperature at room temperature. Resistance reproducibility.

To achieve the above object, the polymer thermistor composite of the present invention comprises 5 wt% (wt%) to 15 wt% of a crystalline polymer, 75 wt% to 90 wt% of a conductive filler, and 1 wt% to 7 wt% of at least three An epoxy group epoxy resin, 0.25 wt% to 0.5 wt% of a curing agent, and 0.5 wt% to 3 wt% of an auxiliary agent.

According to the above technical means, the polymer thermistor composite material of the invention can make the prepared polymer thermistor have lower resistivity, better pressure resistance performance and good resistance reproducibility, so Meets low resistance requirements and is used in high voltage electronic devices.

Specifically, the crystalline polymer may be polyethylene, polypropylene, polyvinylidene difluoride, ethylene/propylene copolymerization. (ethylene/propylene copolymer), ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/methyl acrylate copolymer And an ethylene/ethyl acrylate copolymer, a polyamide, a polycarbonate, a polysulfone or a combination thereof.

Additionally, the electrically conductive filler may be a metal carbide. Specifically, the electrically conductive filler may be titanium carbide, tungsten carbide, graphene, carbon fiber, or a combination thereof.

The curing agent is melamine or 4,4 ' -diaminodiphenyl hydrazine.

The adjuvant comprises an antioxidant and a coupling agent, the antioxidant being a phenolic antioxidant or an amine antioxidant, the coupling agent being a decane coupling agent or a titanate coupling agent.

Further, the epoxy resin having at least three epoxy groups is selected from the group consisting of glycidyl ethers having at least three epoxy groups, esters having at least three epoxy groups, A decane having at least three epoxy groups or a combination thereof. For example, the epoxy resin having at least three epoxy groups may be tetraglycidyl-4, 4'-diaminodiphenyl methane (TGDDM), triglycidyl uridine (triglycidyl) Isocyanurate, TGIC), epoxy modified organic epoxy resin (purchased more confident chemical, commodity number: X-40-2670).

The invention further includes a polymeric thermistor comprising an intermediate layer and an electrode, the intermediate layer comprising the polymeric thermistor composite, the electrode being disposed on the intermediate layer.

The polymer thermistor has a resistance value of 1 milliohm (mΩ) to 40 mΩ in terms of performance of the polymer thermistor.

Preferably, the polymer thermistor has a withstand voltage of 12 volts (V) to 18 volts.

Preferably, the polymer thermistor is subjected to a voltage lower than the withstand voltage performance. After a thousand cycles, the resistance of the polymer thermistor is 10 to 14 times the resistance value before one thousand on-off cycles.

Examples 1 to 4: Polymer thermistor composites

Set a temperature of the dense chain machine at 180 ° C, add a crystalline polymer to the chain mixer and stir, then add a conductive filler with a particle size of 0.1 micron to 50 microns, and then at a speed of 40 revolutions per minute (round Per minute, rpm) dense chain crystalline polymer and conductive filler, and the rotation speed was increased to 80 rpm after 5 minutes.

After mixing at 80 rpm for 10 minutes, an epoxy resin having at least three epoxy groups, a curing agent, an antioxidant, and a coupling agent were added and mixed and smelted at 180 ° C to obtain a composition.

The composition is placed in a mold, the outer layer of the mold is a steel plate and the inner layer is provided with a mirror-finished copper foil, which is pre-pressed at a pressure of 50 kg/cm 2 and a temperature of 180 ° C for 5 minutes; after exhausting, 100 kg is taken. / square centimeter pressure, 180 ° C temperature is pressed for 3 minutes; and repeated pressing with the same parameters; finally, 150 kg / cm ^ 2 pressure, 180 ° C temperature for 5 minutes to form a polymer The thermistor composite materials, the addition ratios of the components in Examples 1 to 4 are listed in Table 1.

In Examples 1 to 4, the total amount of the crystalline polymer, the epoxy resin having at least three epoxy groups, and the curing agent was 11% by weight.

Wherein, the crystalline polymer is polyethylene; the conductive filler is titanium carbide particles, tungsten carbide particles, graphene particles or a combination thereof; and the epoxy resin having at least three epoxy groups is tetraglycidyl-4 , 4 '- diaminodiphenylmethane (tetraglycidyl diamincdiphenylmethane, TGDDM); the curing agent is 4,4' - diaminodiphenyl sulfone; the antioxidant is a phenolic antioxidant 1010 (CAS No.6683-19-8) The coupling agent is a decane coupling agent A-171 (CAS No. 2530-83-8).

Comparative Examples 1 and 2: Polymer Thermistor Composites

The polymer thermistor composite materials of Comparative Examples 1 and 2 were produced in a similar manner to Examples 1 to 4, except that the polymer thermistor composite materials of Comparative Examples 1 and 2 did not include at least three epoxy resins. The epoxy resin and the curing agent of the base, and the addition ratio of each component in Comparative Examples 1 and 2 are listed in Table 1.

Comparative Example 3: Polymer thermistor composite

The polymer thermistor composite material of Comparative Example 3 was produced in a similar manner to that of Example 4, except that the polymer thermistor composite material of the comparative example did not include an epoxy resin having at least three epoxy groups. Further, the epoxy resin added in Comparative Example 3 was an epoxy resin having two epoxy groups (purchased from Changchun Chemical Co., trade name: BE-188EL), and the curing agent purchased from Somar was H143. The addition ratio of each component in Comparative Example 3 is shown in Table 1.

Examples 5 to 8: Polymer thermistors

The polymer thermistor composite materials of Examples 1 to 4 were cut into a rectangular sheet having a thickness of 1.4 mm and an area of 2.6 mm 2 , and then the two metal foil sheets were pressed against the upper and lower surfaces of the sheet as electrodes. Then, the special cushioning material, the mirror copper foil and the steel plate are pressed at a pressure of 70 kg/cm 2 and a temperature of 180 ° C for 30 minutes to form a multilayer structure, which is the polymer thermistor of Examples 5 to 8, according to which This sheet serves as an intermediate layer of the polymer thermistor.

In another embodiment, different sizes of the polymer thermistor composite materials can be cut according to different resistance value requirements, thereby achieving a wider application.

Comparative Examples 4 to 6: Polymer Thermistors

The polymer thermistor composite materials of Comparative Examples 1 to 3 were cut to a thickness of 1.4 A sheet having a diameter of 2.6 mm 2 was fabricated, and the polymer thermistors of Comparative Examples 4 to 6 were produced by press-fitting in a manner similar to that of Examples 5 to 8.

In order to facilitate the comparison of the difference in characteristics between the polymer thermistors of Examples 5 to 8 and Comparative Examples 4 to 6, the resistance values, withstand voltage characteristics, and resistance reproducibility of each of the polymer thermistors were tested below, and the results were Listed in Table 1.

Test Example 1: Measurement of resistance value

The resistance value of each polymer thermistor is measured at room temperature, and the resistance value is additionally calculated as the resistivity according to the size of each polymer thermistor; the resistivity is calculated by multiplying the resistance value by the polymer The cross-sectional area of the thermistor is divided by the thickness of the polymer thermistor.

Test Example 2: Withstand voltage test

According to the standard test method of Underwriters Laboratories Inc. (UL), each polymer thermistor was subjected to withstand voltage test with a withstand voltage tester (label: ACP OWER, model: ADC4000).

Test Example 3: Resistance Reproducibility Test

In order to test whether the resistance value is reproducible, Test Example 3 first applies a voltage of 6 volts and a current of 20 amps to power off each polymer thermistor, and repeats the steps of energizing and de-energizing (referred to as the on-off cycle). After one thousand times, the resistance value after the on-off cycle is measured by a three-meter electric meter, and compared with the resistance value measured in the test example 1, and the resistance change rate is calculated. The calculation method of the resistance change rate is The resistance value after one thousand on-off cycles was divided by the percentage of the resistance value measured in Test Example 1.

Similarly, in this test example, a voltage of 12 volts and a current of 20 amps were applied to each of the polymer thermistors. After one thousand cycles of on-off, the resistance after the on-off cycle was measured by a three-meter meter. The value is compared with the resistance value measured in Test Example 1, and the resistance change rate is calculated. The resistance change rate is calculated by dividing the resistance value after the on-off cycle in Test Example 1. The percentage of the measured resistance value.

Referring to the experimental results of Table 1, in terms of the measurement results of the resistance values, the polymer thermistors of Examples 5 to 8 have lower resistance values than the polymer thermistors of Comparative Examples 4 to 6 and Low resistivity; for example, the resistance value of Example 5 (6.5 mΩ) is lower than that of Comparative Example 3 (8.6 mΩ), and similarly, the resistance value of Example 6 (6.8 mΩ) is also lower than that of Comparative Example 4. The resistance value (8.8 mΩ); accordingly, the polymer thermistor of the present invention may have a resistance value of 4 mΩ to 7 mΩ and a resistivity of 25 mΩ ̇mm to 50 mΩ ̇mm.

For the results of the withstand voltage test, the polymer thermistors of Examples 5 to 8 have higher withstand voltage performance than the polymer thermistors of Comparative Examples 4 to 6, and the resistance of the polymer thermistor of the present invention The pressure performance can reach 12V to 18V, while the pressure resistance of the comparative example 4 to 6 polymer thermistors is only 8V.

For the test results of the resistance reproducibility, the resistance values of the polymer thermistors of Examples 5 to 8 before the on-off cycle were between 4 mΩ and 7 mΩ, after one thousand on-off cycles (6V/20A). After that, the resistance value rises to 55mΩ to 90mΩ, and the resistance value changes by about 10 times to 13 times; even if the applied voltage is increased to 12V, after one thousand on-off cycles (12V/20A), the polymer heat The resistance of the varistor is only slightly higher than the voltage of 6V, which is roughly between 55mΩ and 95mΩ, and the resistance value varies by about 12 times to 14 times.

In contrast, the polymer thermistors of Comparative Examples 4 to 6 have a resistance value between 8 mΩ and 10 mΩ before the on-off cycle, and after a thousand on-off cycles (6 V/20 A), the resistance value rises to 3000mΩ to 3300mΩ, the resistance value is increased by about 350 times to 390 times; and when the applied voltage is raised to 12V, the polymer thermistors of Comparative Examples 4 to 6 are burned in the experiment, and Comparative Example 4 can be confirmed. The polymer thermistor of 6 cannot withstand an applied voltage exceeding 8V.

The polymer thermistors of Example 8 and Comparative Example 6 were specifically compared. The difference between Example 8 and Comparative Example 6 was that the epoxy resin used in Example 8 had three epoxy groups, and was used in Comparative Example 6. The epoxy resin has only two epoxy groups.

The resistance value (4.8 mΩ) of Example 8 was significantly lower than that of Comparative Example 6 in terms of the resistance value (8.4 mΩ). With respect to the withstand voltage performance, the withstand voltage performance of Example 8 was 15 V, and the withstand voltage performance of Comparative Example 6 was only 8 V. When the resistance reproducibility was tested, the resistance value change ratio of Comparative Example 6 was as high as 383 times under the operating condition of 6 V/20 A, which was much larger than the resistance value change rate of Example 8, and the polymer heat of Comparative Example 6 was further used. The varistor cannot withstand the operating voltage of 12V, so it is directly burned under the operating conditions of 12V/20A.

In summary, the polymer thermistor made of the polymer thermistor composite of the present invention has low electrical resistivity, good pressure resistance and good electrical resistance reproducibility at room temperature.

Claims (10)

A polymer thermistor composite comprising: 5 wt% to 15 wt% of a crystalline polymer; 75 wt% to 90 wt% of a conductive filler; 1 wt% to 7 wt% of at least 3 epoxy Base epoxy resin; 0.25 weight percent to 0.5 weight percent curing agent; 0.5 weight percent to 3 weight percent adjuvant. The polymer thermistor composite material according to claim 1, wherein the crystalline polymer is polyethylene, polypropylene, polyvinylidene fluoride, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/acrylic acid Ester copolymer or composition thereof. The polymer thermistor composite according to claim 1, wherein the conductive filler is titanium carbide, tungsten carbide, graphene, carbon fiber or a combination thereof. The polymer thermistor composite according to claim 1, wherein the curing agent is melamine or 4,4 ' -diaminodiphenyl hydrazine. The polymer thermistor composite according to claim 1, wherein the auxiliary agent comprises an antioxidant and a coupling agent, and the antioxidant is a phenolic antioxidant or an amine antioxidant, and the coupling agent is a decane coupling. A crosslinking agent or a titanate coupling agent. The polymer thermistor composite according to claim 1, wherein the epoxy resin having at least three epoxy groups is selected from the group consisting of glycidol having at least three epoxy groups. An ether, a urate having at least three epoxy groups, and a siloxane having at least three epoxy groups. A polymer thermistor comprising: an intermediate layer comprising the polymer thermistor composite according to any one of claims 1 to 6; and an electrode disposed on a surface of the intermediate layer. The polymer thermistor according to claim 7, wherein the polymer thermistor has a resistance value of 1 milliohm to 40 milliohm. The polymer thermistor according to claim 7, wherein the polymer thermistor has a withstand voltage of 12 volts to 18 volts. The polymer thermistor according to claim 9, wherein the polymer thermistor has a resistance value of one thousand times after performing one thousand on-off cycles at a voltage lower than the withstand voltage performance. The resistance value before the on-off cycle is 10 to 14 times.