CN102585502B - A preparation method of high-temperature polymer-based PTC material with delayed NTC effect - Google Patents

Abstract

The invention relates to a preparation method of a high-temperature polymer PTC material with delayed NTC effect. Materials include: conductive carbon black (CB), polymer matrix polyphenylene sulfide (PPS) and polytetrafluoroethylene (PTFE), and its formula is: CB content 3%~15%, PPS content 42.5%~67.9% by mass percentage %, PTFE content 25.5%~48.5%, of which the mass ratio of PPS to PTFE is 5/5~7/3; the preparation method is to modify the CB coupling agent, and then disperse it with PPS powder and PTFE powder in absolute ethanol , after mixing uniformly by ball milling, the solvent is volatilized, and then hot-pressed and sintered at a certain temperature to obtain a CB/PPS/PTFE composite material. The high-temperature polymer PTC material with delayed NTC effect of the present invention is characterized in that it does not need to use cross-linking equipment to radiate and cross-link to eliminate the NTC effect of the material, which reduces the manufacturing cost and simplifies the production process; the room temperature resistivity of the composite material can be passed Adjust the CB content and the weight ratio of PPS and PTFE to adjust.

Description

A preparation method of high-temperature polymer-based PTC material with delayed NTC effect

technical field

The invention relates to a polymer-based PTC composite material in the field of modern electronics and electrical engineering, and relates to a preparation method of a high-temperature polymer-based PTC material with delayed NTC effect.

technical background

At present, the manufacture of polymer PTC materials mainly uses single-component crystalline or semi-crystalline polymers such as polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), and polyvinylidene fluoride (PVDF) as matrix materials. The melting point of the matrix material is generally less than 150 °C, so that the final polymer-based PTC material does not have a high service temperature. At the same time, such PTC materials often need radiation crosslinking to eliminate the NTC effect during processing, otherwise, when the temperature of the material rises close to the melting point of the polymer matrix due to energization during use, the polymer will be deformed or even burned. However, the radiation crosslinking treatment process of PTC materials requires the use of expensive crosslinking equipment, which will increase the production cost of the material. With the rapid development of modern science and technology, the application fields of polymer PTC materials continue to expand, and it is necessary to develop polymer-based PTC materials with convenient processing, low manufacturing cost, higher service temperature (PTC transition temperature higher than 200 ℃), and excellent comprehensive performance. The current PE, EVA, PP and PVDF one-component polymer-based PTC materials cannot meet the requirements of high temperature use at 200 °C. Using a semi-crystalline polymer material with a high melting point as a matrix is the basic method to increase the service temperature of a polymer-based PTC material. Two or more polymers are blended to form a multi-component composite system, which can make the composite material different from a single polymer. The novel and unique performance of the material matrix realizes the complementary advantages of each component, and even exhibits new functions. Therefore, multi-polymer matrix blend composites have attracted more and more attention in the research and development of polymer-based PTC materials.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a high-temperature polymer-based PTC material with significantly delayed NTC effect.

A kind of preparation method of the high-temperature polymer-based PTC material with delayed NTC effect of the present invention is characterized in that:

1) Raw material: The high-temperature polymer-based PTC material with delayed NTC effect has the following material composition: conductive filler CB, polymer matrix material PPS and PTFE; the CB conductive filler accounts for 3.0% of the total mass of the composite material ~15.0%; the polymer matrix PPS content is 42.5%~67.9%, and the PTFE content is 25.5%~48.5%, wherein the mass ratio of PPS to PTFE is 5/5~7/3; the average particle size of the CB conductive filler is 50nm, used after being treated with a silane coupling agent, wherein the mass ratio of the silane coupling agent to CB is 100:1; the melting point of the polymer matrix PPS is 285°C, and the average particle size is 20 μm; the polymer matrix The melting point of the matrix PTFE is 327 °C, the melt viscosity is 10 ¹⁰ Pa·s, and the average particle size is 25 μm;

2) Surface treatment of CB conductive filler: Ultrasonic disperse and stir the CB powder at room temperature to form a suspension in absolute ethanol, then add the coupling agent and continue stirring for 10-30 minutes; then add deionized water, in Ultrasonic dispersion and stirring at 40-60°C for 15-60 minutes; centrifuge the powder, wash with absolute ethanol for 1-3 times, vacuum-dry at 60-120°C for 2-5 hours, cool to room temperature naturally before use ; Wherein the coupling agent is γ-aminopropyltriethoxysilane;

3) Composite: Weigh the PPS and PTFE powder and the CB powder modified by the silane coupling agent in step (2), so that the mass percentage of the CB conductive filler is 3.0~15.0%; the mass percentage of the polymer matrix PPS 42.5%~67.9%; the mass percentage of PTFE is 25.5%~48.5%; the mass ratio of PTFE to PPS is 5/5~7/3; then the CB powder, PPS powder and PTFE powder are dispersed in ethanol and ball milled After mixing evenly, the solvent was evaporated in an oven, and then dried in a vacuum oven at 120 °C for 1 h to obtain a mixed powder;

4) Molding: put the mixed powder in a cemented carbide mold, hot press at 330~380°C under a pressure of 100 MPa for 15 minutes, and cool to room temperature to obtain a disc with a diameter of 20 mm and a thickness of 1~3 mm sample.

The invention has the following beneficial effects: the polymer PTC composite material has a transition temperature as high as 250°C and can be used as a high-temperature PTC material; the NTC effect of the composite material is delayed from 295°C to about 335°C, which is delayed by about 40°C, avoiding The expensive radiation cross-linking process is simplified, the manufacturing process of PTC materials is simplified, and the production cost is reduced; the composite material uses high-temperature-resistant polymer matrix PPS and PTFE, which are non-combustible, which ensures the safety of the material and does not require additional additions Toxic halogen-containing flame retardant; the composite material can change the conductivity of the composite material by adjusting the content of CB and the weight ratio of PPS and PTFE, so the room temperature conductivity of the composite material can be controlled more accurately.

Description of drawings

Fig. 1 is the process flow sheet that the present invention prepares polymer PTC composite material;

Fig. 2 is the DSC curve of the CB/PPS/PTFE composite material when the CB conductive filler content is 8 wt%, and the polymer matrix PPS and PTFE mass ratio are respectively 7/3, 6/4, 5/5;

Figure 3 shows that the CB conductive filler content is 8wt%, PPS/PTFE=5/5 (w/w), CB/PPS/PTFE composite material

resistance-temperature curve;

Figure 4 shows that the CB conductive filler content is 8wt%, PPS/PTFE=7/3 (w/w), CB/PPS/PTFE composite material

resistance-temperature curve;

Fig. 5 is that CB conductive filler content is 12wt%, PPS/PTFE=5/5 (w/w), the resistance-temperature curve of CB/PPS/PTFE composite material;

Figure 6 shows that the CB conductive filler content is 9wt%, PPS/PTFE=5/5 (w/w), CB/PPS/PTFE composite material

resistance-temperature curve;

Figure 7 shows that the CB conductive filler content is 9wt%, PPS/PTFE=6/4 (w/w), CB/PPS/PTFE composite material

resistance-temperature curve;

Figure 8 shows that the CB conductive filler content is 9wt%, PPS/PTFE=7/3 (w/w), CB/PPS/PTFE composite material

resistance-temperature curve.

Detailed ways

The present invention will be further described in detail below in conjunction with specific embodiments. The embodiment is only an illustration of the present invention, and does not constitute a limitation to the present invention. The embodiments are examples of practical applications, which are easy to grasp and verify for those skilled in the art. If some changes are made on the basis of the present invention, then the essence does not go beyond the scope of the present invention.

Example 1

(1) At room temperature, 100 g of CB conductive filler powder is ultrasonically dispersed and stirred to form a suspension in absolute ethanol, and then 1 g of coupling agent (γ-aminopropyltriethoxysilane) is added and stirred continuously 10~30 minutes; then add deionized water, ultrasonically disperse at 40~60°C and stir for 15~60 minutes; centrifuge the powder, and then use absolute ethanol to wash 1~3 times, then vacuum at 60~120°C Dry for 2-5 hours, then use after cooling to room temperature naturally;

(2) Weigh 3.1269 g PPS and 3.1269 g PTFE powder and 0.5438 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 8%, polymer matrix PPS mass The percentage content is 46%, and the mass percentage content of PTFE is 46%, wherein the mass ratio of PPS and PTFE is 5/5; disperse CB powder, PPS powder and PTFE powder in ethanol, mix them evenly by ball milling, and evaporate the solvent in an oven , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: Put the mixed powder in a cemented carbide mold, hot press at 360 °C for 15 minutes under a pressure of 100 MPa, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1~3 mm sample;

(4) The preparation flow diagram of the composite material in Examples 1-6 is shown in accompanying drawing 1; the sample 5-10 mg sample obtained in step (3) is cut with a blade, in nitrogen, the heating rate is under the condition of 20 ℃/min Measure the DSC curve of the sample, the results are shown in the curve c in the accompanying drawing 2; the two ends of the sample obtained in step (3) are coated with conductive silver paste and treated at 100°C for 1h, and stabilized for 24h after natural cooling, so that the silver paste and the chip material Reach the ohmic contact, and then test the resistance-temperature characteristics of the sample. The results are shown in Figure 3: the room temperature resistivity is 151 Ω cm; Occurs after a delay to 335 °C, a delay of 40 °C.

Example 2

(1) The surface treatment process of CB conductive filler powder is the same as example 1;

(2) Weigh 4.4291 g PPS and 1.8982 g PTFE powder and 0.5502 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 8%, polymer matrix PPS mass The percentage content is 64.4%, and the mass percentage content of PTFE is 27.6%, wherein the mass ratio of PPS and PTFE is 7/3; disperse CB powder, PPS powder and PTFE powder in ethanol, mix them evenly by ball milling, and evaporate the solvent in an oven , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: Put the mixed powder in a cemented carbide mold, hot-press at 380 °C for 15 minutes under a pressure of 50 MPa, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1-3 mm sample;

(4) The DSC curve test condition of the sample is the same as that of Example 1, and the results are shown in curve a in the accompanying drawing 2; ; The PTC transition starts from around 250 ℃ and ends at 290 ℃, with a PTC intensity of 4.7; the NTC effect occurs after a delay of 45 ℃ from 290 ℃ to 335 ℃.

Example 3

(1) The surface treatment process of CB conductive filler powder is the same as example 1;

(2) Weigh 2.4684 g PPS and 2.4684 g PTFE powder and 0.6732 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 12%, polymer matrix PPS mass The percentage content is 44%, and the mass percentage content of PTFE is 44%, wherein the mass ratio of PPS and PTFE is 5/5; disperse CB powder, PPS powder and PTFE powder in ethanol, mix them evenly by ball milling, and evaporate the solvent in an oven , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: Put the mixed powder in a cemented carbide mold, hot press at 340 °C under 100 MPa pressure for 15 minutes, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1~3 mm sample;

(4) The test method of sample resistance-temperature characteristics is the same as in Example 1, and the results are shown in Figure 5: the room temperature resistivity is 30 Ω cm; the PTC transition starts from about 250 °C and ends at 295 °C, and the PTC intensity is 0.8; The effect occurs after a delay from 295 °C to 335 °C, a delay of 40 °C.

Example 4

(1) The surface treatment process of CB conductive filler powder is the same as example 1;

(2) Weigh 2.9514 g PPS and 2.9514 g PTFE powder and 0.5838 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 9%, polymer matrix PPS mass The percentage content is 45.5%, and the mass percentage content of PTFE is 45.5%, wherein the mass ratio of PPS and PTFE is 5/5; disperse CB powder, PPS powder and PTFE powder in ethanol, mix them evenly by ball milling, and evaporate the solvent in an oven , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: put the mixed powder in a cemented carbide mold, hot press at 360 °C for 15 minutes under a pressure of 80 MPa, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1~3 mm sample;

(4) The test method of sample resistance-temperature characteristics is the same as in Example 1, and the results are shown in Figure 6: the room temperature resistivity is 102 Ω cm; the PTC transition starts from about 250 ℃ and ends at 295 ℃, and the PTC intensity is 2.4; the NTC The effect occurs after a delay from 295 °C to 335 °C, a delay of 40 °C.

Example 5

(1) The surface treatment process of CB conductive filler powder is the same as example 1;

(2) Weigh 3.7152 g PPS and 2.4768 g PTFE powder and 0.6124 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 9%, polymer matrix PPS mass The percentage content is 54.6%, and the mass percentage content of PTFE is 36.4%, wherein the mass ratio of PPS and PTFE is 6/4; disperse CB powder, PPS powder and PTFE powder in ethanol, mix them evenly by ball milling, and evaporate the solvent in an oven , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: Put the mixed powder in a cemented carbide mold, hot press at 340 °C and 50 MPa for 15 minutes, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1~3 mm sample;

(4) The DSC curve test condition of sample is the same as embodiment 1, and the results are shown in the curve b in accompanying drawing 2; ; The PTC transition starts from around 250 ℃ and ends at 285 ℃, with a PTC intensity of 3.7; the NTC effect occurs after a delay of 40 ℃ from 285 ℃ to 330 ℃.

Example 6

(1) The surface treatment process of CB conductive filler powder is the same as example 1;

(2) Weigh 3.8418 g PPS and 1.6465 g PTFE powder and 0.5428 g of CB powder modified by silane coupling agent in step (1); make the mass percentage of CB conductive filler be 9%, polymer matrix PPS mass The percentage content is 63.7%, the mass percentage content of PTFE is 27.3%, and the mass ratio of PPS and PTFE is 7/3; the CB powder, PPS powder and PTFE powder are dispersed in ethanol, and the solvent is evaporated in an oven after mixing evenly by ball milling , and then dried in a vacuum oven at 120°C for 1 h to obtain a mixed powder;

(3) Molding: Put the mixed powder in a cemented carbide mold, hot press at 340 °C and 50 MPa for 15 minutes, and cool to room temperature to obtain a disc shape with a diameter of 20 mm and a thickness of 1~3 mm sample;

(4) The test method of sample resistance-temperature characteristics is the same as in Example 1, and the results are shown in Figure 6: the room temperature resistivity is 896 Ω cm; the PTC transition starts from about 250 ℃ and ends at 300 ℃, and the PTC intensity is 4.8; the NTC The effect occurs after a delay from 300 °C to 335 °C, a delay of 35 °C.

Claims (1)

1. preparation method with the high temperature polymer matrix PTC material that postpones the NTC effect is characterized in that method is:

1) raw material: described high temperature polymer matrix PTC material with delay NTC effect has following material to form: conductive filler material CB, polymer matrix material PPS and PTFE; Described CB conductive filler material accounts for 3.0% ~ 15.0% of matrix material total mass; Described polymeric matrix PPS content 42.5% ~ 67.9%, PTFE content 25.5% ~ 48.5%, wherein PPS and PTFE mass ratio are 5/5 ~ 7/3; Described CB conductive filler material median size is 50nm, uses after silane coupling agent is processed, and wherein the mass ratio of silane coupling agent and CB is 1:100; Described polymeric matrix PPS fusing point is 285 ℃, and median size is 20 μ m; Described polymeric matrix PTFE fusing point is 327 ℃, and melt viscosity is 10 ¹⁰Pas, median size is 25 μ m;

2) surface treatment of CB conductive filler material: make it in dehydrated alcohol, form suspension by ultra-sonic dispersion and stirring in the CB powder under the room temperature, then add and continue behind the coupling agent to stir 10 ~ 30 minutes; Add subsequently deionized water, at 40 ~ 60 ℃ of lower ultra-sonic dispersion and stirred 15 ~ 60 minutes; The centrifugation powder, then use absolute ethanol washing 1 ~ 3 time after, 60 ~ 120 ℃ of lower vacuum-dryings 2 ~ 5 hours, use after naturally cooling to room temperature; Wherein coupling agent is γ-aminopropyl triethoxysilane;

3) compound: take by weighing the silane coupler modified CB powder that obtains in PPS and PTFE powder and the step (2), the quality percentage composition that makes the CB conductive filler material is 3.0 ~ 15.0%; Polymeric matrix PPS quality percentage composition is 42.5% ~ 67.9%; PTFE quality percentage composition is 25.5% ~ 48.5%; Wherein PTFE and PPS mass ratio are 5/5 ~ 7/3; Then CB powder, PPS powder and PTFE powder are disperseed in ethanol, ball milling mixes afterwards evaporating solvent in baking oven, then places dry 1 h under 120 ℃ of conditions of vacuum drying oven, obtains mixed powder;

4) moulding: as in the sintered-carbide die, in hot pressing 15 minutes under 100 MPa pressure under 330 ~ 380 ℃, obtaining diameter behind the cool to room temperature is 20 mm with mixed powder, and thickness is the disc-shaped sample of 1 ~ 3 mm.

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