WO2019242684A1 - 一种耐疲劳导电复合材料及其制备方法 - Google Patents

一种耐疲劳导电复合材料及其制备方法 Download PDF

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WO2019242684A1
WO2019242684A1 PCT/CN2019/092069 CN2019092069W WO2019242684A1 WO 2019242684 A1 WO2019242684 A1 WO 2019242684A1 CN 2019092069 W CN2019092069 W CN 2019092069W WO 2019242684 A1 WO2019242684 A1 WO 2019242684A1
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carbon fiber
nano
acid
carbon
micro
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PCT/CN2019/092069
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English (en)
French (fr)
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王杨勇
夏永峰
侯献才
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珠海安润普科技有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables

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  • the invention relates to the technical field of rubber conductive composite materials and preparation methods thereof, in particular to a fatigue-resistant conductive silicone rubber composite material and a preparation method thereof.
  • Dispersing various conductive fillers in insulating silicone rubber to prepare conductive silicone rubber is one of the most commonly used methods for preparing conductive silicone rubber.
  • the conductive silicone rubber prepared by this method has the advantages of stable resistance time characteristics, controllable resistance temperature coefficient, and high use temperature. It has been widely used in antistatic materials, electromagnetic shielding materials, positive / negative temperature coefficient materials, sensors, and wearable products.
  • the conductive filler of conductive silicone rubber has a crucial impact on its conductivity.
  • Commonly used conductive fillers are metal and carbon. In metal-based fillers, the price of gold and silver is too high, and other metals are easily oxidized. In addition, due to the large metal density, it is not easy to uniformly disperse in the polymer, and the filling amount is generally high. Therefore, in the industrial production of conductive silicone rubber, carbon-based conductive fillers are mostly used.
  • Silicone rubber has the advantages of heat resistance, cold resistance, non-toxicity, biological aging resistance, physiological inertia, small reaction to human tissues, and good physical and mechanical properties. Therefore, conductive silicone rubber has great application potential in wearable electronic products.
  • Existing carbon-based conductive fillers mainly include conductive carbon black, graphite, carbon nanotubes, graphene, and carbon fibers. Carbon black and graphite due to their larger particle sizes tend to cause the mechanical properties of the composite materials (such as tensile strength, elongation at break, and fatigue resistance) to fall more during the addition process; and carbon nanotubes and graphene as nanometers Fillers.
  • Chinese patent application with publication number CN107325416A reports a method using a mixture of graphene and metal particles as a conductive filler, silicon rubber, EPDM rubber, and natural rubber as a matrix material.
  • the prepared rubber composite material has good aging resistance.
  • conductivity Chinese patent application with publication number CN107400368A reports a method using a mixture of graphene and carbon nanotubes as a conductive filler, a silicone rubber matrix material, and a prepared rubber composite material having low density and good physical properties.
  • the surface of the carbon fiber is subjected to acid oxidation treatment, which can generate hydroxyl, carbonyl and nitro groups (Sharma M, Gao S, E, Sharma H, Wei L, Bijwe J. Carbon fiber surfaces and composite interphases, Composites Science and Technology, 2014, 102: 35-50).
  • acid oxidation treatment can generate hydroxyl, carbonyl and nitro groups (Sharma M, Gao S, E, Sharma H, Wei L, Bijwe J. Carbon fiber surfaces and composite interphases, Composites Science and Technology, 2014, 102: 35-50).
  • the effect of acid oxidation treatment on the surface of carbon fibers is that the surface of oxidized carbon fibers has polarity, and the fibers have the same polarity with each other, which reduces the agglomeration of carbon fibers in the rubber matrix; the second is that the surface of carbon fibers becomes cleaner, which is beneficial to fibers and rubber.
  • the increase in the polarity of the surface of the carbon fiber is conducive to increasing the van der Waals force between the fiber and the polymer chain, thereby improving the mechanical properties of the composite material.
  • the number of oxygen-containing groups generated by the acid oxidation treatment method in the prior art still has room for further improvement.
  • nano fillers have a large specific surface area and high surface activity.
  • fillers for polymer composites they have the advantages of small additions and excellent mechanical properties of the composites, while fillers with diameters below 30 nanometers have the advantages More obvious (Shao-Yun, Fu, Xi-Qiao, Feng, Bernd, Lauke, Yiu-Wing, Mai.Effects of particle size, particle / matrix interface adhesion, particle loading, mechanical properties, composites: Composites: Part, B, 2008, 39 (6): 933–961).
  • the amount of addition generally needs to be more than 6 to 8 parts.
  • nanomaterials have very high surface energy and large specific surface area. They are extremely prone to blocking and agglomeration during the preparation of composite materials. When the amount of addition exceeds 5 parts, the agglomeration is more serious.
  • the amount of addition is relatively large (generally not less than 15 parts), which will cause a significant decline in the mechanical properties of composite materials.
  • tiny silver streaks or cracks are easy to appear inside the rubber composite material.
  • a first object of the present invention is to provide a silicone rubber-based conductive composite material having good conductive stability and fatigue resistance.
  • a second object of the present invention is to provide a method for preparing a silicone rubber-based conductive composite material having good conductive stability and fatigue resistance.
  • the present invention provides a fatigue-resistant conductive composite material, including silicone rubber and a vulcanizing agent, wherein, based on 100 parts by mass of the silicone rubber, the fatigue-resistant conductive composite material also includes 2 to 6 masses. Parts of carbon nanotubes, 2 to 8 parts by mass of nano carbon fibers and 5 to 15 parts by mass of micron carbon fibers; nanocarbon fibers and micron carbon fibers are obtained by acid oxidation treatment; the diameter of nanometer carbon fibers is at the nanometer level; the diameter of the micrometer carbon fibers is at the micrometer level, And the length of micron carbon fiber is in the millimeter order.
  • the nano-carbon fiber has a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the micro-carbon fiber has a diameter of 5 to 20 micrometers and a length of 0.1 to 10 millimeters, preferably a length of 0.1 to 3 millimeters.
  • a further technical solution is that the nano carbon fiber and the micro carbon fiber are obtained by surface treatment of a mixed acid solution, and the mixed acid solution is composed of concentrated nitric acid and concentrated sulfuric acid according to a mass ratio of 1: 1.
  • the carbon nanotubes have a tube diameter of 5 to 20 nanometers and a length of 5 to 50 micrometers.
  • the carbon nanotubes are multi-walled carbon nanotubes.
  • the silicone rubber is one or more of methyl silicone rubber, methyl vinyl silicone rubber, methylphenyl vinyl silicone rubber and fluorosilicone rubber.
  • the silicone rubber is 100 parts by mass, and the vulcanizing agent is 1.5 to 2.5 parts by mass, and preferably the vulcanizing agent is 2.0 to 2.5 parts by mass.
  • the vulcanizing agent may be bis-dipenta, that is, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane.
  • a suitable silicone rubber can be selected according to actual needs, and a cross-linked molded product can be prepared by combining with a vulcanizing agent.
  • the present invention provides a method for preparing a fatigue-resistant conductive composite material, including the following steps:
  • Step 1 acid-oxidize the surface of the nano-carbon fiber and the micro-carbon fiber; the diameter of the nano-carbon fiber is at the nanometer level; the diameter of the micro-carbon fiber is at the micrometer level, and the length of the micro-carbon fiber is at the millimeter level;
  • Step 2 Prepare silicone rubber and vulcanizing agent, and based on 100 parts by mass of silicone rubber, prepare 2 to 6 parts by mass of carbon nanotubes, 2 to 8 parts by mass of nano-carbon fibers obtained in step 1 and 5 to 15 parts by mass of step 1 obtained Micron carbon fiber;
  • Step 3 Add silicon rubber to the kneader for refining, add carbon nanotubes, nano carbon fibers, and micro carbon fibers in order to knead, and finally add a vulcanizing agent to knead;
  • Step 4 The compounded rubber obtained in Step 3 is left to vulcanize.
  • a further technical solution is that, in step 1, the diameter of the nano-carbon fiber is 100 to 300 nanometers, and the length is 5 to 20 microns; the diameter of the micron carbon fiber is 5 to 20 microns, and the length is 0.1 to 10 mm, preferably 0.1 to 3 Mm.
  • the surface acid oxidation treatment step includes dispersing nano carbon fibers and micro carbon fibers in an oxidizing acid solution, stirring and reacting, and washing the treated nano carbon fibers and micro carbon fibers to a pH of 6 to 7, Dry again.
  • the stirring step is stirring at 60 ° C for 3 hours
  • the washing step is repeated washing with deionized water
  • the drying step is drying at 120 ° C for 3 hours.
  • a further technical solution is that the acid solution is composed of concentrated nitric acid and concentrated sulfuric acid according to a mass ratio of 1: 1, and the mass ratio of the nano-carbon fiber and the micro-carbon fiber to the acid solution is 1:10, respectively.
  • the vulcanizing agent is 2.0 to 2.5 parts by mass, and preferably, the vulcanizing agent is 2.0 to 2.5 parts by mass.
  • the vulcanizing agent is bis-dipenta, which is 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane.
  • step 3 the silicone rubber is added to the rubber mill for refining for 0-8 minutes, preferably for 1 to 5 minutes, and the refining temperature is 20 to 60 ° C; after the carbon nanotubes are added, the nanometers are added.
  • the mixing time after the carbon fiber, after adding the micron carbon fiber, and after adding the vulcanizing agent is 5 to 15 minutes, preferably 2 to 10 minutes, and the mixing temperature is 20 to 60 ° C.
  • the standing time is 24 hours.
  • the vulcanization step includes primary vulcanization and secondary vulcanization.
  • the vulcanization temperature of the primary vulcanization is 160 to 180 ° C
  • the vulcanization pressure is 10 to 15 MPa
  • the vulcanization time is 10.
  • the vulcanization temperature of the secondary vulcanization is 150 to 200 ° C, preferably 150 to 180 ° C
  • the vulcanization time is 4 to 6 hours.
  • a method for preparing a fatigue-resistant conductive silicone rubber is also provided.
  • the fatigue-resistant conductive silicone rubber is prepared by using any of the fatigue-resistant conductive composite materials described above.
  • the preparation method includes step S1. Carbon fiber and micron carbon fiber are respectively subjected to acid oxidation treatment on the surface to obtain acid-oxidized nano-carbon fiber and acid-oxidized micro-carbon fiber, respectively; the diameter of nano-carbon fiber is at the nanometer level; the diameter of the micro-carbon fiber is at the micro-meter level, and the length of the micro-carbon fiber is at the millimeter level; steps S2, kneading and vulcanizing 100 parts by mass of silicone rubber, 2 to 6 parts by mass of carbon nanotubes, 2 to 8 parts by mass of acid-oxidized carbon nanofibers, 5 to 15 parts by mass of acid-oxidized micron carbon fibers, and a vulcanizing agent to obtain Fatigue-resistant conductive silicone rubber.
  • step S2 includes: adding silicon rubber to the kneader for refining, and then adding carbon nanotubes, acid-oxidized nano-carbon fibers, acid-oxidized micro-carbon fibers, and vulcanizing agent in order to obtain a kneaded rubber, preferably refining
  • the mixing time is 1 to 5 minutes, and the mixing time after adding carbon nanotubes, acid-oxidized nano-carbon fibers, acid-oxidized micro-carbon fibers, and vulcanizing agents is preferably 2 to 10 minutes, and the temperature of each mixing is 20 to 60 ° C;
  • the rubber compound is vulcanized after being left to stand.
  • the above-mentioned acid oxidation treatment step includes: dispersing the nano-carbon fiber and the micro-carbon fiber in an oxidizing acid solution and performing an acid oxidation reaction under stirring conditions to obtain an acid-oxidized carbon fiber system; and cleaning each of the acid-oxidized carbon fiber systems.
  • the pH is 6 to 7, and then dried to obtain acid-oxidized nano-carbon fibers and acid-oxidized micro-carbon fibers.
  • the acid solution is preferably composed of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 1: 0.5 to 1.5, and more preferably in a mass ratio of 1: 1. It is more preferable that the mass ratios of the nano-carbon fiber and the micro-carbon fiber to the acid solution are respectively 1: 8 to 12, and further preferably 1:10.
  • the above-mentioned time for placing the compounded rubber is 24-72 hours.
  • the vulcanization step includes primary vulcanization and secondary vulcanization performed in sequence, and more preferably, the vulcanization temperature of the primary vulcanization is 160 to 180 ° C, and the vulcanization pressure is 10 to 15 MPa.
  • the curing time is 10 to 20 minutes; further preferably, the curing temperature of the secondary curing is 150 to 200 ° C., and the curing time is 4 to 6 hours.
  • an electronic wearable device which includes a fatigue-resistant conductive silicone rubber, and the fatigue-resistant conductive silicone rubber is prepared by using any one of the preparation methods described above.
  • the present invention uses carbon nanotubes in a conductive silicone rubber system, and simultaneously adds two types of carbon fibers with different diameters.
  • the carbon nanotubes and carbon fibers with different diameters have a good synergy effect, and finally a high fatigue resistance and electrical conductivity are obtained.
  • the length of micron-sized carbon fibers reaches the millimeter level, which can act as a conductive bridge on the silver streaks or cracks caused by fatigue, ensuring that the composite material still has good conductive stability after small silver streaks or cracks appear.
  • Carbon nanotubes mainly provide short-range conductive paths, but the excessive addition will easily cause the rubber to harden.
  • carbon nanofibers and carbon nanotubes can be added to form short-range conductive paths together, which not only ensures the stability of the conductive paths, but also ensures the stability of the conductive paths.
  • Mechanical properties of rubber The addition of carbon nanotubes and nano-carbon fibers can also greatly improve the electrical conductivity, tensile strength, hardness and fatigue resistance of composite materials.
  • the volume conductivity of the silicone rubber-based conductive composite material provided or prepared by the present invention is 1 to 10 S ⁇ cm -1 .
  • Rubber tensile test samples are prepared according to the national standard GB / T 1701-2001. The tensile breaking strength is 8 to 15 MPa, and the elongation at break is 400 to 600%.
  • the rubber sample was subjected to cyclic stretching, the elongation of the cyclic stretching was 40%, and the frequency of the cyclic stretching was once per second. After being stretched for 1,000 times in a cycle for 5 minutes, the volume conductivity of some rubber samples changed less than 1%.
  • the rubber composite material prepared by using the composite filler in the present invention has obvious advantages in the process of multiple stretching, high fatigue resistance, good electrical stability, and is particularly suitable for wearable electronic products such as smart shoes, including smart shoes. Smart insoles and smart socks.
  • FIG. 1 is a schematic diagram of the principle of performing acid oxidation treatment on a carbon fiber surface in the prior art.
  • FIG. 2 is a schematic view of a cross-sectional structure of a fatigue-resistant conductive composite material after a crack occurs in an embodiment of the present invention.
  • 1 is a crack
  • 2 is a micron carbon fiber.
  • the silicone rubber conductive material in the prior art cannot have both stable conductivity and fatigue resistance.
  • this application provides a fatigue resistant conductive composite material and fatigue resistance. Preparation method of conductive silicone rubber.
  • a fatigue-resistant conductive composite material including silicone rubber and a vulcanizing agent. Based on 100 parts by mass of the silicone rubber, the fatigue-resistant conductive composite material further includes 2 to 6 parts by mass of Carbon nanotubes, 2 to 8 parts by mass of nano carbon fibers and 5 to 15 parts by mass of micron carbon fibers; nano carbon fibers and micron carbon fibers are obtained by acid oxidation treatment; the diameter of nano carbon fibers is at the nanometer level; the diameter of micron carbon fibers is at the micron level, And the length of micron carbon fiber is in the millimeter order.
  • the present invention uses carbon nanotubes in a conductive silicone rubber system, and simultaneously adds two types of carbon fibers with different diameters.
  • the carbon nanotubes and carbon fibers with different diameters have a good synergy effect, and finally a high fatigue resistance and electrical conductivity are obtained.
  • the length of micron-sized carbon fibers reaches the millimeter level, which can act as a conductive bridge on the silver streaks or cracks caused by fatigue, ensuring that the composite material still has good conductive stability after small silver streaks or cracks appear.
  • Carbon nanotubes mainly provide short-range conductive paths, but the excessive addition will easily cause the rubber to harden.
  • carbon nanofibers and carbon nanotubes can be added to form short-range conductive paths together, which not only ensures the stability of the conductive paths, but also ensures the stability of the conductive paths.
  • Mechanical properties of rubber The addition of carbon nanotubes and nano-carbon fibers can also greatly improve the electrical conductivity, tensile strength, hardness and fatigue resistance of composite materials.
  • the volume conductivity of the silicone rubber-based conductive composite material provided or prepared by the present invention is 1 to 10 S ⁇ cm -1 .
  • Rubber tensile test samples are prepared according to the national standard GB / T 1701-2001. The tensile breaking strength is 8 to 15 MPa, and the elongation at break is 400 to 600%.
  • the rubber sample was subjected to cyclic stretching, the elongation of the cyclic stretching was 40%, and the frequency of the cyclic stretching was once per second. After being stretched for 1,000 times, it was left for 5 minutes, and its volume conductivity changed less than 1%.
  • the rubber composite material prepared by using the composite filler in the present invention has obvious advantages in the process of multiple stretching, high fatigue resistance, good electrical stability, and is particularly suitable for wearable electronic products such as smart shoes, including smart shoes Smart insoles and smart socks.
  • the diameter of the nano-carbon fiber is 100 to 300 nanometers, and the length is 5 to 20 micrometers; preferably, the diameter of the micron carbon fiber is 5 to 20 micrometers, preferably 0.1 to 10 millimeters in length, and more preferably 0.1 to 10 millimeters in length. 3 mm.
  • the size of the nano-carbon fiber and the micro-carbon fiber are within the above range, they can be more uniformly dispersed in the rubber matrix, and the carbon nanotubes, nano-carbon fibers, and micro-carbon fibers can be better compounded to improve the electrical conductivity of the composite material and Fatigue resistance.
  • the above acid oxidation treatment preferably uses a mixed acid solution, and the mixed acid solution is composed of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 1: 0.5 to 1.5, and preferably in a mass ratio of 1: 1.
  • the invention further uses a mixed acid to treat the surface of the nano-carbon fiber and the micro-carbon fiber.
  • the mixed acid can generate richer oxygen-containing groups on the surface of the carbon fiber, further avoiding agglomeration of the carbon fiber, and improving the carbon fiber and
  • the bonding force between the rubber matrices further improves the fatigue strength and electrical stability of the composite material.
  • the above-mentioned carbon nanotubes have a tube diameter of 5 to 20 nanometers and a length of 5 to 50 micrometers; preferably, the carbon nanotubes are multi-walled carbon nanotubes.
  • the silicone rubber used in the present application may be one commonly used in the prior art.
  • the above-mentioned silicone rubber is one of methyl silicone rubber, methyl vinyl silicone rubber, methylphenyl vinyl silicone rubber, and fluorosilicone rubber. Or more; based on 100 parts by mass of the silicone rubber, preferably 1.5 to 2.5 parts by mass of the vulcanizing agent, and more preferably 2.0 to 2.5 parts by mass. To improve the curing efficiency.
  • a method for preparing a fatigue-resistant conductive silicone rubber is provided.
  • the fatigue-resistant conductive silicone rubber is prepared by using the above-mentioned fatigue-resistant conductive composite material.
  • the preparation method includes: Step S1, Carbon fiber and micron carbon fiber are respectively subjected to acid oxidation treatment on the surface to obtain acid-oxidized nano-carbon fiber and acid-oxidized micro-carbon fiber, respectively; the diameter of nano-carbon fiber is at the nanometer level; the diameter of the micro-carbon fiber is at the micro-meter level, and the length of the micro-carbon fiber is at the millimeter level; steps S2, kneading and vulcanizing 100 parts by mass of silicone rubber, 2 to 6 parts by mass of carbon nanotubes, 2 to 8 parts by mass of acid-oxidized carbon nanofibers, 5 to 15 parts by mass of acid-oxidized micron carbon fibers, and a vulcanizing agent to obtain Fatigue-resistant conductive silicone rubber.
  • the preparation method of the present invention uses carbon nanotubes, nano-carbon fibers, and micro-carbon fibers as conductive fillers of silicone rubber, and the preparation steps include acid oxidation treatment of nano-carbon fibers and micro-carbon fibers to finally obtain a high fatigue resistance and conductive stability.
  • Good silicone rubber the length of micron carbon fiber reaches millimeter level, which can act as a conductive bridge on the silver streaks or cracks caused by fatigue, ensuring that the composite material still has good conductivity stability after small silver streaks or cracks appear.
  • the invention adopts a specific order to add fillers for mixing, which can make the fillers uniformly dispersed, and reduce the longer micron carbon fibers being broken during the mixing process, thereby ensuring the fatigue resistance of the composite material.
  • the compounding of the rubber compound can be performed by an open mill or by an internal mixer.
  • the above-mentioned step S2 includes: adding silicon rubber to a kneader for refining, and then sequentially adding carbon nanotubes, acid-oxidized nano-carbon fibers, acid-oxidized micro-carbon fibers, and vulcanizing agent for mixing,
  • the kneaded rubber is obtained, and the time for refining is preferably 1 to 5 minutes.
  • the kneading time after adding carbon nanotubes, acid-oxidized nano-carbon fibers, acid-oxidized micro-carbon fibers, and vulcanizing agents is 2 to 10 minutes.
  • the temperature is 20 to 60 ° C; the compounded rubber is left to vulcanize.
  • conductive fillers are added to the silicone rubber for mixing and vulcanizing the rubber in order, so that carbon nanotubes and two kinds of carbon fibers with different diameters are introduced into the conductive silicone rubber system.
  • the above-mentioned acid oxidation treatment step preferably includes: dispersing the nano-carbon fiber and the micro-carbon fiber in an oxidizing acid solution and performing an acid oxidation reaction under stirring conditions to obtain acid-oxidized carbon fibers, respectively.
  • each acid-oxidized carbon fiber system is washed to a pH of 6 to 7, and then dried to obtain acid-oxidized nano-carbon fibers and acid-oxidized micro-carbon fibers
  • the acid solution is composed of concentrated nitric acid and concentrated sulfuric acid according to a mass ratio of 1: 0.5 to 1.5
  • the composition is further preferably in a mass ratio of 1: 1, and the mass ratios of the nano-carbon fiber and the micro-carbon fiber to the acid solution are respectively 1: 8 to 12, and further preferably 1:10.
  • the mixed acid can generate richer oxygen-containing groups on the surface of carbon fiber, further avoid the agglomeration of carbon fiber, and improve the carbon fiber and rubber matrix. The binding force between them further improves the fatigue strength and electrical stability of the composite.
  • the vulcanization step includes a primary vulcanization and a secondary vulcanization in order.
  • the curing time is 10 to 20 minutes; further preferably, the curing temperature of the secondary curing is 150 to 200 ° C., and the curing time is 4 to 6 hours.
  • an electronic wearable device which includes a fatigue-resistant conductive silicone rubber, and the fatigue-resistant conductive silicone rubber is prepared by using any one of the preparation methods described above.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid and concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain nano-carbon fiber or micro-carbon fiber after acid oxidation treatment.
  • the nano-carbon fiber has a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of the micro-carbon fiber is 5 Up to 20 microns and a length of 0.1 to 3 mm.
  • the volume conductivity of the silicone rubber conductive composite material prepared in this embodiment is 5.4 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 13.2 MPa and an elongation at break of 483%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times in a cycle and left for 5 minutes, the volume conductivity was reduced by 0.5%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 2.4 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 11.8 MPa and an elongation at break of 443%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times, it was left for 5 minutes, and its volume conductivity decreased by 0.6%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeatedly deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 1.5 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 10.3 MPa and an elongation at break of 421%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times in a cycle and left for 5 minutes, the volume conductivity decreased by 0.8%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 8.9 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, the tensile breaking strength was 11.7 MPa, and the elongation at break was 401%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times in a cycle and left for 5 minutes, the volume conductivity was reduced by 0.2%.
  • Example 1 The steps described in Example 1 were used to change the mass fraction of silicone rubber / multi-walled carbon nanotubes / nano-carbon fibers / micron carbon fibers to prepare the fatigue-resistant composite materials of Examples 5-9. And a silicon rubber composite material containing only multi-walled carbon nanotubes, nano-carbon fibers, micro-carbon fibers, and the amount of fillers reaching the percolation threshold was prepared as Comparative Examples 1 to 8.
  • the nano-carbon fibers, micro-carbon fibers, and multi-walled carbon nanotubes used in each of the examples and comparative examples are the same as in Example 1.
  • the nano-carbon fiber used has a diameter of 100 to 300 nanometers and a length of 20 to 50 micrometers; the micrometer carbon fiber has a diameter of 5 to 20 micrometers and a length of 0.5 to 5 millimeters, and multi-walled carbon nanometers
  • the tube has a diameter of 10 to 30 nanometers and a length of 20 to 70 microns.
  • Example 2 The difference from Example 1 is that the mass ratio of concentrated nitric acid and concentrated sulfuric acid in the mixed acid solution used in the acid oxidation treatment is 1: 0.5.
  • Example 2 The difference from Example 1 is that the mass ratio of concentrated nitric acid and concentrated sulfuric acid in the mixed acid solution used in the acid oxidation treatment is 1: 1.5.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid and concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain nano-carbon fiber or micro-carbon fiber after acid oxidation treatment.
  • the nano-carbon fiber has a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of the micro-carbon fiber is 5 Up to 20 microns and a length of 0.1 to 3 mm.
  • the process conditions for primary vulcanization are as follows: vulcanization temperature 160 ° C, vulcanization pressure 10MPa, and vulcanization time 20 minutes.
  • the process conditions for secondary vulcanization are as follows: at 150 ° C. Cured for 6 hours to obtain a conductive composite of silicone rubber.
  • the volume conductivity of the silicone rubber conductive composite material prepared in this embodiment is 4.95 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 12.1 MPa and an elongation at break of 478%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times in a cycle and left for 5 minutes, the volume conductivity decreased by 2.4%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 2.38 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 11.2 MPa and an elongation at break of 427%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times, it was left for 5 minutes, and its volume conductivity decreased by 1.2%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeatedly deionized water Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the process conditions for primary vulcanization are as follows: vulcanization temperature 165 ° C, vulcanization pressure 15MPa, and vulcanization time 15 minutes.
  • the conditions for secondary vulcanization are as follows: vulcanization at 160 ° C. 5 hours, a conductive composite of silicone rubber was obtained.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 1.53 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, with a breaking strength of 9.8 MPa and an elongation at break of 436%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times, it was left for 5 minutes, and its volume conductivity decreased by 3.2%.
  • the nano-carbon fiber and the micro-carbon fiber are respectively subjected to acid oxidation treatment, and the process of the acid oxidation treatment is as follows: the nano-carbon fiber or the micro-carbon fiber is dispersed in an oxidizing acid solution.
  • the mass ratio of concentrated nitric acid to concentrated sulfuric acid in the acid solution is 1: 1, and the mass ratio of nano-carbon fiber or micro-carbon fiber to the acid solution is 1:10.
  • Magnetic stirring is performed at 60 ° C for 3 hours, and the carbon fiber after the acid oxidation treatment is repeated with deionized water. Wash to pH 6 to 7, and dry at 120 ° C for 3 hours to obtain acid-treated nano-carbon fibers or micro-carbon fibers.
  • the nano-carbon fibers have a diameter of 100 to 300 nanometers and a length of 5 to 20 micrometers; the diameter of micron carbon fibers is 5 to 20 Microns with a length of 0.1 to 3 mm.
  • the volumetric conductivity of the conductive composite material of the silicone rubber prepared in this embodiment is 8.74 S ⁇ cm -1 .
  • Rubber tensile test samples were prepared according to the national standard GB / T 1701-2001, the tensile breaking strength was 11.2 MPa, and the elongation at break was 418%.
  • the elongation of cyclic stretching is 40%, and the frequency of cyclic stretching is 1 time per second. After being stretched for 1,000 times in a cycle and left for 5 minutes, the volume conductivity decreased by 1.8%.
  • Examples 5 to 16 and Comparative Examples 1 to 8 are shown in Table 1 below.
  • the fatigue resistance test uses the dumbbell-shaped sample in the national standard GB / T 1701-2001, the elongation during stretching is 40%, and the frequency is 1 time / second.
  • the conductive composite material provided by the embodiment of the present invention has higher volume conductivity and tensile strength. After cyclic stretching, the decrease in volume conductivity is small, much lower than that in Comparative Examples 1-3, and it can maintain good mechanical properties. As shown in Figure 2, carbon fibers in the composite material with a length of millimeters can act as conductive bridges on fatigue-induced silver streaks or cracks, and are compounded with nano-fillers in the rubber matrix to maintain the composite material's long-term use. Electrical stability.
  • the composite material of the invention has good fatigue resistance and conductive stability, and is suitable for wearable electronic products, such as smart footwear products (including smart shoes, smart insoles and smart socks, etc.), smart seat cushions, mattresses, etc. For flexible stress testing and monitoring areas and products. Taking our company's smart shoes / pads as an example, this type of product realizes the identification of different states of the wearer and the movement of the wearer by arranging pressure switches with different numbers and different conduction thresholds at different positions in the two-dimensional plane of the sole of the product. "Smart" monitoring of motion parameters during the process. This kind of intelligent footwear products have a single output signal, simple processing method and judgment logic, and save energy because the pressure switch consumes power only in the on state. The use of the composite material of the present invention in smart footwear products can improve product performance and product life.

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Abstract

本发明涉及一种耐疲劳导电复合材料及其制备方法，该复合材料包括硅橡胶和硫化剂，并且以硅橡胶为100质量份计还包括2至6质量份碳纳米管，2至8质量份纳米碳纤维和5至15质量份的微米碳纤维；纳米碳纤维和微米碳纤维经酸氧化处理得到；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级且长度在毫米级。该制备方法包括酸氧化处理、混炼和硫化步骤。本发明的耐疲劳导电复合材料具有良好的耐疲劳性能和导电稳定性，适用于可穿戴电子类产品如智能鞋类等。

Description

一种耐疲劳导电复合材料及其制备方法 技术领域
本发明涉及橡胶导电复合材料及其制备方法技术领域，具体涉及一种耐疲劳导电硅橡胶复合材料及其制备方法。
背景技术
将各种导电填料分散于绝缘的硅橡胶中制得导电的硅橡胶，是制备导电硅橡胶最常用的方法之一。通过这种方法制备的导电硅橡胶具有电阻时间特性稳定、电阻温度系数可控及使用温度较高等优点。它已广泛用于抗静电材料、电磁屏蔽材料、正/负温度系数材料、传感器以及可穿戴产品等方面。导电硅橡胶的导电填料对其导电性有至关重要的影响，常用的导电填料有金属系和炭系两大类。在金属系填料中，金、银的价格太高，其它金属又易被氧化。另外，由于金属密度较大，不易均匀分散在聚合物中，填充量一般较高。因此在导电硅橡胶的工业生产中，多使用炭系导电填料。
近年来，随着可穿戴电子类产品的蓬勃发展，柔性的、对皮肤无伤害的导电高分子材料又获得了一个新的增长点。硅橡胶具有耐热、耐寒、无毒、耐生物老化、生理惰性、对人体组织反应小、物理力学性能较好等优点，因此，导电硅橡胶在可穿戴电子类产品中有巨大的应用潜力。现有的炭基导电填料主要包括导电炭黑、石墨、碳纳米管、石墨烯以及碳纤维。炭黑和石墨因其粒径较大，在添加过程中易导致复合材料的力学性能(如拉伸强度、断裂伸长率、耐疲劳性)下降较多；而碳纳米管、石墨烯作为纳米填料，在工业化使用的过程中添加量较大时非常容易出现填料在橡胶基体中的团聚现象，从而导致复合材料的力学性能的下降；而具有微米结构的碳纤维，存在纤维和橡胶基体之间的界面问题，因此在国内外很多文献中，多采用表面氧化或者表面修饰来解决碳纤维和橡胶基体的界面问题。例如，公开号为CN107459682A的中国专利申请报道了一种采用硝酸将碳纤维表面氧化的工艺，并将表面改性的碳纤维作为导电填料，天然橡胶作为基体材料，制备了纤维和橡胶界面性能很好的复合材料。公开号CN107325416A的中国专利申请报道了一种采用石墨烯和金属颗粒的混合物作为导电填料，硅橡胶、三元乙丙橡胶以及天然橡胶作为基体材料，所制备的橡胶复合材料具有好的耐老化性和导电性。公开号为CN107400368A的中国专利申请报道了一种采用石墨烯和碳纳米管的混合物作为导电填料，硅橡胶基体材料，所制备的橡胶复合材料具有低的密度和良好的物理性能。
如图1所示，对碳纤维表面进行酸氧化处理能够在碳纤维的表面产生的羟基、羰基以及硝基等基团(Sharma M,Gao S,
Figure PCTCN2019092069-appb-000001
E,Sharma H,Wei L,Bijwe J.Carbon fiber surfaces and composite interphases,Composites Science and Technology,2014,102:35-50)。碳纤维表面酸氧化处理的作用一是氧化碳纤维表面带有了极性，而且纤维彼此极性相同，从而减少了碳纤维在橡胶基体中的团聚；二是碳纤维表面变得更加干净，有利于纤维和橡胶之间的粘结；三是碳 纤维表面极性的增加有利于提高纤维和高分子链之间的范德华力，从而改善复合材料的力学性能。但现有技术中的酸氧化处理方法产生的含氧基团数量还有进一步提高的空间。
现有的研究表明，纳米填料具有较大的比表面积和高的表面活性，作为高分子复合材料的填料，具有添加量小、复合材料力学性能优异的优势，而直径在30纳米以下的填料优势更明显(Shao-Yun Fu,Xi-Qiao Feng,Bernd Lauke,Yiu-Wing Mai.Effects of particle size,particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites,Composites:Part B,2008,39(6):933–961)。但是，仅使用纳米碳材料作为导电填料，要实现复合材料具有较好的导电性(达到渗滤阈值)，研究表明添加量一般需要达到6至8份以上。然而纳米材料具有很高的表面能和大的比表面积，在制备复合材料的过程中极易粘连团聚，当添加量超过5份时，团聚较为严重。而使用微米级别的碳纤维作导电填料，要达到较高的电导率，其添加量则比较大(一般不小于15份)，这会造成复合材料力学性能的大幅度下降。此外，在材料长期使用的过程中，橡胶复合材料内部很容易出现微小的银纹或裂纹。
发明内容
针对现有技术的不足，本发明的第一目的是提供一种具有良好的导电稳定性和耐疲劳性的硅橡胶基导电复合材料。
本发明的第二目的是提供一种具有良好的导电稳定性和耐疲劳性的硅橡胶基导电复合材料的制备方法。
为实现本发明的第一目的，本发明提供了一种耐疲劳导电复合材料，包括硅橡胶和硫化剂，其中，以硅橡胶为100质量份计，耐疲劳导电复合材料还包括2至6质量份碳纳米管，2至8质量份纳米碳纤维和5至15质量份的微米碳纤维；纳米碳纤维和微米碳纤维经酸氧化处理而得；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级，且微米碳纤维的长度在毫米级。
进一步的技术方案是，纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至10毫米，优选长度为0.1至3毫米。
进一步的技术方案是，纳米碳纤维和微米碳纤维由混合酸液进行表面处理而得，混合酸液由浓硝酸和浓硫酸按照质量比1：1组成。
进一步的技术方案是，碳纳米管的管径为5至20纳米，长度为5至50微米。优选地，碳纳米管为多壁碳纳米管。
进一步的技术方案是，硅橡胶为甲基硅橡胶、甲基乙烯基硅橡胶、甲基苯基乙烯基硅橡胶和氟硅橡胶中的一种或多种。
进一步的技术方案是，硅橡胶为100质量份计，硫化剂为1.5至2.5质量份，优选硫化剂的质量份为2.0～2.5。硫化剂可以为双二五，即2,5-二甲基-2,5-二(叔丁基过氧基)己烷。
本发明可以根据实际需要选择合适的硅橡胶，并与硫化剂配合制备交联成型产品。
为实现本发明的第二目的，本发明提供了一种耐疲劳导电复合材料的制备方法，包括以下步骤：
步骤一：对纳米碳纤维和微米碳纤维进行表面的酸氧化处理；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级，且微米碳纤维的长度在毫米级；
步骤二：准备硅橡胶和硫化剂，并且以硅橡胶为100质量份计，准备2至6质量份碳纳米管、2至8质量份步骤一得到的纳米碳纤维以及5至15质量份步骤一得到的微米碳纤维；
步骤三：将硅橡胶加入炼胶机中炼制，依次加入碳纳米管、纳米碳纤维、微米碳纤维进行混炼，最后加入硫化剂进行混炼；
步骤四：将步骤三得到的混炼胶放置后进行硫化。
进一步的技术方案是，在步骤一中，纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至10毫米，优选为0.1～3毫米。
进一步的技术方案是，表面酸氧化处理步骤包括将纳米碳纤维和微米碳纤维分别分散在具有氧化性的酸液中，搅拌进行反应，将处理后的纳米碳纤维和微米碳纤维清洗至pH为6至7，再进行干燥。优选地，搅拌步骤为60℃搅拌3小时，清洗步骤为采用去离子水反复清洗，干燥步骤为120℃干燥3小时。
进一步的技术方案是，酸液由浓硝酸和浓硫酸按照质量比1:1组成，纳米碳纤维和微米碳纤维与酸液的质量比分别为1:10。
进一步的技术方案是，以硅橡胶为100质量份计，硫化剂为2.0至2.5质量份，优选所述硫化剂的质量份为2.0～2.5。硫化剂为双二五，即2,5-二甲基-2,5-二(叔丁基过氧基)己烷。
进一步的技术方案是，在步骤三中，将硅橡胶加入炼胶机中炼制0-8分钟，优选1-5分钟后，炼制温度为20至60℃；加入碳纳米管后、加入纳米碳纤维后、加入微米碳纤维后以及加入硫化剂后的混炼时间分别为5至15分钟，优选为2至10分钟，混炼温度为20至60℃。
进一步的技术方案是，在步骤四中，放置时间为24小时，硫化的步骤包括一次硫化和二次硫化，一次硫化的硫化温度为160至180℃，硫化压力为10至15MPa，硫化时间为10至30分钟，优选为10至20分钟；二次硫化的硫化温度为150至200℃，优选为150～180℃，硫化时间为4至6小时。
根据本发明的另一方面，还提供了一种耐疲劳导电硅橡胶的制备方法，采用上述任一种的耐疲劳导电复合材料制备耐疲劳导电硅橡胶，该制备方法包括：步骤S1，对纳米碳纤维和微米碳纤维分别进行表面的酸氧化处理，分别得到酸氧化纳米碳纤维和酸氧化微米碳纤维；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级，且微米碳纤维的长度在毫米级；步骤S2，将100质量份硅橡胶、2至6质量份的碳纳米管、2至8质量份的酸氧化纳米碳纤维、5至15质量份的酸氧化微米碳纤维以及硫化剂进行混炼、硫化，得到耐疲劳导电硅橡胶。
进一步地，上述步骤S2包括：将硅橡胶加入炼胶机中炼制，然后依次加入碳纳米管、酸氧化纳米碳纤维、酸氧化微米碳纤维、硫化剂进行混炼，得到混炼胶，优选炼制的时间为1～5分钟，优选碳纳米管、酸氧化纳米碳纤维、酸氧化微米碳纤维、硫化剂各自加入后的混炼时间为2～10分钟，各混炼的温度为20～60℃；将混炼胶放置后进行硫化。
进一步地，上述酸氧化处理步骤包括：将纳米碳纤维和微米碳纤维分别分散在具有氧化性的酸液中并在搅拌条件下进行酸氧化反应，分别得到酸氧化碳纤维体系；将各酸氧化碳纤维体系清洗至pH为6至7，再进行干燥，得到酸氧化纳米碳纤维和酸氧化微米碳纤维，优选酸液由浓硝酸和浓硫酸按照质量比1:0.5～1.5组成，进一步优选按照质量比1:1组成，更优选纳米碳纤维和微米碳纤维分别与酸液的质量比分别为1:8～12，进一步优选为1:10。
进一步地，上述将混炼胶放置的时间为24～72小时，优选硫化步骤包括依次进行的一次硫化和二次硫化，更优选一次硫化的硫化温度为160至180℃，硫化压力为10至15MPa，硫化时间为10至20分钟；进一步优选二次硫化的硫化温度为150至200℃，硫化时间为4至6小时。
根据本发明的又一方面，提供了一种电子可穿戴设备，包括耐疲劳导电硅橡胶，该耐疲劳导电硅橡胶采用上述任一种的制备方法制备而成。
本发明在导电硅橡胶体系中使用碳纳米管，同时添加了两种不同直径的碳纤维，碳纳米管以及不同直径的碳纤维之间具有很好的协同效应，最终得到一种耐疲劳性高、导电稳定性好的硅橡胶。其中，直径为微米级别的碳纤维的长度达到了毫米级别，能够在疲劳产生的银纹或裂纹上充当导电桥梁，保证复合材料在出现了小的银纹或裂纹后依然有较好的导电稳定性。碳纳米管主要是提供近程导电通路，但添加量过大易导致橡胶变硬，因此可通过添加碳纳米纤维和碳纳米管一起组成近程导电通路，不仅保证导电通路的稳定性，也保证橡胶的力学性能。碳纳米管、纳米碳纤维的加入也能够较大幅度提高复合材料的电导率、拉伸强度、硬度以及耐疲劳性能。
本发明提供或制备的硅橡胶基导电复合材料的体积电导率在1至10S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，拉伸断裂强度为8至15MPa，断裂伸长率为400至600％。将橡胶样品进行循环拉伸，循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，有些橡胶样品的体积电导率变化小于1％。本发明采用复合填料制备的橡胶复合材料在多次拉伸的过程中有明显的优势，耐疲劳性高，导电稳定性好，尤其适用于可穿戴电子类产品如智能鞋类，包括智能鞋，智能鞋垫和智能袜等。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1是现有技术中对碳纤维表面进行酸氧化处理的原理示意图。
图2是本发明实施例中耐疲劳导电复合材料产生裂纹后剖面结构示意图，图2中1为裂纹，2为微米碳纤维。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
如本申请背景技术所分析的，现有技术中的硅橡胶导电材料不能同时兼具稳定的导电性和耐疲劳性，为了解决该问题，本申请提供了一种耐疲劳导电复合材料及耐疲劳导电硅橡胶的制备方法。
在本申请一种典型的实施方式中，提供了一种耐疲劳导电复合材料，包括硅橡胶和硫化剂，以硅橡胶为100质量份计，耐疲劳导电复合材料还包括2至6质量份的碳纳米管，2至8质量份的纳米碳纤维和5至15质量份的微米碳纤维；纳米碳纤维和微米碳纤维经酸氧化处理而得；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级，且微米碳纤维的长度在毫米级。
本发明在导电硅橡胶体系中使用碳纳米管，同时添加了两种不同直径的碳纤维，碳纳米管以及不同直径的碳纤维之间具有很好的协同效应，最终得到一种耐疲劳性高、导电稳定性好的硅橡胶。其中，直径为微米级别的碳纤维的长度达到了毫米级别，能够在疲劳产生的银纹或裂纹上充当导电桥梁，保证复合材料在出现了小的银纹或裂纹后依然有较好的导电稳定性。碳纳米管主要是提供近程导电通路，但添加量过大易导致橡胶变硬，因此可通过添加碳纳米纤维和碳纳米管一起组成近程导电通路，不仅保证导电通路的稳定性，也保证橡胶的力学性能。碳纳米管、纳米碳纤维的加入也能够较大幅度提高复合材料的电导率、拉伸强度、硬度以及耐疲劳性能。
本发明提供或制备的硅橡胶基导电复合材料的体积电导率在1至10S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，拉伸断裂强度为8至15MPa，断裂伸长率为400至600％。将橡胶样品进行循环拉伸，循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率变化小于1％。本发明采用复合填料制备的橡胶复合材料在多次拉伸的过程中有明显的优势，耐疲劳性高，导电稳定性好，尤其适用于可穿戴电子类产品如智能鞋类，包括智能鞋，智能鞋垫和智能袜等。
在一种实施例中，上述纳米碳纤维的直径为100至300纳米，长度为5至20微米；优选微米碳纤维的直径为5至20微米，优选长度为0.1至10毫米，更优选长度为0.1至3毫米。当纳米碳纤维和微米碳纤维的尺寸在上述范围内时，能够更均匀地分散在橡胶基体中，且碳纳米管、纳米碳纤维和微米碳纤维之间能够更好地复配，提高复合材料的导电率以及耐疲劳强度。
为了优化酸氧化效果，优选上述酸氧化处理采用混合酸液，混合酸液由浓硝酸和浓硫酸按照质量比1:0.5～1.5组成，优选按照质量比1：1组成。本发明进一步采用混合酸处理纳米碳 纤维和微米碳纤维的表面，与现有单一酸处理碳纤维表面相比，混合酸能够在碳纤维表面产生更丰富的含氧基团，进一步避免碳纤维的团聚，提高碳纤维和橡胶基体之间的结合力，从而进一步提高复合材料的耐疲劳强度和导电稳定性。
在一种实施例中，上述碳纳米管的管径为5至20纳米，长度为5至50微米；优选碳纳米管为多壁碳纳米管。通过上述管径和长度的控制，可以有效缓解碳纳米管的团聚。
用于本申请的硅橡胶可以为现有技术中常用的硅橡胶，优选上述硅橡胶为甲基硅橡胶、甲基乙烯基硅橡胶、甲基苯基乙烯基硅橡胶和氟硅橡胶中的一种或多种；以硅橡胶为100质量份计，优选硫化剂为1.5至2.5质量份，更优选为2.0～2.5质量份。以提高硫化效率。
在本申请另一种典型的实施方式中，提供了一种耐疲劳导电硅橡胶的制备方法，采用上述的耐疲劳导电复合材料制备耐疲劳导电硅橡胶，该制备方法包括：步骤S1，对纳米碳纤维和微米碳纤维分别进行表面的酸氧化处理，分别得到酸氧化纳米碳纤维和酸氧化微米碳纤维；纳米碳纤维的直径在纳米级；微米碳纤维的直径在微米级，且微米碳纤维的长度在毫米级；步骤S2，将100质量份硅橡胶、2至6质量份的碳纳米管、2至8质量份的酸氧化纳米碳纤维、5至15质量份的酸氧化微米碳纤维以及硫化剂进行混炼、硫化，得到耐疲劳导电硅橡胶。
本发明的制备方法采用碳纳米管、纳米碳纤维以及微米碳纤维作为硅橡胶的导电填充物，并且制备步骤包括对纳米碳纤维和微米碳纤维进行酸氧化处理，最终得到一种耐疲劳性高、导电稳定性好的硅橡胶。其中微米碳纤维的长度达到了毫米级别，能够在疲劳产生的银纹或裂纹上充当导电桥梁，保证复合材料在出现了小的银纹或裂纹后依然有较好的导电稳定性。本发明采用特定次序添加填料进行混炼，可以使得填料分散均匀，并且减少较长的微米碳纤维在混炼过程中被折断，从而保证复合材料的耐疲劳性能。胶料的混炼可以采用开炼机进行开炼或采用密炼机进行密炼。
在本申请一种优选的实施例中，上述步骤S2包括：将硅橡胶加入炼胶机中炼制，然后依次加入碳纳米管、酸氧化纳米碳纤维、酸氧化微米碳纤维、硫化剂进行混炼，得到混炼胶，优选炼制的时间为1～5分钟，优选碳纳米管、酸氧化纳米碳纤维、酸氧化微米碳纤维、硫化剂各自加入后的混炼时间为2～10分钟，各混炼的温度为20～60℃；将混炼胶放置后进行硫化。
在上述步骤中，按次序在硅橡胶中添加导电填充物进行混炼以及对混炼胶进行硫化，从而在导电硅橡胶体系中引入碳纳米管以及两种不同直径的碳纤维，各填充物之间充分发挥上述的协同效应。
为了进一步提高碳纤维表面的含氧基团，优选上述酸氧化处理步骤包括：将纳米碳纤维和微米碳纤维分别分散在具有氧化性的酸液中并在搅拌条件下进行酸氧化反应，分别得到酸氧化碳纤维体系；将各酸氧化碳纤维体系清洗至pH为6至7，再进行干燥，得到酸氧化纳米碳纤维和酸氧化微米碳纤维，优选酸液由浓硝酸和浓硫酸按照质量比1:0.5～1.5组成，进一步优选按照质量比1:1组成，更优选纳米碳纤维和微米碳纤维分别与酸液的质量比分别为1:8～12，进一步优选为1:10。采用混合酸处理纳米碳纤维和微米碳纤维的表面，与现有单一酸处理碳纤维表面相比，混合酸能够在碳纤维表面产生更丰富的含氧基团，进一步避免碳纤维 的团聚，提高碳纤维和橡胶基体之间的结合力，从而进一步提高复合材料的耐疲劳强度和导电稳定性。
为了优化硫化效果，优选将混炼胶放置的时间为24～72小时，优选硫化步骤包括依次进行的一次硫化和二次硫化，更优选一次硫化的硫化温度为160至180℃，硫化压力为10至15MPa，硫化时间为10至20分钟；进一步优选二次硫化的硫化温度为150至200℃，硫化时间为4至6小时。
在本申请又一种典型的实施方式中，提供了一种电子可穿戴设备，包括耐疲劳导电硅橡胶，该耐疲劳导电硅橡胶采用上述任一种的制备方法制备而成。比如智能鞋类产品，包括智能鞋、智能鞋垫和智能袜等。
以下将结合实施例和对比例进一步说明本申请的有益效果。
实施例1
本实施例的耐疲劳导电复合材料的制备方法如下：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸和浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维与酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸氧化处理后的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、6份、3份以及5份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制2分钟至完全包辊，加入碳纳米管混炼10分钟，继续加入纳米碳纤维混炼5分钟，再加入微米碳纤维混炼10分钟，最后加入硫化剂2份并混炼5分钟。硅橡胶以及添加填料后混炼的温度控制在40±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度160℃，硫化压力10MPa，硫化时间15分钟；二次硫化的工艺条件如下：在150℃下硫化6小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶导电复合材料的体积电导率为5.4S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为13.2MPa，断裂伸长率为483％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小0.5％。
实施例2
本实施例的耐疲劳导电复合材料的制备方法如下：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维和微米碳纤维的质量份数分别为100份、2份、5份以及8份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在密炼机上炼制1分钟，加入碳纳米管混炼5分钟，继续加入纳米碳纤维混炼5分钟，再加入微米碳纤维混炼5分钟，最后加入硫化剂2份混制5分钟。炼制的温度控制在35±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度170℃，硫化压力12MPa，硫化时间15分钟；二次硫化的条件如下：在180℃下硫化4小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为2.4S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为11.8MPa，断裂伸长率为443％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小0.6％。
实施例3
本实施例的耐疲劳导电复合材料通过以下步骤制备：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、1份、6份以及10份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制3分钟至完全包辊后，加入碳纳米管混炼10分钟，继续加入纳米碳纤维混炼10分钟，再加入微米碳纤维混炼10分钟，最后加入硫化剂2.5份混炼5分钟。混炼温度控制在40±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度165℃，硫化压力15MPa，硫化时间20分钟；二次硫化的条件如下：在160℃下硫化5小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为1.5S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为10.3MPa，断裂伸长率为421％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小0.8％。
实施例4
本实施例的耐疲劳导电复合材料通过以下步骤制备：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、4份、6份以及12份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制3分钟至完全包辊后，加入碳纳米管混炼10分钟，继续加入纳米碳纤维混炼10分钟，再加入微米碳纤维混炼10分钟，最后加入硫化剂2.5份混炼5分钟。硅橡胶开炼和加入其它组分后混炼的温度控制在45±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度170℃，硫化压力15MPa，硫化时间20分钟；二次硫化的条件如下：在170℃下硫化5小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为8.9S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，拉伸断裂强度为11.7MPa，断裂伸长率为401％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小0.2％。
实施例5至9
采用实施例1中描述的步骤，改变硅橡胶/多壁碳纳米管/纳米碳纤维/微米碳纤维的质量份数，制备实施例5至9的耐疲劳复合材料。并且制备仅含有多壁碳纳米管、纳米碳纤维、微米碳纤维且填料添加量达到渗滤阈值的硅橡胶复合材料，作为对比例1至8。各实施例和对比例所采用的纳米碳纤维、微米碳纤维和多壁碳纳米管均和实施例1相同。
实施例10
与实施例1不同之处在于，所采用的纳米碳纤维的直径为100至300纳米，长度为20至50微米；微米碳纤维的直径为5至20微米，长度为0.5至5毫米，多壁碳纳米管的管径为10至30纳米，长度为20至70微米。
实施例11
与实施例1不同之处在于，酸氧化处理所采用的混合酸液中浓硝酸和浓硫酸的质量比为1:0.5。
实施例12
与实施例1不同之处在于，酸氧化处理所采用的混合酸液中浓硝酸和浓硫酸的质量比为1:1.5。
实施例13
本实施例的耐疲劳导电复合材料的制备方法如下：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸和浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维与酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸氧化处理后的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、6份、3份以及5份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制2分钟至完全包辊，加入碳纳米管混炼5分钟，继续加入纳米碳纤维混炼3分钟，再加入微米碳纤维混炼3分钟，最后加入硫化剂2.5份并混炼4分钟。硅橡胶以及添加填料后混炼的温度控制在40±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度160℃，硫化压力10MPa，硫化时间20分钟；二次硫化的工艺条件如下：在150℃下硫化6小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶导电复合材料的体积电导率为4.95S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为12.1MPa，断裂伸长率为478％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小2.4％。
实施例14
本实施例的耐疲劳导电复合材料的制备方法如下：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维和微米碳纤维的质量份数分别为100份、2份、5份以及8份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在密炼机上炼制1分钟，加入碳纳米管混炼3分钟，继续加入纳米碳纤维混炼5分钟，再加入微米碳纤维混炼3分钟，最后加入硫化剂1.5份混制2分钟。炼制的温度控制在35±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度170℃，硫化压力12MPa，硫化时间10分钟；二次硫化的条件如下：在180℃下硫化4小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为2.38S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为11.2MPa，断裂伸长率为427％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小1.2％。
实施例15
本实施例的耐疲劳导电复合材料通过以下步骤制备：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、1份、6份以及10份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制3分钟至完全包辊后，加入碳纳米管混炼3分钟，继续加入纳米碳纤维混炼5分钟，再加入微米碳纤维混炼5分钟，最后加入硫化剂2份混炼2分钟。混炼温度控制在40±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度165℃，硫化压力15MPa，硫化时间15分钟；二次硫化的条件如下：在160℃下硫化5小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为1.53S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，断裂强度为9.8MPa，断裂伸长率为436％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小3.2％。
实施例16
本实施例的耐疲劳导电复合材料通过以下步骤制备：
(1)对纳米碳纤维和微米碳纤维分别进行酸氧化处理，酸氧化处理的工艺如下：将纳米碳纤维或微米碳纤维分散在具有氧化性的酸液中。该酸液中浓硝酸与浓硫酸质量比为1:1，纳米碳纤维或微米碳纤维和酸液质量比为1:10。60℃磁力搅拌3小时，将酸氧化处理后的碳纤维用去离子水反复清洗至pH为6至7，120℃干燥3小时得到酸处理的纳米碳纤维或微米碳纤维，其中的纳米碳纤维的直径为100至300纳米，长度为5至20微米；微米碳纤维的直径为5至20微米，长度为0.1至3毫米。
(2)称取原料，其中硅橡胶、多壁碳纳米管、纳米碳纤维以及微米碳纤维的质量份数分别为100份、4份、6份以及12份，多壁碳纳米管的管径为5至20纳米，长度为5至50微米。
(3)将硅橡胶在开炼机上炼制2分钟至完全包辊后，加入碳纳米管混炼5分钟，继续加入纳米碳纤维混炼5分钟，再加入微米碳纤维混炼5分钟，最后加入硫化剂2.5份混炼3分钟。硅橡胶开炼和加入其它组分后混炼的温度控制在45±5℃。
(4)将混炼均匀的胶料放置24小时后进行硫化，一次硫化的工艺条件如下：硫化温度170℃，硫化压力15MPa，硫化时间13分钟；二次硫化的条件如下：在200℃下硫化4小时，得到硅橡胶的导电复合材料。
本实施例所制备的硅橡胶的导电复合材料的体积电导率为8.74S·cm -1。橡胶拉伸测试样品根据国标GB/T 1701-2001来制备，拉伸断裂强度为11.2MPa，断裂伸长率为418％。循环拉伸的伸长率为40％，循环拉伸的频率为每秒1次。循环拉伸1000次后放置5分钟，其体积电导率减小1.8％。
实施例5至16与对比例1至8的组分、力学性能、导电性能以及耐疲劳性能如下表1所示。其中，耐疲劳性测试采用国标GB/T 1701-2001中的哑铃型样品，拉伸过程中伸长率40％，频率为1次/秒。
表1实施例5至16和对比例1至8的组分及性能
Figure PCTCN2019092069-appb-000002
Figure PCTCN2019092069-appb-000003
Figure PCTCN2019092069-appb-000004
Figure PCTCN2019092069-appb-000005
Figure PCTCN2019092069-appb-000006
由以上实施例可见，与单独添加多壁碳纳米管、纳米碳纤维或微米碳纤维的硅橡胶复合材料相比，本发明实施例所提供的导电复合材料具有较高的体积导电率和拉伸强度。经过循环拉伸后，体积电导率下降比例较小，远远低于对比例1-3的体积电导率下降比例，且能够保持较好的力学性能。如图2所示，复合材料中长度达到了毫米级别碳纤维能够在疲劳产生的银纹或裂纹上充当导电桥梁，并且与橡胶基体中的纳米填料复配，能够保持复合材料在长期使用过程中的导电稳定性。
本发明的复合材料具有良好的耐疲劳性能和导电稳定性，适用于可穿戴电子类产品等，例如智能鞋类产品(包括智能鞋，智能鞋垫和智能袜等)、智能座垫、床垫等对柔性压力测试和监测领域和产品。以本公司的智能鞋/垫为例，这类产品通过在产品对应的足底二维平面内不同位置布置不同数目和不同导通阈值的压力开关，实现对穿者不同状态的识别以及在运动过程中的运动参数监测的“智能”。这类智能鞋类产品，输出信号单一，处理方法和判断逻辑简单，因压力开关只在导通状态才会消耗电量而更节能。在智能鞋类产品中采用本发明的复合材料，能够改善产品性能，提高产品寿命。
最后需要强调的是，以上仅为本发明的优选实施例，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种变化和更改，例如复合材料中还可以添加其他填充物或改性剂等，凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (15)

  1. 一种耐疲劳导电复合材料，包括硅橡胶和硫化剂，其特征在于：
    以所述硅橡胶为100质量份计，所述耐疲劳导电复合材料还包括2至6质量份的碳纳米管，2至8质量份的纳米碳纤维和5至15质量份的微米碳纤维；
    所述纳米碳纤维和所述微米碳纤维经酸氧化处理而得；所述纳米碳纤维的直径在纳米级；所述微米碳纤维的直径在微米级，且所述微米碳纤维的长度在毫米级。
  2. 根据权利要求1所述的一种耐疲劳导电复合材料，其特征在于：
    所述纳米碳纤维的直径为100至300纳米，长度为5至20微米；优选所述微米碳纤维的直径为5至20微米，优选长度为0.1至10毫米，优选长度为0.1至3毫米。
  3. 根据权利要求1所述的一种耐疲劳导电复合材料，其特征在于：
    所述酸氧化处理采用混合酸液，所述混合酸液由浓硝酸和浓硫酸按照质量比1:0.5～1.5组成，优选按照质量比1：1组成。
  4. 根据权利要求1至3任一项所述的一种耐疲劳导电复合材料，其特征在于：
    所述碳纳米管的管径为5至20纳米，长度为5至50微米；优选所述碳纳米管为多壁碳纳米管。
  5. 根据权利要求1至3任一项所述的一种耐疲劳导电复合材料，其特征在于：
    所述硅橡胶为甲基硅橡胶、甲基乙烯基硅橡胶、甲基苯基乙烯基硅橡胶和氟硅橡胶中的一种或多种；
    以所述硅橡胶为100质量份计，优选所述硫化剂为1.5至2.5质量份，优选所述硫化剂为2.0至2.5质量份。
  6. 一种耐疲劳导电复合材料的制备方法，其特征在于包括以下步骤：
    步骤一：对纳米碳纤维和微米碳纤维进行表面的酸氧化处理；所述纳米碳纤维的直径在纳米级；所述微米碳纤维的直径在微米级，且所述微米碳纤维的长度在毫米级；
    步骤二：准备硅橡胶和硫化剂，并且以硅橡胶为100质量份计，准备2至6质量份碳纳米管、2至8质量份步骤一所得的纳米碳纤维以及5至15质量份步骤一所得的微米碳纤维；
    步骤三：将硅橡胶加入炼胶机中炼制，然后依次加入碳纳米管、纳米碳纤维、微米碳纤维进行混炼，最后加入硫化剂进行混炼；
    步骤四：将步骤三所得的混炼胶放置后进行硫化。
  7. 根据权利要求6所述的一种耐疲劳导电复合材料的制备方法，其特征在于：
    在步骤一中，所述纳米碳纤维的直径为100至300纳米，长度为5至20微米；所述微米碳纤维的直径为5至20微米，长度为0.1至10毫米，优选长度为0.1至3毫米；所述酸氧化处理步骤包括将纳米碳纤维和微米碳纤维分别分散在具有氧化性的酸液中，搅拌进行反应，将处理后的纳米碳纤维和微米碳纤维清洗至pH为6至7，再进行干燥。
  8. 根据权利要求7所述的一种耐疲劳导电复合材料的制备方法，其特征在于：
    所述酸液由浓硝酸和浓硫酸按照质量比1:1组成，所述纳米碳纤维和所述微米碳纤维与所述酸液的质量比分别为1:10。
  9. 根据权利要求6至8任一项所述的一种耐疲劳导电复合材料的制备方法，其特征在于：
    在步骤二中，以硅橡胶为100质量份计，硫化剂为1.5至2.5质量份，优选所述硫化剂的质量份为2.0～2.5；
    在步骤三中，将硅橡胶加入炼胶机中炼制0-8分钟后，优选1-5分钟后，依次加入碳纳米管后、加入纳米碳纤维后、加入微米碳纤维后以及加入硫化剂后的混炼时间分别为2至15分钟，优选为2至10分钟；混炼温度为20至60℃。
  10. 根据权利要求6至8任一项所述的一种耐疲劳导电复合材料的制备方法，其特征在于：
    在步骤四中，放置时间为24至72小时，硫化步骤包括一次硫化和二次硫化，所述一次硫化的硫化温度为160至180℃，硫化压力为10至15MPa，硫化时间为10至30分钟，优选为10至20分钟；所述二次硫化的硫化温度为150至200℃，优选为150～180℃，硫化时间为4至6小时。
  11. 一种耐疲劳导电硅橡胶的制备方法，其特征在于：采用权利要求1至5中任一项所述的耐疲劳导电复合材料制备所述耐疲劳导电硅橡胶，所述制备方法包括：
    步骤S1，对纳米碳纤维和微米碳纤维分别进行表面的酸氧化处理，分别得到酸氧化纳米碳纤维和酸氧化微米碳纤维；所述纳米碳纤维的直径在纳米级；所述微米碳纤维的直径在微米级，且所述微米碳纤维的长度在毫米级；
    步骤S2，将100质量份硅橡胶、2至6质量份的碳纳米管、2至8质量份的所述酸氧化纳米碳纤维、5至15质量份的所述酸氧化微米碳纤维以及硫化剂进行混炼、硫化，得到耐疲劳导电硅橡胶。
  12. 根据权利要求11所述的制备方法，其特征在于：所述步骤S2包括：
    将所述硅橡胶加入炼胶机中炼制，然后依次加入所述碳纳米管、所述酸氧化纳米碳纤维、所述酸氧化微米碳纤维、所述硫化剂进行混炼，得到混炼胶，优选所述炼制的时间为1～5分钟，优选所述碳纳米管、所述酸氧化纳米碳纤维、所述酸氧化微米碳纤维、所述硫化剂各自加入后的混炼时间为2～10分钟，各所述混炼的温度为20～60℃；
    将所述混炼胶放置后进行硫化。
  13. 根据权利要求11所述的制备方法，其特征在于：所述酸氧化处理步骤包括：
    将纳米碳纤维和微米碳纤维分别分散在具有氧化性的酸液中并在搅拌条件下进行酸氧化反应，分别得到酸氧化碳纤维体系
    将各所述酸氧化碳纤维体系清洗至pH为6至7，再进行干燥，得到所述酸氧化纳米碳纤维和酸氧化微米碳纤维，优选所述酸液由浓硝酸和浓硫酸按照质量比1:0.5～1.5组成，进一步优选按照质量比1:1组成，更优选所述纳米碳纤维和所述微米碳纤维分别与所述酸液的质量比分别为1:8～12，进一步优选为1:10。
  14. 根据权利要求11所述的制备方法，其特征在于：
    将所述混炼胶放置的时间为24～72小时，优选所述硫化步骤包括依次进行的一次硫化和二次硫化，更优选所述一次硫化的硫化温度为160至180℃，硫化压力为10至15MPa，硫化时间为10至20分钟；进一步优选所述二次硫化的硫化温度为150至200℃，更优选为150～180℃，硫化时间为4至6小时。
  15. 一种电子可穿戴设备，包括耐疲劳导电硅橡胶，其特征在于，所述耐疲劳导电硅橡胶采用权利要求6至14中任一项所述的制备方法制备而成。
PCT/CN2019/092069 2018-06-21 2019-06-20 一种耐疲劳导电复合材料及其制备方法 WO2019242684A1 (zh)

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