Deep eutectic solvent coated carbon black conductive filler as well as preparation method and application thereof

Abstract

The invention discloses a deep eutectic solvent coated carbon black conductive filler as well as a preparation method and application thereof. The method comprises the following steps: combining a hydrogen bond donor and a hydrogen bond acceptor together through a strong hydrogen bond effect to form a deep eutectic solvent, and enabling the deep eutectic solvent and oxygen-containing groups on the surfaces of conductive carbon black particles to form hydrogen bond interaction through a grinding means to obtain the carbon black coated with the deep eutectic solvent. The conductive filler obtained by the method is not easy to agglomerate and can be uniformly dispersed in a polymer matrix. When the conductive filler is applied to the composite material, the reinforcing effect of the conductive carbon black is exerted, and meanwhile the conductivity of the composite material can be remarkably improved. The novel conductive filler has the advantages of simple process preparation, safety, high efficiency and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and particularly relates to a method for coating carbon black conductive filler with a deep eutectic solvent. Background Art

[0002] Conductive carbon black has become the most widely used reinforcing filler and conductive filler in the field of composite materials due to its high conductivity and good processing characteristics. The conductive mechanism of conductive carbon black follows the percolation theory. Only when the addition amount reaches the percolation threshold will the conductivity of the composite material jump by an order of magnitude and the conductivity will be sharply enhanced. However, as the content of conductive carbon black continues to increase, the hardness of the matrix increases significantly, limiting its application in flexible devices. This phenomenon is due to the high specific surface area of ​​conductive carbon black, which makes it difficult to disperse evenly in the polymer matrix. The strong van der Waals force between particles easily causes high hysteresis and heat accumulation during dynamic deformation, resulting in a decrease in mechanical properties, which ultimately accelerates the degradation of the composite material and shortens its service life.

[0003] To this end, researchers have conducted a series of explorations around this issue. In related research, the use of mixed filler systems to improve the dispersibility of conductive carbon black has become a topic widely reported in the literature. However, the mixed conductive filler system involves a combination of multiple fillers, and each filler has a different influence on the material properties, which makes the regulation of material properties more complicated. In addition, ionic liquids (ILs) also have unique advantages in improving the dispersibility of conductive carbon black. Certain functional groups of IL (such as hydroxyl, amino, etc.) form hydrogen bonds with oxygen-containing functional groups (such as carboxyl, hydroxyl, etc.) on the surface of conductive carbon black, which can enhance the interaction between IL and conductive carbon black, thereby improving the dispersion of conductive carbon black in IL. Szadkowsk et al. (Szadkowski, B.; Marzec, A.; Zaborski, M. Use of carbon black as a reinforcing nano-filler in conductivity-reversible elastomer composites [J]. Polymer Testing, 2020, 81: 106222.) added IL as a dispersant to the conductive carbon black-filled nitrile rubber (NBR) matrix, and observed through scanning electron microscopy (SEM) that the addition of IL significantly improved the dispersion of conductive carbon black in the NBR matrix, prompting the system to form more conductive paths.

[0004] It is worth noting that the volatile residues of ILs may cause biocompatibility and environmental issues. In contrast, deep eutectic solvents, as a low-melting eutectic mixture composed of hydrogen bond donors and hydrogen bond acceptors, have a unique hydrogen bond network structure that can achieve filler dispersion at the nanoscale through the synergistic effect of interfacial permeation and shear. This dispersion mechanism is more efficient and controllable. Summary of the Invention

[0005] The present invention aims to provide a deep eutectic solvent-coated carbon black conductive filler, its preparation method, and application. This deep eutectic solvent-coated carbon black, as a conductive filler, can be uniformly dispersed in a polymer matrix and exhibits excellent compatibility with the polymer. This conductive carbon black can enhance the conductivity of the composite material while reinforcing the composite material.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a deep eutectic solvent-coated carbon black conductive filler comprises the following steps:

[0008] (1) A hydrogen bond donor and a hydrogen bond acceptor are taken and combined together by strong hydrogen bonds to form a deep eutectic solvent that is liquid at room temperature;

[0009] (2) Conductive carbon black is treated with a deep eutectic solvent by grinding to obtain a deep eutectic solvent-coated carbon black conductive filler.

[0010] In the above method, in step (1), the hydrogen bond donor is one or more molecules containing carboxyl, hydroxyl, amino, and amide groups.

[0011] In the above method, in step (1), the hydrogen bond acceptor is one or more molecules composed of metal halides and quaternary ammonium salts with anionic and cationic structures and containing fluorine, chlorine, bromine, and iodine elements.

[0012] In the above method, in step (1), the hydrogen bond donor is specifically selected from one or more of acrylic acid, succinic acid, oxalic acid, methacrylic acid, terephthalic acid, citric acid, phenylacetic acid, capric acid, ethanol, ethylene glycol, butanediol, glycerol, xylitol, ethylenediamine, aminoxime, urea, acetamide, and N-methylacetamide;

[0013] The hydrogen bond acceptor is specifically selected from one or more of zinc chloride, aluminum chloride, ferric chloride, lithium chloride, potassium chloride, betaine, choline chloride, choline acetate, tetrabutylammonium acetate, tetrabutylammonium chloride, choline fluoride, benzalkonium chloride, and tetradecyldimethylpyridinium bromide.

[0014] In the above method, in step (1), the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 0.1:1 to 3:1.

[0015] In the above method, in step (1), the deep eutectic solvent is prepared by a stirring and mixing method: weighed hydrogen bond acceptors and hydrogen bond donors are stirred, mixed or ground under an inert gas atmosphere until a uniform deep eutectic solvent solution is formed; the stirring and mixing process is performed at a temperature of 30 to 150° C. for a time of 0.1 to 6 hours.

[0016] In the above method, in step (2), the mass ratio between the deep eutectic solvent and the conductive carbon black is 1:30 to 1:3.

[0017] In the above method, in step (2), the grinding means is achieved by using a mortar or a ball mill, and the grinding time is 5 to 60 minutes.

[0018] The deep eutectic solvent-coated carbon black conductive filler in the present invention is used as a conductive filler in the field of composite materials. The conductive filler is uniformly dispersed in the polymer matrix and has good compatibility with the polymer. While the conductive carbon black reinforces the composite material, it also improves the conductivity of the material.

[0019] The principle of the present invention is: under the action of strong shear force during the grinding process, the van der Waals force between carbon black particles is destroyed, the agglomerated carbon black particles dissociate, the deep eutectic solvent penetrates into the carbon black particles, and forms hydrogen bonds with active groups such as oxygen on the carbon black surface, thereby coating the carbon black surface to obtain a deep eutectic solvent-coated carbon black conductive filler.

[0020] The present invention has the beneficial effects of effectively reducing carbon black agglomeration and improving its dispersion in the polymer matrix. While the carbon black exerts a reinforcing effect, the anions and cations within the deep eutectic solvent on its surface, together with the carbon black, enhance the conductivity of the polymer, thereby improving the mechanical and electrical properties of the polymer matrix. The conductive filler described in the present invention has a simple preparation method, a wide range of raw material sources, and good controllability, and has great application value in the field of polymer conductive composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the infrared spectrum of choline chloride, glycerol and deep eutectic solvent 1 in Example 1 of the present invention.

[0022] Figure 2a and Figure 2b They are transmission electron microscope images of the conductive carbon black in Example 2 of the present invention and the prepared deep eutectic solvent-coated carbon black 2, respectively.

[0023] Figure 3 This is a sensing test of the XNBR-20C prepared in Example 8 of the present invention to small movements of the human body such as finger bending. DETAILED DESCRIPTION

[0024] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0025] Example 1

[0026] Choline chloride and glycerol were mixed in a molar ratio of 3:1 and stirred at 120°C for 0.1 h to obtain a uniform, transparent deep eutectic solvent 1. Deep eutectic solvent 1 was mixed with conductive carbon black in a mass ratio of 1:30 and ground using a ball mill for 5 min to obtain deep eutectic solvent-coated carbon black 1.

[0027] The infrared spectra of choline chloride, glycerol and deep eutectic solvent 1 are shown in Figure 2. Figure 1 As shown, 1091cm -1 The stretching vibration peak of CO is at 1093 cm. When choline chloride and glycerol form a deep eutectic solvent, the CO peak of choline chloride shifts to 1093 cm. -1 953cm -1 The bending vibration of NCC at 951 cm -1 . And 3482cm in glycerol -1 The stretching vibration peak of -OH at 3351 cm-1 shifts to 3351 cm-1 in deep eutectic solvents. -1 The shift of the above peaks indicates that a strong hydrogen bond is formed between choline chloride and glycerol, proving the successful synthesis of the deep eutectic solvent.

[0028] Example 2

[0029] Zinc chloride and terephthalic acid were mixed at a molar ratio of 0.1:1 and stirred at 30°C for 6 hours to obtain a uniform, transparent deep eutectic solvent 2. Deep eutectic solvent 2 was mixed with conductive carbon black at a mass ratio of 1:3 and ground in a mortar for 60 minutes to obtain deep eutectic solvent-coated carbon black 2.

[0030] Figure 2a and Figure 2b The following are transmission electron micrographs of conductive carbon black and deep eutectic solvent-coated carbon black 2. The conductive carbon black is severely agglomerated in the rubber matrix. By comparison, individual deep eutectic solvent-coated carbon black particles 2 are clearly dispersed within the matrix. A layer of deep eutectic solvent is present between the modified conductive carbon black particles. This indicates that the deep eutectic solvent coats the surface of the conductive carbon black particles, significantly reducing their tendency to agglomerate and significantly improving their dispersion within the matrix. This confirms the successful modification of the conductive carbon black by the deep eutectic solvent.

[0031] Example 3

[0032] Benzalkonium chloride, aluminum chloride, and ethylenediamine were mixed in a molar ratio of 1:1:2 and stirred at 70°C for 3 hours to obtain a uniform, transparent deep eutectic solvent 3. Deep eutectic solvent 3 was mixed with conductive carbon black in a mass ratio of 3:10 and ground in a mortar for 30 minutes to obtain deep eutectic solvent-coated carbon black 3.

[0033] Example 4

[0034] Choline fluoride, potassium chloride, and citric acid were mixed in a molar ratio of 1:0.5:1 and stirred at 150°C for 0.5 h to obtain a uniform, transparent deep eutectic solvent 4. Deep eutectic solvent 4 was mixed with conductive carbon black in a mass ratio of 1:5 and ground in a ball mill for 25 min to obtain deep eutectic solvent-coated carbon black 4.

[0035] Example 5

[0036] Ferric chloride, tetrabutylammonium chloride, and urea were mixed in a molar ratio of 1:1:1 and stirred at 100°C for 4 hours to obtain a uniform, transparent deep eutectic solvent 4. Deep eutectic solvent 5 was mixed with conductive carbon black in a mass ratio of 1:10 and ground in a ball mill for 40 minutes to obtain deep eutectic solvent-coated carbon black 5.

[0037] Example 6

[0038] A nitrile rubber composite was prepared using deep eutectic solvent-coated carbon black 1. The basic formula is shown in Table 1. The prepared rubber compound was vulcanized according to the normal vulcanization time, subjected to tensile testing according to the GB / T 528-2009 standard, and its electrical conductivity was measured using a four-probe resistance tester.

[0039] Table 1

[0040]

[0041]

[0042] Note: Units in the table are parts by mass (phr). In NBR-nC, n represents the number of parts of deep eutectic solvent-coated carbon black added. St: stearic acid; CZ: N-cyclohexyl-2-benzothiazolesulfenamide; DM: dibenzothiazyl disulfide; S: sulfur; CB: deep eutectic solvent-coated carbon black.

[0043] Table 2 shows the tensile strength and electrical conductivity of the composite materials with different amounts of deep eutectic solvent-coated carbon black 1 added. It can be seen that with the increase in the amount of conductive filler added, the tensile strength of the composite material increases significantly, indicating that the conductive filler has an excellent reinforcement effect and the electrical conductivity of the material also steadily increases. The electrical conductivity of the composite material with 20 phr of deep eutectic solvent-coated carbon black 1 is increased by nearly six orders of magnitude compared to the composite material without conductive filler added.

[0044] Table 2

[0045]

[0046] Example 7

[0047] A styrene-butadiene rubber composite was prepared using carbon black 2 coated with a deep eutectic solvent. The basic formula is shown in Table 3. The prepared rubber compound was vulcanized according to the normal vulcanization time, subjected to tensile testing according to the standard GB / T 528-2009, and its electrical conductivity was tested using a four-probe resistance tester.

[0048] Table 3

[0049]

[0050] Note: The units in the table are parts by mass (phr). In SBR-nC, n represents the number of added parts of deep eutectic solvent-coated carbon black. St: stearic acid; CZ: N-cyclohexyl-2-benzothiazolesulfenamide; DM: dibenzothiazyl disulfide; S: sulfur; CB: deep eutectic solvent-coated carbon black.

[0051] Table 4 shows the tensile strength and electrical conductivity of the composite materials with different amounts of deep eutectic solvent coated carbon black 2. It can be seen that with the increase of the amount of conductive filler added, the tensile strength of the composite material increases significantly, indicating that the conductive filler has an excellent reinforcement effect and the electrical conductivity of the material is steadily improved. The tensile strength of the composite material with 50phr deep eutectic solvent coated carbon black 2 is 17.61MPa, and the electrical conductivity can reach 1.30*10 2 S / m.

[0052] Table 4

[0053]

[0054]

[0055] Example 8

[0056] A carboxylated nitrile rubber composite was prepared by coating carbon black 3 with a deep eutectic solvent. The basic formula is shown in Table 5. The prepared rubber compound was vulcanized according to the normal vulcanization time and subjected to tensile testing according to the GB / T 528-2009 standard. Its electrical conductivity was measured using a four-probe resistance tester, and the sensor performance of the composite was tested using a digital multimeter.

[0057] Table 5

[0058]

[0059] Note: The units in the table are parts by mass (phr). In XNBR-nC, n represents the number of parts of deep eutectic solvent-coated carbon black added. St: stearic acid; CZ: accelerator; DM: accelerator; S: sulfur; CB: deep eutectic solvent-coated carbon black.

[0060] Table 6 shows the tensile strength and electrical conductivity of the composite materials with different amounts of deep eutectic solvent coated carbon black 3. It can be seen that with the increase of the amount of conductive filler added, the tensile strength of the composite material increases significantly, indicating that the conductive filler has an excellent reinforcement effect and the electrical conductivity of the material also increases steadily. The tensile strength of the composite material with 20phr deep eutectic solvent coated carbon black 3 is 11.04MPa, and the electrical conductivity can reach 2.16*10 -1 S / m. Figure 3 The sensitivity of XNBR-20C in detecting tiny movements of the human body, such as finger bending, was demonstrated, indicating that the material has application value in fields such as strain sensors.

[0061] Table 6

[0062]

[0063] Example 9

[0064] The deep eutectic solvent-coated carbon black prepared in Examples 1-5 was mixed with natural rubber to prepare a natural rubber composite material. The prepared vulcanized rubber is Example 9.

[0065] A natural rubber composite material was prepared by mixing unmodified conductive carbon black with natural rubber, and the prepared vulcanized rubber was used as a comparative example.

[0066] The basic formulas of Example 9 and the comparative example are shown in Table 7.

[0067] Table 7

[0068]

[0069]

[0070] Note: The unit in the table is parts by mass (phr). The addition amounts of other additives in rubber are as follows: ZnO 5phr, St 2phr, CZ 1.5phr, DM 0.5phr, S1.5phr.

[0071] Table 8 shows the conductivity of Example 9 and the comparative example. It can be seen from the table that when 20 phr of conductive filler is added, the conductivity of the composite material prepared in Example 9 is significantly higher than that of the composite material prepared in the comparative example. The conductivity of the comparative example is 1.04*10 -3S / m, while the conductivity of Example 9 can be improved by nearly two orders of magnitude. This demonstrates that deep eutectic solvent-coated carbon black has outstanding advantages in preparing conductive composite materials. On the one hand, because the deep eutectic solvent itself has excellent conductivity, under the action of an applied voltage, the anions and cations within the deep eutectic solvent will migrate, thereby improving the conductivity of the composite material. On the other hand, the deep eutectic solvent imparts more excellent dispersibility to the conductive carbon black. As the content of deep eutectic solvent-coated carbon black increases, the conductive carbon black particles contact each other within the polymer matrix, forming a conductive path, which greatly improves the conductivity.

[0072] Table 8

[0073]

[0074] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a deep eutectic solvent-coated carbon black conductive filler, characterized in that: The following steps are involved: (1) A hydrogen bond donor and a hydrogen bond acceptor are taken and combined together by strong hydrogen bonds to form a deep eutectic solvent that is liquid at room temperature; (2) Conductive carbon black is treated with a deep eutectic solvent by grinding to obtain a deep eutectic solvent-coated carbon black conductive filler.

2. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (1), the hydrogen bond donor is one or more molecules containing carboxyl, hydroxyl, amino, and amide groups.

3. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (1), the hydrogen bond acceptor is one or more molecules composed of anion and cation structures of metal halides and quaternary ammonium salts, and containing fluorine, chlorine, bromine, and iodine elements.

4. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (1), the hydrogen bond donor is specifically selected from one or more of acrylic acid, succinic acid, oxalic acid, methacrylic acid, terephthalic acid, citric acid, phenylacetic acid, capric acid, ethanol, ethylene glycol, butanediol, glycerol, xylitol, ethylenediamine, amidoxime, urea, acetamide, and N-methylacetamide; The hydrogen bond acceptor is specifically selected from one or more of zinc chloride, aluminum chloride, ferric chloride, lithium chloride, potassium chloride, betaine, choline chloride, choline acetate, tetrabutylammonium acetate, tetrabutylammonium chloride, choline fluoride, benzalkonium chloride, and tetradecyldimethylpyridinium bromide.

5. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (1), the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 0.1:1 to 3:

1.

6. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (1), the preparation method of the deep eutectic solvent is a stirring and mixing method: the weighed hydrogen bond acceptor and hydrogen bond donor are stirred, mixed or ground under an inert gas atmosphere until a uniform deep eutectic solvent solution is formed; the temperature during the stirring and mixing process is 30 to 150° C. and the time is 0.1 to 6 hours.

7. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (2), the mass ratio between the deep eutectic solvent and the conductive carbon black is 1:30 to 1:

3.

8. The method for preparing the deep eutectic solvent-coated carbon black conductive filler according to claim 1, characterized in that: In step (2), the grinding means is achieved by a mortar or a ball mill, and the grinding time is 5 to 60 minutes.

9. A deep eutectic solvent-coated carbon black conductive filler prepared by the preparation method according to any one of claims 1 to 8.

10. The deep eutectic solvent-coated carbon black conductive filler according to claim 9 is used as a conductive filler in the field of composite materials. The conductive filler is uniformly dispersed in the polymer matrix and has good compatibility with the polymer. While the conductive carbon black has a reinforcing effect on the composite material, it also improves the conductivity of the material.

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