A hindered phenol-modified carbon nanotube / isoprene rubber composite material and its preparation method

Abstract

The present invention relates to a hindered phenol-modified carbon nanotube / isoprene rubber composite material and a preparation method thereof. The composite material comprises isoprene rubber, hindered phenol-modified carbon nanotubes, a vulcanizing agent, a vulcanization accelerator, and a plasticizer. The present invention utilizes a dicyclopentadiene-based hindered phenol antioxidant grafted onto the surface of the carbon nanotubes, significantly enhancing the compatibility of the carbon nanotubes with the isoprene rubber, improving the dispersibility of the carbon nanotubes in the isoprene rubber, preventing agglomeration, and effectively improving the mechanical properties of the isoprene rubber. Furthermore, grafting the easily migrated hindered phenol antioxidant onto the carbon nanotube filler effectively secures the antioxidant within the rubber, reducing antioxidant loss during use and improving the long-term aging resistance of the rubber.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and particularly relates to a hindered phenol-modified carbon nanotube / isoprene rubber composite material and a preparation method thereof. Background Art

[0002] Rubber materials are a crucial class of polymers, widely used in mining, transportation, construction, machinery, electronics, and other fields. Isoprene rubber, a synthetic rubber with properties similar to natural rubber, is widely used in the tire manufacturing industry. However, due to its structural differences, isoprene rubber exhibits inferior mechanical properties compared to natural rubber, necessitating the use of certain reinforcing agents to modify it.

[0003] Currently, researchers have systematically studied the reinforcement of isoprene rubber. The addition of inorganic fillers such as carbon black and silica can improve the mechanical properties of rubber materials. However, as demand for higher performance in rubber increases, traditional inorganic fillers are no longer able to meet these demands. Carbon nanotubes (CNTs) are a newly discovered nanomaterial with excellent properties, including high mechanical strength, good flexibility, and excellent electrical and thermal conductivity. Composites prepared by compounding CNTs with rubber as fillers have high application value. However, CNTs are not compatible with rubber and easily aggregate in the composite material. Once aggregated, this negatively impacts the rubber's performance. Patent CN110669342 proposes treating CNTs with silicone oil oligomers and dispersants to prepare a CNT pre-dispersion, which can improve the dispersibility of CNTs in silicone rubber. Patent CN102924763 proposes using plasma modification technology to deposit a polyacrylic acid film on the surface of CNTs, and then using a coupling method to improve the interfacial bonding between the CNTs and the rubber. The additives used in the above method are ineffective additives for rubber, which increases the production cost of rubber.

[0004] Furthermore, rubber typically operates in relatively high-temperature environments, and isoprene rubber has poor thermal stability. Prolonged exposure to high-temperature air can significantly shorten the rubber's service life. Therefore, a certain percentage of antioxidants or anti-aging agents are often added to rubber to slow down its thermal oxidative aging. However, antioxidants generally have a relatively low molecular weight, and over time, some of the antioxidants can migrate out of the rubber product, reducing its protective effectiveness. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a hindered phenol-modified carbon nanotube / isoprene rubber composite material and a preparation method thereof. Compared with traditional isoprene rubber, the composite material has the advantages of better mechanical properties and longer aging time.

[0006] The present invention provides a hindered phenol-modified carbon nanotube / isoprene rubber composite material, which comprises the following components in parts by mass:

[0007]

[0008]

[0009] Wherein, the hindered phenol-modified carbon nanotubes are modified with a hindered phenol antioxidant based on dicyclopentadiene.

[0010] The hindered phenol antioxidant based on dicyclopentadiene is a butylated product of p-cresol-dicyclopentadiene resin or a derivative thereof, and contains one or more functional groups, including hydroxyl groups, amino groups, etc., and preferably, the functional group is hydroxyl groups.

[0011] The vulcanizing agent is one of sulfur (including common sulfur and insoluble sulfur), dithiomorpholine, and 4-4'-dimorpholine disulfide, or a combination thereof.

[0012] The vulcanization accelerator is one of N,N-tetramethyl dithiodithioamide (accelerator TMTD), dipentamethylenethiuram tetrasulfide (accelerator DPTT), and 2,2'-dibenzothiazole disulfide (accelerator DM).

[0013] The tackifier is one of phenolic tackifying resin, C5 petroleum resin and C5 hydrogenated petroleum resin.

[0014] The present invention provides a method for preparing a hindered phenol-modified carbon nanotube / isoprene rubber composite material, comprising the following steps:

[0015] (1) Concentrated sulfuric acid and concentrated nitric acid are mixed, carbon nanotubes are added to the mixed acid, stirred thoroughly for reaction, diluted with deionized water, filtered under reduced pressure, and the solid is dried to obtain surface carboxyl-treated carbon nanotubes;

[0016] (2) mixing the carboxylated carbon nanotubes obtained in step (1) with thionyl chloride to react and convert the carboxyl groups into acyl chloride groups with higher activity;

[0017] (3) mixing the acylated carbon nanotubes obtained in step (2) with a hindered phenol antioxidant based on dicyclopentadiene, stirring and reacting to obtain hindered phenol-modified carbon nanotubes;

[0018] (4) According to the proportion, the hindered phenol-modified carbon nanotubes, isoprene rubber and other rubber processing aids obtained in step (3) are mixed and vulcanized to obtain a hindered phenol-modified carbon nanotube / isoprene rubber composite material.

[0019] The carbon nanotubes include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes, preferably multi-walled carbon nanotubes.

[0020] In step (1), the mass ratio of concentrated sulfuric acid to concentrated nitric acid is 1:1; the mass ratio of carbon nanotubes to mixed acid is 1:20-1:50; the reaction temperature is 100-150° C., and the reaction time is 4-8 hours.

[0021] The mass ratio of the carboxylated carbon nanotubes to thionyl chloride in step (2) is 1:5-1:10, the reaction temperature is 90-120° C., and the reaction time is 2-4 hours.

[0022] The mass ratio of the acylated carbon nanotubes to the hindered phenol antioxidant in step (3) is 1:1-1:3, the reaction temperature is 120-150° C., and the reaction time is 0.5-1 h.

[0023] Beneficial effects

[0024] The present invention uses a hindered phenol antioxidant based on dicyclopentadiene to be grafted onto the surface of carbon nanotubes, significantly improving the compatibility of the carbon nanotubes with isoprene rubber, improving the dispersion of the carbon nanotubes in the isoprene rubber, preventing agglomeration, and effectively enhancing the mechanical properties of the isoprene rubber. Furthermore, grafting the easily migrated hindered phenol antioxidant onto the carbon nanotube filler effectively secures the antioxidant within the rubber, reducing antioxidant loss during use and improving the rubber's long-term aging resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the preparation process of the present invention. DETAILED DESCRIPTION

[0026] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0027] Example 1

[0028] 20 g of multi-walled carbon nanotubes were mixed with 500 g of mixed acid (a mixture of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1), stirred at 120°C for 4 h, and then diluted with deionized water. The mixture was then filtered under reduced pressure and the solid was dried to obtain surface carboxyl-treated carbon nanotubes.

[0029] 10 g of carboxylated carbon nanotubes were mixed with 100 g of thionyl chloride, stirred at 100 °C for 2 h, filtered, washed with ether, and dried to obtain acylated carbon nanotubes, which were then mixed and coupled with 10 g of antioxidant CPL (purchased from Jilin Herun Chemical Co., Ltd.) to obtain hindered phenol-modified carbon nanotubes.

[0030] Hindered phenol-modified carbon nanotubes, isoprene rubber, and a phenolic tackifying resin are mixed in an internal mixer. Sulfur and TMTD accelerator are then added for vulcanization to produce an isoprene rubber with long-term thermal stability. The mass ratio of isoprene rubber, carbon nanotubes, sulfur, TMTD accelerator, and phenolic tackifying resin is 100:2:2:1:3.

[0031] Example 2

[0032] 20 g of multi-walled carbon nanotubes were mixed with 750 g of mixed acid (a mixture of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1), stirred at 120°C for 4 h, and then diluted with deionized water. The mixture was then filtered under reduced pressure and the solid was dried to obtain surface carboxyl-treated carbon nanotubes.

[0033] 10 g of antioxidant CPL (purchased from Jilin Herun Chemical Co., Ltd.) was dissolved in carbon tetrachloride, 1 g of N-bromosuccinimide and 0.02 g of benzoyl peroxide were added, heated to 40°C and stirred for 0.5 h, the solvent was removed, 10 g of 30% sodium hydroxide solution was added, stirred for 0.5 h, and the solvent was removed to obtain hydroxylated antioxidant CPL.

[0034] 10 g of carboxylated carbon nanotubes were mixed with 80 g of thionyl chloride, stirred at 100 ° C for 2 h, filtered, washed with ether and dried to obtain acylated carbon nanotubes, which were then mixed and coupled with 10 g of hydroxylated antioxidant CPL to obtain hindered phenol-modified carbon nanotubes.

[0035] Hindered phenol-modified carbon nanotubes, isoprene rubber, and a phenolic tackifying resin are mixed in an internal mixer. Sulfur and TMTD accelerator are then added for vulcanization to produce an isoprene rubber with long-term thermal stability. The mass ratio of isoprene rubber, carbon nanotubes, sulfur, TMTD accelerator, and phenolic tackifying resin is 100:2:2:1:3.

[0036] Example 3

[0037] 20 g of multi-walled carbon nanotubes were mixed with 750 g of mixed acid (a mixture of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1), stirred at 120°C for 4 h, and then diluted with deionized water. The mixture was then filtered under reduced pressure and the solid was dried to obtain surface carboxyl-treated carbon nanotubes.

[0038] 10 g of antioxidant CPL (purchased from Jilin Herun Chemical Co., Ltd.) was dissolved in carbon tetrachloride, 1 g of N-bromosuccinimide and 0.02 g of benzoyl peroxide were added, heated to 40°C and stirred for 0.5 h, the solvent was removed, 10 g of 30% sodium hydroxide solution was added, stirred for 0.5 h, and the solvent was removed to obtain hydroxylated antioxidant CPL.

[0039] 10 g of carboxylated carbon nanotubes were mixed with 80 g of thionyl chloride, stirred at 100 ° C for 2 h, filtered, washed with ether and dried to obtain acylated carbon nanotubes, which were then mixed and coupled with 10 g of hydroxylated antioxidant CPL to obtain hindered phenol-modified carbon nanotubes.

[0040] Hindered phenol-modified carbon nanotubes, isoprene rubber and C5 hydrogenated petroleum resin are placed in an internal mixer for mixing, and then sulfur and accelerator DPTT are added for vulcanization treatment, wherein the mass ratio of isoprene rubber, carbon nanotubes, sulfur, accelerator DPTT and C5 hydrogenated petroleum resin is 100:2:2:1:3.

[0041] Comparative Example 1

[0042] Conventional carbon nanotubes, isoprene rubber, and a phenolic tackifying resin are mixed in an internal mixer, and then sulfur and N,N-tetramethyldithiodithioamide are added for vulcanization to produce the isoprene rubber. The mass ratio of isoprene rubber, carbon nanotubes, sulfur, N,N-tetramethyldithiodithioamide, and phenolic tackifying resin is 100:2:2:1:3.

[0043] Comparative Example 2

[0044] Conventional carbon nanotubes, isoprene rubber, an antioxidant (CPL), and rubber additives are mixed in an internal mixer, and then sulfur and an accelerator are added for vulcanization to produce the isoprene rubber. The mass ratio of the isoprene rubber, carbon nanotubes, antioxidant (CPL), sulfur, N,N-tetramethyldithiodithioamide, and phenolic tackifying resin is 100:2:2:2:1:3.

[0045] Comparative Example 3

[0046] 20 g of multi-walled carbon nanotubes were mixed with 500 g of mixed acid (a mixture of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1), stirred at 120°C for 4 h, and then diluted with deionized water. The mixture was then filtered under reduced pressure and the solid was dried to obtain surface carboxyl-treated carbon nanotubes.

[0047] 10 g of carboxylated carbon nanotubes were mixed with 100 g of thionyl chloride, stirred at 100° C. for 2 h, filtered, washed with ether, and dried to obtain acylated carbon nanotubes, which were then mixed and coupled with 10 g of antioxidant 1010 (purchased from BASF AG) to obtain hindered phenol-modified carbon nanotubes.

[0048] Antioxidant 1010-modified carbon nanotubes, isoprene rubber, and a phenolic tackifying resin were mixed in an internal mixer. Sulfur and TMTD (accelerator) were then added for vulcanization to produce thermally stable isoprene rubber. The mass ratio of isoprene rubber, carbon nanotubes, sulfur, TMTD (accelerator), and phenolic tackifying resin was 100:2:2:1:3.

[0049] Comparative Example 4

[0050] 20 g of multi-walled carbon nanotubes were mixed with 750 g of mixed acid (a mixture of concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 1:1), stirred at 120°C for 4 h, and then diluted with deionized water. The mixture was then filtered under reduced pressure and the solid was dried to obtain surface carboxyl-treated carbon nanotubes.

[0051] 10 g of carboxylated carbon nanotubes were mixed with 80 g of thionyl chloride, stirred at 100° C. for 2 h, filtered, washed with ether, and dried to obtain acylated carbon nanotubes, which were then mixed and coupled with 10 g of antioxidant 1076 (purchased from BASF AG) to obtain hindered phenol-modified carbon nanotubes.

[0052] Hindered phenol-modified carbon nanotubes, nitrile rubber and C5 hydrogenated petroleum resin are placed in an internal mixer for mixing, and then sulfur and accelerator DPTT are added for vulcanization treatment, wherein the mass ratio of nitrile rubber, carbon nanotubes, sulfur, accelerator DPTT and C5 hydrogenated petroleum resin is 100:2:2:1:3.

[0053] The thermal stability of the composite material was tested using a TGA thermal stability analyzer. (Test conditions: temperature range: room temperature-800°C, heating rate: 10°C / min, sample mass: 1g)

[0054]

[0055] Comparing the experimental results of Examples 1-3 with those of Comparative Examples 1 / 2, it can be shown that the thermal stability of the composite material prepared by grafting the antioxidant CPL onto carbon nanotubes and then mixing it with rubber is significantly better than the effect of directly adding the antioxidant to the rubber. This is because the antioxidant is grafted onto the carbon nanotubes and then mixed into the rubber, which has less escape loss and more effective ingredients than when it is directly added to the rubber.

[0056] Comparing the experimental results of Examples 1-3 with those of Comparative Examples 1 / 2 shows that in the composite materials made by grafting antioxidants CPL, antioxidant 1010, and antioxidant 1076 onto carbon nanotubes and then mixing them with rubber, there is no significant difference in the heat aging resistance of different groups. This is because different types of antioxidants can all play a role in heat aging resistance in a short period of time without showing significant performance differences.

[0057] The tensile strength and elongation at break of the composite material were tested using a universal testing machine. (Test conditions: experimental temperature 24°C, humidity 65%, tensile rate 250mm / min)

[0058]

[0059] Comparing the experimental results of Examples 1-3 with those of Comparative Examples 1 / 2, it can be shown that the long-term thermal stability of the composite material prepared by grafting the antioxidant CPL onto carbon nanotubes and then mixing it with rubber is significantly better than the effect of directly adding the antioxidant to the rubber. This is because after the antioxidant is grafted onto the surface of the carbon nanotubes, it plays an "anchoring" role in the rubber and remains effective in the rubber for a longer time.

[0060] Comparing the experimental results of Examples 1-3 with Comparative Examples 3 / 4 shows that the composite materials made by grafting antioxidants CPL, 1010, and 1076 onto carbon nanotubes and then mixing them with rubber exhibit significantly greater thermal stability and mechanical properties than the antioxidants 1010 and 1076. This is because the structure of antioxidant CPL is very similar to that of isoprene rubber, resulting in better compatibility. Therefore, antioxidant CPL improves the dispersion of carbon nanotubes, while carbon nanotubes reduce the escape loss of antioxidant CPL. These two effects create a synergistic effect, enhancing the overall performance of isoprene rubber.

Claims

1. A hindered phenol-modified carbon nanotube / isoprene rubber composite material, characterized by: By mass, it includes the following components: 100 parts of isoprene rubber; 1-10 parts of hindered phenol-modified carbon nanotubes; 1-5 parts of vulcanizing agent; 0.2-1.5 parts of vulcanization accelerator; 1-10 parts of plasticizer; The hindered phenol-modified carbon nanotubes are modified with a hindered phenol antioxidant based on dicyclopentadiene, and the hindered phenol antioxidant based on dicyclopentadiene is a butylated product of p-cresol-dicyclopentadiene resin; The specific steps are: (1) Concentrated sulfuric acid and concentrated nitric acid are mixed, carbon nanotubes are added to the mixed acid, stirred thoroughly for reaction, diluted with deionized water, filtered under reduced pressure, and the solid is dried to obtain surface carboxyl-treated carbon nanotubes; (2) mixing the carboxylated carbon nanotubes obtained in step (1) with thionyl chloride to react and convert the carboxyl groups into acyl chloride groups with higher activity to obtain acylated carbon nanotubes; (3) The acylated carbon nanotubes obtained in step (2) are mixed with a hindered phenol antioxidant based on dicyclopentadiene, and the mixture is stirred for reaction to obtain hindered phenol-modified carbon nanotubes.

2. The composite material according to claim 1, characterized in that: The vulcanizing agent is one of sulfur and dithiomorpholine or a combination thereof.

3. The composite material according to claim 1, characterized in that: The vulcanization accelerator is one of N,N-tetramethyl dithiodithioamide, dipentylene thiuram tetrasulfide, and 2,2'-dibenzothiazole disulfide.

4. The composite material according to claim 1, characterized in that: The plasticizer is one of phenolic tackifying resin, C5 petroleum resin and C5 hydrogenated petroleum resin.

5. A method for preparing the hindered phenol-modified carbon nanotube / isoprene rubber composite material according to claim 1, comprising the following steps: (1) Concentrated sulfuric acid and concentrated nitric acid are mixed, carbon nanotubes are added to the mixed acid, stirred thoroughly for reaction, diluted with deionized water, filtered under reduced pressure, and the solid is dried to obtain surface carboxyl-treated carbon nanotubes; (2) mixing the carboxylated carbon nanotubes obtained in step (1) with thionyl chloride to react and convert the carboxyl groups into acyl chloride groups with higher activity to obtain acylated carbon nanotubes; (3) mixing the acylated carbon nanotubes obtained in step (2) with a hindered phenol antioxidant based on dicyclopentadiene, stirring and reacting to obtain hindered phenol-modified carbon nanotubes; (4) The hindered phenol-modified carbon nanotubes, isoprene rubber and other components obtained in step (3) are mixed and vulcanized to obtain a hindered phenol-modified carbon nanotube / isoprene rubber composite material.

6. The preparation method according to claim 5, characterized in that: The carbon nanotubes include at least one of single-walled carbon nanotubes and multi-walled carbon nanotubes.

7. The preparation method according to claim 5, characterized in that: The mass ratio of concentrated sulfuric acid to concentrated nitric acid in step (1) is 1:1; the mass ratio of carbon nanotubes to mixed acid is 1:20-1:50; the reaction temperature is 100-150° C., and the reaction time is 4-8 hours.

8. The preparation method according to claim 5, characterized in that: The mass ratio of the carboxylated carbon nanotubes to thionyl chloride in step (2) is 1:5-1:10, the reaction temperature is 90-120° C., and the reaction time is 2-4 h.

9. The preparation method according to claim 5, characterized in that: The mass ratio of the acylated carbon nanotubes to the hindered phenol antioxidant in step (3) is 1:1-1:3, the reaction temperature is 120-150° C., and the reaction time is 0.5-1 h.

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