Phenolic resin material as well as preparation method and application thereof in 3D printing

Abstract

The invention discloses a phenolic resin material as well as a preparation method and application thereof in 3D printing, and relates to the technical field of high polymer materials. When the phenolic resin material is prepared, hydroxylated carbon nanotubes react with isocyanate propyl triethoxy silane to prepare pre-modified carbon nanotubes, and then the pre-modified carbon nanotubes react with 2-chloroethyl triethoxy silane to prepare modified carbon nanotubes; the preparation method comprises the following steps: reacting vanillin with 5-amino-1, 2-dihydro-2-methyl-3H-1, 2, 4-triazole-3-thioketone and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in sequence, so as to obtain pre-modified vanillin; reacting the pre-modified vanillin with divinyl disulfide to obtain modified vanillin; the modified vanillin, phenol and formaldehyde react to prepare modified phenolic resin, and then the modified phenolic resin reacts with the modified carbon nanotubes to prepare the phenolic resin material. The phenolic resin material prepared by the invention has good flame retardance, heat resistance, aging resistance, self-repairing property and mechanical property.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, in particular to a phenolic resin material, a preparation method thereof and application thereof in 3D printing. BACKGROUND

[0002] In recent years, the establishment of an environmentally friendly society is advocated all over the world, and the use of biomass modified polymers in the field of composite materials is an important strategic direction of the material industry. The popularization and application of biomass materials can improve the utilization rate of resources, reduce the dependence on chemical products, reduce production and environmental costs, and alleviate the energy crisis. Phenolic resin is a common industrial product, widely used, and the output is sufficient, so modifying phenolic resin with biomass raw materials is a manifestation of the establishment of an environmentally friendly society.

[0003] The main chain structure of phenolic resin determines its good heat resistance, electrical insulation performance, corrosion resistance, and dimensional stability, but the rigid benzene ring structure of its main chain leads to low impact strength and high brittleness, which greatly limits the application of phenolic resin. In addition, the phenolic hydroxyl group in phenolic resin has strong polarity and reactivity, and is easily oxidized under high temperature or light conditions to form a quinone structure. The quinone structure is unstable and can further initiate chain reaction, leading to molecular chain rupture or crosslinking structure damage, thereby causing the mechanical properties of the material to decrease. In order to improve the performance of phenolic resin and expand its application, it is necessary to modify phenolic resin to meet different industrial needs. Therefore, the present application prepares a phenolic resin material with good flame retardance, heat resistance, aging resistance, self-repairing and mechanical properties to meet the application requirements in 3D printing. SUMMARY

[0004] The present application aims to provide a phenolic resin material, a preparation method thereof and application thereof in 3D printing to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the present application provides the following technical solutions:

[0006] A phenolic resin material is prepared by reacting modified vanillin, phenol and formaldehyde to obtain modified phenolic resin, and then reacting with modified carbon nanotubes.

[0007] As an optimization, the modified vanillin is prepared by reacting pre-modified vanillin with divinyl disulfide.

[0008] As an optimization, the pre-modified vanillin is prepared by sequentially reacting vanillin with 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0009] As an optimization, the modified carbon nanotubes are prepared by reacting pre-modified carbon nanotubes with 2-chloroethyltriethoxysilane.

[0010] As an optimization, the pre-modified carbon nanotubes are prepared by reacting hydroxylated carbon nanotubes with isocyanate propyl triethoxysilane.

[0011] A preparation method of a phenolic resin material, comprising the following preparation steps:

[0012] (1) Pre-modified carbon nanotubes, 2-chloroethyltriethoxysilane, sodium hydroxide, and toluene are uniformly mixed in a mass ratio of 1: (0.28-0.32): (0.0018-0.0022): (3-5), ultrasonic dispersion is performed for 20-30 min, stirring is performed at 60-70 °C and 200-300 r / min for 1-2 h, deionized water with a mass of 0.09-0.11 times that of the pre-modified carbon nanotubes is added at a uniform rate of 5 ml / min, stirring is performed at 60-70 °C and 200-300 r / min for 4-6 h, centrifugal separation is performed at 8000-10000 rpm for 10-12 min, the obtained precipitate is washed with deionized water for 2-4 times, and vacuum drying is performed at 40-50 °C for 10-12 h to obtain modified carbon nanotubes;

[0013] (2) Pre-modified vanillin, divinyl disulfide, azobisisobutyronitrile, and N,N-dimethylformamide are uniformly mixed in a mass ratio of 1: (0.12-0.14): (0.002-0.004): (15-20) under a nitrogen atmosphere, stirring is performed at 65-75 °C and 200-300 r / min for 20-24 h, N,N-dimethylformamide is removed by vacuum distillation, washing is performed with anhydrous ethanol for 2-4 times, and vacuum drying is performed at 40-50 °C for 10-12 h to obtain modified vanillin;

[0014] (3) Modified phenolic resin, anhydrous ethanol, and potassium hydroxide are uniformly mixed in a mass ratio of 1: (10-12): (0.002-0.003) at 75-85 °C, modified carbon nanotubes with a mass of 0.04-0.06 times that of the modified phenolic resin are added, stirring is performed at 55-65 °C and 200-300 r / min for 6-8 h, and vacuum distillation is performed to obtain a phenolic resin material.

[0015] As optimization, the preparation step of the pre-modified carbon nanotube in step (1) is as follows: under nitrogen atmosphere, hydroxylated carbon nanotubes, propyl triethoxysilane isocyanate, dibutyl tin dilaurate and toluene are uniformly mixed in a mass ratio of 1:(0.8-1.2):(0.001-0.002):(10-12), ultrasonic treatment is performed for 30-40 min, stirring is performed at 80-90℃ and 200-300 r / min for 4-6 h, centrifugal separation is performed at 8000-10000 rpm for 10-12 min, the obtained precipitate is washed with toluene for 3-5 times, and vacuum drying is performed at 40-50℃ for 10-12 h to obtain the pre-modified carbon nanotube.

[0016] As optimization, the preparation step of the pre-modified vanillin in step (2) is as follows: vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione and anhydrous ethanol are uniformly mixed in a mass ratio of 1:(0.85-0.9):(15-20), stirring is performed at 60-70℃ and 200-300 r / min for 8-10 h, vanillin is added in an amount of 1.4-1.5 times of the mass of the vanillin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added, stirring is performed at 75-80℃ and 200-300 r / min for 10-12 h, the solvent is removed by rotary evaporation, the obtained product is washed with anhydrous ethanol and deionized water for 2-4 times respectively, and vacuum drying is performed at 40-50℃ for 10-12 h to obtain the pre-modified vanillin.

[0017] As optimization, the preparation step of the modified phenolic resin in step (3) is as follows: the pre-modified vanillin, phenol and 20wt% sodium hydroxide aqueous solution are uniformly mixed in a mass ratio of 1:(5-7):(0.8-1), stirring is performed at 50-60℃ and 200-300 r / min for 10-20 min, the molar ratio of phenolic hydroxyl group to aldehyde group is 1:1.8, the polyformaldehyde is added in three times, stirring is performed at 60-70℃ and 200-300 r / min for 1-1.5 h, the temperature is increased to 80-90℃, stirring is performed at 200-300 r / min for 1.5-2 h, and vacuum distillation is performed to obtain the modified phenolic resin.

[0018] As optimization, the hydroxylated carbon nanotube has an inner diameter of 3-5 nm, an outer diameter of 8-15 nm and a length of 0.2-2 μm, and is purchased from Shanghai Jizisheng Chemical Technology Co., Ltd.

[0019] As optimization, the addition interval of the polyformaldehyde is 10-15 min.

[0020] A phenolic resin material in the application of 3D printing.

[0021] As optimization, the reaction process of the pre-modified vanillin is as follows:

[0022] .

[0023] As optimization, the reaction process of the modified vanillin is as follows:

[0024] .

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] In the preparation of the phenolic resin material, the hydroxylated carbon nanotube is reacted with propyl triethoxysilane isocyanate to obtain a pre-modified carbon nanotube; the pre-modified carbon nanotube is reacted with 2-chloroethyl triethoxysilane to obtain a modified carbon nanotube; vanillin is sequentially reacted with 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a pre-modified vanillin; the pre-modified vanillin is reacted with divinyl disulfide to obtain a modified vanillin; the modified vanillin, phenol and formaldehyde are reacted to obtain a modified phenolic resin; and the modified phenolic resin is reacted with the modified carbon nanotube to obtain the phenolic resin material.

[0027] Firstly, the hydroxylated carbon nanotube has good mechanical properties as a nanoparticle, and in the combustion process, the carbon nanotube can promote the formation of a carbon layer, thereby improving the flame retardant performance of the material; the hydroxyl group on the hydroxylated carbon nanotube is reacted with the isocyanate group on propyl triethoxysilane isocyanate to introduce a siloxane group on the carbon nanotube, and then hydrolysis condensation is carried out with 2-chloroethyl triethoxysilane to form a Si-O-Si group; the bond energy of the Si-O bond is higher than that of the C-C bond, and the flexibility is good, so the introduction of the Si-O bond improves the heat resistance of the phenolic resin material, and also plays a toughening role; and the silicon element is oxidized and decomposed at high temperature to generate inorganic residues mainly composed of silicon dioxide, which is attached to the surface of the material and cooperates with P and N elements to further improve the flame retardant performance of the material; at the same time, the introduction of the chlorine element on the carbon nanotube improves the aging resistance of the phenolic resin material by reacting with the phenolic hydroxyl group on the modified phenolic resin.

[0028] Secondly, vanillin and 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione Schiff base reaction occurs, and the generated imine structure can react with the P-H bond on 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide to introduce phosphorus element on vanillin. The phosphorus element can capture free radicals in the combustion process, thereby improving the flame retardant performance of the phenolic resin material. At the same time, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione contains a large amount of N element, which cooperates with the phosphorus element to further improve the flame retardant performance of the phenolic resin material; the thiol group on the pre-modified vanillin reacts with the double bond on the divinyl disulfide to introduce a disulfide bond in the material. The disulfide bond can be excited to break or recombine under the condition of light or heating, thereby giving the phenolic resin material good self-repairing performance.

[0029] Finally, the phenolic hydroxyl group on the modified phenolic resin reacts with the chlorine on the modified carbon nanotube to prepare a phenolic resin material; the phenolic hydroxyl group has strong polarity and reactivity and is easily oxidized under the condition of high temperature or light to generate a quinone structure. The quinone structure is unstable and can further initiate a chain reaction, leading to molecular chain rupture or crosslinking structure damage, thereby causing the mechanical properties of the material to decrease. The modified phenolic resin reacts with the modified carbon nanotube to reduce the number of phenolic hydroxyl groups in the material, thereby improving the aging resistance of the material. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0031] Embodiment 1

[0032] A preparation method of a phenolic resin material, comprising the following preparation steps:

[0033] (1) under the atmosphere of nitrogen, the hydroxylated carbon nanotube, propyl triethoxysilane isocyanate, dibutyl tin dilaurate, toluene were mixed uniformly according to the mass ratio of 1:0.8:0.001:10, ultrasonic dispersion for 30 min, stirring at 80℃ and 200 r / min for 4 h, centrifugal separation at 8000 rpm for 10 min, the obtained precipitate was washed with toluene for 3 times, vacuum drying at 40℃ for 10 h, to obtain the pre-modified carbon nanotube; the pre-modified carbon nanotube, 2-chloroethyl triethoxysilane, sodium hydroxide, toluene were mixed uniformly according to the mass ratio of 1:0.28:0.0018:3, ultrasonic dispersion for 20 min, stirring at 60℃ and 200 r / min for 1 h, adding deionized water at a rate of 5 ml / min, stirring at 60℃ and 200 r / min for 4 h, cooling to room temperature, centrifugal separation at 8000 rpm for 10 min, the obtained precipitate was washed with deionized water for 2 times, vacuum drying at 40℃ for 10 h, to obtain the modified carbon nanotube;

[0034] (2) vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione, anhydrous ethanol were mixed uniformly according to the mass ratio of 1:0.85:15, stirring at 60℃ and 200 r / min for 8 h, adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with 1.4 times of vanillin mass, stirring at 75℃ and 200 r / min for 10 h, rotary evaporation to remove the solvent, washing with anhydrous ethanol and deionized water for 2 times respectively, vacuum drying at 40℃ for 10 h, to obtain the pre-modified vanillin; under the atmosphere of nitrogen, the pre-modified vanillin, divinyl disulfide, azobisisobutyronitrile, N,N-dimethylformamide were mixed uniformly according to the mass ratio of 1:0.12:0.002:15, stirring at 65℃ and 200 r / min for 20 h, removing N,N-dimethylformamide by vacuum distillation, washing with anhydrous ethanol for 2 times, vacuum drying at 40℃ for 10 h, to obtain the modified vanillin;

[0035] (3) the modified vanillin, phenol, 20wt% sodium hydroxide aqueous solution were mixed uniformly according to the mass ratio of 1:5:0.8, stirring at 50℃ and 200 r / min for 10 min, adding paraformaldehyde according to the molar ratio of phenolic hydroxyl group to aldehyde group of 1:1.8, adding three times with an interval of 10 min, stirring at 60℃ and 200 r / min for 1 h, increasing the temperature to 80℃ and stirring at 200 r / min for 1.5 h, vacuum distillation, to obtain the modified phenolic resin; the modified phenolic resin, anhydrous ethanol, potassium hydroxide were mixed uniformly according to the mass ratio of 1:10:0.002 at 75℃, adding the modified carbon nanotube with 0.04 times of the modified phenolic resin mass, stirring at 55℃ and 200 r / min for 6 h, vacuum distillation, to obtain the phenolic resin material.

[0036] Example 2

[0037] A preparation method of a phenolic resin material, comprising the following preparation steps:

[0038] (1) under a nitrogen atmosphere, uniformly mixing hydroxylated carbon nanotubes, propyl triethoxysilane isocyanate, dibutyl tin dilaurate, toluene according to a mass ratio of 1:1:0.0015:11, ultrasonic dispersion for 35 min, stirring at 85°C and 250 r / min for 5 h, centrifugal separation at 9000 rpm for 11 min, washing the obtained precipitate with toluene for 4 times, vacuum drying at 45°C for 11 h, to obtain pre-modified carbon nanotubes; uniformly mixing the pre-modified carbon nanotubes, 2-chloroethyl triethoxysilane, sodium hydroxide, toluene according to a mass ratio of 1:0.3:0.002:4, ultrasonic dispersion for 25 min, stirring at 65°C and 250 r / min for 1.5 h, uniformly dropping deionized water at a rate of 5 ml / min and with a quantity of 0.1 times of the mass of the pre-modified carbon nanotubes, stirring at 65°C and 250 r / min for 5 h, cooling to room temperature, centrifugal separation at 9000 rpm for 11 min, washing the obtained precipitate with deionized water for 3 times, vacuum drying at 45°C for 11 h, to obtain modified carbon nanotubes;

[0039] (2) uniformly mixing vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione, anhydrous ethanol according to a mass ratio of 1:0.88:18, stirring at 65°C and 250 r / min for 9 h, adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with a quantity of 1.45 times of the mass of vanillin, stirring at 78°C and 250 r / min for 11 h, removing the solvent by rotary evaporation, washing with anhydrous ethanol and deionized water for 3 times respectively, vacuum drying at 45°C for 11 h, to obtain pre-modified vanillin; under a nitrogen atmosphere, uniformly mixing the pre-modified vanillin, divinyl disulfide, azobisisobutyronitrile, N,N-dimethylformamide according to a mass ratio of 1:0.13:0.003:18, stirring at 70°C and 250 r / min for 22 h, removing N,N-dimethylformamide by reduced pressure distillation, washing with anhydrous ethanol for 3 times, vacuum drying at 45°C for 11 h, to obtain modified vanillin;

[0040] (3) mixing modified vanillin, phenol, 20wt% sodium hydroxide aqueous solution according to mass ratio 1:6:0.9 uniformly, stirring at 55℃, 250r / min for 15min, adding paraformaldehyde according to molar ratio of phenolic hydroxyl group to aldehyde group 1:1.8, adding paraformaldehyde for three times with interval of 13min, stirring at 65℃, 250r / min for 1.25h, increasing temperature to 85℃, stirring at 250r / min for 1.75h, distilling under reduced pressure, to prepare modified phenolic aldehyde resin; mixing modified phenolic aldehyde resin, anhydrous ethanol, potassium hydroxide according to mass ratio 1:11:0.0025 uniformly at 80℃, adding modified carbon nanotube of 0.05 times of modified phenolic aldehyde resin, stirring at 60℃, 250r / min for 7h, distilling under reduced pressure, to prepare phenolic aldehyde resin material.

[0041] Example 3

[0042] A preparation method of a phenolic aldehyde resin material, comprising the following preparation steps:

[0043] (1) mixing hydroxylated carbon nanotube, propyl triethoxysilane isocyanate, dibutyl tin dilaurate, toluene according to mass ratio 1:1.2:0.002:12 uniformly under nitrogen atmosphere, ultrasonic dispersion for 40min, stirring at 90℃, 300r / min for 6h, centrifugal separation at 10000rpm for 12min, washing the obtained precipitate with toluene for 5 times, vacuum drying at 50℃ for 12h, to prepare pre-modified carbon nanotube; mixing pre-modified carbon nanotube, 2-chloroethyl triethoxysilane, sodium hydroxide, toluene according to mass ratio 1:0.32:0.0022:5 uniformly, ultrasonic dispersion for 30min, stirring at 70℃, 300r / min for 2h, adding deionized water of 0.11 times of pre-modified carbon nanotube at a rate of 5ml / min, stirring at 70℃, 300r / min for 6h, cooling to room temperature, centrifugal separation at 10000rpm for 12min, washing the obtained precipitate with deionized water for 4 times, vacuum drying at 50℃ for 12h, to prepare modified carbon nanotube;

[0044] (2) Vanillin, 5-amino-1, 2-dihydro-2-methyl-3H-1, 2, 4-triazole-3-thione and anhydrous ethanol were mixed uniformly at a mass ratio of 1:0.9:20, and stirred at 300 r / min at 70°C for 10 h. Vanillin was added at 1.5 times the mass of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and stirred at 300 r / min at 80°C for 12 h. The solvent was removed by rotary evaporation, and washed with anhydrous ethanol and deionized water four times respectively, and dried at 50°C under vacuum for 12 h to obtain pre-modified vanillin. The pre-modified vanillin, divinyl disulfide, azobisisobutyronitrile and N, N-dimethylformamide were mixed uniformly at a mass ratio of 1:0.14:0.004:20 under a nitrogen atmosphere, and stirred at 300 r / min at 75°C for 24 h. N, N-dimethylformamide was removed by distillation under reduced pressure, washed with anhydrous ethanol four times, and dried at 50°C under vacuum for 12 h to obtain modified vanillin.

[0045] (3) The modified vanillin, phenol and 20wt% sodium hydroxide aqueous solution were mixed uniformly at a mass ratio of 1:7:1, and stirred at 300 r / min at 60°C for 20 min. Paraformaldehyde was added in three portions at an interval of 15 min, and stirred at 300 r / min at 70°C for 1.5 h. The temperature was increased to 90°C, and stirred at 300 r / min for 2 h. Distillation was performed under reduced pressure to obtain a modified phenolic resin. The modified phenolic resin, anhydrous ethanol and potassium hydroxide were mixed uniformly at a mass ratio of 1:12:0.003 at 85°C. Modified carbon nanotubes were added at 0.06 times the mass of the modified phenolic resin, and stirred at 300 r / min at 65°C for 8 h. Distillation was performed under reduced pressure to obtain a phenolic resin material.

[0046] Comparative Example 1

[0047] The preparation method of the phenolic resin material of Comparative Example 1 is different from that of Example 2 in that step (1) is not performed, and step (3) is modified as follows: the modified vanillin, phenol and 20wt% sodium hydroxide aqueous solution were mixed uniformly at a mass ratio of 1:6:0.9, and stirred at 250 r / min at 55°C for 15 min. Paraformaldehyde was added in three portions at an interval of 13 min, and stirred at 250 r / min at 65°C for 1.25 h. The temperature was increased to 85°C, and stirred at 250 r / min for 1.75 h. Distillation was performed under reduced pressure to obtain a modified phenolic resin. The modified phenolic resin, anhydrous ethanol and potassium hydroxide were mixed uniformly at a mass ratio of 1:11:0.0025 at 80°C. Hydroxylated carbon nanotubes were added at 0.05 times the mass of the modified phenolic resin, and stirred at 250 r / min at 60°C for 7 h. Distillation was performed under reduced pressure to obtain a phenolic resin material. The remaining steps are the same as those of Example 2.

[0048] Comparative Example 2

[0049] The preparation method of the phenolic resin material of Comparative Example 2 is different from that of Example 2 in that step (1) is not performed, and step (3) is modified as follows: the modified vanillin, phenol, and 20 wt% sodium hydroxide aqueous solution are uniformly mixed at a mass ratio of 1:6:0.9, stirred at 55°C and 250 r / min for 15 min, the polyformaldehyde is added in three portions with an interval of 13 min, and stirred at 65°C and 250 r / min for 1.25 h, the temperature is increased to 85°C, and stirred at 250 r / min for 1.75 h, and then distilled under reduced pressure to obtain the phenolic resin material. The remaining steps are the same as those of Example 2.

[0050] Comparative Example 3

[0051] The preparation method of the phenolic resin material of Comparative Example 3 is different from that of Example 2 in that step (2) is different, and step (2) is modified as follows: the vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione, and anhydrous ethanol are uniformly mixed at a mass ratio of 1:0.88:18, and stirred at 65°C and 250 r / min for 9 h, the vanillin is added in an amount of 1.45 times the mass of 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide, and stirred at 78°C and 250 r / min for 11 h, the solvent is removed by rotary evaporation, and washed with anhydrous ethanol and deionized water for 3 times respectively, and dried at 45°C under vacuum for 11 h to obtain the modified vanillin. The remaining steps are the same as those of Example 2.

[0052] Comparative Example 4

[0053] The preparation method of the phenolic resin material of Comparative Example 4 is different from that of Example 2 in that step (2) is different, and step (2) is modified as follows: the vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione, and anhydrous ethanol are uniformly mixed at a mass ratio of 1:0.88:18, and stirred at 65°C and 250 r / min for 9 h, the solvent is removed by rotary evaporation, and washed with anhydrous ethanol and deionized water for 3 times respectively, and dried at 45°C under vacuum for 11 h to obtain the modified vanillin. The remaining steps are the same as those of Example 2.

[0054] Comparative Example 5

[0055] The preparation method of the phenolic resin material of Comparative Example 5 is different from that of Example 2 in that step (2) is not performed, and step (3) is modified as follows: vanillin, phenol, and 20wt% sodium hydroxide aqueous solution are uniformly mixed at a mass ratio of 1:6:0.9, stirring is performed at 55°C and 250r / min for 15min, polyformaldehyde is added in three times at an interval of 13min, stirring is performed at 65°C and 250r / min for 1.25h, the temperature is increased to 85°C, stirring is performed at 250r / min for 1.75h, and the modified phenolic resin is prepared by distillation under reduced pressure; the modified phenolic resin, anhydrous ethanol, and potassium hydroxide are uniformly mixed at a mass ratio of 1:11:0.0025 at 80°C, 0.05 times the mass of the modified phenolic resin of modified carbon nanotubes is added, stirring is performed at 60°C and 250r / min for 7h, and the phenolic resin material is prepared by distillation under reduced pressure. The remaining steps are the same as those of Example 2.

[0056] Test Example 1

[0057] Flame-retardant performance and heat-resistant performance test:

[0058] Flame-retardant performance test: the phenolic resin materials obtained in each example and comparative example are tested according to GB / T2406.2-2009 “Plastics-Determination of the burning behavior of plastics-Part 2: Guidance on the measurement of flame characteristics-Test 2: Vertical flame test” to test the limiting oxygen index, 5 samples are tested in each group, and the average value is taken.

[0059] Vertical burning test: the test is performed by using a vertical-horizontal burning tester according to ASTM D3801-2010, 5 samples are tested in each group, and the average value is taken.

[0060] Heat-resistant performance test: 2g of the phenolic resin material prepared in each example and test example is weighed, denoted as m0, and placed in a dried and weighed crucible, the mass of the crucible is denoted as m1, then the crucible is placed in a muffle furnace and calcined to 800°C, after cooling to room temperature, the crucible and the remaining resin are placed in a balance, denoted as m2, and the carbon residue rate is calculated as (m2-m1) / m0x100%, 5 samples are tested in each group, and the average value is taken.

[0061] The results are shown in Table 1.

[0062] Table 1

[0063] limiting oxygen index UL 94 rating char yield example 1 52.93% V-0 65.47% example 2 53.07% V-0 65.95% example 3 52.85% V-0 65.33% comparative example 1 49.89% V-1 57.64% comparative example 2 47.68% V-1 55.93% comparative example 3 52.95% V-0 63.87% comparative example 4 44.35% V-2 60.31% comparative example 5 41.26% V-2 59.65%

[0064] As can be seen from the experimental data of Examples 1-3 and Comparative Examples 1-5 in Table 1, the phenolic resin material prepared by the present application has good flame-retardant and heat-resistant performance.

[0065] By comparison, the limiting oxygen index and UL 94 grade of examples 1~3 and comparative examples 1~2 show that carbon nanotubes can promote the formation of carbon layer during combustion, thereby improving the flame retardant performance of the material; the hydroxylated carbon nanotubes are successively reacted with propyl triethoxysilane isocyanate and 2-chloroethyl triethoxysilane to introduce a large amount of silicon elements into the material. Silicon elements will undergo thermal oxidative decomposition at high temperature combustion to generate inorganic residues mainly composed of silicon dioxide, which adhere to the surface of the material, thereby improving the flame retardant performance of the phenolic resin material.

[0066] By comparison, the limiting oxygen index of examples 1~3 is greater than that of comparative examples 4~5, which shows that the Schiff base reaction of vanillin and 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione generates an imine structure that can react with the P-H bond on 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide to introduce phosphorus elements on vanillin. Phosphorus elements can capture free radicals during combustion, thereby improving the flame retardant performance of the phenolic resin material. At the same time, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazole-3-thione contains a large amount of N elements, which synergistically flame-retard with phosphorus elements to further improve the flame retardant performance of the phenolic resin material.

[0067] By comparison, the carbon residue rate of examples 1~3 is greater than that of comparative examples 1~2, which shows that the reaction of the hydroxyl groups on the hydroxylated carbon nanotubes with the isocyanate groups on propyl triethoxysilane introduces siloxane groups on the carbon nanotubes. Hydrolysis and condensation with 2-chloroethyl triethoxysilane form Si-O-Si groups. The bond energy of Si-O bond is higher than that of C-C bond, and it is flexible. Therefore, the introduction of Si-O bond improves the heat resistance of the phenolic resin material.

[0068] Test Example 2

[0069] Mechanical properties, aging resistance, and self-repairing performance test:

[0070] The specific test method is as follows:

[0071] Tensile strength test method: the phenolic resin materials prepared in each example and comparative example are made into samples of the same size according to GB / T2567-2021 "Resin cast performance test method", and the tensile strength of the sample is tested at a test speed of 2mm / min. Calculate the tensile strength X. Each group is tested in parallel for 5 times, and the average value is taken.

[0072] Bending strength test: the phenolic resin materials prepared in each example and the comparative example were made into test samples of the same size, and the bending strength of the test sample was tested according to GB / T 2567-2021 “Resin cast performance test method”, the test was carried out at a test speed of 2 mm / min, the bending strength was calculated, each group was tested in parallel for 5 times, and the average value was taken.

[0073] Aging resistance performance test: the phenolic resin materials prepared in each example and the comparative example were made into test samples of the same size, and the artificial accelerated aging test was carried out according to GB / T 16422.3-2022 “Plastics - Laboratory light source exposure test method - Part 3: fluorescent ultraviolet lamp”, the aging time was 360 h, the tensile strength Y was tested again, and the performance decline rate = 1-Y / Xx100% was calculated.

[0074] Self-repairing performance: the phenolic resin materials prepared in each example and the comparative example were made into test samples of the same size according to GB / T 2567-2021 “Resin cast performance test method”, a crack with a depth of 0.5 mm was cut on the surface of the test sample, and the test sample was placed in a constant temperature oven at 140 DEG C for 24 h, the tensile strength Z was tested again, and the self-repairing efficiency = Z / Xx100% was calculated, each group was tested in parallel for 5 times, and the average value was taken.

[0075] The results are shown in Table 2.

[0076] Table 2

[0077] tensile strength / MPa flexural strength / MPa performance degradation rate self-repairing efficiency example 1 44.47 79.39 16.35% 88.45% example 2 44.69 79.58 16.21% 89.03% example 3 44.53 79.41 16.29% 88.76% comparative example 1 43.41 62.17 40.58% 88.52% comparative example 2 38.13 61.82 41.16% 88.68% comparative example 3 43.95 79.47 16.37% 52.93% comparative example 4 44.26 79.23 16.25% 53.08% comparative example 5 44.53 79.25 16.30% 52.61%

[0078] From the experimental data comparison of examples 1-3 and comparative examples 1-5 in Table 2, it can be found that the phenolic resin material prepared by the application has good mechanical properties, aging resistance and self-repairing performance.

[0079] By comparison, the tensile strength of examples 1-3 is greater than that of comparative example 2, which shows that the hydroxylated carbon nanotube as a nanoparticle has good mechanical properties, and when added to the phenolic resin, the mechanical properties of the phenolic resin material are improved.

[0080] By comparison, the bending strength of examples 1-3 is greater than that of comparative examples 1-2, which shows that the hydroxyl group on the hydroxylated carbon nanotube reacts with the isocyanate group on the propyl triethoxysilane, and the siloxane group is introduced on the carbon nanotube, and then hydrolysis and condensation with 2-chloroethyl triethoxysilane to form Si-O-Si group, the bond energy of Si-O bond is higher than that of C-C bond, so that the material has good toughness, and the mechanical properties of the phenolic resin material are improved.

[0081] By comparison, the performance decline rate of examples 1~3 is less than that of comparative examples 1~2, which indicates that the phenolic hydroxyl group has strong polarity and reactivity, and is easy to be oxidized under high temperature or light conditions to generate quinone structure. The quinone structure is unstable, which can further induce chain reaction, leading to molecular chain rupture or crosslinking structure damage, thus resulting in the decline of the mechanical properties of the material. The reaction of the modified phenolic resin and the modified carbon nanotube reduces the number of phenolic hydroxyl groups in the material, thereby improving the aging resistance of the material.

[0082] By comparison, the self-repairing efficiency of examples 1~3 is greater than that of comparative examples 3~5, which indicates that the thiol group on the pre-modified vanillin reacts with the double bond on the divinyl disulfide to generate a disulfide bond in the material. The disulfide bond can induce bond rupture or recombination under light or heating conditions, thereby giving the phenolic resin material good self-repairing performance.

[0083] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A phenolic resin material, characterized in that, The phenolic resin material is prepared by reacting modified vanillin, phenol, and formaldehyde to obtain modified phenolic resin, and then reacting it with modified carbon nanotubes. The modified vanillin is prepared by reacting pre-modified vanillin with divinyl disulfide; The pre-modified vanillin was prepared by reacting vanillin sequentially with 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazol-3-thione and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The modified carbon nanotubes are prepared by reacting pre-modified carbon nanotubes with 2-chloroethyltriethoxysilane; The pre-modified carbon nanotubes are prepared by reacting hydroxylated carbon nanotubes with propyltriethoxysilane isocyanate.

2. A method for preparing a phenolic resin material, characterized in that, The preparation steps include the following: (1) Mix pre-modified carbon nanotubes, 2-chloroethyltriethoxysilane, sodium hydroxide and toluene in a mass ratio of 1:(0.28~0.32):(0.0018~0.0022):(3~5) until uniform, disperse by ultrasonication for 20~30 min, stir at 60~70℃ for 1~2 h, add deionized water at a rate of 5 ml / min at a uniform rate of 0.09~0.11 times the mass of pre-modified carbon nanotubes, stir at 60~70℃ for 4~6 h, cool to room temperature, centrifuge, wash and dry to obtain modified carbon nanotubes; (2) Under a nitrogen atmosphere, pre-modified vanillin, divinyl disulfide, azobisisobutyronitrile, and N,N-dimethylformamide were mixed evenly in a mass ratio of 1:(0.12~0.14):(0.002~0.004):(15~20), and stirred at 65~75℃ for 20~24h. The mixture was then distilled under reduced pressure, washed, and dried to obtain modified vanillin. (3) Modified phenolic resin, anhydrous ethanol, and potassium hydroxide are mixed evenly at 75-85℃ in a mass ratio of 1:(10~12):(0.002~0.003). Modified carbon nanotubes of 0.04~0.06 times the mass of modified phenolic resin are added. The mixture is stirred and reacted at 55~65℃ for 6~8h. The mixture is then distilled under reduced pressure to obtain phenolic resin material.

3. The method for preparing a phenolic resin material according to claim 2, characterized in that, The preparation steps of the pre-modified carbon nanotubes in step (1) are as follows: under a nitrogen atmosphere, hydroxylated carbon nanotubes, propyltriethoxysilane isocyanate, dibutyltin dilaurate, and toluene are mixed evenly in a mass ratio of 1:(0.8~1.2):(0.001~0.002):(10~12), sonicated for 30~40 min, stirred at 80~90℃ for 4~6 h, centrifuged, washed, and dried to obtain the pre-modified carbon nanotubes.

4. The method for preparing a phenolic resin material according to claim 2, characterized in that, The preparation steps of the pre-modified vanillin in step (2) are as follows: Vanillin, 5-amino-1,2-dihydro-2-methyl-3H-1,2,4-triazol-3-thione, and anhydrous ethanol are mixed evenly at a mass ratio of 1:(0.85~0.9):(15~20), and stirred at 60~70℃ for 8~10h. Then, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (1.4~1.5 times the mass of vanillin) is added, and stirred at 75~80℃ for 10~12h. The mixture is then rotary evaporated, washed, and dried to obtain the pre-modified vanillin.

5. The method for preparing a phenolic resin material according to claim 2, characterized in that, The preparation steps of the modified phenolic resin in step (3) are as follows: Modified vanillin, phenol, and 20wt% sodium hydroxide aqueous solution are mixed evenly in a mass ratio of 1:(5~7):(0.8~1), stirred at 50~60℃ for 10~20min, and paraformaldehyde is added in three portions according to a molar ratio of phenolic hydroxyl to aldehyde group of 1:1.

8. The mixture is stirred at 60~70℃ for 1~1.5h, heated to 80~90℃, stirred and reacted for 1.5~2h, and then distilled under reduced pressure to obtain the modified phenolic resin.

6. The method for preparing a phenolic resin material according to claim 3, characterized in that, The hydroxylated carbon nanotubes have an inner diameter of 3-5 nm, an outer diameter of 8-15 nm, and a length of 0.2-2 μm.

7. The method for preparing a phenolic resin material according to claim 5, characterized in that, The paraformaldehyde was added at intervals of 10-15 minutes.

8. The application of a phenolic resin material prepared by the method according to any one of claims 2 to 7 in 3D printing.