Preparation method of high-strength nanometer aramid plate

Abstract

The application discloses a preparation method of a high-strength nanometer aramid plate. The preparation method is as follows: after nanometer aramid dispersion is formed into a gel state through vacuum filtration, the surface of the nanometer aramid dispersion is soaked and coated with a carboxymethyl cellulose / TEMPO oxidized nanocellulose mixed solution, then the nanometer aramid gel is adhered together layer by layer according to the thickness requirement, after complete drying through a hot plate, the nanometer aramid gel is hot-pressed by using a hot press, and finally the nanometer aramid plate with excellent mechanical properties such as bending strength, bending toughness, tensile strength and tensile toughness is obtained. The application expands the application range of the nanometer aramid and provides a thought for the development of low-density and high-strength plate materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of nanomaterials, and particularly relates to a preparation method of high-strength nanometer aramid plate. BACKGROUND

[0002] Aromatic polyamide fiber, also known as aramid fiber, is made of polyamide macromolecular compounds, has extremely strong intermolecular binding force, high strength, high modulus, high heat resistance, high chemical resistance and excellent flame retardant performance, and is widely used in high-performance composite materials, bulletproof materials, electronic materials, textiles and other fields. In recent years, a kind of nanometer aramid fiber prepared by a DMSO / KOH system has appeared. This kind of nanometer aramid fiber not only has a small size (about 20 nm in diameter) and a large aspect ratio (generally greater than 500), but also has extremely high strength and acid and alkali resistance.

[0003] Low-density and high-strength plates have wide application prospects in the fields of automobiles, aerospace, military and wind power generation. At present, common lightweight and high-strength plates mainly include carbon fiber plates, glass fiber plates and aramid fiber plates. These high-performance plates are mainly composed of high-performance fibers and epoxy resin or phenolic resin, and the tensile strength and bending strength thereof can generally reach hundreds of megapascals, and have achieved wide application. However, these fiber plates have a great defect. Due to the low elongation of the internal high-performance fibers, the plates have high brittleness, and the bending strain and tensile strain thereof are generally not more than 2.5%, and cracks are easily generated.

[0004] Due to the high specific surface area and high aspect ratio, a material prepared by using nanometer aramid as raw material is expected to have high strain capacity and toughness. Since nanometer aramid needs to be formed in the state of a dispersion liquid, it is difficult to directly prepare a plate with high basis weight and high thickness. Therefore, it is necessary to refer to the forming method of a laminated plate, to bond one layer of nanometer aramid together through an adhesive, and finally to form the plate through hot pressing. However, due to the chemical inertness inherited from aramid fibers, a general adhesive is difficult to achieve good results. Moreover, for the bending performance of the plate, the adhesive force and the strength of the adhesive have high requirements. SUMMARY

[0005] In order to overcome the defects and deficiencies of the prior art, the purpose of the present application is to provide a preparation method of high-strength nanometer aramid plate.

[0006] The present application provides a preparation method of high-strength nanometer aramid plate, comprising the following steps:

[0007] (1) disperse p-aramid short fibers in dimethyl sulfoxide (DMSO) and add KOH, and obtain a nanometer aramid dispersion after stirring for a period of time;

[0008] (2) After the nano aramid dispersion is water protonated, a hydrogel is formed by vacuum filtration;

[0009] (3) A nano cellulose is prepared by TEMPO oxidation method, and is dispersed into a carboxymethyl cellulose solution according to a proportion to obtain an adhesive;

[0010] (4) The nano aramid hydrogel obtained in step (2) is immersed into the adhesive in step (3), and several layers of the nano aramid hydrogel immersed in the adhesive are adhered together layer by layer;

[0011] (5) The nano aramid hydrogel adhered together in step (4) is heated and dried on an electric hot plate, and then is subjected to hot pressing treatment.

[0012] Preferably, the nano aramid dispersion in step (1) has a concentration of 2-4 mg / L, and the stirring time is 5-7 days.

[0013] Preferably, in step (1), the para-aramid short-cut fiber is 1 part by mass, dimethyl sulfoxide is 250-500 parts by volume, and KOH is 1.5-3.0 parts by mass.

[0014] Preferably, the step of preparing the nano cellulose by TEMPO oxidation in step (3) is as follows: bleached coniferous wood pulp is dispersed in water, 2,2,6,6-tetramethylpiperidine N-oxide, sodium bromide are added and stirred to be uniformly dispersed; then sodium hypochlorite solution is added to perform TEMPO oxidation reaction, and the pH of the suspension is maintained at 10-10.5; after the reaction is completed, the suspension is filtered and washed by centrifugation until the pH of the filtrate reaches neutral; the treated suspension is subjected to fine fiberization treatment by a microjet homogenizer, and finally TEMPO-oxidized nano cellulose is obtained.

[0015] Further preferably, the specific steps of step (3) are as follows: 10 g of bleached coniferous wood pulp is dispersed in 1000 mL of water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide and 1 g of sodium bromide are added and stirred to be uniformly dispersed; then sodium hypochlorite solution is added to perform TEMPO oxidation reaction, and the pH of the suspension is maintained at 10-10.5; after the reaction is completed, the suspension is filtered and washed by centrifugation until the pH of the filtrate reaches neutral; the treated suspension is subjected to fine fiberization treatment by a microjet homogenizer, and finally TEMPO-oxidized nano cellulose is obtained.

[0016] Further preferably, in the fine fiberization treatment by the microjet homogenizer, the homogenization pore size is 87-400 μm, the homogenization pressure is 69-172 MPa, the concentration of the homogenization suspension is 0.2-1.5%, and the homogenization frequency is 2-10 times.

[0017] Further preferably, in the fibrillation treatment of the micro-fluidizer, the optimal homogenization aperture is 200 μm, the homogenization pressure is 138 MPa, the homogenization suspension concentration is 0.8%, and the homogenization frequency is 8 times.

[0018] Preferably, the adhesive solid concentration in step (3) is 0.5-2.0 wt%, and the mass ratio of carboxymethyl cellulose and TEMPO-oxidized nanocellulose in the adhesive is 10:3-5:5.

[0019] Preferably, the nanofiber aramid hydrogel in step (4) is immersed in the adhesive for 1-10 min.

[0020] Preferably, the heating drying temperature in step (5) is 60-120℃, and the heating drying time is 12-36 h; the heat pressing temperature is 60-120℃, the heat pressing time is 5-20 min, and the heat pressing pressure is 5-15 MPa.

[0021] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0022] (1) The present application uses nanofiber aramid with high specific surface area and high aspect ratio as the main body of the plate, and the hydrogen bond binding strength between the carbonyl and imino groups in its own fiber network is moderate, which can exist as a sacrificial bond during the deformation of the main material, and can absorb a large amount of energy and realize a higher strain of the material in the process of continuous breaking and re-forming.

[0023] (2) For the adhesive used to bond nanofiber aramid, it needs to have the ability to form a strong bond with nanofiber aramid. The present application uses carboxymethyl cellulose as the main body of the adhesive, which has a large number of carboxymethyl groups. These carboxymethyl groups have high electronegativity and can form strong hydrogen bond with the carbonyl and imino groups of nanofiber aramid. In order to improve the strength of the adhesive itself, carboxymethyl cellulose and TEMPO-oxidized nanocellulose containing a large number of carboxyl groups are compounded to prepare the adhesive. After the composite adhesive is used to bond nanofiber aramid, the TEMPO-oxidized nanocellulose forms a dense and high-strength nanofiber network between the nanofiber aramid layers. Among them, amorphous carboxymethyl cellulose acts as a filler to reduce the porosity of the nanofiber network, thereby improving the density of the nanofiber network and further improving its strength.

[0024] (3) In order to improve the adhesion of the adhesive to nanofiber aramid, the present application immerses the nanofiber aramid in the adhesive when it is just formed into a gel state by suction filtration, so that the adhesive can penetrate into the nanofiber aramid fiber network, greatly increasing the bonding area and bonding opportunities between the two, and improving the adhesion between the nanofiber aramid layers. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1A photograph of the nanomodified aramid plate prepared in Example 3.

[0026] Figure 2 Bending stress-strain curves of the nanomodified aramid plates prepared in Examples 1-4.

[0027] Figure 3 Tensile stress-strain curves of the nanomodified aramid plate prepared in Example 3. DETAILED DESCRIPTION

[0028] The application will be further described in conjunction with the examples and drawings, but the embodiments of the application are not limited thereto.

[0029] The para-aramid short-cut fibers used in the embodiments of the application are Kevlar 49 from the U.S. DuPont Company, and the bleached conifer pulp, carboxymethyl cellulose and other chemicals can be directly purchased from the market; the carboxymethyl cellulose has a degree of substitution of 0.9 and a viscosity of 1500-3100 mPa·s.

[0030] Example 1

[0031] The preparation method of the high-strength nanomodified aramid plate in this embodiment is as follows:

[0032] (1) 1 g of para-aramid short-cut fibers was dispersed in 500 mL of DMSO, 1.5 g of KOH was added, and continuous stirring was performed for 7 days to obtain a nanomodified aramid dispersion with a concentration of 2 mg / L.

[0033] (2) The carboxymethyl cellulose powder was weighed according to the proportion, and the carboxymethyl cellulose was dissolved in deionized water to obtain an adhesive, and the concentration of carboxymethyl cellulose in the adhesive was 1.0 wt%.

[0034] (3) 100 mL of DMSO was added to 132.47 mL of the nanomodified aramid dispersion. Then 132.47 mL of deionized water was added to protonate the nanomodified aramid, and then the solution was sheared at a rotation speed of 40000 r / min for 5 min. The solution was ultrasonically treated at a power of 800 W for 5 min, and then the nanomodified aramid hydrogel was obtained by vacuum filtration.

[0035] (4) The obtained nanomodified aramid hydrogel was immersed in the adhesive for 1 min and then taken out; the nanomodified aramid hydrogel immersed in the adhesive was bonded together layer by layer, and the number of layers was 20.

[0036] (5) The nanomodified aramid hydrogel bonded together was placed on an electric hot plate and heated and dried at 80°C for 12 h, and then a hot press was used for hot pressing treatment at 80°C and a pressure of 10 MPa for 15 min.

[0037] Example 2

[0038] The preparation method of the high-strength nanometer aramid plate in this embodiment is as follows:

[0039] (1) 1 g of p-aramid short-cut fiber was dispersed in 500 mL of DMSO, 1.5 g of KOH was added, and continuous stirring was performed for 7 days to obtain a nanometer aramid dispersion with a concentration of 2 mg / L.

[0040] (2) 10 g of absolutely dry bleached coniferous wood pulp was dispersed in 1 L of ionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, and 1 g of sodium bromide were added and stirred to be uniformly dispersed. Then, 75 mmol of sodium hypochlorite solution was added to perform TEMPO oxidation reaction, and the pH of the suspension was kept stable at 10-10.5. After the reaction was completed, the suspension was filtered and washed by centrifugation until the pH of the filtrate reached neutral. The treated suspension was fine-fiberized at a concentration of 0.8 wt% using a microfluidizer, using a 200 μm pore size, and homogenized 8 times at a pressure of 138 MPa, and finally TEMPO-oxidized nanocellulose with a carboxyl content of 1.15 mmol / g was obtained.

[0041] (3) The carboxymethyl cellulose powder and the TEMPO-oxidized nanocellulose suspension were weighed according to the proportion, the carboxymethyl cellulose was dissolved in deionized water, and then the TEMPO-oxidized nanocellulose was dispersed into the carboxymethyl cellulose solution, and finally the adhesive was obtained. The absolute dry mass ratio of carboxymethyl cellulose and TEMPO-oxidized nanocellulose in the adhesive was 9:1, and the solid content concentration of the adhesive was 1.0 wt%.

[0042] (4) 100 mL of DMSO was added to 132.47 mL of nanometer aramid dispersion. Then 132.47 mL of deionized water was added to protonate the nanometer aramid, and then the solution was sheared at a speed of 40000 r / min for 5 min. The solution was ultrasonically treated at a power of 800 W for 5 min, and then nanometer aramid hydrogel was obtained by vacuum filtration.

[0043] (5) The obtained nanometer aramid hydrogel was immersed in the adhesive for 1 min and then taken out; the nanometer aramid hydrogel immersed in the adhesive was bonded together layer by layer, and the number of layers was 20.

[0044] (6) The nanometer aramid hydrogel bonded together was placed on an electric hot plate and heated and dried at 80℃ for 12 h, and then a hot press was used for hot pressing treatment at 80℃ and a pressure of 10 MPa for 15 min.

[0045] Example 3

[0046] The preparation method of the high-strength nanometer aramid plate in this embodiment is as follows:

[0047] (1) 1 g of para-aramid short-cut fibers were dispersed in 500 mL of DMSO, 1.5 g of KOH was added, and continuous stirring was performed for 7 days to obtain a nanometer aramid dispersion with a concentration of 2 mg / L.

[0048] (2) 10 g of absolutely dry bleached coniferous wood pulp was dispersed in 1 L of ionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, and 1 g of sodium bromide were added and stirred to be uniformly dispersed. Then, 75 mmol of sodium hypochlorite solution was added to perform TEMPO oxidation reaction, and the pH of the suspension was kept stable at 10-10.5. After the reaction was completed, the suspension was filtered and washed by centrifugation until the pH of the filtrate reached neutral. The treated suspension was fine-fiberized at a concentration of 0.8 wt% using a microfluidizer, using a 200 μm pore size, and homogenized 8 times at a pressure of 138 MPa to finally obtain TEMPO-oxidized nanocellulose with a carboxyl content of 1.15 mmol / g.

[0049] (3) The carboxymethyl cellulose powder and the TEMPO-oxidized nanocellulose suspension were weighed according to the proportion, the carboxymethyl cellulose was dissolved in deionized water, and then the TEMPO-oxidized nanocellulose was dispersed into the carboxymethyl cellulose solution to finally obtain the adhesive. The absolute dry mass ratio of carboxymethyl cellulose and TEMPO-oxidized nanocellulose in the adhesive was 7:3, and the solid content concentration of the adhesive was 1.0 wt%.

[0050] (4) 100 mL of DMSO was added to 132.47 mL of nanometer aramid dispersion. Then, 132.47 mL of deionized water was added to protonate the nanometer aramid, and then the solution was sheared at a speed of 40,000 r / min for 5 min. The solution was ultrasonically treated at a power of 800 W for 5 min, and then nanometer aramid hydrogel was obtained by vacuum filtration.

[0051] (5) The obtained nanometer aramid hydrogel was immersed in the adhesive for 1 min and then taken out; the nanometer aramid hydrogel immersed in the adhesive was bonded together layer by layer, and the number of layers was 20.

[0052] (6) The nanometer aramid hydrogel bonded together was placed on a hot plate and heated and dried at 80°C for 12 h, and then a hot press was used for hot pressing treatment at 80°C and a pressure of 10 MPa for 15 min.

[0053] Example 4

[0054] The preparation method of the high-strength nanometer aramid plate in this embodiment is as follows:

[0055] (1) 1 g of para-aramid short-cut fibers were dispersed in 500 mL of DMSO, 1.5 g of KOH was added, and continuous stirring was performed for 7 days to obtain a nanometer aramid dispersion with a concentration of 2 mg / L.

[0056] (2) 10 g of absolutely dry bleached softwood pulp was dispersed in 1 L of deionized water, 160 mg of 2,2,6,6-tetramethylpiperidine N-oxide, 1 g of sodium bromide were added and stirred to disperse uniformly. Then 75 mmol of sodium hypochlorite solution was added to carry out TEMPO oxidation reaction, and the pH of the suspension was kept stable at 10-10.5. After the reaction was completed, the suspension was filtered and washed by centrifugation until the pH of the filtrate reached neutral. The treated suspension was fine fiberized at a concentration of 0.8 wt% using a microfluidizer homogenizer, using a 200 μm pore size, homogenized 8 times at a pressure of 138 MPa, and finally obtained TEMPO-oxidized nanocellulose with a carboxyl content of 1.15 mmol / g.

[0057] (3) The carboxymethyl cellulose powder and the TEMPO-oxidized nanocellulose suspension were weighed according to the proportion, the carboxymethyl cellulose was dissolved in deionized water, and then the TEMPO-oxidized nanocellulose was dispersed into the carboxymethyl cellulose solution, and finally the adhesive was obtained. The absolute dry mass ratio of carboxymethyl cellulose and TEMPO-oxidized nanocellulose in the adhesive was 5:5, and the solid concentration of the adhesive was 1.0 wt%.

[0058] (4) 100 mL of DMSO was added to 132.47 mL of nanofibril dispersion. Then 132.47 mL of deionized water was added to protonate the nanofibril, and then the solution was sheared at a speed of 40000 r / min for 5 min. The solution was ultrasonically treated at a power of 800 W for 5 min, and then nanofibril hydrogel was obtained by vacuum filtration.

[0059] (5) The obtained nanofibril hydrogel was immersed in the adhesive for 1 min and then taken out; the nanofibril hydrogel immersed in the adhesive was bonded together layer by layer, and the number of layers was 20.

[0060] (6) The nanofibril hydrogel bonded together was placed on a hot plate and heated and dried at 80°C for 12 h, and then a hot press was used for hot pressing treatment at 80°C and a pressure of 10 MPa for 15 min.

[0061] The nanofibril plates prepared in Examples 1-4 were subjected to three-point bending test, and the tensile strength of Example 3 was detected. The mass ratio of carboxymethyl cellulose / TEMPO-oxidized nanofibril adhesive used in Examples 1-4 was 10:0, 9:1, 7:3, and 5:5, respectively. The nanofibril plates were sawn into long strips with a size of 5 mm x 40 mm, and a universal mechanical tester was used to test the mechanical properties of the samples. Each group of samples was repeated at least 5 times, and the average value was taken, and the average value of the test results is shown in Table 1.

[0062] Table 1. Mechanical test results of a high-strength nanofibril plate

[0063]

[0064] Note: The bending and stretching in parentheses represent bending test or stretching test as shown in Table 1 and Figure 2 The maximum bending stress of the nanofibril plate prepared by Example 1 with pure carboxymethyl cellulose as the binder is 157.20±6.11 MPa, the Young's modulus is 2.99±0.39 GPa, the breaking strain is 13.99±0.38%, and the toughness is 20.94±6.22 MJ / m 3 After introducing TEMPO-oxidized nanocellulose, a stable fiber-reinforced network structure is constructed between the nanofibril plate layers, and the physical properties of the nanofibril plate are significantly improved, with a maximum bending stress of 214.20±3.16 MPa, a Young's modulus of 4.13±0.06 GPa, a breaking strain of 21.38±3.73%, and a toughness of 36.97±6.31 MJ / m 3 The tensile properties of the nanofibril plate of Example 3 are also detected, with a maximum tensile stress of 177.35±15.55 MPa, a Young's modulus of 1.47±0.34 GPa, a breaking strain of 36.33±3.40%, and a toughness of 47.94±3.21 MJ / m 3 .

[0065] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for preparing a high-strength nanofibril plate, characterized by, The method comprises the following steps: (1) dispersing para-aramid short fibers in dimethyl sulfoxide and adding KOH to obtain a nano aramid dispersion after stirring for a period of time; (2) adding water to the nano aramid dispersion to protonate the nano aramid dispersion, and then forming a hydrogel by vacuum filtration; (3) preparing nano cellulose by a TEMPO oxidation method, and dispersing the nano cellulose in a carboxymethyl cellulose solution to obtain an adhesive; the adhesive has a solid concentration of 0.5-2.0 wt%, and the mass ratio of carboxymethyl cellulose to TEMPO-oxidized nano cellulose in the adhesive is 10:3-5:5; (4) immersing the nano aramid hydrogel obtained in step (2) in the adhesive in step (3) for 1-10 min; and adhering several layers of the nano aramid hydrogel immersed in the adhesive together layer by layer; (5) placing the nano aramid hydrogel adhered together in step (4) on an electric hot plate to dry, and then performing hot pressing treatment on the nano aramid hydrogel using a hot press.

2. The method for preparing the high-strength nano-aramid board according to claim 1, characterized in that: In step (1), the nano aramid dispersion has a concentration of 2-4 mg / L, and the stirring time is 5-7 days.

3. The method for preparing the high-strength nano-aramid board according to claim 1, characterized in that: In step (1), the para-aramid short fibers are 1 part by mass, the dimethyl sulfoxide is 250-500 parts by volume, and the KOH is 1.5-3.0 parts by mass.

4. The method for preparing the high-strength nano-aramid board according to claim 1, characterized in that: The specific steps of preparing the TEMPO-oxidized nano cellulose in step (3) are as follows: dispersing bleached coniferous wood pulp in water, adding 2,2,6,6-tetramethylpiperidine N-oxide and sodium bromide, and stirring to disperse uniformly; then adding sodium hypochlorite solution to perform TEMPO oxidation reaction, and maintaining the pH of the suspension at 10-10.5; after the reaction is completed, the suspension is filtered and washed by centrifugation until the pH of the filtrate reaches neutrality; and the treated suspension is subjected to fine fiberization treatment by a micro-jet homogenizer to finally obtain TEMPO-oxidized nano cellulose.

5. The method for preparing the high-strength nano-aramid board according to claim 4, characterized in that: The TEMPO-oxidized nano cellulose has a final carboxyl content of 0.8-1.5 mmol / g; in the fine fiberization treatment by the micro-jet homogenizer, the homogenization pore size is 87-400 μm, the homogenization pressure is 69-172 MPa, the homogenization suspension concentration is 0.2-1.5 wt%, and the homogenization frequency is 2-10 times.

6. The method for preparing the high-strength nano-aramid board according to claim 1, characterized in that: In step (5), the temperature of the electric hot plate is 60-120 °C, and the drying time is 12-36 h; in the hot pressing treatment in step (5), the hot pressing temperature is 60-120 °C, the time is 12-36 h, and the pressure is 5-15 MPa.

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