Peeling or exfoliating boron nitride nanoplatelets, methods of making, and applications in reinforced polyurea composites

Abstract

The application relates to a kind of exfoliated or exfoliation modified boron nitride nanosheet and its preparation method and the application of reinforcing polyurea composite material, wherein the exfoliation modified boron nitride nanosheet, the thickness is 2.31+ / -0.14nm, and the surface amino grafting rate is 3~5%.The exfoliated boron nitride nanosheet (B-BN) is prepared by using mechanical chemical energy, solvent-free high-efficiency exfoliation, and the exfoliation modified boron nitride nanosheet (M-BN) is prepared by using m-xylylenediamine (MXDA) to modify the exfoliated boron nitride nanosheet (B-BN) by ball milling.The exfoliated boron nitride nanosheet has a larger specific surface area, which improves the dispersibility in the polyurea matrix;In addition to the large specific surface area of the exfoliation modified boron nitride nanosheet, the surface also contains amino groups, which can be linked with the isocyanate component by covalent bond, improve the interfacial action with the polyurea system, and enhance the mechanical properties, impact resistance and electrical insulation of the polyurea elastomer.

Description

TECHNICAL FIELD

[0001] The present application relates to aerospace, low-speed impact resistance, electrically insulating coating and other application fields, and particularly relates to a peeling or peeling modified boron nitride nanosheet, a preparation method thereof and application of the boron nitride nanosheet in reinforcing polyurea composite materials. BACKGROUND

[0002] Polyurea elastomer is a new environmentally friendly material, which has the advantages of high mechanical strength, fast curing, good adhesion, adjustable hardness, insensitivity to humidity and temperature, and the characteristics of green environmental protection, small toxicity, no pollution and no volatile gas. The polyurea elastomer is a block copolymer composed of soft segments and hard segments, which is generated by the reaction of isocyanate, amino-terminated polyether and chain extender. The hard segment generally refers to the isocyanate and chain extender components in the polyurea system, which has strong polarity due to the presence of urea groups, and has strong interaction with surrounding molecules, and the chain segment conformation is difficult to change. The soft segment is mainly composed of amino-terminated polyether with flexible structure, and has small internal rotation resistance and generally presents a curled state. Due to the polarity difference between the soft and hard segments of the polyurea and the double coordination hydrogen bond effect between the urea bonds, the polyurea elastomer has a large degree of microphase separation, and the microphase separation structure has a great influence on the mechanical properties, energy absorption properties, thermal properties and many other properties of the polyurea elastomer material. In recent years, polyurea materials have been widely used in protective structures to improve the impact resistance of the structures under impact load. Although the impact resistance is improved to a certain extent, the mechanical properties and electrical insulation of the polyurea elastomer do not meet the expected effect under the condition of a certain coating thickness, and it is difficult to meet the actual demand.

[0003] Therefore, adding a reinforcing phase to the polyurea has become a hot spot in recent research, and finding a suitable reinforcing phase has become a pressing problem today.

[0004] The boron nitride nanosheet particles prepared by the gas phase deposition method have small particle size, but the thickness is uneven, the specific surface area is small, and the dispersibility in the polymer matrix is poor, which is easy to agglomerate and lose the expected reinforcing and toughening effect on the polymer. The conventional technology for peeling two-dimensional nanosheet is time-consuming, low in efficiency, needs organic solvents, and has a large environmental pollution. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a kind of exfoliated or exfoliation modified boron nitride nanosheet and its preparation method and the application of enhanced polyurea composite, the exfoliated boron nitride nanosheet (B-BN) is prepared by using mechanical chemical energy, solvent-free high efficiency exfoliation product, the exfoliation modified boron nitride nanosheet (M-BN) is obtained by using m-xylylenediamine (MXDA) to modify the exfoliated boron nitride nanosheet (B-BN) by ball milling, the exfoliation modified boron nitride nanosheet has more uniform thickness, greater specific surface area, and the surface can be modified by amino group to have good dispersibility in polymer matrix and form strong interfacial action. The exfoliation modified boron nitride nanosheet prepared by the method is added as a reinforcing phase to polyurea coating, so that the polyurea coating has excellent mechanical properties and impact resistance, and also has excellent electrical insulation, achieving the purpose of enhancing polyurea elastomer coating.

[0006] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0007] The exfoliated boron nitride nanosheet of the present application has a thickness of 2.31±0.14 nm.

[0008] The exfoliation modified boron nitride nanosheet of the present application has a thickness of 2.31±0.14 nm, and the surface contains amino groups with a surface amino grafting rate of 3-5%.

[0009] The preparation method of the exfoliated boron nitride nanosheet of the present application comprises the following steps:

[0010] Step (1): Put the measured boron nitride nanosheet and non-polar solvent into a high-speed blender and stir at high speed to obtain a boron nitride solution.

[0011] In step (1), the non-polar solvent is one or more of deionized water and anhydrous ethanol.

[0012] In step (1), the mass ratio of boron nitride nanosheet to non-polar solvent is 1:(250-500).

[0013] In step (1), the speed of the high-speed blender is 20000-30000 r / min, and the stirring time is 5-35 min, preferably 10-25 min.

[0014] Step (2): Centrifuge the boron nitride solution in a high-speed centrifuge, dry the centrifuged boron nitride nanosheet for standby use, and obtain the exfoliated boron nitride nanosheet.

[0015] In step (2), the speed of the high-speed centrifuge is 2000-3500 rpm, and the drying temperature is 60-80℃.

[0016] The preparation method of the exfoliated modified boron nitride nanosheet of the present application comprises the following steps:

[0017] The exfoliated boron nitride nanosheet and meta-xylene diamine (MXDA) are put into a ball mill tank according to a metering ratio, and after ball milling, the exfoliated modified boron nitride nanosheet is obtained by washing and drying.

[0018] The mass ratio of the exfoliated boron nitride nanosheet to MXDA is 1:(1-1.5).

[0019] In the preparation method of the exfoliated modified boron nitride nanosheet, the ball milling medium in the ball mill tank is preferably zirconium oxide balls, and the ratio of the material balls is 1:45; the small zirconium oxide balls have a diameter of 1 mm, the large zirconium oxide balls have a diameter of 10 mm, and the mass ratio of the small zirconium oxide balls to the large zirconium oxide balls is 4:1.

[0020] In the preparation method of the exfoliated modified boron nitride nanosheet, the ball milling time is 4-6 h, the ball milling speed is 500-600 r / min, and during the ball milling process, the ball mill works for 30 min and stops for 10 min, and 40 min is one cycle, and a total of 6-9 cycles are worked. Through ball milling, the exfoliated boron nitride nanosheet is modified by amino groups.

[0021] In the preparation method of the exfoliated modified boron nitride nanosheet, the solvent for washing the boron nitride nanosheet is one of deionized water or anhydrous ethanol, and the washing frequency is 1-2 times; the drying is carried out by using a freeze dryer for freeze drying under the conditions of vacuum 0.1 MPa and-56℃ for 12 h.

[0022] The application of the exfoliated or exfoliated modified boron nitride nanosheet to enhance the polyurea composite material, and the preparation method thereof are as follows:

[0023] S1: Under the condition of nitrogen protection, the metered isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dimethylacetamide (DMAc), and the exfoliated boron nitride nanosheet and / or the exfoliated modified boron nitride nanosheet are mixed and stirred to obtain an isocyanate / boron nitride mixture.

[0024] In S1, the mass ratio of IPDI, HDI, and DMAc is (3.1-3.3):(1.0-1.2):(0.67-0.74), the reaction temperature is 25℃, the mixing and stirring time is 30 min-60 min, and the stirring speed is 1000 r / min-1500 r / min.

[0025] In S1, the addition amount of the exfoliated boron nitride nanosheet or the exfoliated modified boron nitride nanosheet accounts for 0.05%-0.5% of the total mass of the polyurea composite material.

[0026] In S1, IPDI, HDI and DMAc are all subjected to vacuum dehydration treatment before use. The vacuum pressure is -0.1MPa and the dehydration temperature is 110℃~120℃.

[0027] S2: The measured polyaspartic acid ester NH2885 was added to the isocyanate / boron nitride mixture, and after mixing and stirring, a polyurea composite material mixture was obtained.

[0028] In S2, polyaspartic acid ester The amount of NH2885 added is 45-50% of the total mass of the polyurea composite material.

[0029] In step S2, the reaction temperature is 20–30°C, the mixing time is 2–5 min, and the stirring speed is 1500–3000 r / min. Drying is performed in a vacuum oven at 0.1 MPa and 80°C for 72 h. Type II standard tensile specimens are prepared according to GB / T 528-1998. The impact-resistant coating is made into a 100 mm × 2.5 mm × 2 mm size based on the aluminum alloy substrate dimensions, and the coating is bonded to the aluminum alloy substrate using epoxy resin adhesive. The electrical insulating disc has a diameter of 50 mm and a thickness of 1.5 mm.

[0030] When exfoliated boron nitride nanosheets are added, the polyurea composite material mixture is injected into a standard tensile mold, vacuumed, and dried to obtain a tensile part. The tensile strength of the tensile part is tested to be 13.0 MPa–17.5 MPa, and the elongation at break is 115%–157%. The polyurea composite material mixture is then poured onto a polytetrafluoroethylene (PTFE) plate, smoothed using a coating machine, and allowed to stand to obtain an impact-resistant coating. The impact strength of this coating is tested to be 407 kJ / m. 2 ~451kJ / m 2 .

[0031] When exfoliated modified boron nitride nanosheets are added, the polyurea composite material mixture is injected into a standard tensile mold, vacuumed, and dried to obtain a tensile part. The tensile strength of the tensile part is tested to be 14 MPa–21 MPa, and the elongation at break is 163%–214%. The polyurea composite material mixture is then poured onto a polytetrafluoroethylene (PTFE) plate, smoothed using a coating machine, and allowed to stand to obtain an impact-resistant coating. The impact strength of this coating is tested to be 418 kJ / m. 2 ~480kJ / m 2 The polyurea composite material mixture was poured into a mold to form an electrically insulating disc, and the volume resistivity was measured to be 1.53 × 10⁻⁶. 14 Ω·cm~2.54×10 15 Ω·cm.

[0032] The beneficial effects of the present application are:

[0033] The present application uses a high-efficiency, non-polluting method to exfoliate and modify boron nitride nanosheets. The exfoliated boron nitride nanosheets have a larger specific surface area, and the dispersibility in the polyurea matrix is improved to a certain extent, so that the interfacial action in the polyurea system can be strengthened to a certain extent. The exfoliated and modified boron nitride nanosheets have a larger specific surface area, and the surface of the boron nitride nanosheets contains amino groups, so that they have better dispersibility in the polyurea system, can be linked with the isocyanate component by covalent bond, improve the interfacial action with the polyurea system, and enhance the mechanical properties and impact resistance of the polyurea elastomer. By enhancing the dispersibility of boron nitride nanosheets in the polyurea system, the electrical insulation of the polyurea elastomer is enhanced.

[0034] The boron nitride nanosheets have surface effect and small size effect. The surface of the modified boron nitride nanosheets contains amino groups, can undergo physical and chemical crosslinking with the isocyanate component, can form a more ideal interface with a force much larger than van der Waals force, is beneficial to stress transfer and absorption, and achieves the effect of toughening. Compared with traditional polyurea elastomer materials, the use of modified boron nitride nanosheets as the reinforcing phase of polyurea can significantly improve the mechanical properties and electrical insulation of the polyurea elastomer material, and has obvious improvement in tensile strength, elongation at break, impact resistance and volume resistance of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The tensile strength test results of the present application comparative examples 1-6 and examples 1-10 are shown in Table 1.

[0036] Figure 2 The elongation at break test results of the present application comparative examples 1-6 and examples 1-10 are shown in Table 2.

[0037] Figure 3 The impact strength test results of the present application comparative examples 1-6 and examples 1-10 are shown in Table 3.

[0038] Figure 4 The volume resistance test results of the present application comparative examples 7-14 and examples 11-17 are shown in Table 4. DETAILED DESCRIPTION

[0039] The present application will be further described in detail below in combination with examples.

[0040] In the following examples, the test scheme of boron nitride / polyurea elastomer composite material includes the following steps:

[0041] (1) The prepared boron nitride / polyurea elastomer composite material is cured at 0.1 MPa vacuum and 80℃ for 3 days, and cured at room temperature for 7-10 days.

[0042] (2) The standard tensile piece of the prepared boron nitride / polyurea elastomer composite material is subjected to a tensile test; the boron nitride / polyurea elastomer composite material is made into a test specimen according to the size requirement, and subjected to an impact resistance test.

[0043] The tensile rate of the boron nitride / polyurea elastomer composite material is 10 mm / min; the impact speed set in the impact resistance test is 3.8 m / s, and the hammer body is selected as a simply supported beam 25J.

[0044] (3) The prepared boron nitride / polyurea elastomer composite material is subjected to a volume resistance test: the boron nitride / polyurea elastomer composite material is made into a test specimen according to the size requirement, and subjected to a volume resistance test.

[0045] The size of the boron nitride / polyurea elastomer composite material is 50 mm in diameter and 1.5 mm in thickness, and the high resistance instrument needs to be preheated for 5 min before testing.

[0046] In the following examples, boron nitride nanosheets (BN) are purchased from Shanghai Superwei Nanotechnology Co., Ltd., the thickness of the boron nitride nanosheets is about 50 nm, and the surface is free of amino groups.

[0047] In the following examples, the exfoliated boron nitride nanosheets (B-BN) and the exfoliated modified boron nitride nanosheets (M-BN) are prepared by the following method:

[0048] Step (1): Put 1 g of boron nitride nanosheets and a mixed solution of 200 g of anhydrous ethanol and 100 g of water into a high-speed blender; stir at a speed of 20,000 r / min for 20 min to obtain a boron nitride solution.

[0049] Step (2): Centrifuge the boron nitride solution in a high-speed centrifuge, wherein the speed of the high-speed centrifuge is 3,000 rpm, and the centrifuged boron nitride nanosheets are dried at 70°C for standby, to obtain exfoliated boron nitride nanosheets (B-BN);

[0050] Step (3): Put the exfoliated boron nitride nanosheets and 1 g of m-xylylenediamine (MXDA) into a ball mill jar according to a material ball ratio of 1:45, the ball milling speed is 500-600 r / min, the ball milling time is 4-6 h, and the ball mill works for 30 min and stops for 10 min during the ball milling process, 40 min is one cycle, and a total of 6-9 cycles are worked; after ball milling, wash with deionized water, freeze-drying machine is used for freeze-drying, and freeze-drying is carried out under the conditions of vacuum 0.1 MPa and -56°C for 12 h for standby.

[0051] After testing, the thickness of the exfoliated boron nitride nanosheet (B-BN) obtained is 2.31±0.14 nm, and the thickness of the exfoliated modified boron nitride nanosheet (M-BN) is 2.31±0.14 nm. Through TGA testing, the surface amino grafting rate is about 3.50%.

[0052] Comparative Example 1

[0053] (1) The preparation method of the polyurea elastomer coating with a thickness of 2 mm includes the following steps:

[0054] The content of each raw material in Comparative Example 1

[0055]

[0056] 1. Metal substrate surface pretreatment: Use 800-1000 mesh sandpaper to polish the metal substrate surface to a smooth finish, then place the polished metal substrate in anhydrous ethanol solution and use ultrasonic cleaning to clean the surface of the metal substrate for 1-2 h, with an ultrasonic frequency of 100 KHz. After cleaning, place the metal substrate in an oven at 60-80°C and dry for 1-2 h for standby;

[0057] 2. Brush the metal surface special primer on the surface of the dried metal substrate, with a brushing thickness of 0.2 mm. After brushing, stand by for 4 h for standby;

[0058] 3. Weigh 10.91% by mass of IPDI, 32.72% by mass of HDI, and 7.32% by mass of DMAc, and place them in a vacuum oven. Dehydrate at 110-120°C and -0.1 MPa for 4 h. Place the dehydrated IPDI, HDI, and DMAc in a three-necked flask and stir at 25°C under nitrogen for 30 min, with a stirring machine speed of 1300 r / min;

[0059] 4. Weigh 49.05% by mass of NH2885, and place it in a vacuum oven. Dehydrate at 110-120°C and -0.1 MPa for 4 h. Add the dehydrated NH2885 to the three-necked flask and mechanically stir for 3 min under nitrogen protection to mix uniformly, with a stirring machine speed of 2200 r / min, to obtain a mixed solution.

[0060] Comparative Example 2

[0061] The content of each raw material in Comparative Example 2

[0062]

[0063]

[0064] 1. Surface pretreatment of metal substrate: Use 800-1000 grit sandpaper to polish the surface of the metal substrate until it is smooth. Then, put the polished metal substrate into anhydrous ethanol solution and use ultrasonic cleaning to clean the surface of the metal substrate for 1-2 hours. The ultrasonic frequency is 100KHz. After cleaning, put the metal substrate into an oven at 60℃-80℃ to dry for 1-2 hours for later use.

[0065] 2. Apply a metal surface primer to the dried metal substrate surface, with a coating thickness of 0.2mm, and let it stand for 4 hours after application.

[0066] 3. Weigh out 10.91% IPDI, 32.72% HDI, and 7.32% DMAc by mass, and place them in a vacuum oven for vacuum dehydration at 110℃~120℃ and -0.1MPa for 4 hours. Place the dehydrated IPDI, HDI, and DMAc in a three-necked flask, add 0.05% boron nitride nanosheets (BN) of the polyurea material by mass to the three-necked flask, and stir for 30 minutes at 25℃ and nitrogen purging, with the stirrer speed at 1300 r / min.

[0067] 4. Weigh out 49.05% of the mass fraction. NH2885 was placed in a vacuum oven and dehydrated under vacuum conditions of 110℃~120℃ and -0.1MPa for 4 hours; the dehydrated... NH2885 was added to a three-necked flask and mechanically stirred for 3 minutes under nitrogen protection to ensure uniform mixing. The stirring speed was 2200 r / min to obtain the mixture.

[0068] Comparative Example 3

[0069] Content of each raw material in Comparative Example 3

[0070]

[0071] The difference from Comparative Example 2 is the content of boron nitride nanosheets (BN).

[0072] Comparative Example 4

[0073] Content of each raw material in Comparative Example 4

[0074]

[0075]

[0076] The difference from Comparative Example 2 is the content of boron nitride nanosheets (BN).

[0077] Comparative Example 5

[0078] The content of each raw material in Comparative Example 5

[0079]

[0080] The content of boron nitride nanosheets (BN) is different from that in Comparative Example 2.

[0081] Comparative Example 6

[0082] The content of each raw material in Comparative Example 6

[0083]

[0084] The content of boron nitride nanosheets (BN) is different from that in Comparative Example 2.

[0085] Example 1

[0086] The content of each raw material in Example 1

[0087]

[0088] 1. Metal substrate surface pretreatment: The metal substrate surface is polished to a smooth finish using 800-1000 mesh sandpaper, then the polished metal substrate is placed in anhydrous ethanol solution and the metal substrate is surface cleaned using ultrasonic cleaning for 1-2 h, the ultrasonic frequency is 100 KHz, after cleaning the metal substrate is placed in an oven at 60-80°C and dried for 1-2 h for standby;

[0089] 2. A metal surface special primer is brushed on the surface of the dried metal substrate, the brushing thickness is 0.2 mm, after brushing, it is placed for standby for 4 h;

[0090] 3. 10.91% by mass of IPDI, 32.72% by mass of HDI, and 7.32% by mass of DMAc are weighed and placed in a vacuum oven, and dehydrated at 110-120°C and -0.1 MPa for 4 h; the dehydrated IPDI, HDI, and DMAc are placed in a three-necked flask, 0.05% by mass of the exfoliated boron nitride nanosheets (B-BN) accounting for the mass percentage of the polyurea mixed solution are added to the three-necked flask, and stirred at 25°C under nitrogen for 30 min, the stirring speed is 1300 r / min;

[0091] 4. 49.05% by mass of NH2885 is weighed and placed in a vacuum oven, and dehydrated at 110-120°C and -0.1 MPa for 4 h; the dehydrated NH2885 is added to the three-necked flask, and mechanically stirred for 3 min under nitrogen protection to mix uniformly, the stirring speed is 2200 r / min, and a mixed solution is obtained.

[0092] Example 2

[0093] Raw material content in Example 2

[0094]

[0095] The difference from Comparative Example 2 is the type (B-BN) and content of boron nitride nanosheets.

[0096] Example 3

[0097] Raw material content in Example 3

[0098]

[0099] The difference from Comparative Example 2 is the type (B-BN) and content of boron nitride nanosheets.

[0100] Example 4

[0101] Raw material content in Example 4

[0102]

[0103] The difference from Comparative Example 2 is the type (B-BN) and content of boron nitride nanosheets.

[0104] Example 5

[0105] Raw material content in Example 5

[0106]

[0107] The difference from Comparative Example 2 is the type (B-BN) and content of boron nitride nanosheets.

[0108] Example 6

[0109] Raw material content in Example 6

[0110]

[0111] 1. Metal substrate surface pretreatment: The metal substrate surface is polished to a smooth finish using 800-1000 mesh sandpaper, then the polished metal substrate is placed in anhydrous ethanol solution and the metal substrate is surface cleaned using ultrasonic cleaning for 1-2 h, the ultrasonic frequency is 100 KHz, after cleaning the metal substrate is placed in an oven at 60-80°C and dried for 1-2 h for standby;

[0112] 2. Brush the metal surface special primer on the surface of the dried metal substrate, the brushing thickness is 0.2 mm, after brushing, stand for 4 h for standby;

[0113] 3, respectively, mass fraction 10.91% IPDI, mass fraction 32.72% HDI, mass fraction 7.32% DMAc, placed in a vacuum oven, at 110 ℃ to 120 ℃, -0.1 MPa conditions under vacuum dehydration 4h; IPDI, HDI and DMAc after dehydration in a three-necked flask, mass fraction 0.05% modified boron nitride nanosheet (M-BN) is added to the three-necked flask, stirring at 25 ℃, nitrogen gas conditions for 30 min, stirring machine speed of 1300 r / min;

[0114] 4, mass fraction 49.05% of NH2885, placed in a vacuum oven, at 110 ℃ to 120 ℃, -0.1 MPa conditions under vacuum dehydration 4h; dehydration of NH2885 is added to the three-necked flask, under the condition of nitrogen protection mechanical stirring 3 min to make it mixed evenly, stirring machine speed of 2200 r / min, to get the mixed solution.

[0115] Example 7

[0116] Example 7 in each raw material content

[0117]

[0118] Different from example 1 is the type of boron nitride nanosheet (M-BN) and content.

[0119] Example 8

[0120] Example 8 in each raw material content

[0121]

[0122] Different from example 1 is the type of boron nitride nanosheet (M-BN) and content.

[0123] Example 9

[0124] Example 9 in each raw material content

[0125]

[0126] Different from example 1 is the type of boron nitride nanosheet (M-BN) and content.

[0127] Example 10

[0128] Example 10 in each raw material content

[0129]

[0130] The difference from Example 1 is the type (M-BN) and content of boron nitride nanosheets.

[0131] Comparative Example 7

[0132] Content of each raw material in Comparative Example 7

[0133]

[0134] 1. Take 10.91% by mass of IPDI, 32.72% by mass of HDI, and 7.32% by mass of DMAc, respectively, and place them in a vacuum oven under the conditions of 110°C to 120°C and -0.1 MPa for 4 h of vacuum dehydration. Place the dehydrated IPDI, HDI, and DMAc in a three-necked flask, and stir them at 25°C under the condition of nitrogen filling for 30 min at a stirring machine speed of 1300 r / min.

[0135] 2. Take 49.05% by mass of NH2885, and place it in a vacuum oven under the conditions of 110°C to 120°C and -0.1 MPa for 4 h of vacuum dehydration. Add the dehydrated NH2885 to the three-necked flask, and mechanically stir it for 3 min under the condition of nitrogen protection to uniformly mix it at a stirring machine speed of 2200 r / min to obtain a mixed solution.

[0136] Comparative Example 8

[0137] Content of each raw material in Comparative Example 8

[0138]

[0139] 1. Take 10.91% by mass of IPDI, 32.72% by mass of HDI, and 7.32% by mass of DMAc, respectively, and place them in a vacuum oven under the conditions of 110°C to 120°C and -0.1 MPa for 4 h of vacuum dehydration. Place the dehydrated IPDI, HDI, and DMAc in a three-necked flask, and add 0.1% by mass of boron nitride nanosheets (BN) to the three-necked flask, and stir them at 25°C under the condition of nitrogen filling for 30 min at a stirring machine speed of 1300 r / min.

[0140] 2. Take 49.05% by mass of NH2885, and place it in a vacuum oven under the conditions of 110°C to 120°C and -0.1 MPa for 4 h of vacuum dehydration. Add the dehydrated NH2885 to the three-necked flask, and mechanically stir it for 3 min under the condition of nitrogen protection to uniformly mix it at a stirring machine speed of 2200 r / min to obtain a mixed solution, which is prepared into a conductive disc for testing.

[0141] Comparative Example 9

[0142] Content of each raw material in Comparative Example 9

[0143]

[0144] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0145] Comparative Example 10

[0146] Content of each raw material in Comparative Example 10

[0147]

[0148] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0149] Comparative Example 11

[0150] Content of each raw material in Comparative Example 11

[0151]

[0152]

[0153] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0154] Comparative Example 12

[0155] Content of each raw material in Comparative Example 12

[0156]

[0157] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0158] Comparative Example 13

[0159] Content of each raw material in Comparative Example 13

[0160]

[0161] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0162] Comparative Example 14

[0163] Content of each raw material in Comparative Example 14

[0164]

[0165] The content of boron nitride nanosheets was different from that in Comparative Example 7.

[0166] Example 11

[0167] The content of each raw material in Example 11

[0168]

[0169] 1. Take 10.91% by mass of IPDI, 32.72% by mass of HDI, and 7.32% by mass of DMAc, and place them in a vacuum oven, and vacuum dehydrate at 110°C to 120°C and -0.1 MPa for 4 hours. Place the dehydrated IPDI, HDI, and DMAc in a three-necked flask, add 0.1% by mass of modified boron nitride nanosheets (M-BN) to the three-necked flask, and stir at 25°C under nitrogen for 30 minutes at a stirring speed of 1300 r / min.

[0170] 2. Take 49.05% by mass of NH2885, and place it in a vacuum oven, and vacuum dehydrate at 110°C to 120°C and -0.1 MPa for 4 hours. Add the dehydrated NH2885 to a three-necked flask, and mechanically stir for 3 minutes under nitrogen to mix them uniformly at a stirring speed of 2200 r / min, to obtain a mixed solution.

[0171] Example 12

[0172] The content of each raw material in Example 12

[0173]

[0174] The difference from Example 9 is the type and content of boron nitride nanosheets (M-BN).

[0175] Example 13

[0176] The content of each raw material in Example 13

[0177]

[0178] The difference from Example 9 is the type and content of boron nitride nanosheets (M-BN).

[0179] Example 14

[0180] The content of each raw material in Example 14

[0181]

[0182] The difference from Example 9 is the type and content of boron nitride nanosheets (M-BN).

[0183] Example 15

[0184] The content of each raw material in Example 15

[0185]

[0186] The type (M-BN) and content of boron nitride nanosheets were different from those in Example 9.

[0187] Example 16

[0188] The content of each raw material in Example 16

[0189]

[0190] The type (M-BN) and content of boron nitride nanosheets were different from those in Example 9.

[0191] Example 17

[0192] The content of each raw material in Example 17

[0193]

[0194]

[0195] The type (M-BN) and content of boron nitride nanosheets were different from those in Example 9.

[0196] Construction method:

[0197] (1) Pour the mixed solution prepared in Comparative Examples 1-6 and Examples 1-10 into a tensile member mold to prepare a standard tensile member, and dry it at a vacuum of 0.1 MPa and 80°C for 3 days, and then cure it at room temperature for 7-10 days; pour the mixed solution onto a polytetrafluoroethylene plate, dry it at a vacuum of 0.1 MPa and 80°C for 3 days, and then cure it at room temperature for 7-10 days, and then cut the cured polyurea elastomer coating into a predetermined size using a laser cutting machine according to the size requirements of the sample;

[0198] (2) Tensile test

[0199] The polyurea elastomer tensile members obtained in Comparative Examples 1-6 and Examples 1-10 were subjected to a tensile test using a universal tensile testing machine, and the experimental data were recorded to analyze the change in tensile properties of the material.

[0200] (3) Impact test

[0201] The polyurea elastomer material obtained in Comparative Examples 1-6 and Examples 1-10 was subjected to an impact resistance test using a simply supported beam impact testing machine, and the experimental data were recorded to analyze the change in impact resistance of the material.

[0202] (4) Electrical insulation test

[0203] The polyurea elastomer materials obtained from Comparative Examples 7-14 and Examples 11-17 were tested for volume resistance by a high resistance meter, and the experimental data were recorded to analyze the change of volume resistance of the materials.

[0204] Table 1 Tensile strength of boron nitride / polyurea elastomer coating

[0205]

[0206]

[0207] Table 2 Impact resistance of boron nitride / polyurea elastomer coating

[0208]

[0209] Table 3 Volume resistance of boron nitride / polyurea elastomer coating

[0210]

[0211]

[0212] In order to more intuitively see the influence of the change, the tensile properties of different boron nitride / polyurea elastomer composite materials are shown in Figure 1 , the impact resistance of different boron nitride / polyurea elastomer composite materials is shown in Figure 2 , and the electrical insulation of different boron nitride / polyurea elastomer composite materials is shown in Figure 3 . As shown in the above table, when the content of modified boron nitride nanosheet is 0.1wt%, the tensile strength and elongation at break of the polyurea coating reach the maximum values of 20.59 MPa and 213.55%, respectively, which are increased by 56.62% and 67.43% compared with the pure polyurea coating. The tensile strength and elongation at break of the BN / polyurea coating and the B-BN / polyurea coating do not increase significantly. When the content of modified boron nitride is 0.1wt%, the impact resistance of the polyurea coating is the best, and the impact strength reaches 479.38kJ / m 2 , which is increased by about 22.24% compared with the pure polyurea coating. The impact strength of the BN / polyurea coating and the B-BN / polyurea coating does not increase significantly. When the mass fraction of boron nitride reaches 15.0wt%, the volume resistance of the polyurea coating reaches 1.98×10 15 Ω·cm, which is increased by about 2 orders of magnitude compared with the volume resistance of the pure polyurea coating (see Figure 4 ).

[0213] Comparative Example

[0214] The exfoliated modified boron nitride nanosheet was added to diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), NH1420, NH2885 and the like are mixed because they have poor film-forming properties and cannot enhance the polyurea elastomer composite.

[0215] It is shown that the exfoliated boron nitride nanosheet does not have an enhancing effect on all materials.

[0216] Example 18

[0217] The boron nitride nanosheet is exfoliated for different times, 10 min, 20 min and 40 min respectively, and the thickness is tested by AFM, the results show that the thickness of the boron nitride nanosheet exfoliated for 10 min is about 4.32 nm, the thickness of the boron nitride nanosheet exfoliated for 20 min and 40 min is not much different, which is 3.32 nm and 3.01 nm respectively, considering the preparation efficiency, the exfoliation time selected in this experiment is 20 min.

[0218] It is shown that the exfoliation time has an effect on the thickness of boron nitride, the longer the exfoliation time, the smaller the thickness of the boron nitride nanosheet.

[0219] The above only describes the preferred embodiments of the present application and cannot limit the protection scope of the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A type of exfoliated modified boron nitride nanosheet, characterized in that, The exfoliated modified boron nitride nanosheets have a thickness of 2.31±0.14 nm and contain amino groups on their surface with a surface amino grafting rate of 3-5%. The exfoliated modified boron nitride nanosheets were prepared using the following method: Step (1): The measured boron nitride nanosheets and polar solvent are placed in a high-speed stirrer and stirred at high speed to obtain a boron nitride solution; the polar solvent is one or more of deionized water and anhydrous ethanol. Step (2): Centrifuge the boron nitride solution in a high-speed centrifuge, take the centrifuged boron nitride nanosheets and dry them for later use to obtain the exfoliated boron nitride nanosheets; Step (3): The exfoliated boron nitride nanosheets and m-phenylenediamine (MXDA) are placed in a ball mill jar according to the stoichiometric ratio, milled, washed and dried to obtain exfoliated modified boron nitride nanosheets; wherein the mass ratio of exfoliated boron nitride nanosheets to MXDA is 1:(1~1.5).

2. The method for preparing exfoliated modified boron nitride nanosheets according to claim 1, characterized in that, Includes the following steps: Step (1): The measured boron nitride nanosheets and polar solvent are placed in a high-speed stirrer and stirred at high speed to obtain a boron nitride solution; the polar solvent is one or more of deionized water and anhydrous ethanol. Step (2): Centrifuge the boron nitride solution in a high-speed centrifuge, take the centrifuged boron nitride nanosheets and dry them for later use to obtain the exfoliated boron nitride nanosheets; Step (3): The exfoliated boron nitride nanosheets and m-phenylenediamine (MXDA) are placed in a ball mill jar according to the stoichiometric ratio, milled, washed and dried to obtain exfoliated modified boron nitride nanosheets; wherein the mass ratio of exfoliated boron nitride nanosheets to MXDA is 1:(1~1.5).

3. The method for preparing exfoliated modified boron nitride nanosheets according to claim 2, characterized in that, In step (1), the mass ratio of boron nitride nanosheets to polar solvent is 1:(250-500); and / or, the speed of the high-speed stirrer is 20000-30000 r / min, and the stirring time is 5-35 min.

4. The method for preparing exfoliated modified boron nitride nanosheets according to claim 2, characterized in that, In step (2), the speed of the high-speed centrifuge is 2000-3500 rpm, and the drying temperature is 60-80℃.

5. The method for preparing exfoliated modified boron nitride nanosheets according to claim 2, characterized in that, In the preparation method of the exfoliated modified boron nitride nanosheets, the ball milling media used in the ball mill jar is zirconia balls, and the ball-to-material ratio is 1:45; the diameter of the small zirconia balls is 1 mm, the diameter of the large zirconia balls is 10 mm, and the mass ratio of the small zirconia balls to the large zirconia balls is 4:

1. And / or, the ball milling time is 4 to 6 hours, the ball milling speed is 500 to 600 r / min, during the ball milling process, the ball mill works for 30 minutes and stops for 10 minutes, 40 minutes is one cycle, and a total of 6 to 9 cycles are worked.

6. The application of the exfoliated modified boron nitride nanosheet reinforced polyurea composite material according to claim 1, characterized in that, Its preparation method is as follows: S1: Under nitrogen protection, the metered isophorone diisocyanate, hexamethylene diisocyanate, dimethylacetamide and exfoliated modified boron nitride nanosheets are mixed and stirred to obtain an isocyanate / boron nitride mixture. S2: Add the measured amount of polyaspartic acid ester Desmophen® NH2885 to the isocyanate / boron nitride mixture, and after mixing and stirring, obtain the polyurea composite material mixture.

7. The application according to claim 6, characterized in that, In S1, the mass ratio of IPDI to HDI to DMAc is (3.1~3.3):(1.0~1.2):(0.67~0.74), the reaction temperature is 25℃, the mixing and stirring time is 30min~60min, and the stirring speed is 1000r / min~1500r / min; And / or, the amount of exfoliated modified boron nitride nanosheets added is 0.05% to 0.5% of the total mass of the polyurea composite material; And / or, in S2, the amount of polyaspartic acid ester Desmophen®NH2885 added is 45-50% of the total mass of the polyurea composite material; the reaction temperature is 20-30℃; the mixing and stirring time is 2-5 min; and the stirring speed is 1500 r / min-3000 r / min.

8. The application according to claim 6, characterized in that, When exfoliated modified boron nitride nanosheets are added, the polyurea composite material mixture is injected into a standard tensile mold, vacuumed, and dried to obtain a tensile part. The tensile strength of the tensile part is tested to be 14 MPa–21 MPa, and the elongation at break is 163%–214%. The polyurea composite material mixture is then poured onto a polytetrafluoroethylene (PTFE) plate, smoothed using a coating machine, and allowed to stand to obtain an impact-resistant coating. The impact strength of this coating is tested to be 418 kJ / m. 2 ~480kJ / m 2 The polyurea composite material mixture was poured into a mold to form an electrically insulating disc, and the volume resistivity was measured to be 1.53 × 10⁻⁶. 14 Ω·cm~2.54×10 15 Ω·cm.

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