Bamboo fiber molded composite material and preparation method thereof

Abstract

The application belongs to the technical field of fiber composites, and particularly relates to a bamboo fiber molding composite material and a preparation method thereof. The preparation method of the bamboo fiber molding composite material comprises the following steps: S1, first, pretreated bamboo fibers are obtained by spraying treatment of bamboo fibers with acrylate epoxidized soybean oil ester; then, modified bamboo fibers are obtained by surface coating of the pretreated bamboo fibers with diphenyl methane diisocyanate; S2, first, a bamboo fiber preformed body is obtained by cold pressing forming of the modified bamboo fibers; then, a resin liquid is obtained by mixing and stirring of an epoxy resin, a curing agent and a catalyst; and then, resin transfer molding is performed on the bamboo fiber preformed body and the resin liquid, and heat curing is performed, so that the bamboo fiber molding composite material is obtained. In the application, the bamboo fibers are used as the main material, and the resin transfer molding is performed in cooperation with the epoxy resin material, so that the composite material has good mechanical properties, and the glass transition temperature of the material is improved.

Description

Technical Field

[0001] This invention belongs to the field of fiber composite materials technology, specifically relating to a bamboo fiber molded composite material and its preparation method. Background Technology

[0002] Natural fibers are one of the most abundant resources in nature. They are easily decomposed, biodegradable, renewable, and cost-effective. Natural fibers are mainly divided into plant fibers, animal fibers, and mineral fibers. Plant fibers have received widespread attention in recent years due to their wide availability, recyclability, biodegradability, and high specific performance. Based on the location of the fiber on the plant, plant fibers can be divided into leaf fibers (sisal, abaca, etc.), seed fibers (coconut, cotton, etc.), and stem fibers (flax, jute, bamboo, etc.). Bamboo fiber, often referred to as "natural glass fiber," has good elasticity, high modulus, low density, and high tensile and compressive strength. Bamboo itself has a short growth cycle and fast growth rate, and contains approximately 60% cellulose. The fibers are longitudinally arranged, and the microfiber angle is relatively small, thus giving bamboo fiber highly specific mechanical properties.

[0003] Bamboo fiber, prepared from bamboo processing residues, can be combined with a polymer matrix to create bamboo fiber molding composites, which can replace plastics and promote environmental protection and sustainable development. Currently, common processes for preparing bamboo fiber molding composites include extrusion molding, cold-pressing and hot-pressing, autoclave molding, filament winding, and vacuum-assisted resin transfer molding. These processes primarily utilize vacuum pressure to drive resin flow and impregnate the fiber reinforcement. After overall curing at room temperature or under heating conditions, a composite material with a specific fiber content is demolded.

[0004] Chinese patent (publication number CN111516073B) discloses a method for preparing bamboo fiber molding composite material. The method involves: crushing bamboo strips into a loose state, immersing them in a nano-calcium carbonate solution, adding a chelating agent, and performing a flash explosion treatment to obtain modified bamboo fiber crude product. The residual solution is filtered to obtain a crude bamboo basic tissue. The crude bamboo fiber is then immersed in a nano-calcium carbonate solution and ultrasonically treated to obtain modified bamboo fiber. The residual solution is filtered to obtain a crude bamboo basic tissue. The two crude bamboo basic tissue products are combined, washed, and dried to obtain the bamboo basic tissue. This tissue is then soaked in water, a thickener is added, stirred, and filtered to obtain a modified bamboo basic tissue. The dried modified bamboo fiber and the modified bamboo basic tissue are mixed and molded to obtain the bamboo fiber molding composite material. However, this bamboo fiber molding composite material does not include a polymer resin material, resulting in poor mechanical properties and a lack of research on its heat resistance.

[0005] Therefore, there is an urgent need for a bamboo fiber molding composite material, which uses bamboo fiber as the main material and combines it with epoxy resin for resin transfer molding, so that the resulting composite material has both good mechanical properties and can significantly improve the glass transition temperature of the material. Summary of the Invention

[0006] The purpose of this invention is to provide a bamboo fiber molding composite material and its preparation method. This invention first pre-treats bamboo fibers by spraying them with acrylate-epoxidized soybean oil ester, then modifies them by surface coating with diphenylmethane diisocyanate. Next, the modified bamboo fibers are cold-pressed to obtain a bamboo fiber preform. Epoxy resin, curing agent, and catalyst are mixed and stirred to obtain a resin liquid. Finally, the bamboo fiber preform and resin liquid are resin-transfer molded and thermo-cured to obtain the bamboo fiber molding composite material. Through the synergistic effect of multiple components, the flexural strength and tensile strength of the material are effectively improved, while also achieving good heat resistance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing bamboo fiber molding composite material, comprising the following steps:

[0009] S1. First, bamboo fiber is sprayed with acrylate epoxidized soybean oil ester to obtain pretreated bamboo fiber; then, the surface of the pretreated bamboo fiber is coated with diphenylmethane diisocyanate to obtain modified bamboo fiber.

[0010] S2. First, the modified bamboo fiber is cold-pressed to obtain a bamboo fiber preform. Then, epoxy resin, curing agent and catalyst are mixed and stirred to obtain a resin liquid. Then, the bamboo fiber preform and the resin liquid are resin-transfer molded and thermo-cured to obtain a bamboo fiber molded composite material.

[0011] As a preferred embodiment, the cold pressing step is as follows: after the modified bamboo fiber is laid out, it is cold pressed in a cold press at 2~4MPa for 6~8 minutes, and then transferred to an oven to dry at 50~60℃ for 30~36 hours.

[0012] As a preferred embodiment, the mixing conditions are: stirring at a speed of 300~400 r / min for 10~20 min.

[0013] As a preferred embodiment, the resin transfer molding step is as follows: placing the bamboo fiber preform in a mold, adding the resin liquid to a resin tank, and performing injection molding under vacuum conditions of 0.06MPa~0.08MPa and injection pressure of 0.6~0.8MPa.

[0014] As a preferred embodiment, the thermosetting conditions are as follows: first, cure at 80~90℃ for 50~60 min, then cure at 100~110℃ for 100~120 min, and finally cure at 120~130℃ for 120~140 min.

[0015] As a preferred embodiment, the resin liquid in step S2 comprises, by weight, 90-100 parts epoxy resin, 10-20 parts curing agent, and 2-4 parts catalyst.

[0016] As a preferred embodiment, the epoxy resin may be present in parts by weight of 90, 92, 94, 96, 98, or 100 parts, etc.

[0017] As a preferred embodiment, the curing agent may be present in weight parts of 10, 12, 14, 16, 18, or 20 parts, etc.

[0018] As a preferred embodiment, the catalyst may be present in 2, 3, or 4 parts by weight, etc.

[0019] As a preferred embodiment, the spraying treatment step is as follows: by weight, 20-30 parts of acrylate epoxidized soybean oil ester are added to 180-200 parts of acetone and stirred for 20-30 minutes to obtain a spraying liquid. Then, the spraying liquid is sprayed onto the surface of 90-100 parts of bamboo fiber and dried at 65-75°C for 30-40 minutes to obtain pretreated bamboo fiber.

[0020] As a preferred embodiment, the surface coating step is as follows: by weight, 12-18 parts of diphenylmethane diisocyanate and 1.2-1.8 parts of dibutyltin dilaurate are mixed and coated on the surface of 90-100 parts of the pretreated bamboo fiber, and then transferred to an oven for heat treatment at 100-105°C for 8-10 minutes to obtain modified bamboo fiber.

[0021] This invention first mixes epoxidized soybean oil ester with highly active epoxy groups and acrylate double bonds with acetone and sprays it onto the surface of bamboo fiber. Then, diphenylmethane diisocyanate (MDI) is added and dibutyltin dilaurate is used as an organotin catalyst. Through heat treatment, the isocyanate groups of MDI react with the hydroxyl groups on the surface of bamboo fiber and epoxidized soybean oil ester, thereby preparing modified bamboo fiber with epoxy groups and carbon-carbon double bonds on the surface.

[0022] As a preferred embodiment, the epoxy resin is a hyperbranched epoxy resin and an epoxy acrylate resin.

[0023] As a preferred embodiment, the mass ratio of the hyperbranched epoxy resin to the epoxy acrylate resin is (2~4):1.

[0024] As a preferred embodiment, the hyperbranched epoxy resin has an epoxy value of 0.1~0.2 mol / 100g, VOC ≤5%, and a molecular weight of 3000~5000g / mol.

[0025] The epoxy resin of this invention is a blend of hyperbranched epoxy resin and epoxy acrylate resin. The former has a highly branched and three-dimensional spherical structure, while the latter has both epoxy resin and acrylate active groups. By controlling the mass ratio of the two, a good synergistic effect is achieved, thereby improving the overall performance of the composite material.

[0026] As a preferred embodiment, the curing agent is selected from one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

[0027] As a preferred embodiment, the catalyst is selected from one or more of 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, and benzoyl peroxide.

[0028] As a preferred embodiment, the catalyst is 2-methylimidazole and benzoyl peroxide.

[0029] As a preferred embodiment, the mass ratio of 2-methylimidazole to benzoyl peroxide in the catalyst is (1~3):1.

[0030] The catalyst and curing agent of this invention can promote the curing of the epoxy resin matrix of the molding composite material and accelerate the cross-linking reaction of the matrix resin, thereby improving the overall performance of the bamboo fiber molding composite material.

[0031] Secondly, the present invention provides a bamboo fiber molding composite material prepared by the preparation method described in the first aspect.

[0032] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0033] (1) The modified bamboo fiber of the present invention introduces polymer chain segments on the surface to enhance the interfacial adhesion with the epoxy resin matrix, effectively transfer the load and reduce the phenomenon of stress cracking and delamination, and significantly improve the bending strength and tensile strength of the molded composite material; at the same time, the network structure on the surface of the modified bamboo fiber can restrict the movement of molecular chain segments, inhibit the softening and slippage of the matrix at high temperature, effectively raise the glass transition temperature of the composite material, and obtain good high-temperature dimensional stability.

[0034] (2) The unique highly branched and three-dimensional spherical structure of the hyperbranched epoxy resin in the compound epoxy resin of this invention can absorb and dissipate impact energy and avoid inducing microcracks. The benzene rings and ester bonds in the epoxy acrylate resin molecular chain help to form a rigid network. The two work together to effectively withstand external loads, thereby improving the mechanical properties of bamboo fiber molding composite materials. In addition, the hyperbranched epoxy resin increases the crosslinking points through the multifunctional group structure, while the epoxy acrylate resin provides carbon-carbon double bonds to promote further crosslinking. The highly crosslinked network restricts the free movement of polymer chain segments, significantly improving the glass transition temperature of the material.

[0035] (3) In this invention, 2-methylimidazole and benzoyl peroxide are preferably used as a composite catalyst. 2-methylimidazole is used as a promoter of the epoxy-anhydride system, while benzoyl peroxide is used as a thermal free radical initiator to promote the reaction of carbon-carbon double bonds. By controlling the amount of composite catalyst, a good dual curing effect is ensured, and the mechanical properties and glass transition temperature of the composite material are greatly improved. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0037] Figure 1 The images show the FTIR spectra of modified bamboo fiber and ordinary bamboo fiber in Example 1 of this invention.

[0038] Figure 2 XPS images of modified bamboo fiber and ordinary bamboo fiber in Example 1 of this invention. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Bamboo fiber, brand name HBS-L10, purchased from Fujian Haibos Chemical Technology Co., Ltd.

[0041] Acrylate epoxidized soybean oil ester, product number PB42770, purchased from Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0042] Diphenylmethane diisocyanate, brand name MDI-100, was purchased from Wanhua Chemical Group Co., Ltd.

[0043] Dibutyltin dilaurate, CAS No. 77-58-7, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0044] Hyperbranched epoxy resin, model HyPer E102, with an epoxy value of 0.15mol / 100g, a VOC of 4.2%, and a molecular weight of 3500g / mol, was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd.

[0045] Epoxy acrylate resin, model EBECRYL 3700 / 18 OT, purchased from ZINS, Germany;

[0046] The standard epoxy resin, NPEL127E, was purchased from Nan Ya Electronic Materials (Kunshan) Co., Ltd.

[0047] Methyltetrahydrophthalic anhydride, CAS No. 19438-64-3, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0048] Methylhexahydrophthalic anhydride, CAS No. 19438-60-9, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0049] Methylnadic anhydride, CAS No. 25134-21-8, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0050] 2-Methylimidazole, CAS No. 693-98-1, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0051] 2-Ethylimidazole, CAS No. 1072-62-4, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0052] 2-Ethyl-4-methylimidazole, CAS No. 931-36-2, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0053] Benzoyl peroxide, CAS No. 94-36-0, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0054] Example 1

[0055] This embodiment provides a method for preparing bamboo fiber molding composite material, including the following steps:

[0056] S1. By weight, 30 parts of acrylate epoxidized soybean oil ester were added to 200 parts of acetone and stirred for 30 minutes to obtain a spraying liquid. The spraying liquid was then sprayed onto the surface of 100 parts of bamboo fiber and dried at 75°C for 30 minutes to obtain pretreated bamboo fiber. 18 parts of diphenylmethane diisocyanate and 1.8 parts of dibutyltin dilaurate were mixed and coated onto the surface of 100 parts of the pretreated bamboo fiber. The mixture was then transferred to an oven and heat-treated at 105°C for 8 minutes to obtain modified bamboo fiber.

[0057] S2. After the modified bamboo fiber is laid out, it is cold-pressed in a cold press at 4 MPa for 6 min, and then transferred to an oven to dry at 60℃ for 30 h to obtain a bamboo fiber preform. 100 parts of epoxy resin (80 parts of hyperbranched epoxy resin and 20 parts of epoxy acrylate resin), 20 parts of curing agent methyltetrahydrophthalic anhydride, and 4 parts of catalyst (3 parts of 2-methylimidazole and 1 part of benzoyl peroxide) are mixed and stirred at 400 r / min for 10 min to obtain a resin liquid. The bamboo fiber preform is placed in a mold, and the resin liquid is added to a resin tank. Injection molding is performed under a vacuum of 0.08 MPa and an injection pressure of 0.8 MPa. The preform is first cured at 90℃ for 50 min, then cured at 110℃ for 100 min, and finally cured at 130℃ for 120 min to obtain a bamboo fiber molded composite material.

[0058] Example 2

[0059] This embodiment provides a method for preparing bamboo fiber molding composite material, including the following steps:

[0060] S1. By weight, 20 parts of acrylate epoxidized soybean oil ester were added to 180 parts of acetone and stirred for 20 minutes to obtain a spraying liquid. The spraying liquid was then sprayed onto the surface of 90 parts of bamboo fiber and dried at 65°C for 40 minutes to obtain pretreated bamboo fiber. 12 parts of diphenylmethane diisocyanate and 1.2 parts of dibutyltin dilaurate were mixed and coated onto the surface of 90 parts of the pretreated bamboo fiber. The mixture was then transferred to an oven and heat-treated at 100°C for 10 minutes to obtain modified bamboo fiber.

[0061] S2. After the modified bamboo fiber is laid out, it is cold-pressed in a cold press at 2 MPa for 8 min, and then transferred to an oven to dry at 50℃ for 36 h to obtain a bamboo fiber preform. 90 parts of epoxy resin (60 parts of hyperbranched epoxy resin and 30 parts of epoxy acrylate resin), 10 parts of curing agent methylhexahydrophthalic anhydride, and 2 parts of catalyst (1 part of 2-methylimidazole and 1 part of benzoyl peroxide) are mixed and stirred at 300 r / min for 20 min to obtain a resin liquid. The bamboo fiber preform is placed in a mold, and the resin liquid is added to a resin tank. Injection molding is performed under a vacuum of 0.06 MPa and an injection pressure of 0.6 MPa. The preform is first cured at 80℃ for 60 min, then cured at 100℃ for 120 min, and finally cured at 120℃ for 140 min to obtain a bamboo fiber molded composite material.

[0062] Example 3

[0063] This embodiment provides a method for preparing bamboo fiber molding composite material, including the following steps:

[0064] S1. By weight, 25 parts of acrylate epoxidized soybean oil ester were added to 190 parts of acetone and stirred for 25 minutes to obtain a spraying liquid. The spraying liquid was then sprayed onto the surface of 95 parts of bamboo fiber and dried at 70°C for 35 minutes to obtain pretreated bamboo fiber. 15 parts of diphenylmethane diisocyanate and 1.5 parts of dibutyltin dilaurate were mixed and coated onto the surface of 95 parts of the pretreated bamboo fiber. The mixture was then transferred to an oven and heat-treated at 103°C for 9 minutes to obtain modified bamboo fiber.

[0065] S2. After the modified bamboo fiber is laid out, it is cold-pressed in a cold press at 3MPa for 7min, and then transferred to an oven to dry at 55℃ for 34h to obtain a bamboo fiber preform. 95 parts of epoxy resin (70 parts of hyperbranched epoxy resin and 25 parts of epoxy acrylate resin), 15 parts of curing agent methylnadic anhydride, and 3 parts of catalyst (2 parts of 2-methylimidazole and 1 part of benzoyl peroxide) are mixed and stirred at 350r / min for 15min to obtain a resin liquid. The bamboo fiber preform is placed in a mold, and the resin liquid is added to a resin tank. Injection molding is performed under a vacuum of 0.07MPa and an injection pressure of 0.7MPa. The preform is first cured at 85℃ for 55min, then at 105℃ for 110min, and finally at 125℃ for 130min to obtain a bamboo fiber molded composite material.

[0066] Comparative Example 1

[0067] The difference between this comparative example and Example 1 is that ordinary bamboo fiber (brand name HBS-L10) was used instead of modified bamboo fiber in the preparation of bamboo fiber preforms.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that the epoxy resin was changed to 95 parts of hyperbranched epoxy resin and 5 parts of epoxy acrylate resin.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that the epoxy resin was changed to 50 parts of hyperbranched epoxy resin and 50 parts of epoxy acrylate resin.

[0072] Comparative Example 4

[0073] The difference between this comparative example and Example 1 is that the epoxy resin was changed to 80 parts of hyperbranched epoxy resin and 20 parts of conventional epoxy resin.

[0074] Comparative Example 5

[0075] The difference between this comparative example and Example 1 is that the epoxy resin was changed to 80 parts of conventional epoxy resin and 20 parts of epoxy acrylate resin.

[0076] Comparative Example 6

[0077] The difference between this comparative example and Example 1 is that the catalyst was changed to 4 parts of 2-methylimidazole.

[0078] Comparative Example 7

[0079] The difference between this comparative example and Example 1 is that the catalyst was changed to 4 parts of benzoyl peroxide.

[0080] Performance testing

[0081] (1) Water absorption test: The test shall be conducted in accordance with the requirements of GB / T 1462-2005 Test method for water absorption of fiber reinforced plastics.

[0082] (2) Bending strength test: The test shall be conducted in accordance with the requirements of GB / T 1449-2005 Test method for bending properties of fiber reinforced plastics.

[0083] (3) Tensile strength test: The test shall be conducted in accordance with the requirements of GB / T 1447-2005 Test method for tensile properties of fiber reinforced plastics.

[0084] (4) Glass transition temperature test: The glass transition temperature (Tg) of the examples and comparative examples was tested using a thermomechanical analyzer (DMA850, TA Instruments, USA). The double cantilever beam mode was used, the temperature range was 30~200℃, the heating rate was 5℃ / min, the amplitude was 20μm, and the frequency was 1Hz.

[0085] Table 1 Performance Test Results

[0086]

[0087] This invention first sprays bamboo fiber with acrylate-epoxidized soybean oil to obtain pretreated bamboo fiber, then coats the surface with diphenylmethane diisocyanate to obtain modified bamboo fiber, then cold-presses the modified bamboo fiber to obtain a bamboo fiber preform, then mixes and stirs a compounded epoxy resin, curing agent and compounded catalyst to obtain a resin liquid, and finally resin transfer molding of the bamboo fiber preform and resin liquid, followed by thermosetting to obtain a bamboo fiber molding composite material (Examples 1 to 3), which has the best comprehensive performance.

[0088] Compared to Example 1, using ordinary bamboo fiber (brand name HBS-L10) instead of modified bamboo fiber in the preparation of bamboo fiber preforms resulted in a decrease in the mechanical properties and glass transition temperature of the composite material due to the lack of modified bamboo fiber (Comparative Example 1). Compared to Example 1, the epoxy resin was changed to 95 parts hyperbranched epoxy resin and 5 parts epoxy acrylate resin. The insufficient amount of epoxy acrylate resin led to poor compounding, resulting in a decrease in the mechanical properties and glass transition temperature of the composite material (Comparative Example 2). Compared to Example 1, the epoxy resin was changed to 50 parts hyperbranched epoxy resin and 50 parts epoxy acrylate resin. The insufficient amount of hyperbranched epoxy resin led to poor compounding, resulting in a decrease in the mechanical properties and glass transition temperature of the composite material (Comparative Example 3). Compared to Example 1, the epoxy resin was changed to... Comparative Example 4: 80 parts hyperbranched epoxy resin and 20 parts conventional epoxy resin were used, but the composite material lacked the effect of epoxy acrylate resin. The mechanical properties of the composite material deteriorated, and the glass transition temperature decreased. Comparative Example 5: 80 parts conventional epoxy resin and 20 parts epoxy acrylate resin were used instead of the epoxy resin. The mechanical properties of the composite material deteriorated, and the glass transition temperature decreased. Comparative Example 6: 4 parts 2-methylimidazole were used instead of the catalyst. The mechanical properties of the composite material deteriorated, and the glass transition temperature decreased. Comparative Example 7: 4 parts benzoyl peroxide were used instead of the catalyst. The mechanical properties of the composite material deteriorated, and the glass transition temperature decreased. Comparative Example 8: 4 parts benzoyl peroxide were used instead of the catalyst. The mechanical properties of the composite material deteriorated, and the glass transition temperature decreased. Comparative Example 9: 4 parts benzoyl peroxide were used instead of the catalyst.

Claims

1. A method for preparing a bamboo fiber molding composite material, characterized in that, Includes the following steps: S1. First, bamboo fiber is sprayed with acrylate epoxidized soybean oil ester to obtain pretreated bamboo fiber; then, the surface of the pretreated bamboo fiber is coated with diphenylmethane diisocyanate to obtain modified bamboo fiber. S2. First, the modified bamboo fiber is cold-pressed to obtain a bamboo fiber preform. Then, epoxy resin, curing agent and catalyst are mixed and stirred to obtain a resin liquid. Then, the bamboo fiber preform and the resin liquid are resin-transfer molded and thermo-cured to obtain a bamboo fiber molded composite material.

2. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The components of the resin liquid in step S2, by weight, include: 90-100 parts epoxy resin, 10-20 parts curing agent, and 2-4 parts catalyst.

3. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The spraying treatment steps are as follows: by weight, 20-30 parts of acrylate epoxidized soybean oil ester are added to 180-200 parts of acetone and stirred for 20-30 minutes to obtain a spraying liquid. Then, the spraying liquid is sprayed onto the surface of 90-100 parts of bamboo fiber and dried at 65-75°C for 30-40 minutes to obtain pretreated bamboo fiber.

4. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The surface coating step is as follows: by weight, 12-18 parts of diphenylmethane diisocyanate and 1.2-1.8 parts of dibutyltin dilaurate are mixed and coated on the surface of 90-100 parts of the pretreated bamboo fiber, and then transferred to an oven for heat treatment at 100-105°C for 8-10 minutes to obtain modified bamboo fiber.

5. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The epoxy resin is a hyperbranched epoxy resin and an epoxy acrylate resin; The mass ratio of the hyperbranched epoxy resin to the epoxy acrylate resin is (2~4):

1.

6. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The hyperbranched epoxy resin has an epoxy value of 0.1~0.2 mol / 100g, VOC ≤5%, and a molecular weight of 3000~5000g / mol.

7. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The curing agent is selected from one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

8. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The catalyst is selected from one or more of 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, and benzoyl peroxide.

9. The method for preparing a bamboo fiber molding composite material according to claim 1, characterized in that, The catalyst is 2-methylimidazole and benzoyl peroxide; The mass ratio of 2-methylimidazole to benzoyl peroxide in the catalyst is (1~3):

1.

10. A bamboo fiber molding composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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