Flame-retardant plant fiber composite and method for producing same

Abstract

The application provides a kind of flame-retardant plant fiber composite material and its preparation method, the preparation method includes the following steps: using biomass phenolic compound modification phosphorus-containing flame retardant, and low temperature melting glass powder, two-dimensional sheet nanosheet compound constructs flame-retardant system;The composite fiber reinforced phase is pretreated;Through the distribution optimization of flame-retardant system achieved by layering hot pressing molding.The flame-retardant plant fiber composite material designed by the application considers the combustion characteristics of plant fiber composite material, and the distribution optimization design can greatly reduce the amount of flame retardant;No toxic solvent is used in the process, and it has good safety and environmental friendliness;At the same time, it has excellent flame retardant performance.

Description

Technical Field

[0001] This invention relates to the field of flame retardant treatment technology, specifically to a flame retardant plant fiber composite material and its preparation method. Background Technology

[0002] Plant fiber reinforced resin matrix composites, prepared using plant fibers as the reinforcing phase and resin as the matrix, offer advantages such as being environmentally friendly, lightweight, and having a high specific modulus. They can partially replace traditional fiber-reinforced composites in fields such as landscaping, construction, automotive parts, and sporting goods. Due to the increasing demand for lightweight and green products in daily life and the new energy vehicle industry, the annual growth rate of plant fiber reinforced composites is expected to remain around 11.8% in the coming years. However, plant fibers and resin matrices have high flammability, posing a fire hazard in engineering applications. A fire could cause serious personal injury and property damage. Improving the flame retardancy of composite materials is a key issue for further promoting their application.

[0003] In the existing technology, the work on flame retardant modification of plant fiber reinforced composite materials still mainly focuses on adding traditional flame retardants.

[0004] Chinese invention patent application number CN201610194141.0 discloses a flame-retardant natural fiber composite board and its preparation method. It uses phosphorus-containing flame retardants and inorganic boron flame retardants to treat both the raw material natural fiber and thermoplastic resin fiber with flame retardancy, ensuring the excellent flame retardant effect of the natural fiber composite board.

[0005] Chinese invention patent application number CN202310192414.8 discloses a flame-retardant natural fiber reinforced thermoplastic composite material and its manufacturing method. It uses a siloxane-containing ionic liquid to treat the fiber surface and grafts the ionic liquid onto the surface of the natural fiber. This ionic liquid has excellent flame retardancy and improves the flame retardant performance of the natural fiber composite material.

[0006] Chinese invention patent application number CN201210223106.9 discloses a flame-retardant natural fiber composite material and its preparation method. Nano-additives and functionalized DOPO are used to treat polylactic acid matrix and natural fibers respectively to obtain a flame-retardant natural fiber reinforced polylactic acid composite material with good flame-retardant and mechanical properties.

[0007] However, current flame retardant methods for plant fiber reinforced composites mostly rely on adding traditional flame retardants through random blending within the composite material. This approach fails to consider the unique combustion characteristics of plant fiber reinforced composites compared to pure polymers, nor does it take into account real-world fire scenarios in engineering applications. According to flame retardant theory, once a fire occurs, the flame retardant in the pyrolysis zone rapidly activates, forming a physical barrier to prevent thermal decomposition in the unpyrolysis zone. However, this also results in the flame retardant remaining in the condensed phase, unable to exert its flame-retardant effect and reducing its efficiency. Summary of the Invention

[0008] This invention is made to solve the above-mentioned problems, and aims to provide a flame-retardant plant fiber composite material and its preparation method, which has good flame-retardant efficiency.

[0009] This invention provides a method for preparing a flame-retardant plant fiber composite material, characterized by the following steps: S1, dispersing a phosphorus-containing flame retardant in deionized water, continuously stirring until uniformly dispersed, adding a phenolic compound, adjusting the pH value according to the type of phenolic compound, stirring thoroughly, filtering, washing with deionized water, drying in an oven, and grinding thoroughly to obtain powder A; S2, dispersing powder A in deionized water, adjusting the pH value, adding a phenolic compound and stirring, adding NiCl2·6H2O, centrifuging, washing, drying, grinding and sieving to obtain powder B; S3, placing epoxy resin and curing agent in a container and stirring to obtain pure epoxy resin; S4, mixing two-dimensional sheet-like nanosheets, low-temperature molten glass powder with powder B, then mixing and stirring with the epoxy resin matrix, adding curing agent and stirring to obtain a flame-retardant composite material. S5. Select the required type of plant fiber, cut, wash and dry it, and uniformly coat the plant fiber surface with pure epoxy resin to obtain plant fiber prepreg A; S6. Select the required type of plant fiber, cut, wash and dry it, and uniformly coat the plant fiber surface with epoxy resin containing flame retardant to obtain plant fiber prepreg B; S7. Take several layers of plant fiber prepreg A as required and place them in a mold, lay them flat layer by layer, and pre-cur them for 0.2-0.8h to obtain plant fiber pre-cured layer A. Lay several layers of plant fiber prepreg B on plant fiber pre-cured layer A and pre-cur them for 0.2-0.8h to obtain plant fiber pre-cured layer B. Then cure it at 100-140℃ for 1-3h and cool it to room temperature to obtain a 3-9mm plant fiber reinforced resin matrix composite material with flame retardant distribution structure.

[0010] The method for preparing flame-retardant plant fiber composite materials provided by the present invention may also have the following characteristics: wherein the plant fiber is one or more of flax fiber, ramie fiber, kenaf fiber, sisal fiber, cotton fiber, jute fiber, bamboo fiber and seaweed fiber; the phosphorus-containing flame retardant in step S1 is one or more of high-polymerization degree ammonium polyphosphate, ammonium pyrophosphate, ammonium tripolyphosphate and ammonium tetrapolyphosphate; and the phenolic group-containing compound in step S1 is one or more of polydopamine, tannic acid, tea polyphenols and proanthocyanidins.

[0011] The method for preparing flame-retardant plant fiber composite materials provided by the present invention may also have the following feature: in step S1, 1-7 wt% sodium hydroxide or 1-5 wt% hydrochloric acid is used to adjust the pH to the desired target value.

[0012] The preparation method of flame-retardant plant fiber composite material provided by the present invention may also have the following features: in step S1, after dispersing the phosphorus-containing flame retardant in deionized water, the stirring time is 0.5-10h and the temperature is 20-80℃; the drying is vacuum drying at a temperature of 40-90℃; and the deionized water washing is performed 3-6 times to fully remove residual sodium hydroxide or hydrochloric acid.

[0013] The method for preparing flame-retardant plant fiber composite materials provided by the present invention may also have the following feature: wherein the two-dimensional sheet-like nanosheets in step S3 are one or more of graphene, graphene oxide, boron nitride and molybdenum disulfide.

[0014] The method for preparing flame-retardant plant fiber composite material provided by the present invention may also have the following feature: wherein, in step S3, the mass ratio of epoxy resin to curing agent is 50:(10-16).

[0015] The method for preparing flame-retardant plant fiber composite material provided by the present invention may also have the following characteristics: wherein, in step S4, the ratio of epoxy resin matrix, powder B, low-temperature molten glass powder, two-dimensional sheet-like nanosheets and curing agent is 30:6:(2-4):(1-2):(2-4).

[0016] The method for preparing flame-retardant plant fiber composite materials provided by the present invention may also have the following features: wherein, in step S5, the flame retardant distribution structure of the plant fiber reinforced resin matrix composite material is one or more of a biomimetic gradient structure and a sandwich structure, and when the distribution structure is a biomimetic gradient structure, several layers of plant fiber prepreg B are laid on top of plant fiber prepreg A.

[0017] The method for preparing flame-retardant plant fiber composite materials provided by the present invention may also have the following features: wherein, in step S5, the flame retardant distribution structure of the plant fiber reinforced resin matrix composite material is one or more of a biomimetic gradient structure and a sandwich structure, and when the distribution structure is a sandwich structure, several layers of plant fiber prepreg B are respectively laid above and below the plant fiber prepreg A.

[0018] The present invention also provides a flame-retardant plant fiber composite material, characterized in that it is prepared according to the preparation method of the flame-retardant plant fiber composite material according to any one of the above claims.

[0019] The role and effect of invention

[0020] According to the present invention, a flame-retardant plant fiber composite material and its preparation method are used in aviation and automotive interiors. Depending on the location of the structural components, the fire mode can be divided into unilateral thermal radiation fire and bilateral thermal radiation fire. Based on the fire mode, the present invention can directionally distribute the flame retardant in the thermal radiation area of ​​the real fire scene through structural control, which can realize the efficient utilization of the flame retardant, avoid the thermal decomposition of the composite material in the unpyrolysis area, and also prevent the flame retardant from remaining in the condensed phase.

[0021] This invention, by regulating the distribution of the flame-retardant system, significantly reduces the amount of flame retardant used while maintaining flame-retardant performance. After structural regulation and distribution optimization, the required amount can be reduced by 30%-50%. This flame-retardant system, requiring only about 7%, can achieve a limiting oxygen index of over 30% for the composite material, achieving a V-0 rating in the UL-94 test. Furthermore, it reduces the peak heat release rate and peak toxic gas release rate by 50%, exhibiting excellent flame-retardant performance, good flame-retardant efficiency, and significant potential for widespread application. Attached Figure Description

[0022] Figure 1 This is a comparison of the surface morphology of ammonium polyphosphate in Example 1 and Comparative Example 1 of the present invention;

[0023] Figure 2 The changes in surface element content are observed when ammonium polyphosphate in Comparative Example 1 and ammonium polyphosphate in Example 1 are processed into powder A and powder B.

[0024] Figure 3 The limiting oxygen index of the flame-retardant composite materials in Embodiment 1, Example 2, and Comparative Example 1 of this invention; and

[0025] Figure 4 The CO release rate of the flame-retardant composite materials in Example 1, Example 2 and Comparative Example 1 of this invention was tested using a cone calorimeter. Detailed Implementation

[0026] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the preparation method of the flame-retardant plant fiber composite material of this invention.

[0027] Example 1

[0028] The specific preparation method of the flame-retardant plant fiber composite material in this embodiment is as follows:

[0029] S1, take 20g of ammonium polyphosphate and place it in 1000ml of deionized water. Stir magnetically at 30℃ for 0.5 hours until it is evenly dispersed to obtain ammonium polyphosphate dispersion. Then add 0.6g of tris(hydroxymethyl)aminomethane and 0.5g of dopamine hydrochloride. At the same time, adjust the pH to 8.5 with NaOH solution. Stir continuously at room temperature for 12 hours. Centrifuge at 1000rpm for 5min. Then wash three times with deionized water, dry in an oven at 80℃, and grind into powder A using a ball mill.

[0030] S2, disperse 5g of powder A in 150mL of deionized water, adjust the pH to 3 with hydrochloric acid while stirring continuously, then add 0.8g of tannic acid and stir continuously at 50℃ for 2 hours. Slowly add 2.0g of NiCl2·6H2O to the solution. Finally, centrifuge at 800rpm for 3min, wash three times with deionized water, dry, grind, and sieve to obtain powder B.

[0031] S3. Take an appropriate amount of epoxy resin and diethylenetriamine and place them in a container at a ratio of 50:13, and stir continuously for 0.5 hours to obtain pure epoxy resin.

[0032] S4. Take an appropriate amount of epoxy resin, powder B, low melting point glass powder, graphene oxide nanosheets and diethylenetriamine and mix them in a ratio of 30:6:2:1:2. Stir evenly to obtain epoxy resin with added flame retardant system.

[0033] S5. Soak unidirectional flax fibers in a 2wt% sodium hydroxide solution for 3 hours. After removing them, wash them three times with deionized water. Then, immerse the flax fabric in deionized water at 30°C for 30 minutes. After removing it, place it in a vacuum oven at 60°C for 5 hours. Then, coat the surface of the unidirectional flax fibers with pure epoxy resin layer by layer to obtain plant fiber prepreg A.

[0034] S6, epoxy resin with added flame retardant is uniformly coated layer by layer onto the surface of unidirectional flax fiber to obtain plant fiber prepreg B.

[0035] S7. Four layers of plant fiber prepreg A are laid flat and placed in a mold under hot pressing. The gasket thickness is 2mm. The prepreg is pre-cured at 0.5MPa and 80℃ for 0.5 hours. After taking it out, four layers of plant fiber prepreg B are laid on top and bottom respectively. The prepreg is pre-cured at 0.5MPa and 80℃ for 0.5 hours. Then, it is cured at 120℃ for 2 hours. After cooling to room temperature, a flame-retardant sandwich structure composite material G-PFRP with a thickness of 6mm is obtained.

[0036] Example 2

[0037] Based on the preparation method of the flame-retardant plant fiber composite material in Example 1, in this example,

[0038] Replace step S4 with "S4, take an appropriate amount of epoxy resin, powder B, low melting point glass powder, graphene oxide nanosheets and diethylenetriamine and mix them in a ratio of 30:6:2:1:2, stir evenly to obtain epoxy resin A with added flame retardant system; take an appropriate amount of epoxy resin and powder B, low melting point glass powder, graphene oxide nanosheets and diethylenetriamine and mix them in a ratio of 30:6:1:0.5:1, stir evenly to obtain epoxy resin B with added flame retardant system."

[0039] Replace step S6 with “S6, apply epoxy resin A with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg B, apply epoxy resin B with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg C.”

[0040] Replace step S7 with "S7, lay four layers of plant fiber prepreg A flat, place them in a mold under hot pressing, with a gasket thickness of 2mm, pre-cur at 0.5MPa and 80℃ for 0.5 hours, remove and then lay two layers of plant fiber prepreg C and two layers of plant fiber prepreg B on top, pre-cur at 0.5MPa and 80℃ for 0.5 hours, then cure at 120℃ for 2 hours, and after cooling to room temperature, obtain a 6mm thick flame-retardant gradient structure composite material S-PFRP."

[0041] Example 3

[0042] The specific preparation method of the flame-retardant plant fiber composite material in this embodiment is as follows:

[0043] S1, 40g of ammonium polyphosphate was placed in 2000ml of deionized water and magnetically stirred at 40℃ for 1 hour until it was evenly dispersed to obtain an ammonium polyphosphate dispersion; then 1.2g of tris(hydroxymethyl)aminomethane and 1.0g of dopamine hydrochloride were added, and the pH was adjusted to 8.5 with NaOH solution. The mixture was stirred continuously at room temperature for 12 hours, centrifuged at 1000rpm for 5min, washed 3 times with deionized water, dried in an oven at 80℃, and ground into powder A using a ball mill.

[0044] S2, disperse 5g of powder A in 150mL of deionized water, adjust the pH to 3 with hydrochloric acid while stirring continuously, then add 0.8g of tannic acid and stir continuously at 50℃ for 2 hours. Slowly add 2.0g of NiCl2·6H2O to the solution. Finally, centrifuge at 800rpm for 3min, wash three times with deionized water, dry, grind, and sieve to obtain powder B.

[0045] S3. Take an appropriate amount of epoxy resin and diethylenetriamine and place them in a container at a ratio of 50:13, and stir continuously for 1 hour to obtain pure epoxy resin.

[0046] S4. Take an appropriate amount of epoxy resin, powder B, low melting point glass powder, graphene and diethylenetriamine and mix them in a ratio of 30:6:2:1:2. Stir evenly to obtain epoxy resin with added flame retardant system.

[0047] S5. Soak unidirectional flax fibers in a 2wt% sodium hydroxide solution for 3 hours. After removing them, wash them three times with deionized water. Then, immerse the flax fabric in deionized water at 30°C for 30 minutes. After removing it, place it in a vacuum oven at 60°C for 5 hours. Then, coat the surface of the unidirectional flax fibers with pure epoxy resin layer by layer to obtain plant fiber prepreg A.

[0048] S6, epoxy resin with added flame retardant is uniformly coated layer by layer onto the surface of unidirectional flax fiber to obtain plant fiber prepreg B.

[0049] S7. Two layers of plant fiber prepreg A are laid flat and placed in a mold under hot pressing. The gasket thickness is 1 mm. The prepreg is cured at 0.5 MPa and 80°C for 0.5 hours. After taking it out, four layers of plant fiber prepreg B are laid on top and bottom respectively. The prepreg is cured at 0.5 MPa and 80°C for 0.5 hours. Then, it is cured at 120°C for 2 hours. After cooling to room temperature, a flame-retardant sandwich structure composite material with a thickness of 3 mm is obtained.

[0050] Example 4

[0051] Based on the preparation method of the flame-retardant plant fiber composite material in Example 3, in this example,

[0052] Replace step S4 with "S4, take an appropriate amount of epoxy resin, powder B, low melting point glass powder, graphene and diethylenetriamine and mix them in a ratio of 30:6:2:1:2, stir evenly to obtain epoxy resin A with added flame retardant system; take an appropriate amount of epoxy resin and powder B, low melting point glass powder, graphene and diethylenetriamine and mix them in a ratio of 30:6:1:0.5:1, stir evenly to obtain epoxy resin B with added flame retardant system."

[0053] Replace step S6 with “S6, apply epoxy resin A with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg B, apply epoxy resin B with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg C.”

[0054] Replace step S7 with "S7, lay two layers of plant fiber prepreg A flat, place them in a mold under hot pressing, with a gasket thickness of 1 mm, pre-cur at 0.5 MPa and 80°C for 0.5 hours, remove and then lay a layer of plant fiber prepreg C and a layer of plant fiber prepreg B on top, pre-cur at 0.5 MPa and 80°C for 0.5 hours, then cure at 120°C for 2 hours, and after cooling to room temperature, obtain a flame-retardant gradient structure composite material with a thickness of 3 mm."

[0055] Example 5

[0056] The specific preparation method of the flame-retardant plant fiber composite material in this embodiment is as follows:

[0057] S1, 80g of ammonium polyphosphate was placed in 4000ml of deionized water and magnetically stirred at 30℃ for 1 hour until it was evenly dispersed to obtain an ammonium polyphosphate dispersion; then 1.6g of tris(hydroxymethyl)aminomethane and 1.5g of dopamine hydrochloride were added, and the pH was adjusted to 8.5 with NaOH solution. The mixture was stirred continuously at room temperature for 21 hours, centrifuged at 1200rpm for 3min, washed 5 times with deionized water, dried in an oven at 80℃, and ground into powder A using a ball mill.

[0058] S2, 10g of powder A was dispersed in 300mL of deionized water. The pH was adjusted to 3 with hydrochloric acid while continuously stirring. Then, 1.6g of tannic acid was added and the mixture was stirred continuously at 60℃ for 1 hour. 3.0g of NiCl2·6H2O was slowly added to the solution. Finally, the mixture was centrifuged at 1200rpm for 5min, washed three times with deionized water, dried, ground, and sieved to obtain powder B.

[0059] S3. Take an appropriate amount of epoxy resin and diethylenetriamine and place them in a container at a ratio of 50:13, and stir continuously for 1 hour to obtain pure epoxy resin.

[0060] S4. Take an appropriate amount of epoxy resin, powder B, low melting point glass powder, hexagonal boron nitride and diethylenetriamine and mix them in a ratio of 30:6:2:1:2. Stir evenly to obtain epoxy resin with added flame retardant system.

[0061] S5, unidirectional flax fibers are soaked in a 3wt% sodium hydroxide solution for 1 hour, then washed twice with deionized water. The flax fabric is then immersed in deionized water at 50°C for 30 minutes. After being removed, it is placed in a vacuum oven at 70°C for 5 hours. Pure epoxy resin is then evenly coated onto the surface of the unidirectional flax fibers layer by layer to obtain plant fiber prepreg A.

[0062] S6, epoxy resin with added flame retardant is uniformly coated layer by layer onto the surface of unidirectional flax fiber to obtain plant fiber prepreg B.

[0063] S7. Six layers of plant fiber prepreg A are laid flat and placed in a mold under hot pressing. The gasket thickness is 3mm. The mixture is pre-cured at 0.5MPa and 80℃ for 0.5 hours. After removing the mixture, six layers of plant fiber prepreg B are laid on top and bottom of it respectively. The mixture is pre-cured at 0.5MPa and 80℃ for 0.5 hours. Then it is cured at 120℃ for 2 hours. After cooling to room temperature, a flame-retardant sandwich structure composite material with a thickness of 9mm is obtained.

[0064] Example 6

[0065] Based on the preparation method of the flame-retardant plant fiber composite material in Example 5, in this example,

[0066] Replace step S4 with "S4, take an appropriate amount of epoxy resin, powder B, low melting point glass powder, hexagonal boron nitride and diethylenetriamine and mix them in a ratio of 30:6:2:1:2, stir evenly to obtain epoxy resin A with added flame retardant system; take an appropriate amount of epoxy resin and powder B, low melting point glass powder, hexagonal boron nitride and diethylenetriamine and mix them in a ratio of 30:6:1:0.5:1, stir evenly to obtain epoxy resin B with added flame retardant system."

[0067] Replace step S6 with “S6, apply epoxy resin A with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg B, apply epoxy resin B with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg C.”

[0068] Replace step S7 with "S7, lay six layers of plant fiber prepreg A flat, place them in a mold under hot pressing, with a gasket thickness of 3mm, pre-cur at 0.5MPa and 80℃ for 0.5 hours, remove and then lay six layers of plant fiber prepreg B on top, pre-cur at 0.5MPa and 80℃ for 0.5 hours, then cure at 120℃ for 2 hours, and after cooling to room temperature, obtain a flame-retardant gradient structure composite material with a thickness of 9mm."

[0069] Example 7

[0070] Based on the preparation method of flame-retardant plant fiber composite material in Example 1, in this example, the step S4 "mixing appropriate amounts of epoxy resin, powder B, low-melting-point glass powder, graphene oxide nanosheets, and diethylenetriamine in a ratio of 30:6:2:1:2" is replaced with "mixing appropriate amounts of epoxy resin, powder B, low-melting-point glass powder, graphene oxide nanosheets, and diethylenetriamine in a ratio of 30:6:4:2:4".

[0071] Example 8

[0072] Based on the preparation method of the flame-retardant plant fiber composite material in Example 7, in this example,

[0073] Replace step S4 with “S4, take an appropriate amount of epoxy resin, powder B, low melting point glass powder, graphene oxide nanosheets and diethylenetriamine and mix them in a ratio of 30:6:4:2:4, stir evenly to obtain epoxy resin A with added flame retardant system; take an appropriate amount of epoxy resin and powder B, low melting point glass powder, graphene oxide nanosheets and diethylenetriamine and mix them in a ratio of 30:6:2:1:2, stir evenly to obtain epoxy resin B with added flame retardant system.”

[0074] Replace step S6 with “S6, apply epoxy resin A with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg B, apply epoxy resin B with added flame retardant layer by layer evenly to the surface of unidirectional flax fiber to obtain plant fiber prepreg C.”

[0075] Replace step S7 with "S7, lay four layers of plant fiber prepreg A flat, place them in a mold under hot pressing, with a gasket thickness of 2mm, pre-cur at 0.5MPa and 80℃ for 0.5 hours, remove and then lay two layers of plant fiber prepreg C and two layers of plant fiber prepreg B on top, pre-cur at 0.5MPa and 80℃ for 0.5 hours, then cure at 120℃ for 2 hours, and after cooling to room temperature, obtain a 6mm thick flame-retardant gradient structure composite material."

[0076] Comparative Example 1

[0077] S1. Take an appropriate amount of epoxy resin and diethylenetriamine, place them in a container at a ratio of 50:13, and stir continuously for 0.5 hours to obtain pure epoxy resin.

[0078] S2, unidirectional flax fibers are soaked in a 2% sodium hydroxide solution for 3 hours, then washed 3 times with deionized water. The flax fabric is then immersed in a deionized water solvent at 30°C for 30 minutes. After removal, it is placed in a vacuum oven at 60°C, and pure epoxy resin is uniformly coated layer by layer on the surface of the unidirectional flax fibers to obtain plant fiber prepreg A.

[0079] S3, four layers of plant fiber prepreg A are laid flat and placed in a mold under hot pressing. The gasket thickness is 2mm. It is pre-cured at 0.5MPa and 80℃ for 0.5 hours, then cured at 120℃ for 2 hours. After cooling to room temperature, the composite material PFRP is obtained.

[0080] Figure 1 This is a comparison of the surface morphology of ammonium polyphosphate in Example 1 and Comparative Example 1 of the present invention. Figure 2 This refers to the changes in the surface element content of ammonium polyphosphate in Comparative Example 1 and ammonium polyphosphate in Example 1 when processed into powder A and powder B. Figure 3 It is the limiting oxygen index of the flame-retardant composite material in Example 1, Example 2 and Comparative Example 1 of this invention. Figure 4 The CO release rate of the flame-retardant composite materials in Example 1, Example 2 and Comparative Example 1 of this invention was tested using a cone calorimeter.

[0081] like Figure 1-4 As shown, the flexural strength of Comparative Example 1 is 154 MPa, and the peak heat release rate is 416.7 kW / m. 2 .

[0082] like Figure 1 As shown, the microstructure of ammonium polyphosphate in Example 1 and Comparative Example 1 was analyzed using scanning electron microscopy and X-ray energy dispersive spectroscopy. The ammonium polyphosphate in Comparative Example 1 exhibited a blocky structure and a smooth surface, while the surface of the ammonium polyphosphate in Example 1 became rough.

[0083] like Figure 2 As shown, the elemental content on the surface of powder B changed significantly, indicating that the modification was successful.

[0084] like Figure 3 As shown, the limiting oxygen index of Example 1 increased from 20.5% to 30.7%. After distribution optimization, the amount of flame retardant added was reduced by 50% compared to the randomly distributed blending method. The limiting oxygen index of Example 2 increased from 20.5% to 32.8%. After distribution optimization, the amount of flame retardant added was reduced by 33.3% compared to the randomly distributed blending method.

[0085] like Figure 4 As shown, the peak CO release of Comparative Example 1 was 0.26 g / s, the peak CO release of Example 1 was 0.12 g / s, and the peak CO release of Example 2 was 0.16 g / s. This is of great significance for reducing casualties in fires.

[0086] As can be seen from Examples 1-2, by controlling the distribution of the flame retardant system in the composite material, flame retardant composite materials with sandwich and gradient structures were constructed. This demonstrates that distribution control can effectively improve the flame retardant performance of the composite material while reducing the amount of flame retardant added, without deteriorating the original mechanical properties, thus achieving high-efficiency flame retardancy.

[0087] The limiting oxygen index of Example 3 reached 29.8%, and the flexural strength was 165 MPa.

[0088] Example 4 has a limiting oxygen index of 31.7% and a flexural strength of 170 MPa.

[0089] As can be seen from Examples 3-4, by controlling the distribution of the flame retardant system in the composite material, the amount of flame retardant added was significantly reduced. While maintaining the flame retardant performance, the addition of graphene (GO) improved the mechanical properties of the composite material.

[0090] Example 5 achieved a limiting oxygen index of 30.3%, and after distribution optimization, the amount of flame retardant added was reduced by 50% compared to the randomly distributed blending method, with a peak heat release rate of 163.4 kW / m³. 2 .

[0091] Example 6 achieved a limiting oxygen index of 31.6%, and after distribution optimization, the amount of flame retardant added was reduced by 33.3% compared to the randomly distributed blending method, with a peak heat release rate of 220.9 kW / m³. 2 .

[0092] Therefore, in Examples 5-6, by controlling the distribution of the flame retardant system in the composite material, the amount of flame retardant added is reduced while effectively improving the flame retardant performance of the composite material, and at the same time maintaining the original mechanical properties of the composite material, a balance between flame retardancy and mechanical properties is achieved.

[0093] The limiting oxygen index of Example 7 was 33.2%, and the flexural strength decreased by 11.4% compared to Comparative Example 1.

[0094] The limiting oxygen index of Example 8 was 35.7%, and the flexural strength decreased by 10.7% compared to Comparative Example 1.

[0095] Therefore, it can be seen that in Examples 7-8, excessive addition of flame retardant will still affect the mechanical properties of the composite material. Excessive addition will lead to agglomeration, which will affect the mechanical properties of the composite material.

[0096] The role and effect of the embodiments

[0097] According to the present invention, a flame-retardant plant fiber composite material and its preparation method are used in aviation and automotive interiors. Depending on the location of the structural components, the fire mode can be divided into unilateral thermal radiation fire and bilateral thermal radiation fire. Based on the fire mode, the present invention can directionally distribute the flame retardant in the thermal radiation area of ​​the real fire scene through structural control, which can realize the efficient utilization of the flame retardant, avoid the thermal decomposition of the composite material in the unpyrolysis area, and also prevent the flame retardant from remaining in the condensed phase.

[0098] This invention, by regulating the distribution of the flame-retardant system, significantly reduces the amount of flame retardant used while maintaining flame-retardant performance. After structural regulation and distribution optimization, the required amount can be reduced by 30%-50%. This flame-retardant system, requiring only about 7%, can achieve a limiting oxygen index of over 30% for the composite material, achieving a V-0 rating in the UL-94 test. Furthermore, it reduces the peak heat release rate and peak toxic gas release rate by 50%, exhibiting excellent flame-retardant performance, good flame-retardant efficiency, and significant potential for widespread application.

[0099] The flame retardant system and distribution optimization method of the present invention have excellent flame retardant effect, low cost, and simple preparation process. In addition, the experimental process of the present invention does not involve toxic solvents, has high safety, and is environmentally friendly, thus having broad application prospects.

[0100] This invention reduces the amount of flame retardant added by regulating the distribution of the flame retardant system in the composite material, thus saving costs. It also prevents agglomeration caused by excessive flame retardant addition, thereby avoiding affecting the mechanical properties of the composite material.

[0101] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a flame-retardant plant fiber composite material, characterized in that, Specifically, the steps include the following: S1, disperse the phosphorus-containing flame retardant in deionized water, stir continuously until uniformly dispersed, add polydopamine, adjust the pH value, stir thoroughly, filter, wash with deionized water, place in an oven to dry, grind thoroughly to obtain powder A; S2, disperse the powder A in deionized water, adjust the pH value, add tannic acid and stir, add NiCl2·6H2O, centrifuge, wash, dry, grind and sieve to obtain powder B; S3, Place epoxy resin and curing agent in a container and stir to obtain pure epoxy resin; S4, take two-dimensional sheet-like nanosheets, low-temperature molten glass powder and powder B, mix them together, then mix and stir with epoxy resin matrix, add curing agent and stir to obtain epoxy resin with added flame retardant system; S5. Select the desired type of plant fiber, cut, wash and dry it, and uniformly coat the pure epoxy resin onto the surface of the plant fiber to obtain plant fiber prepreg A. S6. Select the desired type of plant fiber, cut, wash and dry it, and uniformly coat the surface of the plant fiber with the epoxy resin containing the flame retardant system to obtain plant fiber prepreg B. S7. According to requirements, several layers of plant fiber prepreg A are placed in a mold and laid flat layer by layer. Pre-curing is performed for 0.2-0.8 hours to obtain plant fiber pre-cured layer A. Several layers of plant fiber prepreg B are then laid on the plant fiber pre-cured layer A and pre-cured for 0.2-0.8 hours to obtain plant fiber pre-cured layer B. Subsequently, it is cured at 100-140℃ for 1-3 hours and cooled to room temperature to obtain a 3-9 mm thick plant fiber reinforced resin matrix composite material with a flame retardant distribution structure. In step S1, the phosphorus-containing flame retardant is one or both of high-polymerization-degree ammonium polyphosphate and ammonium pyrophosphate.

2. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, The plant fiber is one or more of the following: flax fiber, ramie fiber, kenaf fiber, sisal fiber, cotton fiber, jute fiber, bamboo fiber, and seaweed fiber.

3. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S1, the pH is adjusted to the desired target value using 1-7 wt% sodium hydroxide or 1-5 wt% hydrochloric acid.

4. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S1, after dispersing the phosphorus-containing flame retardant in deionized water, the stirring time is 0.5-10 hours and the temperature is 20-80℃; the drying is vacuum drying at a temperature of 40-90℃; the deionized water washing is performed 3-6 times to fully remove residual sodium hydroxide or hydrochloric acid.

5. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, The two-dimensional sheet-like nanosheets in step S3 are one or more of graphene, graphene oxide, boron nitride, and molybdenum disulfide.

6. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S3, the mass ratio of epoxy resin to curing agent is 50:(10-16).

7. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S4, the ratio of epoxy resin matrix, powder B, low-temperature molten glass powder, two-dimensional sheet-like nanosheets and curing agent is 30:6:(2-4):(1-2):(2-4).

8. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S5, the flame retardant distribution structure of the plant fiber reinforced resin matrix composite material is one or more of a biomimetic gradient structure and a sandwich structure. When the distribution structure is a biomimetic gradient structure, the several layers of plant fiber prepreg B are laid on top of the plant fiber prepreg A.

9. The method for preparing the flame-retardant plant fiber composite material according to claim 1, characterized in that: in, In step S5, the flame retardant distribution structure of the plant fiber reinforced resin matrix composite material is one or more of a biomimetic gradient structure and a sandwich structure. When the distribution structure is a sandwich structure, the several layers of plant fiber prepreg B are respectively laid above and below the plant fiber prepreg A.

10. A flame-retardant plant fiber composite material, characterized in that: The flame-retardant plant fiber composite material was prepared by the preparation method according to any one of claims 1-9.

Images