Lva bionic plant fiber flame-retardant composite material and preparation method thereof

Abstract

The invention provides a lava bionic plant fiber flame-retardant composite material and a preparation method thereof, phytic acid, melamine and dopamine are used as main raw materials to synthesize a newest flame retardant, the flame retardant can catalyze cellulose and lignin in plant fibers to form stable carbon at low temperature, and a complete carbon skeleton is reserved; meanwhile, by using cheap low-melting-point glass powder and by virtue of the characteristic of low melting point, the low-melting-point glass powder can melt, flow and attach to a carbon skeleton formed at a low temperature at the initial stage of combustion, so that a compact ceramic protection carbon layer is formed on the carbon skeleton, and heat transfer and thermal degradation of an internal composite material are prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a lava bionic plant fiber flame retardant composite material and a preparation method thereof. Background Art

[0002] As people's environmental awareness gradually increases, the output and application of composite materials using plant fibers as raw materials have shown an increasing trend year by year. However, the limiting oxygen index of plant fibers themselves is relatively low, and their flammable properties greatly limit their further application in areas such as automobiles, rail transit, and construction that have strict requirements on flame retardancy. Therefore, improving the flame retardancy of plant fiber composite materials is a key issue in promoting the expansion of their application areas.

[0003] At present, the main method to improve the flame retardancy of plant fiber reinforced composite materials is to add flame retardants, and commonly used flame retardants mainly include ammonium polyphosphate, aluminum hypophosphite, graphene and nano flame retardants. However, this flame retardant modification method requires a large amount of addition, which leads to damage to the mechanical properties of the composite material, and does not take into account the unique combustion properties of plant fibers. When plant fibers are burned, the components such as cellulose and lignin contained in them can form a porous carbon skeleton structure after combustion, which provides a new idea for the implementation of the present invention.

[0004] Bionic design was formally proposed in 1961, and flame retardant bionic design has also received focus in recent years. Researchers have designed bionic leaf vein structure, bionic fish scale structure, etc. to achieve the balance of flame retardancy and mechanical properties. For example, patent CN115155536A, with the help of the characteristics of mussel adsorption surface, has designed a super hydrophobic flame retardant sponge that can be used for selective adsorption, using polydopamine to attach polypyrrole and silicon dioxide to the surface of melamine sponge, and then the sponge is modified with hexadecyltrimethoxysilane by the method of soaking, so as to achieve selective adsorption of super hydrophobic flame retardant sponge. The sponge has excellent hydrophobic lipophilic properties in oil and lipophilic properties in water, and has super strong adsorption capacity for the emulsion formed by various oils and organic solvents and water, even after multiple cycles of selective adsorption of super hydrophobic sponge can also maintain strong adsorption capacity. And for oil-in-water emulsion, the super hydrophobic sponge can also remove oil and water therein, and due to the flame retardancy of polypyrrole, the sponge has a flame retardant effect and can be used safely in a variety of environments. Invention patent CN111019123A utilizes two-dimensional lemstone nanosheets and graphene oxide nanosheets for compounding, in order to exert the synergistic effect between nanomaterials, greatly improving the flame retardant properties of polyamide 56 polymer. At the same time, dopamine is used to bionic modify the lemstone / graphene oxide nanocomposite material, which significantly improves the compatibility with polyamide 56 polymer and correspondingly improves the mechanical properties of polyamide 56 polymer. Patent CN118084703A discloses an amino acid-based composite flame retardant and its bionic preparation method, which is based on essential amino acids for organisms, and is prepared by phosphating bionic preparation under the action of corresponding metal catalysts / complexing agents to obtain a bio-based phosphated amino acid complex, and then salted with ammonia water, the organic solvent is removed, and the aqueous phase is spray-dried to convert it into the target bio-based composite flame retardant.

[0005] However, the current bionic flame retardant design method cannot meet the flame retardant requirements of plant fiber composite materials, and the existing bionic flame retardant design does not take into account the unique phenomenon that components such as cellulose and lignin in plant fibers can form a porous carbon skeleton structure after combustion. In addition, the current flame retardant modification ignores the mechanical performance requirements of composite materials. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a lava bionic plant fiber flame retardant composite material in order to solve the above problems. The flame retardant composite material has good flame retardant effect, is halogen-free and non-toxic, and can balance the flame retardant and mechanical properties of the composite material.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] A method for preparing a lava bionic plant fiber flame retardant composite material, the steps are as follows:

[0009] S1. Preparation of MPA flame retardant: adding phytic acid (PA) to a melamine (MEL) aqueous solution, stirring at high speed for reaction, and then centrifuging and drying to obtain MPA flame retardant;

[0010] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir it at high speed and adjust the pH value of the mixed solution to 8.5; add dopamine hydrochloride (PDA), stir it at high speed to react, centrifuge and dry the reaction product to obtain MPA@PDA flame retardant;

[0011] S3, prepreg preparation: adding MPA@PDA flame retardant to resin, stirring at high speed by ultrasonic, adding low melting point glass powder (GP) with a particle size of 5-10 μm, continuing ultrasonic stirring, and brushing the stirred mixed resin evenly on the natural fiber fabric, wherein the mass ratio of the mixed resin to the natural fiber fabric is 7:3-5:5, to prepare a natural fiber prepreg;

[0012] S4, compression molding: hot pressing pressure 2-10MPa, hot pressing temperature 50-150°C, hot pressing time 0.5-4h, to prepare lava bionic plant fiber flame retardant composite material.

[0013] As a further improvement of the present invention, the natural fiber fabric is a plant fiber fabric prepared by weaving plant fibers, and the plant fibers are one or more of kenaf fibers, jute fibers, hemp fibers, bamboo fibers, ramie fibers, cotton fibers, and sisal fibers.

[0014] As a further improvement of the present invention, the natural fiber fabric can be a woven fabric or a non-woven fabric, and the natural fiber fabric is a plain weave with a warp and weft density between 40 strands / 10 cm and 100 strands / 10 cm.

[0015] As a further improvement of the present invention, the rotation speed of the high-speed stirring reaction in S1, S2 and S3 is 600-800 rpm, the temperature is 30-90° C., and the time is 6-24 h.

[0016] As a further improvement of the present invention, the mass ratio of phytic acid to melamine in S1 is: (1-1.5): (1.5-2).

[0017] As a further improvement of the present invention, the mass ratio of the MPA flame retardant to dopamine hydrochloride in S2 is 20:(0.5-1).

[0018] As a further improvement of the present invention, the resin in S3 is one or more of epoxy resin, unsaturated polyester resin and phenolic resin.

[0019] As a further improvement of the present invention, the mass ratio of the MPA@PDA flame retardant, the resin and the low-melting-point glass powder in step S3 is: (5-20): 100: (5-10).

[0020] As a further improvement of the present invention, the ultrasonic power of the ultrasonic stirring in S3 is 400w or above.

[0021] The present invention also provides a lava bionic plant fiber flame retardant composite material, which is prepared by the aforementioned preparation method of the lava bionic plant fiber flame retardant composite material. The flame retardant performance of the lava bionic plant fiber flame retardant composite material is higher than UL-94V0 level; the limiting oxygen index is greater than 32%; the tensile strength is greater than 62.MPa; and the flexural strength is greater than 109MPa.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The preparation method of the lava bionic plant fiber flame retardant composite material of the present invention uses phytic acid, melamine and dopamine as main raw materials to synthesize the latest flame retardant, which can catalyze cellulose and lignin in plant fibers to form stable charcoal at low temperature and retain a complete carbon skeleton; at the same time, by using cheap low-melting point glass powder, with the help of its low melting point characteristics, it can begin to melt and flow at the initial stage of combustion and adhere to the carbon skeleton formed at low temperature, so as to form a dense ceramic protective carbon layer on the carbon skeleton, thereby preventing heat transfer and thermal degradation of the internal composite material.

[0024] 2. The preparation method of the lava bionic plant fiber flame retardant composite material of the present invention uses nano-scale low-melting point glass powder and uses ultrasonic stirring to evenly disperse the low-melting point glass powder in the resin during the preparation process, so that it can prevent the movement of the macromolecular chains of the composite material and improve the mechanical properties of the lava bionic plant fiber flame retardant composite material.

[0025] 3. The preparation method of the lava bionic plant fiber flame retardant composite material provided by the present invention is low-cost, clean and environmentally friendly. It can not only achieve excellent flame retardant properties of the composite material, but also improve the mechanical properties of the composite material, which is of great significance for its application in the fields of construction, automobiles, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the process of preparing the lava bionic plant fiber flame retardant composite material of the present application;

[0027] Figure 2 This is a scanning electron microscope image of the carbon layer of the MPA@PDA flame retardant plant fiber composite material in Comparative Example 4.

[0028] Figure 3This is a scanning electron microscope image of the lava bionic plant fiber flame retardant composite material of this application. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The flame retardant performance test standards are: "ASTM D3801 Self-supporting material vertical combustion test" and "GBT 8924-2005 Fiber reinforced plastic combustion performance test method oxygen index method".

[0031] The mechanical properties test standards are: "ASTM D3039 / D3039M-00 Standard Test Method for Tensile Properties of Polymer Matrix Composites" and "ASTM D790-10 Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials".

[0032] See also Figure 1 The method for preparing the lava bionic plant fiber flame retardant composite material of the present application includes the following steps:

[0033] S1. Preparation of MPA flame retardant: adding phytic acid to a melamine aqueous solution, stirring at high speed for reaction, and then centrifuging and drying to obtain MPA flame retardant;

[0034] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L and a pH value of 8.5, and stir it at high speed; add dopamine hydrochloride, stir it at high speed to react, and centrifuge and dry the reaction product to obtain MPA@PDA flame retardant;

[0035] S3, prepreg preparation: grinding the MPA@PDA flame retardant, adding the ground MPA@PDA flame retardant to the resin, stirring at high speed by ultrasonic, adding low-melting-point glass powder with a particle size of 5-10 μm, continuing ultrasonic stirring, and brushing the stirred mixed resin evenly on the natural fiber fabric, wherein the mass ratio of the mixed resin to the natural fiber fabric is 7:3-5:5, to prepare a natural fiber prepreg;

[0036] S4, compression molding: hot pressing pressure 2-10MPa, hot pressing temperature 50-150°C, hot pressing time 0.5-4h, to prepare lava bionic plant fiber flame retardant composite material.

[0037] Among them, in S1, the mass ratio of phytic acid to melamine is: (1-1.5): (1.5-2).

[0038] In S2, the ground MPA flame retardant powder is stirred and mixed with a Tris buffer solution with a concentration of 1.5 g / L. The stirring speed is 600-800 rpm. The stirring process lasts for more than 6 hours and can be up to 24 hours. This ensures that the MPA flame retardant powder is evenly dispersed in the Tris buffer solution, and effectively prevents the MPA flame retardant powder from agglomerating in the Tris buffer solution.

[0039] Furthermore, the mass ratio of MPA flame retardant powder to dopamine hydrochloride is controlled to be 20:(0.5-1), and stirring is also performed at a mixing speed of 600-800rpm; the pH of the mixture formed by mixing MPA flame retardant powder and Tris buffer is adjusted to 8.5 by adding a pH adjuster, and dopamine hydrochloride (PDA) is added thereto under the condition of pH 8.5, and the stirring reaction is continued, and the reaction product is centrifugally dried to obtain MPA@PDA flame retardant. During the stirring reaction, the setting of the pH value can cause dopamine hydrochloride to undergo a self-polymerization reaction, and then form a film coated on the surface of the MPA flame retardant powder; then the prepared lava biomimetic plant fiber flame retardant composite material is rich in dopamine; in this way, during the combustion process of the lava biomimetic plant fiber flame retardant composite material, the dopamine in the composite material can generate non-flammable gas CO on the one hand. 2 and NH 3 , diluting the combustible volatiles and oxygen concentrations produced during the combustion and decomposition of the lava bionic plant fiber flame retardant composite material; on the other hand, the benzene structure in dopamine can capture free radicals in the combustion process, thereby playing a role in free radical quenching and flame retardancy.

[0040] In S3, the resin is one or more of epoxy resin, unsaturated polyester resin, and phenolic resin; the mass ratio of MPA@PDA flame retardant, resin and low-melting point glass powder is: (5-20):100:(5-10); and the ultrasonic power of ultrasonic stirring of MPA@PDA, resin and low-melting point glass powder is 400w or above.

[0041] Furthermore, in S3, the natural fiber fabric is a plant fiber fabric prepared by weaving plant fibers, and the plant fibers are one or more of kenaf fiber, jute fiber, hemp fiber, bamboo fiber, ramie fiber, cotton fiber, and sisal fiber; and the natural fiber fabric can be a woven fabric or a non-woven fabric, and the natural fiber fabric is a plain weave with a warp and weft density between 40 strands / 10cm and 100 strands / 10cm.

[0042] Specifically, the natural fiber fabric can also be a non-plant fiber fabric, as long as it is woven from cellulose fibers. This ensures that during the combustion of the lava bionic plant fiber flame retardant composite material, the natural fiber fabric therein can form a carbon skeleton.

[0043] The following description will describe in detail the preparation method of the lava bionic plant fiber flame retardant composite material of the present application with specific examples; it should be noted that in the following examples, the natural fiber fabric is a plain weave with a warp and weft density of 50 strands / 10 cm.

[0044] Example 1

[0045] The preparation method of lava bionic plant fiber flame retardant composite material comprises the following steps:

[0046] S1. Preparation of MPA flame retardant: 0.04 mol phytic acid solution was added to 0.2 mol / L melamine aqueous solution, stirred at 400 rpm at 85°C for 0.5 h, then centrifuged and dried to obtain MPA flame retardant;

[0047] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir it evenly at 600 rpm at 30°C, adjust the pH of the mixture formed by mixing the MPA flame retardant powder and the Tris buffer to 8.5 by adding a pH adjuster, then add 0.5 g of dopamine hydrochloride, stir it at 600 rpm at 30°C, and then centrifuge and dry it to obtain MPA@PDA flame retardant. In this embodiment, the pH adjuster is a 1 mol / L NaOH solution;

[0048] S3, prepreg preparation: grind the MPA@PDA flame retardant to obtain MPA@PDA flame retardant powder with a particle size of 5-10 μm, mix the MPA@PDA flame retardant powder and epoxy resin in a mass fraction ratio of 5:100, ultrasonically stir (you can try to give an approximate time to determine whether the stirring is complete), rotate at 500 rpm, obtain a mixed resin, and evenly brush the mixed resin on the natural fiber fabric in a mass ratio of 7:3-5:5 of the mixed resin: natural fiber fabric to prepare a natural fiber prepreg;

[0049] S4, compression molding: set the hot pressing pressure to 5 MPa, the hot pressing temperature to 50°C, and the hot pressing time to 4 h, and perform compression molding on the natural fiber prepreg to prepare a lava bionic plant fiber flame retardant composite material.

[0050] Example 2

[0051] The preparation method of lava bionic plant fiber flame retardant composite material comprises the following steps:

[0052] S1. Preparation of MPA flame retardant: 0.04 mol phytic acid solution was added to 0.2 mol / L melamine aqueous solution, stirred at 400 rpm at 85°C for 0.5 h, then centrifuged and dried to obtain MPA flame retardant;

[0053] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir it evenly at 600 rpm at 30°C, adjust the pH of the mixture formed by mixing the MPA flame retardant powder and the Tris buffer to 8.5 by adding a pH adjuster, then add 0.5 g of dopamine hydrochloride, stir it at 600 rpm at 30°C, and then centrifuge and dry it to obtain MPA@PDA flame retardant. In this embodiment, the pH adjuster is a 1 mol / L NaOH solution;

[0054] S3, prepreg preparation: grind the MPA@PDA flame retardant to obtain MPA@PDA flame retardant powder with a particle size of 5-10 μm, mix the MPA@PDA flame retardant powder and epoxy resin in a mass fraction ratio of 5:100, ultrasonically stir at a speed of 500 rpm, then add low-melting point glass powder (the addition amount is 5% of the mass of the epoxy resin), continue ultrasonic stirring to obtain a mixed resin, and evenly brush the mixed resin on the natural fiber fabric in a mass ratio of 7:3-5:5 of the mixed resin: natural fiber fabric to prepare a natural fiber prepreg;

[0055] S4. Compression molding: The natural fiber prepreg is compression molded at a hot pressing pressure of 5 MPa, a hot pressing temperature of 50° C., and a hot pressing time of 4 h to prepare a lava bionic plant fiber flame retardant composite material.

[0056] Example 3

[0057] The preparation method of lava bionic plant fiber flame retardant composite material comprises the following steps:

[0058] S1. Preparation of MPA flame retardant: 0.04 mol phytic acid solution was added to 0.2 mol / L melamine aqueous solution, stirred at 400 rpm at 85°C for 0.5 h, then centrifuged and dried to obtain MPA flame retardant;

[0059] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir it evenly at 600 rpm at 30°C, adjust the pH of the mixture formed by mixing the MPA flame retardant powder and the Tris buffer to 8.5 by adding a pH adjuster, then add 0.5 g of dopamine hydrochloride, stir it at 600 rpm at 30°C, and then centrifuge and dry it to obtain MPA@PDA flame retardant. In this embodiment, the pH adjuster is a 1 mol / L NaOH solution;

[0060] S3, prepreg preparation: grind the MPA@PDA flame retardant to obtain MPA@PDA flame retardant powder with a particle size of 5-10 μm, mix the MPA@PDA flame retardant powder and epoxy resin in a mass fraction ratio of 10:100, ultrasonically stir at a speed of 500 rpm, then add low-melting point glass powder (the addition amount is 10% of the mass of the epoxy resin), continue ultrasonic stirring to obtain a mixed resin, and evenly brush the mixed resin on the natural fiber fabric in a mass ratio of 7:3-5:5 of the mixed resin: natural fiber fabric to prepare a natural fiber prepreg;

[0061] S4. Compression molding: The natural fiber prepreg is compression molded at a hot pressing pressure of 5 MPa, a hot pressing temperature of 50° C., and a hot pressing time of 4 h to prepare a lava bionic plant fiber flame retardant composite material.

[0062] Example 4

[0063] The preparation method of lava bionic plant fiber flame retardant composite material comprises the following steps:

[0064] S1. Preparation of MPA flame retardant: 0.04 mol phytic acid solution was added to 0.2 mol / L melamine aqueous solution, stirred at 400 rpm at 85°C for 0.5 h, then centrifuged and dried to obtain MPA flame retardant;

[0065] S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir it evenly at 600 rpm at 30°C, adjust the pH of the mixture formed by mixing the MPA flame retardant powder and the Tris buffer to 8.5 by adding a pH adjuster, then add 0.5 g of dopamine hydrochloride, stir it at 600 rpm at 30°C, and then centrifuge and dry it to obtain MPA@PDA flame retardant. In this embodiment, the pH adjuster is a 1 mol / L NaOH solution;

[0066] S3, prepreg preparation: grind the MPA@PDA flame retardant to obtain MPA@PDA flame retardant powder with a particle size of 5-10 μm, mix the MPA@PDA flame retardant powder and epoxy resin in a mass fraction ratio of 20:100, ultrasonically stir at a speed of 500 rpm, then add low-melting point glass powder (the addition amount is 10% of the mass of the epoxy resin), continue ultrasonic stirring to obtain a mixed resin, and according to the mass ratio of the mixed resin to natural fiber fabric of 7:3-5:5, then evenly brush the mixed resin on the fiber to make a natural fiber prepreg;

[0067] S4. Compression molding: The natural fiber prepreg is compression molded at a hot pressing pressure of 5 MPa, a hot pressing temperature of 50° C., and a hot pressing time of 4 h to prepare a lava bionic plant fiber flame retardant composite material.

[0068] Comparative Example 1:

[0069] The difference between this comparative example and Example 1 is that the phytic acid in Example 1 is used alone to prepare the plant fiber flame retardant composite material.

[0070] (1) 0.04 mol of phytic acid is prepared into a 100 ml solution, and the plant fiber is modified by using the solution. After the modification, the plant fiber is placed in an oven at 80° C. for 2 h, and then epoxy resin is evenly brushed on the fiber to prepare a natural fiber prepreg;

[0071] (2) Compression molding: The lava bionic plant fiber flame retardant composite material is prepared by compression molding process, with a hot pressing pressure of 2-10 MPa, a hot pressing temperature of 50-150°C, and a hot pressing time of 0.5-4 h.

[0072] Comparative Example 2

[0073] The difference between this comparative example and Example 1 is that melamine is used alone to prepare the plant fiber flame retardant composite material.

[0074] (1) adding 0.2 mol of melamine to epoxy resin, stirring with ultrasound at a speed of 500 rpm, and then brushing the epoxy resin evenly on the fiber to prepare a natural fiber prepreg;

[0075] (2) Compression molding: The lava bionic plant fiber flame retardant composite material is prepared by compression molding process, with a hot pressing pressure of 2-10 MPa, a hot pressing temperature of 50-150°C, and a hot pressing time of 0.5-4 h.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that MPA is used alone to prepare the plant fiber flame retardant composite material.

[0078] (1) adding MPA with a resin mass fraction of 20% to epoxy resin, stirring with ultrasound at a speed of 500 rpm, and then brushing the epoxy resin evenly on the fiber to prepare a natural fiber prepreg;

[0079] (2) Compression molding: The lava bionic plant fiber flame retardant composite material is prepared by compression molding process, with a hot pressing pressure of 2-10 MPa, a hot pressing temperature of 50-150°C, and a hot pressing time of 0.5-4 h.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that MPA@PDA is used alone to prepare the plant fiber flame retardant composite material.

[0082] (1) MPA@PDA with a resin mass fraction of 10% was added to epoxy resin, ultrasonically stirred at a speed of 500 rpm, and then the epoxy resin was evenly brushed on the fiber to prepare a natural fiber prepreg;

[0083] (2) Compression molding: The lava bionic plant fiber flame retardant composite material is prepared by compression molding process, with a hot pressing pressure of 2-10 MPa, a hot pressing temperature of 50-150°C, and a hot pressing time of 0.5-4 h.

[0084] The comparative examples are generally used to prove that the method can improve the performance of the composite material; our solution involves: MPA flame retardant, MPA@PDA flame retardant, preferably a comparative example that can supplement MPA@PDA flame retardant to further illustrate the advantages of the present invention.

[0085] It should be noted that: the present invention detects the flame retardant properties of the composite material by a limiting oxygen index tester and a vertical combustion test. The flame retardant properties of the above embodiments 1-3 and comparative examples 1-2 are shown in Table 1; at the same time, the test results of the mechanical test performance comparison between the above embodiments 1-3 and comparative examples 1-2 are shown in Table 2.

[0086] Table 1 Comparison of flame retardant properties between the examples and the comparative examples

[0087] Test items UL 94 Vertical Burning Limiting oxygen index / % Example 1 NR 23.2 Example 2 NR 24.2 Example 3 V1 26.4 Example 4 V0 32.1 Comparative Example 1 V1 27.8 Comparative Example 2 NR 23.5 Comparative Example 3 V0 30.1 Comparative Example 4 V1 25.8

[0088] Table 2 Comparison of mechanical properties between Example 1 and Comparative Example

[0089]

[0090]

[0091] It can be seen from Examples 1-4 that the flame retardant property of the flame retardant plant fiber reinforced epoxy resin composite material in the present application reaches UL-94V0 level, and the tensile strength and flexural strength are at least 71.8% higher than those of the composite material in Comparative Examples 1-2.

[0092] Further reading Figure 2 As shown, this is a scanning electron microscope image of the plant fiber flame retardant composite material prepared using MPA@PDA alone in Comparative Example 4 of the present application. It can be clearly seen that although a relatively dense carbon layer is formed on the plant fiber carbon layer skeleton, there are still many pores between the carbon layers, and the plant fiber carbon layer skeleton can be clearly seen.

[0093] See also Figure 3 As shown, it is a scanning electron microscope image of the lava bionic plant fiber flame retardant composite material prepared by the preparation method of the lava bionic plant fiber flame retardant composite material of the present application. It can be clearly seen that a dense carbon layer is formed on the surface of the lava bionic plant fiber flame retardant composite material, and the carbon layer is evenly covered on the plant fiber carbon layer skeleton, so that the plant fiber carbon layer skeleton cannot be observed. This is because the low-melting point glass powder is fully filled on the plant fiber carbon layer skeleton during the preparation process. In this way, during the combustion process of the lava bionic plant fiber flame retardant composite material, the low-melting point glass powder will melt and flow at a lower temperature, and then evenly cover the plant fiber carbon layer skeleton, and then form a layer of dense ceramic structure on the plant fiber carbon layer skeleton. In this way, the dense ceramic structure formed by the melting of the low-melting point glass powder can prevent heat transfer during the combustion process and thermal degradation of the internal composite material, thereby achieving a flame retardant effect.

[0094] By comparing Examples 1-4 with Comparative Example 1, it can be seen that the flame retardancy of the plant fiber flame retardant fat composite material prepared by adding phytic acid alone is UL-94V1, the limiting oxygen index is 27.8%, and the tensile strength and flexural strength are 31.23MPa and 48.91MPa, respectively; while the flame retardant performance of the lava bionic plant fiber flame retardant composite material in the present application can reach UL-94V0 level, the limiting oxygen index is 32.1%; the tensile and flexural strengths are 62.56MPa and 109.08MPa or more, respectively; relative to the flame retardant composite material to which phytic acid is added alone, the flame retardant performance rises to UL-94V0 level, the limiting oxygen index is increased by 15.47%, the tensile and flexural strengths are increased by at least 100.32% and 123.0%, respectively, and the flame retardancy and mechanical properties of the composite material prepared by the present application are significantly enhanced.

[0095] By comparing Examples 1-4 with Comparative Example 2, it can be seen that the flame retardancy of the plant fiber flame retardant resin composite material prepared by adding melamine alone is UL-94 non-grade, the limiting oxygen index is 23.5%, and the tensile strength and flexural strength are 36.27MPa and 72.55MPa respectively; while the flame retardant performance of the lava bionic plant fiber flame retardant composite material in the present application is UL-94V0 grade, the limiting oxygen index is 32.1%; the tensile and flexural strengths are 62.56MPa and 109.08MPa or more respectively; relative to the flame retardant composite material to which melamine is added alone, the flame retardant performance is increased from UL-94 non-grade to UL-94V0 grade, the limiting oxygen index is increased by 36.60%, the tensile and flexural strengths are increased by at least 72.48% and 50.4% or more respectively, and the flame retardancy and mechanical properties of the composite material prepared by the present application are significantly enhanced.

[0096] By comparing Examples 1-4 with Comparative Example 3, it can be seen that the flame retardant properties of the plant fiber flame retardant resin composite material prepared by adding MPA alone are UL-94V0 level, the limiting oxygen index is 30.1%, and the tensile strength and flexural strength are 31.43MPa and 59.73MPa respectively; while the flame retardant properties of the lava bionic plant fiber flame retardant composite material in the present application are UL-94V0 level, the limiting oxygen index is 32.1%; the tensile and flexural strengths are 62.56MPa and 109.08MPa or more respectively; relative to the flame retardant composite material to which MPA is added alone, the flame retardant properties increase from a limiting oxygen index of 30.1% to 32.1%, the tensile and flexural strengths increase by more than 99.05% and 82.6% respectively, and the flame retardancy and mechanical properties of the composite material prepared by the present application are significantly enhanced.

[0097] By comparing Examples 1-4 with Comparative Example 4, it can be seen that the flame retardant properties of the plant fiber flame retardant resin composite material prepared by adding MPA@PDA alone are UL-94V1 level, the limiting oxygen index is 25.8%, and the tensile strength and flexural strength are 56.41MPa and 90.87MPa respectively; while the flame retardant properties of the lava bionic plant fiber flame retardant composite material in the present application are UL-94V0 level, the limiting oxygen index is 32.1%; the tensile and flexural strengths are 62.32MPa and 109.08MPa or more respectively; relative to the flame retardant composite material to which MPA@PDA is added alone, the flame retardant properties rise to UL-94V0 level, the limiting oxygen index is increased by 24.42%, the tensile and flexural strengths are increased by 10.48% and 20.04% or more respectively, and the flame retardancy and mechanical properties of the composite material prepared by the present application are significantly enhanced.

[0098] In summary, the flame retardant effect and mechanical properties of plant fiber composite materials modified by phytic acid, melamine, MPA or MPA@PDA alone do not achieve the ideal effect. The flame retardant property of the composite material prepared by the present application reaches UL-94V0 level, so the lava bionic plant fiber flame retardant composite material in the present application can improve the flame retardant property and mechanical properties of the cured product.

[0099] The mechanical properties of the plant fiber composites after adding different flame retardants in the comparative example are poor because the addition of flame retardants affects the interface bonding effect of the composites, so its mechanical properties are poor. However, the plant fiber reinforced composites modified by MPA@PDA-GP have improved the mechanical properties of the composites to varying degrees because MPA@PDA and low-melting-point glass powder limit the movement of the macromolecular chains of the composites.

[0100] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for illustrating the principles of the present invention. Improvements and modifications made without departing from the scope of the present invention fall within the scope of the invention claimed for protection.

Claims

1. A method for preparing a lava bionic plant fiber flame retardant composite material, the steps are as follows: S1. Preparation of MPA flame retardant: adding phytic acid to a melamine aqueous solution, stirring at high speed for reaction, and then centrifuging and drying to obtain MPA flame retardant; S2. Preparation of MPA@PDA flame retardant: Grind the MPA flame retardant into a powder with a particle size of 5-10 μm, add it to a Tris buffer with a concentration of 1.5 g / L, stir at high speed and adjust the pH value of the mixed solution to 8.5; add dopamine hydrochloride, stir at high speed to react, centrifuge and dry the reaction product to obtain MPA@PDA flame retardant; S3, prepreg preparation: grinding the MPA@PDA flame retardant, adding the ground MPA@PDA flame retardant to the resin, stirring at high speed by ultrasonic, adding low-melting-point glass powder with a particle size of 5-10 μm, continuing ultrasonic stirring, and brushing the stirred mixed resin evenly on the natural fiber fabric, wherein the mass ratio of the mixed resin to the natural fiber fabric is 7:3-5:5, to prepare a natural fiber prepreg; S4, compression molding: hot pressing pressure 2-10MPa, hot pressing temperature 50-150°C, hot pressing time 0.5-4h, to prepare lava bionic plant fiber flame retardant composite material.

2. The method for preparing a lava bionic plant fiber fabric flame retardant composite material according to claim 1, characterized in that: The natural fiber fabric is a plant fiber fabric prepared by weaving plant fibers, and the plant fibers are one or more of kenaf fibers, jute fibers, hemp fibers, bamboo fibers, ramie fibers, cotton fibers, and sisal fibers.

3. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The natural fiber fabric can be a woven fabric or a non-woven fabric. The natural fiber fabric is a plain weave with a warp and weft density between 40 strands / 10cm and 100 strands / 10cm.

4. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The high-speed stirring reaction in S1, S2 and S3 has a rotation speed of 600-800 rpm, a temperature of 30-90° C., and a time of 6-24 h.

5. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The mass ratio of phytic acid to melamine in S1 is: (1-1.5): (1.5-2).

6. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The mass ratio of the MPA flame retardant powder to dopamine hydrochloride in S2 is 20:(0.5-1).

7. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The resin in S3 is one or more of epoxy resin, unsaturated polyester resin and phenolic resin.

8. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: In the step S3, the mass ratio of the MPA@PDA flame retardant, the resin and the low-melting-point glass powder is: (5-20): 100: (5-10).

9. The method for preparing a lava bionic plant fiber flame retardant composite material according to claim 1, characterized in that: The ultrasonic power of the ultrasonic stirring in S3 is 400w or above.

10. A lava bionic plant fiber flame retardant composite material, characterized by: The lava bionic plant fiber flame retardant composite material is prepared by the preparation method of any one of claims 1 to 9, wherein the flame retardant performance of the lava bionic plant fiber flame retardant composite material is higher than UL-94V0 level; the limiting oxygen index is greater than 32%; the tensile strength is greater than 62.MPa; and the flexural strength is greater than 109MPa.

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