Preparation method of preform for flame-retardant and smoke-suppressing bamboo fiber composite material

Abstract

The present invention provides a method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material. First, a flame retardant aqueous solution is prepared using low-polymerization degree ammonium polyphosphate and nano-magnesium hydroxide. Then, an integrated process of bamboo fiber flame-retardant modification and fiber preform molding is used to attach the flame retardant to the surface and interior of the bamboo fiber to prepare a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material. The preparation of the flame retardant aqueous solution in the present invention allows the flame retardant to fully impregnate the pore structure of the bamboo fiber, giving full play to the flame retardant advantage of ammonium polyphosphate and the smoke suppression advantage of nano-magnesium hydroxide, while making up for the shortcomings of a single flame retardant. The preform obtained by the present invention is used to prepare a flame-retardant and smoke-suppressing bamboo fiber composite material, which is not only beneficial to improving the performance of the bamboo fiber composite material, but also effectively prevents the loss of the flame retardant, making up for the shortcomings of the bamboo fiber composite material in the field of flame retardancy, and meeting the safety requirements in application fields such as automobiles and furniture.

Description

Technical Field

[0001] The invention belongs to the technical field of bamboo material processing, and particularly relates to a preparation method and application of a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material. Background Art

[0002] Bamboo fiber, a natural plant fiber, boasts advantages such as rapid growth, high specific strength, and affordability. Composite materials made from bamboo fiber are increasingly in demand for applications such as automotive interiors, building materials, and aerospace. However, bamboo fiber is flammable and has a low ignition point. Rapid combustion also releases large amounts of thick smoke, and the "wick effect" of bamboo fiber composites makes them unsuitable for use in certain sectors, particularly the construction industry. Most fire victims die after inhaling smoke and toxic gases, leading to coma and subsequent death. Therefore, bamboo fiber composites must possess both flame retardancy and smoke suppression properties.

[0003] Ammonium polyphosphate, a phosphorus-based flame retardant with low toxicity, low corrosiveness, and excellent thermal stability, is widely used in flame-retardant composite materials. However, ammonium polyphosphate is highly hygroscopic and susceptible to moisture, which can easily migrate to the material surface. Furthermore, combustion of ammonium polyphosphate produces a large amount of smoke, which affects the material's flame retardancy and smoke suppression properties. Nanomagnesium hydroxide, a new nanomaterial, does not release toxic gases or corrosive substances during combustion and can be used at higher processing temperatures, thus exhibiting excellent smoke suppression and thermal stability. However, an addition level of up to 60wt% is typically required to achieve acceptable flame retardancy, and high addition levels inevitably deteriorate the material's mechanical properties.

[0004] Bamboo fiber preforms are a key step in the preparation of flame-retardant and smoke-suppressing bamboo fiber composites. Currently, fiber preforms are commonly prepared using methods such as hand-laying, needle-punching, and non-woven airflow processing. However, for bamboo fibers, hand-laying is highly susceptible to operator skill and proficiency, while needle-punching and non-woven airflow processing can damage the fibers during mechanical processing. The addition of flame retardants can lead to uneven fiber dispersion and inevitably form an isolation layer between the fibers and the matrix, reducing the effective bonding area. This, combined with the effects of physical and mechanical processing, further deteriorates the mechanical properties of the composite material. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide a method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material. The present invention uses low-polymerization ammonium polyphosphate and nano-magnesium hydroxide to prepare a flame retardant aqueous solution. The flame retardant is then attached to the surface and interior of the bamboo fiber using an integrated bamboo fiber flame-retardant modification and fiber preform molding process to produce a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material. The preform obtained by the present invention is used to prepare a flame-retardant and smoke-suppressing bamboo fiber composite material, effectively resolving the difficulty in achieving a combination of flame retardancy, smoke suppression, and mechanical properties during the preparation of bamboo fiber composite materials.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a preform for a flame retardant and smoke suppressing bamboo fiber composite material, the method comprising:

[0007] S1. Preparation of flame retardant aqueous solution: prepared by mixing deionized water and flame retardant, wherein the mass ratio of deionized water to flame retardant is 9:1;

[0008] The flame retardant is composed of the following raw materials in parts by mass: 5-7 parts of ammonium polyphosphate, 3-5 parts of nano magnesium hydroxide, 0.6-1.2 parts of flow modifier, 0.6-0.8 parts of silane coupling agent, and 0.1-0.6 parts of compatibilizer;

[0009] The flame retardant aqueous solution is prepared by: first, grinding ammonium polyphosphate with a powder grinder at a rotation speed of 2000-3000 r / min for 5-8 minutes, so that the particle size of the ammonium polyphosphate powder after grinding is 1-2 μm; then, mixing the flame retardant components with deionized water according to a mass ratio, stirring at 600-800 r / min at room temperature for 30 minutes until the mixture is completely dissolved into a colorless transparent liquid, and then standing to obtain a flame retardant aqueous solution with a concentration of 10%;

[0010] S2. Bamboo fiber pretreatment: Select straight bamboo fibers with no obvious curls and a length of 1.5 to 4.5 cm, place them evenly under microwave radiation for pretreatment, and then evenly spread the treated bamboo fibers on a 60-mesh sieve;

[0011] S3. Preparation of a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials: place the sieve filled with bamboo fibers described in S2 in the flame retardant aqueous solution obtained in S1, and impregnate it under ultrasonic conditions; after the impregnation is completed, take out the sieve, clean the surface of the bamboo fiber, and then place it in a 50°C oven to dry for 48 hours to obtain a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials.

[0012] Preferably, the degree of polymerization of the ammonium polyphosphate in S1 is less than 20, and the particle size is 10 to 15 μm.

[0013] Preferably, the particle size of the nano magnesium hydroxide in S1 is 30 to 50 nm.

[0014] Preferably, the flow modifier in S1 is an amide lubricant, a silicone lubricant or a stearic acid lubricant.

[0015] Preferably, the silane coupling agent in S1 is KH550, KH560 or KH570.

[0016] Preferably, the compatibilizer in S1 is PE-g-MAH, PP-g-MAH or EPDM-g-MAH.

[0017] Preferably, the power of the microwave radiation in S2 is 700-800W, and the time is 30-40s.

[0018] Preferably, the power of the ultrasonic device in S3 is 600-720W, the frequency is 20-40KHz, and the time is 10-20min.

[0019] Preferably, the moisture content of the flame-retardant and smoke-suppressing bamboo fiber composite material preform in S3 is ≤5%.

[0020] The present invention also provides an application of a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material prepared by the preparation method, wherein the preform is used to prepare the flame-retardant and smoke-suppressing bamboo fiber composite material.

[0021] The reaction mechanism of the low polymerization degree ammonium polyphosphate and nano magnesium hydroxide synergistic flame retardant in the present invention is shown in Figure 1 During the combustion process, ammonium polyphosphate will degrade with the loss of water and ammonia to produce polyphosphoric acid (1); nano magnesium hydroxide will degrade due to the loss of water to produce magnesium oxide (2); at the same time, nano magnesium hydroxide provides proton exchange as a synergist, reacts with ammonium polyphosphate, promotes the evolution of water and ammonia and creates bridges between molecular chains, promotes the formation of magnesium metaphosphate, effectively prevents the volatilization of phosphorus and enhances the density of the carbon layer (3). The reaction mechanism of the synergistic flame retardancy of ammonium polyphosphate and nano magnesium hydroxide is a condensation phase mechanism and a gas phase mechanism. On the one hand, the generated substances contribute to the formation of a dense charred layer. On the other hand, non-combustible gases such as ammonia help dilute combustible gases and reduce the heat of the flame, forming a more effective protection for the material. This synergistic flame retardant system not only makes up for the shortcomings of ammonium polyphosphate's poor dispersion performance and large smoke, and nano magnesium hydroxide's low flame retardant efficiency and large addition amount when used separately, but also gives full play to the advantages of ammonium polyphosphate in inhibiting combustion and nano magnesium hydroxide in diluting smoke. Compared with the synthesis of new flame retardants, this system has simple production conditions, is halogen-free, and has low cost, making it suitable for large-scale promotion.

[0022] The present invention has significant technical effects due to the adoption of the above technical solutions:

[0023] 1. The present invention provides a method for preparing a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials, wherein low-polymerization degree ammonium polyphosphate and nano magnesium hydroxide are prepared into a flame retardant aqueous solution, and then a bamboo fiber flame retardant modification and fiber preform molding integrated process is used to attach the flame retardant to the surface and interior of the bamboo fiber to prepare a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials. The preparation process of the preform for flame-retardant and smoke-suppressing bamboo fiber composite materials of the present invention is simple. The preform obtained by the present invention is used to prepare flame-retardant and smoke-suppressing bamboo fiber composite materials, which can solve the problem of difficulty in achieving flame retardant properties, smoke suppression properties and mechanical properties in the preparation process of bamboo fiber composite materials, effectively make up for the shortcomings of bamboo fiber composite materials in the field of flame retardancy, meet the safety requirements in application fields such as automobiles and furniture, and are conducive to the development of bamboo fiber composite materials in more fields. It is of great significance for improving the competitiveness of bamboo fiber composite materials and expanding development paths.

[0024] 2. The present invention uses low-polymerization ammonium polyphosphate and nano-magnesium hydroxide for synergistic flame retardancy, effectively leveraging the flame retardant advantages of the former and the smoke suppression advantages of the latter. It also overcomes the shortcomings of ammonium polyphosphate, which has poor dispersibility and produces a lot of smoke, while nano-magnesium hydroxide has low flame retardant efficiency and requires a large addition amount when used separately. Low-polymerization ammonium polyphosphate and nano-magnesium hydroxide are readily soluble in water. When prepared into a flame retardant aqueous solution, the flame retardant can fully impregnate the pore structure of the bamboo fiber, facilitating its entry into the surface and interior of the bamboo fiber. This also reduces the amount of flame retardant used, fully utilizing their respective advantages in flame retardancy and smoke suppression during combustion, and promoting a synergistic effect in carbonization through esterification and cross-linking reactions.

[0025] 3. The present invention adopts an integrated process of flame-retardant modification of bamboo fiber and fiber preform molding. While impregnating with flame retardant, a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials is prepared by wet layering method. The flame retardant aqueous solution is filled into the solution suspension device, which can give the bamboo fiber excellent dispersibility in the solution under ultrasonic state. The bamboo fiber under suspension and vibration has greater freedom and can be fully dispersed and stretched and interpenetrated in three directions to form an interlocking structure, thereby improving the interface bonding ability. At the same time, the bamboo fiber treated with microwave radiation is cracked due to the destruction of weak points, which is more conducive to the attachment of flame retardant to the inside of the fiber, thereby fully realizing the flame retardant impregnation treatment. The preform structure for flame-retardant bamboo fiber composite materials prepared by the present invention is not only conducive to improving the performance of the composite material, but also can effectively prevent the loss of flame retardant.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a diagram of the synergistic flame retardant reaction mechanism of ammonium polyphosphate and nano-magnesium hydroxide of the present invention.

[0028] Figure 2This is a morphology diagram of the preform for the flame-retardant and smoke-suppressing bamboo fiber composite material according to Example 1 of the present invention. DETAILED DESCRIPTION

[0029] Example 1

[0030] This embodiment is a method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material, which comprises:

[0031] S1. Preparation of flame retardant aqueous solution: prepared by mixing deionized water and flame retardant, wherein the mass ratio of deionized water to flame retardant is 9:1;

[0032] The flame retardant is composed of the following raw materials in parts by mass: 5 parts of ammonium polyphosphate, 5 parts of nano magnesium hydroxide, 0.6 parts of amide lubricant, 0.8 parts of KH550, and 0.6 parts of PE-g-MAH; the degree of polymerization of the ammonium polyphosphate is less than 20, and the particle size is 10 to 15 μm; the particle size of the nano magnesium hydroxide is 30 to 50 nm;

[0033] The flame retardant aqueous solution is prepared by: first, using a powder grinder to grind ammonium polyphosphate at a rotation speed of 3000 r / min for 5 minutes, so that the particle size of the ammonium polyphosphate powder after grinding is 1 to 2 μm; then, mixing the flame retardant components with deionized water according to a mass ratio, stirring at 600 r / min at room temperature for 30 minutes until the mixture is completely dissolved into a colorless transparent liquid, and then allowing the mixture to stand, thereby obtaining a flame retardant aqueous solution with a concentration of 10%;

[0034] S2. Bamboo fiber pretreatment: Select straight bamboo fibers with no obvious curls and a length of 1.5 to 3 cm, and manually sort out impurities and incompletely dispersed fibers. The sorted fibers are evenly placed under microwave radiation at 800 W for 30 seconds, then removed and evenly spread on a 300 mm x 250 mm 60-mesh sieve.

[0035] S3. Preparation of a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials: Place the sieve filled with bamboo fibers described in S2 in an ultrasonic device filled with the flame retardant aqueous solution obtained in S1, and immerse it in an ultrasonic state with a power of 720W and a frequency of 40KHz. At the same time, the bamboo fibers in a suspended and oscillating state are freely dispersed in the aqueous solution and evenly interpenetrate each other. After 20 minutes, take out the sieve, turn the bamboo fibers over onto a dry cloth, and place another layer of dry cloth on it to absorb the residual solution; then place the bamboo fibers with a clean surface in a 50°C oven and dry them for 48 hours. The moisture content is controlled below 5% to obtain a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials.

[0036] Figure 2This is a morphology diagram of the preform for the flame-retardant and smoke-suppressing bamboo fiber composite material prepared in this embodiment; the bamboo fiber length is 1.5 to 3 cm, and the flame retardant content is 15%; the oxygen index value is tested according to the GB / T 2406.2-2009 method, and the results show that the oxygen index is as high as 32.10%, reaching the flame retardant level.

[0037] The preform obtained in this example was made into a flame-retardant and smoke-suppressing bamboo fiber composite material. The matrix was a phenolic resin. The preparation method was as follows: the phenolic resin diluted to a solid content of 15% was evenly sprinkled on the preform, with the ratio of preform to phenolic resin being 8:2. After the resin was completely impregnated, the preform was placed in a mold and hot pressed at 160°C at a speed of 1 min / mm to obtain the flame-retardant and smoke-suppressing bamboo fiber composite material. The cone calorimeter data of the prepared bamboo fiber composite material were as follows: the ignition time was 91 seconds, and the peak heat release rate was 185.07 / kW·m -2 The total heat release is 37.04 / MJ·m -2 The average extinction area is 156.01 / m 2 kg -1 The total smoke rate is 328.87 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 43.61MPa, elastic modulus of 4526.49MPa, impact toughness of 11.51KJ·m -2 .

[0038] Example 2

[0039] This embodiment is a method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material, which comprises:

[0040] S1. Preparation of flame retardant aqueous solution: prepared by mixing deionized water and flame retardant, wherein the mass ratio of deionized water to flame retardant is 9:1;

[0041] The flame retardant is composed of the following raw materials in parts by mass: 6 parts of ammonium polyphosphate, 4 parts of nano magnesium hydroxide, 1 part of silicone lubricant, 0.6 parts of KH560, and 0.4 parts of PP-g-MAH; the degree of polymerization of the ammonium polyphosphate is less than 20, and the particle size is 10 to 15 μm; the particle size of the nano magnesium hydroxide is 30 to 50 nm;

[0042] The flame retardant aqueous solution is prepared by: first, grinding ammonium polyphosphate with a powder grinder at a rotation speed of 2500 r / min for 7 minutes, so that the particle size of the ammonium polyphosphate powder after grinding is 1 to 2 μm; then, mixing the flame retardant components with deionized water according to a mass ratio, stirring at 800 r / min at room temperature for 30 minutes until the mixture is completely dissolved into a colorless transparent liquid, and then allowing the mixture to stand, thereby obtaining a flame retardant aqueous solution with a concentration of 10%;

[0043] S2. Bamboo fiber pretreatment: Select straight bamboo fibers with no obvious curls and a length of 2 to 4.5 cm, and manually sort out impurities and incompletely dispersed fibers. The sorted fibers are evenly placed under microwave radiation at 750 W for 35 seconds, then removed and evenly spread on a 300 mm x 250 mm 60-mesh sieve.

[0044] S3. Preparation of a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials: Place the sieve filled with bamboo fibers described in S2 in an ultrasonic device filled with the flame retardant aqueous solution obtained in S1, and immerse it in an ultrasonic state with a power of 700W and a frequency of 30KHz. At the same time, the bamboo fibers in a suspended and oscillating state are freely dispersed in the aqueous solution and evenly interpenetrate each other. After 15 minutes, take out the sieve, turn the bamboo fibers over onto a dry cloth, and place another layer of dry cloth on it to absorb the residual solution; then place the bamboo fibers with a clean surface in a 50°C oven and dry them for 48 hours. The moisture content is controlled below 5% to obtain a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials.

[0045] The flame-retardant and smoke-suppressing bamboo fiber composite material preform prepared in this embodiment has bamboo fibers with a length of 2 to 4.5 cm and a flame retardant content of 15%. The oxygen index value was tested according to the GB / T 2406.2-2009 method, and the results showed that the oxygen index was as high as 30.47%, reaching the flame-retardant level.

[0046] The preform obtained in this example was made into a flame-retardant and smoke-suppressing bamboo fiber composite material. The matrix was a phenolic resin. The preparation method was as follows: the phenolic resin diluted to a solid content of 15% was evenly sprinkled on the preform, with the ratio of preform to phenolic resin being 8:2. After the resin was completely impregnated, the preform was placed in a mold and hot pressed at 160°C at a speed of 1 min / mm to obtain the flame-retardant and smoke-suppressing bamboo fiber composite material. The cone calorimeter data of the prepared bamboo fiber composite material were as follows: the ignition time was 89 seconds, and the peak heat release rate was 191.02 / kW·m -2 The total heat release is 39.13 / MJ·m -2 The average extinction area is 148.61 / m 2 kg -1 The total smoke rate is 314.71 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 41.46MPa, elastic modulus of 4337.42MPa, impact toughness of 10.81KJ·m -2 .

[0047] Example 3

[0048] This embodiment is a method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material, which comprises:

[0049] S1. Preparation of flame retardant aqueous solution: prepared by mixing deionized water and flame retardant, wherein the mass ratio of deionized water to flame retardant is 9:1;

[0050] The flame retardant is composed of the following raw materials in parts by mass: 7 parts of ammonium polyphosphate, 3 parts of nano magnesium hydroxide, 1.2 parts of stearic acid lubricant, 0.7 parts of KH570, and 0.1 parts of EPDM-g-MAH; the degree of polymerization of the ammonium polyphosphate is less than 20, and the particle size is 10 to 15 μm; the particle size of the nano magnesium hydroxide is 30 to 50 nm;

[0051] The flame retardant aqueous solution is prepared by: first, using a powder grinder to grind ammonium polyphosphate at a rotation speed of 2000 r / min for 8 minutes, so that the particle size of the ammonium polyphosphate powder after grinding is 1 to 2 μm; then, mixing the flame retardant components with deionized water according to a mass ratio, stirring at 700 r / min at room temperature for 30 minutes until the mixture is completely dissolved into a colorless transparent liquid, and then allowing the mixture to stand, thereby obtaining a flame retardant aqueous solution with a concentration of 10%;

[0052] S2. Bamboo fiber pretreatment: Select straight bamboo fibers with a length of 2 to 3 cm and no obvious curls, and manually sort out impurities and incompletely dispersed fibers. The sorted fibers are evenly placed under microwave radiation and treated at 700 W for 40 seconds. After removal, the treated bamboo fibers are evenly spread on a 300 mm x 250 mm 60-mesh sieve.

[0053] S3. Preparation of a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials: Place the sieve filled with bamboo fibers described in S2 in an ultrasonic device filled with the flame retardant aqueous solution obtained in S1, and immerse it in an ultrasonic state with a power of 600W and a frequency of 20KHz. At the same time, the bamboo fibers in a suspended and oscillating state are freely dispersed in the aqueous solution and evenly interpenetrate each other. After 10 minutes, take out the sieve, turn the bamboo fibers over onto a dry cloth, and place another layer of dry cloth on it to absorb the residual solution; then place the bamboo fibers with a clean surface in a 50°C oven and dry them for 48 hours. The moisture content is controlled below 5% to obtain a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials.

[0054] The flame-retardant and smoke-suppressing bamboo fiber composite material preform prepared in this embodiment has bamboo fibers with a length of 2 to 3 cm and a flame retardant content of 15%. The oxygen index value was tested according to the GB / T 2406.2-2009 method, and the results showed that the oxygen index was as high as 30.07%, reaching the flame-retardant level.

[0055] The preform obtained in this example was made into a flame-retardant and smoke-suppressing bamboo fiber composite material. The matrix was a phenolic resin. The preparation method was as follows: the phenolic resin diluted to a solid content of 15% was evenly sprinkled on the preform, with the ratio of preform to phenolic resin being 8:2. After the resin was completely impregnated, the preform was placed in a mold and hot pressed at 160°C at a speed of 1 min / mm to obtain the flame-retardant and smoke-suppressing bamboo fiber composite material. The cone calorimeter data of the prepared bamboo fiber composite material were as follows: the ignition time was 73 seconds, and the peak heat release rate was 181.55 / kW·m -2 The total heat release is 34.99 / MJ·m -2 The average extinction area is 155.85 / m 2 kg -1 The total smoke rate is 379.27 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 39.16MPa, elastic modulus of 4037.58MPa, impact toughness of 10.04KJ·m -2 .

[0056] Comparative Example 1

[0057] Ammonium polyphosphate and nano-magnesium hydroxide are directly mixed, without preparing a flame retardant aqueous solution, and then added to bamboo fibers to form a bamboo fiber composite material. The preparation method is as follows: ammonium polyphosphate and nano-magnesium hydroxide are manually mixed with bamboo fibers according to the mass ratio and laid out to form a bamboo fiber preform; then, phenolic resin diluted to a solid content of 15% is evenly sprinkled on the bamboo fiber preform, with the ratio of bamboo fiber preform to phenolic resin being 8:2. After the resin is completely impregnated, it is placed in a mold and hot pressed at 160°C at a speed of 1 min / mm to obtain a bamboo fiber composite material. The cone calorimeter data of the prepared bamboo fiber composite material are as follows: the ignition time is 59 seconds, and the maximum heat release rate peak is 250.29 / kW·m -2 The total heat release is 43.04 / MJ·m -2 The average extinction area is 200.97 / m 2 kg -1 The total smoke rate is 568.61 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 30.57MPa, elastic modulus of 2827.02MPa, impact toughness of 5.73KJ·m -2 .

[0058] Comparative Example 2

[0059] The bamboo fibers were not treated with microwave radiation. Instead, the preforms were prepared by direct impregnation with a flame retardant solution without ultrasonic treatment. The preforms were then fabricated into bamboo fiber composites. The preparation method included the following steps: The sorted fibers were evenly spread across a 300mm x 250mm 60-mesh sieve and placed in a prepared flame retardant aqueous solution. The fibers were allowed to freely disperse in the aqueous solution for 20 minutes. The sieve was then removed, and the fibers were inverted onto a dry cloth, which was then placed on top to absorb any residual solution. The fibers were then dried in a 50°C oven for 48 hours, with the moisture content controlled below 5%. The preforms had an oxygen index of 25.60%. A phenolic resin diluted to 15% solids was then evenly sprinkled onto the preforms, with the preform and phenolic resin ratio being 8:2. After the preforms were fully impregnated with the resin, they were placed into a mold and hot-pressed at 160°C at a rate of 1 min / mm to produce the bamboo fiber composite. The cone calorimeter data of the prepared bamboo fiber composite material are as follows: the ignition time is 70s, the maximum heat release rate peak is 228.72 / kW·m -2 The total heat release is 39.13 / MJ·m -2 The average extinction area is 178.61 / m 2 kg -1 The total smoke rate is 435.88 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 31.24MPa, elastic modulus of 3266.07Mpa, impact toughness of 6.85KJ·m -2 .

[0060] Comparative Example 3

[0061] Without adding flame retardants, bamboo fiber is directly made into composite materials. The preparation method is as follows: the sorted fibers are evenly placed under microwave radiation and treated at 700W power for 30s before being removed. The treated bamboo fibers are evenly spread on a 300mm×250mm 60-mesh sieve and placed in an ultrasonic device filled with deionized water. Under ultrasonic conditions of 720W power and 40kHz frequency, the bamboo fibers are freely dispersed and evenly interpenetrated in the aqueous solution. After 20 minutes, the sieve is removed and the bamboo fibers are turned over on a dry cloth, and another layer of dry cloth is placed on top to absorb residual moisture. The clean bamboo fibers are then placed in a 50℃ oven and dried for 48 hours with a moisture content of less than 5%. A bamboo fiber preform is obtained, and the oxygen index value tested is only 18.33%. Phenolic resin with a solid content diluted to 15% is evenly sprinkled on the bamboo fiber preform. The ratio of bamboo fiber preform to phenolic resin is 8:2. After the resin is completely impregnated, the preform is placed in a mold and hot pressed at 160℃ at a speed of 1min / mm to obtain a bamboo fiber composite material. The cone calorimeter data of the prepared bamboo fiber composite material are as follows: the ignition time is 40s, the maximum heat release rate peak is 328.33 / kW·m -2 The total heat release is 52.39 / MJ·m -2 The average extinction area is 266.46 / m 2 kg -1 The total smoke rate is 858.46 / m 2 ·m -2 ; Mechanical properties data are: static bending strength of 39.16MPa, elastic modulus of 3878.04MPa, impact toughness of 8.34KJ·m -2 .

[0062] The above data show that compared with Example 1, the flame retardant and mechanical properties of the composite material prepared by adding the flame retardant directly to the bamboo fiber in Comparative Example 1 are reduced. This proves that preparing ammonium polyphosphate and nano magnesium hydroxide into a flame retardant aqueous solution can make the flame retardant fully impregnate the pore structure of the bamboo fiber, which is conducive to entering the surface and interior of the bamboo fiber, giving full play to their respective advantages in flame retardancy and smoke suppression during combustion, and at the same time improving the mechanical properties of the composite material. The results of Comparative Example 2 show that the bamboo fiber treated with microwave radiation is more conducive to the flame retardant adhering to the fiber interior due to the destruction of weak points and cracks, and fully realizing the flame retardant impregnation treatment; at the same time, when the bamboo fiber flame retardant modification and fiber preform molding are integrated, the ultrasonic treatment can give the bamboo fiber excellent dispersibility in the flame retardant aqueous solution. The bamboo fiber under suspension and vibration has greater freedom, can be fully dispersed and stretch in three directions to form an interlocking structure, improve the interface bonding ability, and effectively retard the loss of flame retardant; therefore, the combustion performance and mechanical properties of the bamboo fiber composite material prepared are better than those of the direct impregnation method. The data of Comparative Example 3 show that compared with conventional bamboo fiber composite materials, when the flame retardant and smoke suppression bamboo fiber preform obtained by the preparation method of the present invention is used to synthesize bamboo fiber composite materials, its flame retardant properties are greatly improved, and can reach the flame retardant level. At the same time, the mechanical properties of the material are also improved. This can not only effectively solve the problem that it is difficult to have all the flame retardant properties, smoke suppression properties and mechanical properties in the preparation process of bamboo fiber composite materials, but also make up for the shortcomings of bamboo fiber composite materials in the field of flame retardancy, which is conducive to improving the competitiveness of bamboo fiber composite materials and expanding development paths.

[0063] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material, characterized in that: The method is: S1. Preparation of flame retardant aqueous solution: prepared by mixing deionized water and flame retardant, wherein the mass ratio of deionized water to flame retardant is 9:1; The flame retardant is composed of the following raw materials in parts by mass: 5-7 parts of ammonium polyphosphate, 3-5 parts of nano magnesium hydroxide, 0.6-1.2 parts of a flow modifier, 0.6-0.8 parts of a silane coupling agent, and 0.1-0.6 parts of a compatibilizer; the ammonium polyphosphate has a degree of polymerization of less than 20 and a particle size of 10-15 μm; the nano magnesium hydroxide has a particle size of 30-50 nm; The flame retardant aqueous solution is prepared by: first, grinding ammonium polyphosphate with a powder grinder at a rotation speed of 2000-3000 r / min for 5-8 minutes, so that the particle size of the ammonium polyphosphate powder after grinding is 1-2 μm; then, mixing the flame retardant components with deionized water according to a mass ratio, stirring at 600-800 r / min at room temperature for 30 minutes until the mixture is completely dissolved into a colorless transparent liquid, and then allowing to stand, to obtain a flame retardant aqueous solution with a concentration of 10%; S2. Bamboo fiber pretreatment: Select straight bamboo fibers with no obvious curls and a length of 1.5 to 4.5 cm and evenly place them under microwave radiation for pretreatment. The microwave radiation power is 700 to 800 W and the time is 30 to 40 seconds. Then, the treated bamboo fibers are evenly spread on a 60-mesh sieve. S3. Preparation of a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials: Place the sieve filled with bamboo fibers in S2 into the flame retardant aqueous solution obtained in S1, and immerse it under ultrasonic conditions with an ultrasonic power of 600~720W, a frequency of 20~40KHz, and a time of 10~20min; after the impregnation is completed, remove the sieve, clean the surface of the bamboo fiber, and then place it in a 50℃ oven to dry for 48 hours to obtain a preform for flame-retardant and smoke-suppressing bamboo fiber composite materials.

2. The method for preparing a flame-retardant and smoke-suppressing bamboo fiber composite material preform according to claim 1, characterized in that: The flow modifier described in S1 is an amide lubricant, a silicone lubricant or a stearic acid lubricant.

3. The method for preparing a flame-retardant and smoke-suppressing bamboo fiber composite material preform according to claim 1, characterized in that: The silane coupling agent in S1 is KH550, KH560 or KH570.

4. The method for preparing a flame retardant and smoke suppressing bamboo fiber composite material preform according to claim 1, characterized in that: The compatibilizer described in S1 is PE-g-MAH, PP-g-MAH or EPDM-g-MAH.

5. The method for preparing a flame retardant and smoke suppressing bamboo fiber composite material preform according to claim 1, characterized in that: S3 The moisture content of the preform for the flame retardant and smoke suppressing bamboo fiber composite material is ≤5%.

6. An application of a preform for a flame-retardant and smoke-suppressing bamboo fiber composite material prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The preform is used for preparing a flame-retardant and smoke-suppressing bamboo fiber composite material.

Images