Lignin reinforced basalt fiber resin composite material and preparation method thereof

Abstract

The invention discloses a lignin-reinforced basalt fiber resin composite material and a preparation method thereof, and belongs to the technical field of resin-based composite materials. The composite material is prepared from 35-45 parts of basalt fiber, 30-50 parts of a resin matrix, 5-15 parts of modified lignin, 3-8 parts of a flame-retardant system, 10-20 parts of a curing regulating agent and 0.5-1 part of a defoaming agent. Wherein the modified lignin is obtained through chemical modification of a silane coupling agent, and is used as an interface bridging agent, a flame-retardant synergist and a bio-based reinforcing phase at the same time; the flame-retardant system is a compound system of modified lignin, ammonium polyphosphate and melamine. The preparation method comprises the steps of lignin modification, resin slurry preparation, fiber impregnation, pre-curing and segmented hot press molding. The tensile strength, bending strength, impact toughness, limit oxygen index and other key properties of the prepared composite material are all remarkably improved, and the composite material has the advantages of being excellent in mechanical property and flame retardant property and green and sustainable.

Description

Technical Field

[0001] This invention belongs to the field of resin-based composite materials technology, specifically relating to a lignin-reinforced basalt fiber resin composite material and its preparation method. Background Technology

[0002] Basalt fiber reinforced resin composites are a rapidly developing high-performance material system in recent years, attracting widespread attention for their excellent mechanical properties, good heat resistance, and environmental friendliness. Basalt fiber, as a novel inorganic fiber, originates from natural basalt ore and is prepared through high-temperature melt drawing. It possesses multiple advantages, including high specific strength, corrosion resistance, high-temperature resistance, and moderate cost, making it a strong alternative to glass fiber. However, some problems still need to be addressed in the current technology of basalt fiber reinforced resin composites: 1. Poor interfacial compatibility: The weak interfacial bonding between basalt fiber and resin matrix leads to low stress transfer efficiency and affects the overall mechanical properties of the composite material. 2. Limited flame retardant properties: Although basalt fiber itself has certain high temperature resistance, the resin matrix (especially unsaturated polyester resin, etc.) is usually flammable, which limits the application of composite materials in fields with high fire protection requirements. 3. Limited room for cost optimization: Existing interface modification methods mostly rely on expensive silane coupling agents or other chemical treatment agents, which increases production costs; 4. Insufficient environmental friendliness: Traditional composite materials lack bio-based components in their production and use, making it difficult to meet increasingly stringent environmental protection requirements.

[0003] On the other hand, lignin, as the second most abundant natural polymer in nature, generates millions of tons of byproducts annually from the papermaking and biomass refining industries. However, most of these are used as low-value fuels or directly discarded, limiting its high-value utilization pathways. Lignin's molecular structure contains abundant active functional groups such as phenolic hydroxyl and aldehyde groups, exhibiting good reactivity and char-forming properties, theoretically making it ideal for composite materials. However, due to its poor dispersibility, insufficient thermal stability, and poor compatibility with synthetic resins, its application in composite materials has not been fully developed.

[0004] Existing technologies have included some research attempting to combine lignin with fibrous materials. For example, the existing technology "lignin-wood fiber-polyolefin hybrid composite material" attempts to use lignin in wood-plastic composites, solving some of the problems related to the efficient utilization of lignin. However, this patent mainly focuses on thermoplastic plastic systems and does not involve basalt fiber reinforced resin-based composites. Another existing technology, "basalt fiber reinforced wood-plastic composite material," while introducing basalt fiber reinforcement, remains limited to the wood-plastic composite system (thermoplastic matrix) and does not explore the application potential of lignin in thermosetting resin-based composites.

[0005] Based on the above-mentioned technological status, this patent proposes an innovative solution: by modifying lignin for multiple functions, it can be used simultaneously as an interface modifier, flame retardant synergist, and bio-based filler in basalt fiber reinforced resin composites, achieving the dual goals of performance improvement and environmental friendliness. Summary of the Invention

[0006] In view of the above-mentioned prior art, the present invention provides a lignin-reinforced basalt fiber resin composite material and its preparation method, which solves the problem that the mechanical properties and flame retardant properties of the prior art cannot be simultaneously achieved.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a lignin-reinforced basalt fiber resin composite material is provided, comprising the following raw materials in parts by weight: 35-45 parts of basalt fiber, 30-50 parts of resin matrix, 5-15 parts of modified lignin, 3-8 parts of flame retardant system, 10-20 parts of curing regulator and 0.5-1 part of defoamer.

[0008] Furthermore, the basalt fiber is a fiber fabric that has undergone heat treatment at 400~450℃ and ultrasonic cleaning with acetone, and its areal density is 250g / m². 2 .

[0009] Furthermore, the resin matrix is ​​epoxy resin E-51.

[0010] Furthermore, the modified lignin is prepared by the following steps: dispersing lignin in an ethanol-water solution, adding 12% to 15% of a silane coupling agent by mass of lignin, and reacting at 60°C for 4 hours to obtain the modified lignin.

[0011] Furthermore, the silane coupling agent is KH-550 silane coupling agent.

[0012] Furthermore, the flame retardant system is composed of modified lignin, ammonium polyphosphate, and melamine in a mass ratio of 3:2:1.

[0013] Furthermore, the curing regulator is polyamide 650.

[0014] Furthermore, the other additives include defoamer BYK-1790.

[0015] This invention also provides a method for preparing lignin-reinforced basalt fiber resin composite materials, comprising the following steps: S1: Mix and stir the resin matrix, modified lignin, flame retardant system, curing regulator and defoamer at 50~60℃ for 20~30 minutes to obtain resin slurry; S2: After surface treatment, basalt fiber is impregnated in resin slurry, and then the impregnated material is pre-cured at 80~100℃ for 10~20min; S3: Place the pre-cured material in a mold and perform segmented heating and hot pressing curing to obtain lignin-reinforced basalt fiber resin composite material.

[0016] Furthermore, the segmented heating and hot pressing curing process involves holding the product at 100°C for 10 minutes under a pressure of 5~15MPa, then raising the temperature to 130°C and holding it for 20 minutes, and finally curing it at 160°C for 30 minutes.

[0017] The beneficial effects of this invention are as follows: The lignin-reinforced basalt fiber resin composite material provided by this invention significantly enhances the interfacial bonding force between basalt fibers and the resin matrix by introducing chemically modified lignin as a multifunctional interfacial bridging agent. The active groups in the lignin molecules can form hydrogen bonds or chemical bonds with the fiber surface, while simultaneously forming a flexible interfacial layer in the resin matrix, effectively transferring stress and alleviating stress concentration. This invention also innovatively combines modified lignin with phosphorus... A compound of nitrogen-based flame retardants (ammonium polyphosphate and melamine) was used to construct lignin. phosphorus This nitrogen-based synergistic flame retardant system utilizes lignin's rapid char formation at high temperatures. The lignin, in conjunction with ammonium polyphosphate, promotes the formation of a dense char layer through polyphosphoric acid. Melamine decomposes, releasing non-flammable gases to dilute combustibles, achieving a multi-mechanism synergistic flame retardant effect. Furthermore, lignin, a byproduct of papermaking and biomass refining, is inexpensive and widely available. This invention chemically modifies lignin and introduces it as a functional additive into the composite material system, partially replacing petroleum-based resins. This not only reduces raw material costs but also increases the bio-based content of the material, aligning with the concept of green and sustainable development. Experimental results show that compared to composite materials without modified lignin, the tensile strength of this invention is increased by approximately 25.6%, flexural strength by approximately 26.6%, and impact toughness by approximately 28.9%. The interfacial shear strength is significantly improved, resulting in comprehensive optimization of overall mechanical properties. The limiting oxygen index (LOI) is increased from 25–26% in traditional composite materials to over 32%, demonstrating significantly enhanced flame retardant performance.

[0018] Meanwhile, the preparation method provided by this invention has clear process steps and reasonable parameter ranges, including key steps such as lignin silanization modification, uniform preparation of resin slurry, fiber impregnation and pre-curing, and segmented hot pressing molding. The process is simple, the conditions are mild, it is easy to realize industrial production, and the product performance is stable and reproducible.

[0019] In summary, this invention not only significantly improves mechanical properties and flame retardant properties, but also has outstanding advantages in resource recycling, process feasibility, and environmental friendliness, and has excellent prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a flowchart of the preparation process. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in detail below with reference to examples.

[0022] Example 1 A lignin-reinforced basalt fiber resin composite material comprises the following raw materials in parts by weight: 40 parts basalt fiber, 32 parts epoxy resin E-51, 10 parts modified lignin, 6 parts flame retardant system (modified lignin: ammonium polyphosphate: melamine = 3:2:1), 11.5 parts polyamide 650, and 0.5 parts defoamer; wherein the modified lignin is prepared by the following steps: 100g of lignin is weighed and dispersed in 500mL of ethanol-water solution with a volume ratio of 1:1, 15g of KH-550 silane coupling agent is added, and the mixture is mechanically stirred at 60℃ for 4h. After the reaction is completed, the mixture is filtered, washed, and vacuum dried at 80℃ for 12h to obtain the modified lignin.

[0023] The preparation process in this embodiment is as follows: Figure 1 It is prepared through the following steps: S1: Add epoxy resin E-51, modified lignin, flame retardant system, polyamide 650 and BYK-1790 to the reactor and stir at 55℃ for 25 min to obtain resin slurry. S2: Basalt fiber fabric (area density 250g / m²) 2 The basalt fiber was placed in a muffle furnace and heat-treated at 425°C for 2 hours. Then it was ultrasonically cleaned with acetone solution for 30 minutes and dried at 60°C for later use to obtain surface-treated basalt fiber. The surface-treated basalt fiber was then impregnated in resin slurry and the impregnated material was laid flat and pre-cured in an oven at 90°C for 15 minutes. S3: Place the pre-cured material in a mold, hold it at 100℃ for 10 minutes under a pressure of 10MPa, then raise it to 130℃ and hold it for 20 minutes, and finally cure it at 160℃ for 30 minutes. After curing, let it cool naturally to room temperature and demold to obtain the lignin-reinforced basalt fiber resin composite material.

[0024] Example 2 A lignin-reinforced basalt fiber resin composite material comprises the following raw materials in parts by weight: 40 parts basalt fiber, 34 parts epoxy resin E-51, 8 parts modified lignin, 5 parts flame retardant system (modified lignin: ammonium polyphosphate: melamine = 3:2:1), 12.5 parts polyamide 650, and 0.5 parts defoamer; wherein the modified lignin is prepared by the following steps: 100g of lignin is weighed and dispersed in 500mL of ethanol-water solution with a volume ratio of 1:1, 12g of KH-550 silane coupling agent is added, and the mixture is mechanically stirred at 60℃ for 4h. After the reaction is completed, the mixture is filtered, washed, and vacuum dried at 80℃ for 12h to obtain the modified lignin.

[0025] The preparation process in this embodiment is as follows: Figure 1 It is prepared through the following steps: S1: Add epoxy resin E-51, modified lignin, flame retardant system, polyamide 650 and BYK-1790 to the reactor and stir at 60℃ for 20 min to obtain resin slurry; S2: Basalt fiber fabric (area density 250g / m²) 2 The basalt fiber was placed in a muffle furnace and heat-treated at 450°C for 2 hours. Then it was ultrasonically cleaned with acetone solution for 30 minutes and dried at 60°C for later use to obtain surface-treated basalt fiber. The surface-treated basalt fiber was then impregnated in resin slurry and the impregnated material was laid flat and pre-cured in an oven at 100°C for 10 minutes. S3: Place the pre-cured material in a mold, hold it at 100℃ for 10 minutes under a pressure of 15MPa, then raise it to 130℃ and hold it for 20 minutes, and finally cure it at 160℃ for 30 minutes. After curing, let it cool naturally to room temperature and demold to obtain the lignin-reinforced basalt fiber resin composite material.

[0026] Example 3 A lignin-reinforced basalt fiber resin composite material comprises the following raw materials in parts by weight: 40 parts basalt fiber, 33 parts epoxy resin E-51, 9 parts modified lignin, 6 parts flame retardant system (modified lignin: ammonium polyphosphate: melamine = 3:2:1), 11.5 parts polyamide 650, and 0.5 parts defoamer; wherein the modified lignin is prepared by the following steps: 100g of lignin is weighed and dispersed in 500mL of ethanol-water solution with a volume ratio of 1:1, 13g of KH-550 silane coupling agent is added, and the mixture is mechanically stirred at 60℃ for 4h. After the reaction is completed, the mixture is filtered, washed, and vacuum dried at 80℃ for 12h to obtain the modified lignin.

[0027] The preparation process in this embodiment is as follows: Figure 1 It is prepared through the following steps: S1: Add epoxy resin E-51, modified lignin, flame retardant system, polyamide 650 and BYK-1790 to the reactor and stir at 50°C for 30 minutes to obtain resin slurry. S2: Basalt fiber fabric (area density 250g / m²) 2 The basalt fiber was placed in a muffle furnace and heat-treated at 400°C for 2 hours. Then it was ultrasonically cleaned with acetone solution for 30 minutes and dried at 60°C to obtain surface-treated basalt fiber. The surface-treated basalt fiber was then impregnated in resin slurry and the impregnated material was laid flat and pre-cured in an oven at 80°C for 20 minutes. S3: Place the pre-cured material in a mold, hold it at 100℃ for 10 minutes under a pressure of 5MPa, then raise it to 130℃ and hold it for 20 minutes, and finally cure it at 160℃ for 30 minutes. After curing, let it cool naturally to room temperature and demold to obtain the lignin-reinforced basalt fiber resin composite material.

[0028] Comparative Example 1 A resin composite material comprises the following raw materials in parts by weight: 40 parts basalt fiber, 44 parts epoxy resin E-514, 15.5 parts polyamide 650, and 0.5 parts defoamer; This comparative example was prepared through the following steps: S1: Add epoxy resin E-51, polyamide 650 and BYK-1790 to the reactor and stir at 55°C for 25 minutes to obtain resin slurry; S2: Basalt fiber fabric (area density 250g / m²) 2 The basalt fiber was placed in a muffle furnace and heat-treated at 425°C for 2 hours. Then it was ultrasonically cleaned with acetone solution for 30 minutes and dried at 60°C for later use to obtain surface-treated basalt fiber. The surface-treated basalt fiber was then impregnated in resin slurry and the impregnated material was laid flat and pre-cured in an oven at 90°C for 15 minutes. S3: Place the pre-cured material in a mold, hold it at 100℃ for 10 minutes under a pressure of 10MPa, then raise it to 130℃ and hold it for 20 minutes, and finally cure it at 160℃ for 30 minutes. After curing, let it cool naturally to room temperature and demold to obtain the resin composite material.

[0029] Comparative Example 2 A lignin-reinforced basalt fiber resin composite material comprises the following raw materials in parts by weight: 40 parts basalt fiber, 32 parts epoxy resin E-51, 10 parts lignin, 6 parts flame retardant system (lignin:ammonium polyphosphate:melamine = 3:2:1), 11.5 parts polyamide 650, and 0.5 parts defoamer. This comparative example was prepared through the following steps: S1: Add epoxy resin E-51, lignin, flame retardant system, polyamide 650 and BYK-1790 to the reactor and stir at 55℃ for 25 minutes to obtain resin slurry; S2: Basalt fiber fabric (area density 250g / m²) 2 The basalt fiber was placed in a muffle furnace and heat-treated at 425°C for 2 hours. Then it was ultrasonically cleaned with acetone solution for 30 minutes and dried at 60°C for later use to obtain surface-treated basalt fiber. The surface-treated basalt fiber was then impregnated in resin slurry and the impregnated material was laid flat and pre-cured in an oven at 90°C for 15 minutes. S3: Place the pre-cured material in a mold, hold it at 100℃ for 10 minutes under a pressure of 10MPa, then raise it to 130℃ and hold it for 20 minutes, and finally cure it at 160℃ for 30 minutes. After curing, let it cool naturally to room temperature and demold to obtain the lignin-reinforced basalt fiber resin composite material.

[0030] Experimental Example Performance Testing: The mechanical and flame-retardant properties of the composite materials prepared in the above examples and comparative examples were tested according to the following standards: tensile strength (GB / T1447-2005), flexural strength (GB / T1449-2005), impact toughness (GB / T1043.1-2008), interfacial shear strength (ASTM D2344), and limiting oxygen index (LOI) (GB / T2406.2-2009). The test results are shown in Table 1. A comparison between Comparative Example 1 and Example 1 shows that the present invention, by introducing modified lignin, increases the tensile strength of the composite material by 25.6%, flexural strength by 26.6%, impact toughness by 28.9%, and limiting oxygen index by 23.8%. This fully demonstrates the multifunctional synergistic effect of modified lignin. A comparison between Comparative Example 2 and Example 1 shows that although using unmodified lignin improves performance to some extent, the effect is far less than that of modified lignin. This indicates that chemical modification of lignin is key to its interfacial bridging and flame-retardant synergistic effects, while unmodified lignin cannot function effectively due to poor compatibility.

[0031] The results above show that the mechanical properties of the lignin-reinforced basalt fiber resin composite material of this invention are comprehensively improved. This improvement is mainly attributed to the flexible interface layer formed by lignin between the fiber and the resin, which can effectively transfer stress and alleviate interface stress concentration. Simultaneously, the active groups such as phenolic hydroxyl groups in the lignin molecules can form hydrogen bonds or chemical bonds with the silanol groups on the surface of the basalt fiber, enhancing the interfacial bonding force. When the composite material is subjected to external force, this structure can prevent crack propagation through microcrack deflection and energy dissipation mechanisms, thereby improving the toughness and strength of the material. Another significant advantage is the substantial improvement in the flame retardant properties of the composite material. The limiting oxygen index of traditional basalt fiber composite materials is typically only 25-26%, while this patented technology can increase the limiting oxygen index to over 32%.

[0032] Table 1 Performance Test Results

[0033] While specific embodiments of the present invention have been described in detail, they should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by those skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A lignin-reinforced basalt fiber resin composite material, characterized in that, The raw materials include the following parts by weight: 35-45 parts basalt fiber, 30-50 parts resin matrix, 5-15 parts modified lignin, 3-8 parts flame retardant system, 10-20 parts curing regulator and 0.5-1 part defoamer.

2. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that: The basalt fiber is a fiber fabric that has undergone heat treatment at 400~450℃ and ultrasonic cleaning with acetone.

3. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that: The resin matrix is ​​epoxy resin E-51.

4. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that, The modified lignin is prepared by the following steps: dispersing lignin in an ethanol-water solution, adding 12% to 15% of a silane coupling agent by mass of lignin, and reacting at 60°C for 4 hours to obtain modified lignin.

5. The lignin-reinforced basalt fiber resin composite material according to claim 4, characterized in that, The silane coupling agent is KH-550 silane coupling agent.

6. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that: The flame retardant system is composed of modified lignin, ammonium polyphosphate and melamine in a mass ratio of 2~3:1~2:

1.

7. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that: The curing regulator is polyamide 650.

8. The lignin-reinforced basalt fiber resin composite material according to claim 1, characterized in that: The defoamer is BYK-1790.

9. The method for preparing the lignin-reinforced basalt fiber resin composite material according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Mix and stir the resin matrix, modified lignin, flame retardant system, curing regulator and defoamer at 50~60℃ for 20~30 minutes to obtain resin slurry; S2: After surface treatment, basalt fiber is impregnated in resin slurry, and then the impregnated material is pre-cured at 80~100℃ for 10~20min; S3: Place the pre-cured material in a mold and perform segmented heating and hot pressing curing to obtain lignin-reinforced basalt fiber resin composite material.

10. The method for preparing the lignin-reinforced basalt fiber resin composite material according to claim 9, characterized in that: The segmented heating and hot pressing curing process involves holding the temperature at 100°C for 10 minutes under a pressure of 5-15 MPa, then raising the temperature to 130°C and holding it for 20 minutes, and finally curing at 160°C for 30 minutes.

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