Natural bamboo fiber modified PE composite material and preparation method thereof

Abstract

The invention relates to a natural bamboo fiber modified PE composite material and a preparation method thereof, and belongs to the technical field of composite materials. The composite material comprises an mPE matrix and bamboo fibers treated by a special modified silane coupling agent, the modified coupling agent constructs a structure containing long-chain alkyl and branched thioether quaternary ammonium salt on the surfaces of the bamboo fibers, the structure can be fully entangled with mPE, the branched chain of the structure can be used as a template to induce the mPE to form out-phase crystallization anchoring on an interface, and thus, the composite material has the advantages of high mechanical strength, high mechanical strength and the like. The thioether bond provides flexible toughening, and the quaternary ammonium salt enhances grafting on the surface of the fiber through electrostatic interaction and endows the fiber with an anti-corrosion function. According to the invention, the interface bonding of the fiber and mPE is obviously enhanced, so that the composite material has excellent impact resistance and bending fatigue resistance, can maintain high glossiness, has high glossiness retention rate after being bent, and is especially suitable for high-end appearance decoration materials.

Description

Technical Field

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

[0002] Polyethylene (PE), as one of the most widely produced general-purpose plastics, is widely used due to its excellent chemical stability, processability, and low cost. Metallocene polyethylene (mPE) is polyethylene prepared using metallocene catalysts, and its molecular chains have extremely high regularity, narrow molecular weight distribution, and uniform comonomer distribution. This unique microstructure gives it excellent mechanical properties on a macroscopic scale, especially extremely high transparency and extremely low haze, while also possessing excellent impact strength and puncture resistance. Bamboo fiber is a green and renewable fiber derived from natural bamboo. Its surface has a unique natural texture and rustic beauty, giving products a natural and environmentally friendly artistic value. Combining mPE with bamboo fiber combines the excellent mechanical properties and high transparency of mPE with the decorative properties of bamboo fiber. The mPE coating layer can also effectively prevent the bamboo fiber from decaying due to moisture absorption and microbial erosion, fully showcasing its texture. It has broad application prospects in the field of decorative materials (such as interior decorative panels, furniture veneers, and electronic product casings).

[0003] However, mPE is a non-polar polymer, while bamboo fiber is rich in polar groups such as hydroxyl groups, resulting in extremely poor interfacial compatibility between the two. During the composite process, the weak interfacial bonding force prevents effective stress transfer, leading to a deterioration in the mechanical properties of the composite material. Furthermore, this weak interfacial bonding creates numerous microscopic defects at the interface between the two phases. These defects become light scattering points, severely damaging the high transparency and gloss of the mPE matrix itself, resulting in a dull surface finish that fails to fully showcase the natural texture and beauty of the bamboo fiber. More seriously, when the material is subjected to external forces such as bending or impact, the fiber and mPE matrix are prone to delamination at the interface, producing microcracks and whitening. This optical property degradation caused by deformation is irreversible and will permanently affect the aesthetics and usability of the product.

[0004] In existing technologies, a conventional method to improve the compatibility of polar fibers with non-polar polymers is to modify the surface of the fibers using silane coupling agents, which reduces interfacial energy and improves dispersibility to some extent. However, the compatibility of general coupling modification methods with mPE matrices is insufficient. The fundamental reason is that mPE molecular chains have high regularity and strong crystallinity. The bonding between existing alkyl coupling agents and the mPE matrix mainly relies on simple compatibility and limited physical entanglement, lacking a strong interfacial anchoring mechanism. This weak interaction cannot effectively induce mPE to form a stable crystalline structure at the interface, resulting in limited improvement in the overall mechanical properties of the composite material, especially fatigue toughness. Macroscopically, this manifests as low material strength, easy whitening, wrinkling, and even fracture after repeated bending, and a significant and irreversible decrease in surface gloss after external force deformation. Summary of the Invention

[0005] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a natural bamboo fiber modified PE composite material and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A natural bamboo fiber-modified PE composite material, the core innovation of which lies in the development of a modified silane coupling agent, which is used to treat and modify natural bamboo fibers and then composite them with mPE to improve the interfacial bonding performance of the two. Specifically, it includes the following two aspects:

[0008] In a first aspect, the present invention provides a modified silane coupling agent for treating bamboo fiber, the preparation method of which includes the following steps:

[0009] Step A1: Premix silane coupling agent KH-550, undecene bromide and toluene, then add potassium carbonate and anhydrous magnesium sulfate, heat to 80-100℃ under dry nitrogen protection and stir for 3-4 hours, finally filter the reaction product and evaporate under reduced pressure to obtain intermediate 1.

[0010] Step A2: Premix intermediate 1, tert-butylthiol, acetone, and anhydrous ethanol, then add photoinitiator 651 for mixing. Incubate at room temperature at 25-35 mW / cm². 2 The reaction is stirred under ultraviolet irradiation for 1.5-2 hours, and finally the solvent is removed by rotary evaporation to obtain intermediate 2.

[0011] Step A3: Mix intermediate 2, iodomethane and acetonitrile, pressurize with dry nitrogen to 4-5 bar, heat to 50-60℃ and reflux for 8-10 h, finally release the pressure and rotary evaporate to obtain the modified silane coupling agent.

[0012] In step A1 above, the ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate, and toluene is 10 mmol: 20 mmol: 1.4-1.8 g: 0.5-0.7 g: 100-130 mL, and undecene bromide undergoes a substitution reaction with silane coupling agent KH-550.

[0013] In step A2 above, the ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol is 10 mmol: 20 mmol: 20-30 mg: 50-70 mL: 15-30 mL, and tert-butyl mercaptan undergoes a click addition reaction with intermediate 1.

[0014] In step A3 above, the ratio of intermediate 2, iodomethane, and acetonitrile is 10 mmol: 50-70 mmol: 40-50 mL, and iodomethane reacts with intermediate 2 in a quaternization reaction.

[0015] The synthetic route for the modified silane coupling agent is as follows:

[0016] Secondly, this invention provides a method for modifying natural bamboo fiber and a method for preparing composite materials.

[0017] Modification of natural bamboo fiber: Premix the modified silane coupling agent and ethanol aqueous solution, adjust the pH value to 5 with formic acid, add natural bamboo fiber and heat to 60℃ to soak for 8-12 hours, then neutralize with ammonia water, filter, wash with water, and dry to obtain modified bamboo fiber.

[0018] The ratio of natural bamboo fiber, modified silane coupling agent, and ethanol aqueous solution is 50g:4.2-5.5g:100-120mL. The modified silane coupling agent is hydrolyzed and coupled with natural bamboo fiber.

[0019] Preparation of composite materials: According to the weight percentage, the modified bamboo fiber is 30-45wt%, the lubricant is 0.9-1.4wt%, the antioxidant is 0.1-0.13wt%, and the balance is mPE resin;

[0020] The mPE resin, lubricant, and antioxidant are premixed and fed into the main feed port of the extruder, while the modified bamboo fiber is fed into the side feed port. The processing temperature is controlled within the range of 190-220℃. After extrusion and cooling, the composite material is obtained.

[0021] The beneficial effects of this invention are:

[0022] This invention provides a modified silane coupling agent specifically for mPE / natural bamboo fiber composite systems. Its core value lies in fundamentally reconstructing and optimizing the interfacial phase between the two components, achieving a leap from physical entanglement to synergistic physical-chemical strengthening. The multifunctional interfacial layer constructed on the bamboo fiber surface by this modified silane coupling agent endows the composite material with superior comprehensive performance and lasting aesthetic value through the following synergistic mechanism:

[0023] Modified silane coupling agents introduce a unique chemical structure on the surface of bamboo fibers, consisting of long-chain alkyl groups, branched chains terminated with tert-butyl sulfide, and quaternary ammonium salt cations. This structure initially provides a basis for compatibility through extensive physical entanglement between the long-chain alkyl groups and the mPE molecular chains. More importantly, the spatial dimensions and configuration of the terminally branched tert-butyl sulfide structure closely match the folded portions of the methylene segments in polyethylene crystals. This structural similarity allows it to act as a highly efficient heterogeneous nucleation site during the cooling process of the composite material, significantly reducing the nucleation barrier of mPE and inducing its molecular chains to undergo preferred orientation and regular arrangement at the fiber interface, thereby forming a dense transverse crystalline structure. This interface-induced crystalline layer acts like countless tiny "crystal bridges" between the fiber and the matrix, achieving an effective transfer from nanoscale molecular recognition to macroscale mechanical strength, resulting in a qualitative leap in interfacial bonding strength.

[0024] This invention is crucial for improving the optical properties of composite materials. Voids and debonding caused by traditional weak interfacial bonding are major sources of light scattering, severely impairing gloss. This invention, by inducing the formation of a dense, continuous transverse crystalline interfacial layer, significantly eliminates these microscopic defects. This interfacial layer has a refractive index similar to the mPE matrix and a regular structure, effectively reducing light scattering loss at the interface. This allows the composite material to maintain the inherent high gloss of the mPE matrix, fully showcasing the clear natural texture of bamboo fiber. More importantly, when the material is subjected to bending or other external forces, traditional weak interfaces will generate numerous microcracks and silver streaks due to peeling. These new defects immediately lead to surface whitening and a sharp drop in gloss. The interface provided by this invention, with its high strength from "crystallization anchoring" and excellent deformation capability from the flexible sulfide segments, can effectively inhibit the initiation and propagation of microcracks. Even under repeated bending, the interface maintains its structural integrity, ensuring the long-term stability and durability of the composite material's gloss during use, solving the industry pain point of irreversible degradation of optical properties in decorative materials under stress.

[0025] Meanwhile, the sulfide segments in this molecular structure, with their lower bond energy and longer bond length, endow the interfacial region with excellent flexibility and dynamic response. This flexible unit, acting as a highly efficient stress buffer layer, can effectively absorb and disperse energy through intramolecular chain rotation and conformational changes under external loads or repeated deformation, inhibiting the initiation and propagation of microcracks. This not only significantly improves the impact toughness and fatigue resistance of the composite material, but the enhanced molecular chain mobility in the interfacial region also facilitates the formation of a more complete crystalline structure in mPE, resulting in a synergistic effect of reinforcement and toughening.

[0026] In summary, this invention not only solves the core problem of poor compatibility between polar bamboo fiber and non-polar mPE, but also significantly improves the optical properties of the composite material and its stability during use, providing a reliable technical solution for preparing high-performance, high-value-added, and long-life natural fiber reinforced polymer composite materials. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] I. Preparation of Modified Silane Coupling Agents

[0030] Step A1: Take silane coupling agent KH-550, undecene bromide and toluene premixed, then add potassium carbonate and anhydrous magnesium sulfate, heat to 80℃ under dry nitrogen protection and stir for 4h. The ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate and toluene is 10mmol:20mmol:1.4g:0.5g:100mL. Finally, filter the reaction product to remove salts, and then remove toluene by rotary evaporation under reduced pressure to obtain intermediate 1.

[0031] Step A2: Take intermediate 1, tert-butyl mercaptan, acetone and anhydrous ethanol, premix them, then add photoinitiator 651 to make them miscible. Irradiate with a 365nm ultraviolet mercury lamp at room temperature, controlling the irradiation intensity to 25mW / cm². 2 The mixture was stirred and reacted for 2 hours. The ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol was 10 mmol: 20 mmol: 20 mg: 50 mL: 15 mL. Finally, the solvents acetone and ethanol were removed by rotary evaporation to obtain intermediate 2.

[0032] Step A3: Take intermediate 2, iodomethane and acetonitrile, mix them, pressurize with dry nitrogen to 4 bar, heat to 50°C and reflux for 10 h. The ratio of intermediate 2, iodomethane and acetonitrile is 10 mmol: 50 mmol: 40 mL. Finally, release the pressure to atmospheric pressure and remove excess iodomethane and solvent acetonitrile by rotary evaporation to obtain the modified silane coupling agent.

[0033] II. Preparation of Composite Materials

[0034] Modification of natural bamboo fiber: A 60% (v / v) ethanol aqueous solution was prepared using ethanol and deionized water. The modified silane coupling agent was premixed with the ethanol aqueous solution, and the pH was adjusted to 5 with formic acid. Natural bamboo fiber was then added and heated to 50°C for 12 hours. The natural bamboo fiber was selected from yellow bamboo fiber from Sichuan Changsheng New Material Technology Co., Ltd., which has a full color and clear texture. Finally, the fiber was neutralized with ammonia water, filtered, washed with water, and dried to obtain modified bamboo fiber.

[0035] Blending and compounding: 30 wt% modified bamboo fiber, 0.9 wt% lubricant (using commercially available LM type raw material), and 0.11 wt% antioxidant (using commercially available antioxidants 1010 and 168 mixed in equal weight ratio) are taken as components, with the balance being mPE resin (commercially available Enable™ 27-03HH resin raw material); the mPE resin, lubricant, and antioxidant are premixed and fed into the main feed port of the extruder, while the modified bamboo fiber is fed into the side feed port. The processing temperature range of the extruder is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 220℃, and Zone 6 210℃. After extrusion and cooling, the composite material is obtained.

[0036] Example 2

[0037] I. Preparation of Modified Silane Coupling Agents

[0038] Step A1: Take silane coupling agent KH-550, undecene bromide and toluene premixed, then add potassium carbonate and anhydrous magnesium sulfate, heat to 90℃ under dry nitrogen protection and stir for 3.5h. The ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate and toluene is 10mmol:20mmol:1.6g:0.6g:110mL. Finally, filter the reaction product to remove salts, and then remove toluene by rotary evaporation under reduced pressure to obtain intermediate 1.

[0039] Step A2: Premix intermediate 1, tert-butyl mercaptan, acetone, and anhydrous ethanol, then add photoinitiator 651 and mix. Irradiate the mixture at room temperature using a 365nm ultraviolet mercury lamp, controlling the irradiation intensity to 30mW / cm². 2The mixture was stirred for 1.7 h. The ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol was 10 mmol: 20 mmol: 25 mg: 60 mL: 20 mL. Finally, the solvents acetone and ethanol were removed by rotary evaporation to obtain intermediate 2.

[0040] Step A3: Take intermediate 2, iodomethane and acetonitrile, mix them, pressurize with dry nitrogen to 5 bar, heat to 55℃ and reflux for 9 h. The ratio of intermediate 2, iodomethane and acetonitrile is 10 mmol: 60 mmol: 45 mL. Finally, release the pressure to atmospheric pressure and remove excess iodomethane and solvent acetonitrile by rotary evaporation to obtain the modified silane coupling agent.

[0041] II. Preparation of Composite Materials

[0042] Modification of natural bamboo fiber: A 60% (v / v) ethanol aqueous solution was prepared using ethanol and deionized water. The modified silane coupling agent was premixed with the ethanol aqueous solution, and the pH was adjusted to 5 with formic acid. Natural bamboo fiber was then added and heated to 50°C for 10 hours. The natural bamboo fiber was selected from yellow bamboo fiber from Sichuan Changsheng New Material Technology Co., Ltd., which has a full color and clear texture. Finally, the fiber was neutralized with ammonia water, filtered, washed with water, and dried to obtain modified bamboo fiber.

[0043] Blending and compounding: The composition consists of 40 wt% modified bamboo fiber, 1.3 wt% lubricant (using commercially available LM type raw material), and 0.13 wt% antioxidant (using commercially available antioxidants 1010 and 168 mixed in equal weight ratios), with the remainder being mPE resin (commercially available Enable™ 27-03HH resin raw material). The mPE resin, lubricant, and antioxidant are premixed and fed into the main feed port of the extruder, while the modified bamboo fiber is fed into the side feed port. The processing temperature range of the extruder is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 220℃, Zone 5 220℃, and Zone 6 210℃. After extrusion and cooling, the composite material is obtained.

[0044] Example 3

[0045] I. Preparation of Modified Silane Coupling Agents

[0046] Step A1: Take silane coupling agent KH-550, undecene bromide and toluene premixed, then add potassium carbonate and anhydrous magnesium sulfate, heat to 100℃ under dry nitrogen protection and stir for 3h. The ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate and toluene is 10mmol:20mmol:1.8g:0.7g:130mL. Finally, filter the reaction product to remove salts, and then remove toluene by rotary evaporation under reduced pressure to obtain intermediate 1.

[0047] Step A2: Premix intermediate 1, tert-butyl mercaptan, acetone, and anhydrous ethanol, then add photoinitiator 651 and mix. Irradiate the mixture at room temperature using a 365nm ultraviolet mercury lamp, controlling the irradiation intensity to 35mW / cm². 2 The mixture was stirred for 1.5 h. The ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol was 10 mmol: 20 mmol: 30 mg: 70 mL: 30 mL. Finally, the solvents acetone and ethanol were removed by rotary evaporation to obtain intermediate 2.

[0048] Step A3: Take intermediate 2, iodomethane and acetonitrile, mix them, pressurize with dry nitrogen to 5 bar, heat to 60°C and reflux for 8 h. The ratio of intermediate 2, iodomethane and acetonitrile is 10 mmol: 70 mmol: 50 mL. Finally, release the pressure to atmospheric pressure and remove excess iodomethane and solvent acetonitrile by rotary evaporation to obtain the modified silane coupling agent.

[0049] II. Preparation of Composite Materials

[0050] Modification of natural bamboo fiber: A 60% (v / v) ethanol aqueous solution was prepared using ethanol and deionized water. The modified silane coupling agent was premixed with the ethanol aqueous solution, and the pH was adjusted to 5 with formic acid. Natural bamboo fiber was then added and heated to 60°C for 8 hours. The natural bamboo fiber was selected from yellow bamboo fiber from Sichuan Changsheng New Material Technology Co., Ltd., which has a full color and clear texture. Finally, the fiber was neutralized with ammonia water, filtered, washed with water, and dried to obtain modified bamboo fiber.

[0051] Blending and compounding: The composition consists of 45 wt% modified bamboo fiber, 1.4 wt% lubricant (using commercially available LM type raw material), and 0.1 wt% antioxidant (using commercially available antioxidants 1010 and 168 mixed in equal weight ratios), with the remainder being mPE resin (commercially available Enable™ 27-03HH resin raw material). The mPE resin, lubricant, and antioxidant are premixed and fed into the main feed port of the extruder, while the modified bamboo fiber is fed into the side feed port. The processing temperature range of the extruder is set as follows: Zone 1 190℃, Zone 2 200℃, Zone 3 210℃, Zone 4 210℃, Zone 5 220℃, and Zone 6 210℃. After extrusion and cooling, the composite material is obtained.

[0052] Example 4

[0053] I. Preparation of Modified Silane Coupling Agents

[0054] Step A1: Take silane coupling agent KH-550, undecene bromide and toluene premixed, then add potassium carbonate and anhydrous magnesium sulfate, heat to 85℃ under dry nitrogen protection and stir for 4h. The ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate and toluene is 10mmol:20mmol:1.47g:0.6g:120mL. Finally, filter the reaction product to remove salts, and then remove toluene by rotary evaporation under reduced pressure to obtain intermediate 1.

[0055] Step A2: Premix intermediate 1, tert-butyl mercaptan, acetone, and anhydrous ethanol, then add photoinitiator 651 and mix. Irradiate the mixture at room temperature using a 365nm ultraviolet mercury lamp, controlling the irradiation intensity to 30mW / cm². 2 The mixture was stirred for 2 hours. The ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol was 10 mmol: 20 mmol: 20 mg: 60 mL: 20 mL. Finally, the solvents acetone and ethanol were removed by rotary evaporation to obtain intermediate 2.

[0056] Step A3: Take intermediate 2, iodomethane and acetonitrile, mix them, pressurize with dry nitrogen to 5 bar, heat to 55℃ and reflux for 9 h. The ratio of intermediate 2, iodomethane and acetonitrile is 10 mmol: 60 mmol: 50 mL. Finally, release the pressure to atmospheric pressure and remove excess iodomethane and solvent acetonitrile by rotary evaporation to obtain the modified silane coupling agent.

[0057] II. Preparation of Composite Materials

[0058] Modification of natural bamboo fiber: A 60% (v / v) ethanol aqueous solution was prepared using ethanol and deionized water. The modified silane coupling agent was premixed with the ethanol aqueous solution, and the pH was adjusted to 5 with formic acid. Natural bamboo fiber was then added and heated to 55°C for 9 hours. The natural bamboo fiber was selected from yellow bamboo fiber from Sichuan Changsheng New Material Technology Co., Ltd., which has a full color and clear texture. Finally, the fiber was neutralized with ammonia water, filtered, washed with water, and dried to obtain modified bamboo fiber.

[0059] Blending and compounding: The composition consists of 37 wt% modified bamboo fiber, 1.1 wt% lubricant (using commercially available LM type raw material), and 0.12 wt% antioxidant (using commercially available antioxidants 1010 and 168 mixed in equal weight ratios), with the remainder being mPE resin (commercially available Enable™ 27-03HH resin raw material). The mPE resin, lubricant, and antioxidant are premixed and fed into the main feed port of the extruder, while the modified bamboo fiber is fed into the side feed port. The processing temperature range of the extruder is set as follows: Zone 1 200℃, Zone 2 210℃, Zone 3 210℃, Zone 4 220℃, Zone 5 220℃, and Zone 6 210℃. After extrusion and cooling, the composite material is obtained.

[0060] In the comparative example, referring to the modification method of natural bamboo fiber in Example 4, n-octyltriethoxysilane was used to replace the modified silane coupling agent, and the rest of the implementation process was exactly the same.

[0061] The composite material prepared above was hot-pressed and molded at 220℃ and 10MPa using a flat vulcanizing machine and then sampled.

[0062] Impact performance was tested according to GB / T 1843-2008 standard; gloss at 45° was tested according to ASTM D2457-21 standard; simulated bending test: a strip specimen with dimensions of 100×30mm was prepared, with a clamping length of 10mm at both ends, and bending parameters of 90°×100 times; the gloss of the specimen was tested again and the rate of change was calculated; the specific test results are shown in Table 1:

[0063] Table 1 <![CDATA[Impact strength / kJ·m -2 > Gloss (45°) Gloss change rate / % Example 1 11.9 37.2 -6.6 Example 2 11.4 33.4 -14.8 Example 3 9.7 25.1 -20.9 Example 4 12.5 30.6 -8.7 Comparative Example 8.8 21.5 -47.3

[0064] As shown in Table 1, the gloss of the composite material surface gradually decreased as the bamboo fiber content increased from 30 wt% to 45 wt%. This is in line with expectations, because the introduction of bamboo fiber will form microscopic unevenness on the material surface, causing diffuse reflection of light and thus reducing the specular gloss. Nevertheless, even at a high filling amount of 45 wt% and after repeated bending, the material still maintained an acceptable gloss. This is due to the high transparency of mPE itself and the excellent interfacial bonding brought by the modified silane coupling agent of this invention, which avoids severe light scattering caused by interfacial defects.

[0065] The impact strength did not increase monotonically with the increase of bamboo fiber content, but reached a higher value in Example 4. This indicates that under this ratio, the reinforcing and toughening effect of the fiber and the interfacial bonding effect reached the best balance. However, the impact strength of all examples was higher than that of the comparative example, which fully demonstrates the effectiveness of the interfacial modification of the present invention in improving toughness.

[0066] The composite material of the example has higher impact strength and better structural stability of the product. In the gloss test, the example has better gloss and the gloss decrease after bending is significantly lower than that of the comparative example.

[0067] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0068] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A natural bamboo fiber modified PE composite material, characterized in that, The specific components are: 30-45 wt% modified bamboo fiber, 0.9-1.4 wt% lubricant, and 0.1-0.13 wt% antioxidant, with the balance being mPE resin; The modified bamboo fiber is obtained by coupling natural bamboo fiber with a modified silane coupling agent, wherein the modified silane coupling agent is prepared by the following method: Step A1: Premix silane coupling agent KH-550, undecene bromide and toluene, then add potassium carbonate and anhydrous magnesium sulfate, heat to 80-100℃ under dry nitrogen protection and stir for 3-4 hours to prepare intermediate 1; Step A2: Premix intermediate 1, tert-butyl mercaptan, acetone, and anhydrous ethanol, then add photoinitiator 651 for miscibility, and incubate at room temperature at 25-35 mW / cm 2 The mixture was subjected to ultraviolet irradiation and stirring for 1.5-2 hours to produce intermediate 2. Step A3: Mix intermediate 2, iodomethane and acetonitrile, pressurize with dry nitrogen to 4-5 bar, heat to 50-60℃ and reflux for 8-10 hours to prepare modified silane coupling agent.

2. The natural bamboo fiber modified PE composite material according to claim 1, characterized in that, The ratio of silane coupling agent KH-550, undecene bromide, potassium carbonate, anhydrous magnesium sulfate and toluene is 10 mmol: 20 mmol: 1.4-1.8 g: 0.5-0.7 g: 100-130 mL.

3. The natural bamboo fiber modified PE composite material according to claim 2, characterized in that, The ratio of intermediate 1, tert-butyl mercaptan, photoinitiator 651, acetone and anhydrous ethanol is 10 mmol: 20 mmol: 20-30 mg: 50-70 mL: 15-30 mL.

4. The natural bamboo fiber modified PE composite material according to claim 3, characterized in that, The ratio of intermediate 2, iodomethane, and acetonitrile is 10 mmol: 50-70 mmol: 40-50 mL.

5. The natural bamboo fiber modified PE composite material according to claim 4, characterized in that, The preparation method of modified bamboo fiber is as follows: premix the modified silane coupling agent and the ethanol aqueous solution, adjust the pH value to 5 with formic acid, add natural bamboo fiber and heat to 60℃ to soak for 8-12 hours, then neutralize with ammonia water, filter, wash with water, and dry to obtain modified bamboo fiber.

6. The natural bamboo fiber modified PE composite material according to claim 5, characterized in that, The ratio of natural bamboo fiber, modified silane coupling agent, and ethanol aqueous solution is 50g: 4.2-5.5g: 100-120mL.

7. A method for preparing a natural bamboo fiber modified PE composite material according to any one of claims 1-6, characterized in that, Specifically, the process involves premixing mPE resin, lubricant, and antioxidant and feeding them into the main feed port of the extruder, while modified bamboo fiber is fed into the side feed port. The processing temperature is controlled within the range of 190-220℃. After extrusion and cooling, the composite material is obtained.

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