Low-temperature-resistant impact-resistant nylon material and preparation method thereof

Abstract

The application discloses a low-temperature-resistant and impact-resistant nylon material and a preparation method thereof, and relates to the technical field of polymer materials. 3+ The Fe ions provided by the trivalent iron salt are simultaneously connected to the carboxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals and the citrate macromolecular plasticizer through coordination bonds, and the citrate macromolecular plasticizer is anchored on the surface of the carboxylated bio-based cellulose nanocrystals. The modified nylon material of the application breaks through the limitation that traditional elastomers lose toughening effect due to glassification at extremely low temperatures, and the material still exhibits excellent notched impact strength in an ultralow-temperature environment of-60 DEG C to-70 DEG C, effectively widening the extreme service temperature interval of the nylon material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a low-temperature resistant and impact-resistant nylon material and its preparation method. Background Technology

[0002] Polyamide (commonly known as nylon), as an important engineering plastic, has been widely used in automotive parts, electronics, aerospace and machinery manufacturing due to its excellent mechanical strength, wear resistance, chemical corrosion resistance and easy processing. However, because the nylon macromolecular chain contains a large number of amide groups, it has the characteristics of strong polarity and easy crystallization, which causes conventional nylon materials to exhibit obvious brittleness under low temperature conditions (especially sub-zero environments), and the notched impact strength drops sharply, which seriously limits the application of nylon materials in extremely cold regions and low temperature working environments.

[0003] To improve the low-temperature impact resistance of nylon materials, existing technologies typically employ blending modification for toughening. The most common modification methods include adding small-molecule plasticizers and blending with elastomers (such as EVA, POE, etc.) through extrusion. For example, Chinese patent document 202311480794.1 discloses a low-temperature toughened PA6, which uses PA6 blended with EVA elastomer and adds small-molecule glycerol plasticizer, haloferric nanotubes, and organosilicon chain extenders, and is prepared through conventional melt blending extrusion. However, conventional modification methods, represented by this existing technology, still have the following inherent technical defects: First, using small-molecule substances such as glycerol as plasticizers, they are very easy to migrate and precipitate to the surface during material processing and long-term use, resulting in a significant decrease in the low-temperature toughness of the material after long-term use. Secondly, the glass transition temperature of the selected common elastomer (such as EVA) is usually around -35℃. When it is in an ultra-low temperature environment below -50℃, the molecular chain segments inside the elastomer will freeze and cannot effectively dissipate the impact energy through cavitation or crimping when it is impacted, thus causing the ultra-low temperature toughening mechanism to completely fail. Third, relying solely on conventional chain extension and nanofiller reinforcement fails to fundamentally reconstruct the energy dissipation mechanism within nylon materials, and cannot solve the problem of the lack of energy dissipation mechanism at ultra-low temperatures.

[0004] Therefore, there is an urgent need to develop a new type of low-temperature resistant and impact-resistant modified nylon to solve the problems of easy precipitation of small molecule plasticizers and failure of toughening mechanism under ultra-low temperature environment in existing technologies. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a low-temperature resistant and impact-resistant nylon material and its preparation method. This invention completely solves the industry pain points of small molecule plasticizer precipitation and toughening failure under ultra-low temperature conditions by constructing an unconventional modification system of "coordination-immobilized macromolecular plasticization" and "crystal-induced ultra-low temperature energy dissipation." Furthermore, during the research and development process, this invention further explores and proposes a technical solution involving the introduction of silane coupling agents to construct an external flexible shielding layer, thus solving the agglomeration problem of the composite carrier during high-temperature melting.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature resistant and impact-resistant nylon material is prepared from raw materials containing the following components: nylon matrix, coordination composite toughening carrier and long-chain alkylsilane coupling agent; The coordination composite toughening carrier includes carboxylated bio-based cellulose nanocrystals (CNC-COOH), citrate macromolecular plasticizer, and ferric salt (Fe). 3+ Salt); The carboxylated bio-based cellulose nanocrystals, citrate macromolecular plasticizer, and ferric salt are connected via Fe... 3+ Metallic coordination bonds are combined; One end of the long-chain alkylsilane coupling agent condenses with the free hydroxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals, and its long-chain alkyl segment forms a hydrophobic flexible shielding layer around the coordination composite toughening carrier.

[0007] Preferably, the nylon matrix is ​​selected from at least one of polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 66), or copolymers thereof.

[0008] Preferably, the citrate macromolecular plasticizer is selected from at least one of tributyl citrate, acetylated tributyl citrate, or trioctyl citrate.

[0009] Preferably, the trivalent iron salt is selected from at least one of ferric chloride, ferric sulfate, or ferric nitrate.

[0010] Preferably, the long-chain alkylsilane coupling agent is selected from at least one of octyltrimethoxysilane, dodecyltrimethoxysilane, or hexadecyltrimethoxysilane.

[0011] The second objective of this invention is to provide a method for preparing the aforementioned low-temperature resistant and impact-resistant nylon material, comprising the following steps: (1) One-step liquid phase coordination method: Carboxylated bio-based cellulose nanocrystals, citrate macromolecular plasticizers, ferric salts and long-chain alkylsilane coupling agents are mixed and reacted in an alcohol solvent at room temperature to achieve metal coordination and coupling condensation. After removing the solvent, a coordination composite toughening carrier with a flexible shielding layer is obtained. (2) Conventional melt blending: The coordination composite toughening carrier obtained in step (1) is mixed with the nylon matrix in proportion and then added to a twin-screw extruder for melt blending, extrusion and granulation to obtain low-temperature resistant and impact-resistant modified nylon.

[0012] 1. This invention breaks with the conventional approach of small-molecule free plasticizers, employing carboxylated bio-based cellulose nanocrystals (CNC-COOH) with a large specific surface area as the substrate carrier, utilizing Fe... 3+ The excellent coordination ability of metal ions immobilizes the citrate macromolecular plasticizer on the surface of nanocrystals. The macromolecular plasticizer itself has extremely low mobility, and combined with the high bond energy of Fe... 3+ Coordination bonds bind the material to the nanocarrier, completely eliminating the risk of plasticizer precipitation and ensuring the long-term performance stability of the material. More importantly, unlike the conventional weak hydrogen bonding interactions, Fe... 3+ Coordinate bonds have higher bond energy and can still maintain the ability to break and rebuild in an ultra-low temperature environment of -70℃. When subjected to external impact, the coordinate bonds break and slide to recombine, which can continuously and effectively absorb and dissipate impact energy.

[0013] 2. This invention starts with the intrinsic crystal form of the nylon matrix and utilizes the interfacial induction effect of functionalized cellulose nanocrystals as highly efficient nucleation inducing agents to regulate the crystallization behavior of the nylon matrix. Conventional nylon matrices are mainly composed of tightly packed α crystals, and the molecular chain segments are locked at low temperatures, making them prone to brittle fracture under impact. However, this invention utilizes the special chemical environment and geometric configuration of the composite carrier surface to induce the formation of a large number of more loosely arranged γ crystals during the crystallization process of nylon. The chain segment mobility in the γ crystals is significantly enhanced, giving the matrix excellent low-temperature toughness. More uniquely, during the ultra-low temperature impact process, stress-induced phase transformation from α crystals to γ ​​crystals or transformation of γ crystals to other high-energy-consuming conformations occurs inside the material. This phase transformation process dissipates a large amount of impact energy, successfully breaking through the temperature limit of traditional elastomer cavitation toughening.

[0014] 3. This invention creatively introduces long-chain alkylsilane coupling agents for interface modification. During the liquid-phase coordination preparation of the carrier, the silanol groups of the silane coupling agent undergo dehydration condensation with the free hydroxyl groups on the CNC surface, while its long-chain alkyl groups extend outward to form a "flexible hydrocarbon brush" covering the outer periphery of the carrier. This structure provides strong steric hindrance during the high-temperature melt extrusion of modified nylon, effectively preventing thermal agglomeration between nanocarriers and ensuring their uniform nanoscale dispersion in the nylon matrix. At the same time, these long-chain alkyl groups can generate good microcompatibility with the long aliphatic hydrocarbon chains of the nylon matrix, forming an ultra-low temperature buffer elastic layer at the interface between the two phases.

[0015] Based on the above mechanism, the correlation formula between the core energy dissipation and structural parameters involved in the system of this invention is described as follows: (1) Formula for total energy dissipation during impact fracture of the system: ; The parameters are defined as follows: This refers to the total energy dissipated by the low-temperature resistant and impact-resistant nylon material when it fractures due to an external transient impact; To pass through Fe 3+ The energy dissipated by the reversible dynamic fracture and in-situ reconstruction of the metal coordination network under stress; This refers to the additional phase transition energy absorbed and dissipated during the impact process due to stress-induced crystal transformation (especially the transformation from α crystal to γ ​​crystal). The energy dissipated by the plastic yielding deformation of the nylon matrix itself; The flexible hydrocarbon brush interface layer formed by long-chain alkylsilane coupling agents absorbs buffer energy through chain segment friction and elastic deformation.

[0016] (2) Formula for crystal form induction index: In this invention, the induction efficiency of the coordination composite toughening support for γ-phase formation can be characterized by the phase induction index: ; The parameters are defined as follows: The crystal induction index represents the crystal form induction index. The larger the value, the more stable the foundation of the intrinsic toughening mechanism at ultra-low temperatures in the material system. The integral area of ​​characteristic diffraction peaks belonging to the γ crystal form in wide-angle X-ray diffraction (WAXD) tests; The integral area of ​​the characteristic diffraction peaks belonging to the α crystal form in the WAXD test; This represents the steric hindrance effect factor provided by long-chain alkylsilane coupling agents; This represents the equivalent length of the alkyl carbon chain in the coupling agent structure.

[0017] (3) Formula for coordination crosslinking network density: The density of the coordination network established between cellulose nanocrystals and macromolecular plasticizers is defined according to the following relationship: ; The parameters are defined as follows: This represents the density of the dynamic coordination crosslinking network introduced within the modified nylon system due to the addition of a composite carrier; This represents the mass of ferric ions that actually participate in coordination during the preparation of the coordination composite toughening support; It is Avogadro's constant; To obtain the total volume of the modified nylon system; This represents the molar mass of the ferric ion; The effective coordination coefficient is used to characterize the proportion of coordination bonds that have successfully participated in dynamic recombination without being completely blocked by steric hindrance.

[0018] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows: 1. The modified nylon material of the present invention breaks through the limitation of traditional elastomers that lose their toughening effect due to glassization at extremely low temperatures. The material can still exhibit excellent notched impact strength in ultra-low temperature environments of -60℃ to -70℃, effectively expanding the extreme service temperature range of nylon materials.

[0019] 2. This invention securely locks macromolecular plasticizers onto nanocrystalline carriers through coordination bonds, fundamentally eliminating the migration and precipitation problems caused by small molecule free radicals, and ensuring the high performance stability and surface smoothness of modified nylon products under long-term, harsh environments.

[0020] 3. The preparation method of the present invention abandons the cumbersome processes in the prior art, such as high temperature and high pressure synthesis of core-shell particles and complex multi-step grafting reaction of castor oil. It adopts a one-step liquid phase mixing preparation of toughening carrier at room temperature combined with conventional twin-screw melt extrusion process, which has extremely low dependence on existing production equipment. The process has a short production flow and significantly reduced energy consumption, and has excellent adaptability and economy for large-scale industrial mass production.

[0021] 4. Unlike the severe anisotropy caused by conventional glass fiber reinforcement (such as a precipitous decline in vertical impact performance), this invention uses a nanoscale composite carrier and intrinsic crystal form control to make the final modified nylon have excellent isotropy, which can effectively resist complex stress impacts from all directions and avoid stress concentration-induced brittle fracture. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the coordination composite toughening carrier structure of the present invention; Figure 2 This is a flowchart illustrating the preparation process of the low-temperature resistant and impact-resistant nylon material of the present invention. Figure 3This is a schematic diagram of the impact energy dissipation mechanism of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. The specific embodiments described herein are merely for explaining the invention and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the essential spirit of this invention without creative effort are within the protection scope of this invention.

[0024] Unless otherwise specified, all reagents and raw materials mentioned in this instruction manual can be obtained through conventional commercial channels.

[0025] Please see the appendix Figure 1 -Appendix Figure 3 This invention relates to a low-temperature resistant and impact-resistant nylon material and its preparation method. Example 1

[0026] This embodiment provides a low-temperature resistant and impact-resistant nylon material and its preparation method.

[0027] The selected raw material components and their mass ratios are as follows: Nylon 6 (PA6, relative viscosity 2.8): 100 parts by weight; Carboxylated bio-based cellulose nanocrystals (CNC-COOH, degree of carboxyl substitution 0.4): 3 parts by weight; Tributyl citrate (macromolecule plasticizer): 2 parts by weight; Anhydrous ferric chloride (Fe) 3+ Salt): 0.5 parts by weight; Hexadecyltrimethoxysilane (long-chain alkylsilane coupling agent): 0.8 parts by weight; Anhydrous ethanol: 50 parts by weight.

[0028] The detailed steps of its preparation method are as follows: Step (1): Preparation of one-step liquid-phase coordination composite support Three parts by weight of carboxylated bio-based cellulose nanocrystals were dispersed in 50 parts by weight of anhydrous ethanol. An ultrasonic disperser was used to disperse the nanocrystals at room temperature (approximately 25°C) for 30 minutes to form a homogeneous suspension. Subsequently, under continuous mechanical stirring (600 r / min), 0.5 parts by weight of anhydrous ferric chloride were completely dissolved in 10 parts by weight of anhydrous ethanol and then slowly added dropwise to the suspension. The mixture was stirred and reacted for 1 hour to allow Fe... 3+ With the carboxyl groups (-COO) on the surface of nanocrystals - Sufficient metal ion coordination occurs.

[0029] Next, 2 parts by weight of tributyl citrate and 0.8 parts by weight of hexadecyltrimethoxysilane were mixed thoroughly and added dropwise to the above reaction system. The mixture was stirred at room temperature for 4 hours. During this process, tributyl citrate reacted with Fe through its electron-rich ester carbonyl group and terminal hydroxyl group. 3+ Unsaturated empty orbitals in the middle generate coordination, thus being firmly "anchored" to the surface of cellulose nanocrystals; Meanwhile, the methoxy group in hexadecyltrimethoxysilane undergoes partial hydrolysis and condenses with the free hydroxyl groups remaining on the surface of cellulose to form a covalent bond. Its long-chain alkyl group containing 16 carbon atoms extends outward and coats the carrier to form a hydrophobic "flexible hydrocarbon brush" shielding layer.

[0030] After the reaction was completed, the mixture was subjected to rotary evaporation under reduced pressure to remove the anhydrous ethanol solvent, and then dried in a vacuum drying oven at 60°C for 12 hours. After grinding and sieving, a coordination composite toughening carrier powder with a flexible external shielding layer was obtained.

[0031] Step (2): Conventional melt blending extrusion granulation The coordination composite toughening carrier powder obtained in step (1) is premixed with 100 parts by weight of nylon 6 resin particles in a high-speed mixer (premixing time 5 minutes), and the mixture is added to the feed port of a co-rotating twin-screw extruder.

[0032] The temperature settings for each zone of the twin-screw extruder are as follows: feeding zone 210℃, melting zone 230℃, mixing zone 240℃, venting zone 240℃, and die head 235℃. The main unit speed is set to 200 r / min.

[0033] Under the strong shearing force and high temperature inside the extruder, the nylon macromolecules melt. The coordinated composite toughening carrier powder is uniformly dispersed into the nylon melt due to the steric hindrance effect of the external long-chain alkyl shielding layer and its compatibility with the nylon chain segments, without any agglomeration. The extruded strip is then cooled in a cooling water tank, pelletized, and dried to finally obtain the desired low-temperature resistant and impact-resistant modified nylon.

[0034] In the system operation mechanism of this embodiment, the total energy dissipated during impact fracture is... The mechanism is perfectly realized; when the nylon material encounters external impact at -65°C, its dense internal structure... Fe in coordination crosslinking network 3+ - The coordination bonds of the citrate ester undergo reversible cleavage, absorbing a large amount of energy. Immediately afterwards, the flexible hydrocarbon brush interface layer elastically slides under pressure, absorbing and buffering energy. ; Simultaneously, when stress is transferred to the nylon matrix, it induces a rapid torsional transformation of the nylon macromolecules surrounding the nanocrystals from their initial state to the γ-crystal form, consuming a huge amount of phase transition energy. This prevents the propagation of micro-cracks into disasters and greatly avoids the brittle fracture of materials. Example 2

[0035] This embodiment provides another low-temperature resistant and impact-resistant nylon material and its preparation method.

[0036] The selected raw material components and their mass ratios are as follows: Nylon 66 (PA66): 100 parts by weight; Carboxylated bio-based cellulose nanocrystals (CNC-COOH, degree of carboxyl substitution 0.5): 5 parts by weight; Acetyl tributyl citrate: 4 parts by weight; Ferric sulfate (Fe) 3+ Salt): 0.8 parts by weight; Dodecyltrimethoxysilane (long-chain alkylsilane coupling agent): 1.5 parts by weight; Anhydrous ethanol: 80 parts by weight.

[0037] The detailed steps of its preparation method are as follows: Step (1): Preparation of one-step liquid-phase coordination composite support Five parts by weight of carboxylated bio-based cellulose nanocrystals were added to 80 parts by weight of anhydrous ethanol and ultrasonically dispersed at room temperature for 40 minutes to form a stable and uniform colloidal dispersion. At a stirring rate of 800 r / min, 0.8 parts by weight of pre-dissolved ferric sulfate solution was added and the reaction was continued for 1.5 hours. The high valence charge and empty orbitals of iron ions formed a preliminary stable strong coordination base with the carboxyl groups.

[0038] Subsequently, a mixture of 4 parts by weight of acetylated tributyl citrate and 1.5 parts by weight of dodecyltrimethoxysilane was gradually added dropwise. The introduction of acetylated tributyl citrate increased the flexible chain segments inside the macromolecule, further enhancing the plasticizing function. Dodecyltrimethoxysilane was grafted onto the surface of nanocellulose via a hydrolysis-condensation process. After stirring at room temperature for 5 hours, unreacted residues were removed by centrifugation and washing, and then instantaneously dried and separated using a spray drying device (inlet air temperature set at 120℃, outlet air temperature at 70℃), resulting in a fluffy coordination composite toughening carrier powder.

[0039] Step (2): Conventional melt blending extrusion granulation Considering the high melting point of Nylon 66, the temperature profile of the twin-screw extruder is set as follows: Zone 1 (feeding) 240℃, Zone 2 260℃, Zone 3 (mixing) 275℃, Zone 4 275℃, Zone 5 270℃, and die head 270℃. The screw speed is set to 250 r / min.

[0040] 100 parts by weight of fully dried nylon 66 granules and the aforementioned coordinated composite toughening carrier were placed in a mixing tank and dry-mixed and coated using low-speed stirring. The mixture was then fed into an extruder via a gravity feeding system. The high-temperature melt of nylon 66 deeply entangled with the flexible carbon-12 chains on the outer layer of the carrier. Simultaneously, due to the crystal induction index of this invention… Medium spatial steric hindrance factor Equivalent length of alkyl carbon chain The synergistic amplification effect of the nylon 66 matrix generates a strong heterogeneous nucleation induction force at the nanocrystal interface during the melt cooling and crystallization process. This forcefully induces the formation of a significantly increased proportion of γ crystals in the nylon 66 matrix, which usually only produces a small amount of α crystals. Through extrusion, water cooling, strip drawing, and pelletizing steps, a low-temperature resistant and impact-resistant nylon material based on nylon 66 is obtained. Example 3

[0041] This embodiment provides another low-temperature resistant and impact-resistant nylon material and its preparation method. This embodiment uses a mixed matrix of nylon 6 and nylon 66 to seek a balance of comprehensive performance.

[0042] The selected raw material components and their mass ratios are as follows: Nylon matrix (composed of 70 parts by weight of nylon 6 and 30 parts by weight of nylon 66): Total 100 parts by weight; Carboxylated bio-based cellulose nanocrystals (CNC-COOH): 4 parts by weight; Trioctyl citrate: 3 parts by weight; Ferric nitrate: 0.6 parts by weight; Octyltrimethoxysilane: 1.0 parts by weight; Isopropanol / anhydrous ethanol mixed solvent (volume ratio 1:1): 60 parts by weight.

[0043] Preparation process: Step (1): Following the same operating logic as in Example 1, CNC-COOH and ferric nitrate were added sequentially to a mixed solvent of isopropanol and anhydrous ethanol for initial coordination (reaction for 1 hour). Then, trioctyl citrate (providing a longer carbon chain structure, resulting in better plasticizing effect and low-temperature molecular fluidity) and octyltrimethoxysilane were added. The mixture was stirred mechanically at room temperature for 4.5 hours. The mixture was then dried in a vacuum drying oven at 80°C for 8 hours using the solvent evaporation method to obtain the coordination composite toughening carrier.

[0044] Step (2): The prepared composite carrier is mixed with nylon 6 / nylon 66 blended resin and melt-blended in a twin-screw extruder. Due to the use of a blended matrix, the processing temperatures of the extruder are set sequentially as follows: 230℃, 255℃, 260℃, 260℃, 250℃. In this embodiment, in addition to the aforementioned mechanism, due to the lattice difference between nylon 6 and nylon 66, the coordination composite toughening carrier further acts as a coupling bridge at the interface between the two phases, with an effective coordination coefficient. Maintaining a high level, a dense and dynamic coordination cross-linking network is formed at the phase interface. After extrusion granulation, the modified nylon exhibits excellent uniformity on a macroscopic scale. Due to its excellent network energy dissipation capability and stable structure, the material has a smooth appearance after long-term hot and cold alternating tests, without any whitening or oiling caused by the precipitation of macromolecular plasticizers, which confirms the perfect establishment of the migration-free system of this invention.

[0045] The modified nylon material prepared in the above embodiments of the present invention significantly reduces the exudation rate of plasticizer during its life cycle while maintaining the excellent mechanical tensile strength of nylon. At the same time, it fully activates the energy dissipation potential of nylon at ultra-low temperatures, enabling the lower limit of the normal operating temperature to be successfully lowered. This solution provides an innovative material with great industrial application value for high-performance nylon structural components required for aerospace, polar equipment, and high-end winter outdoor equipment.

[0046] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, any simple modifications, equivalent substitutions or improvements made to the present invention without departing from the principles and core technical spirit of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-temperature resistant and impact-resistant nylon material, characterized in that, It is prepared from raw materials comprising a nylon matrix, a coordination composite toughening carrier, and a long-chain alkylsilane coupling agent; The coordination composite toughening carrier is composed of carboxylated bio-based cellulose nanocrystals, citrate macromolecular plasticizer, and ferric salt. The ferric salt provides Fe... 3+ Ions simultaneously connect the carboxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals and the citrate macromolecular plasticizer via coordination bonds, thereby anchoring the citrate macromolecular plasticizer to the surface of the carboxylated bio-based cellulose nanocrystals. One end of the long-chain alkylsilane coupling agent is covalently linked to the free hydroxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals through a condensation reaction, and its long-chain alkyl segment extends and coats the periphery of the coordination composite toughening carrier to form a hydrophobic flexible shielding layer.

2. The low-temperature resistant and impact-resistant nylon material according to claim 1, characterized in that, Based on 100 parts by weight of the nylon matrix, the amount of carboxylated bio-based cellulose nanocrystals is 3 to 5 parts by weight, the amount of citrate macromolecular plasticizer is 2 to 4 parts by weight, the amount of trivalent iron salt is 0.5 to 0.8 parts by weight, and the amount of long-chain alkylsilane coupling agent is 0.8 to 1.5 parts by weight.

3. The low-temperature resistant and impact-resistant nylon material according to claim 1, characterized in that, The nylon matrix is ​​selected from at least one of polycaprolactam and polyhexamethylene adipamide.

4. The low-temperature resistant and impact-resistant nylon material according to claim 1, characterized in that, The citrate macromolecular plasticizer is selected from at least one of tributyl citrate, acetylated tributyl citrate, and trioctyl citrate.

5. The low-temperature resistant and impact-resistant nylon material according to claim 1, characterized in that, The ferric salt is selected from at least one of ferric chloride, ferric sulfate, and ferric nitrate.

6. The low-temperature resistant and impact-resistant nylon material according to claim 1, characterized in that, The long-chain alkylsilane coupling agent is selected from at least one of octyltrimethoxysilane, dodecyltrimethoxysilane, and hexadecyltrimethoxysilane.

7. A method for preparing the low-temperature resistant and impact-resistant nylon material according to any one of claims 1 to 6, characterized in that, Includes the following steps: Carboxylated bio-based cellulose nanocrystals were dispersed in an alcohol solvent, and a ferric salt solution was added and stirred to induce a reaction, allowing Fe... 3+ The metal coordinates are formed with the carboxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals; subsequently, a citrate macromolecular plasticizer and a long-chain alkylsilane coupling agent are added to the reaction system, and the reaction is continued with stirring, allowing the citrate macromolecular plasticizer to pass through Fe... 3+ Coordination bonds are anchored on the surface of the carboxylated bio-based cellulose nanocrystals. The silane groups of the long-chain alkylsilane coupling agent undergo condensation with the free hydroxyl groups on the surface of the carboxylated bio-based cellulose nanocrystals to form covalent bonds. Its long-chain alkyl segments extend around the carrier to form a flexible shielding layer. After removing the alcohol solvent, a coordination composite toughened carrier is obtained. The coordination composite toughening carrier is mixed with the nylon matrix and then fed into a twin-screw extruder for melt blending, extrusion, and granulation to obtain the low-temperature resistant and impact-resistant nylon material.

8. The preparation method according to claim 7, characterized in that, The alcohol solvent is selected from at least one of anhydrous ethanol and isopropanol; the carboxylated bio-based cellulose nanocrystals are ultrasonically dispersed in the alcohol solvent at 15°C to 30°C for 20 to 40 minutes, then ferric salt is added and the mixture is reacted for 1 to 1.5 hours under mechanical stirring at 500 r / min to 800 r / min; subsequently, a mixture of the citrate macromolecular plasticizer and the long-chain alkylsilane coupling agent is added, and the mixture is stirred and reacted for another 4 to 5 hours at 15°C to 30°C. After removing the solvent, the mixture is dried to obtain the coordination composite toughening carrier.

9. The preparation method according to claim 7, characterized in that, The twin-screw extruder has a processing temperature of 210°C to 275°C and a screw speed of 200 r / min to 250 r / min.

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