An imine bond enhanced polyolefin self-healing material and a preparation method thereof

Abstract

The application discloses an imine bond reinforced polyolefin self-repairing material and a preparation method thereof. The main chain of the imine bond reinforced polyolefin self-repairing material contains structural units shown in general formula (I) and general formula (II), the side chain contains a structural unit shown in general formula (III), and the main chain and the side chain are connected through a covalent bond. In the formula, x and y are the mole percentages of the structural units in the main chain, x and y are positive numbers satisfying x>0, y>0, x>y and 80%<=x+y<=100%; R is a halogen atom, and R1 is an aliphatic methylene chain or an aromatic group. The imine bond reinforced polyolefin self-repairing material has excellent self-repairing performance and strong service ability, and the opening of self-repairing does not need external stimulation or energy injection. The introduction of the dynamic imine bond can improve the self-repairing efficiency and the mechanical properties of the material, and the comprehensive performance of the material is excellent, and the effect is remarkable.

Description

Technical Field

[0001] This invention belongs to the field of self-healing, specifically relating to an imine bond-reinforced polyolefin self-healing material and its preparation method. Background Technology

[0002] Polyolefins are widely used due to their advantages such as good chemical stability, high specific strength, low manufacturing cost, excellent corrosion resistance, and ease of processing and molding. However, these materials inevitably face damage during use, resulting in microcracks and micro-damage. This micro-damage can rapidly develop into large cracks, and in severe cases, lead to material failure, significantly reducing the service life and operational safety of the pipe material. Self-healing polymer materials can spontaneously or under external stimuli repair damage or microcracks through physical or chemical processes, preventing damage from expanding and causing loss of material properties. This effectively extends the service life of the material and improves its safety and reliability.

[0003] CN111868111A reports a polyolefin self-healing material that achieves self-healing through physical processes. Utilizing the material's microphase separation structure, soft segments can move freely, and the repair process is completed after the chain segments move and entangle at the fracture site. However, this material suffers from long repair times and low efficiency. Furthermore, with increasing self-healing cycles, intermolecular forces weaken, reducing the self-healing effect. In addition, materials relying on free chain segment movement for self-healing often exhibit linear structures, resulting in poor mechanical properties and limited applications. Cross-linking structures can improve the material's mechanical properties but can hinder free chain segment movement, thus affecting self-healing performance.

[0004] An imine bond is a dynamic chemical bond, typically a C=N double bond structure formed by the dehydration condensation reaction of a primary amine and an aldehyde or ketone. If both the aldehyde (or ketone) and the primary amine are aliphatic, the synthesized imine is relatively unstable, and the equilibrium favors the hydrolysis of the imine bond. If at least one of the aldehyde (or ketone) and the primary amine is aromatic, the hydrolytic stability of the synthesized imine increases, and the equilibrium favors the formation of the normal imine bond. Imines are stable under alkaline conditions but readily hydrolyze under acidic conditions; they can be completely hydrolyzed when pH < 6.5. Imines can undergo exchange reactions at room temperature. One reaction involves the hydrolysis equilibrium-induced hydrolysis of the imine back to the original aldehyde (or ketone) and primary amine, with different combinations of aldehydes (or ketones) and primary amines forming new imines. Another reaction involves an amino exchange reaction, where a free primary amine exchanges with the primary amine in the imine, forming a new imine and a new free primary amine. For imines, the hydrolysis equilibrium reaction and the amino exchange reaction can proceed spontaneously at room temperature even without a catalyst.

[0005] Introducing imine bonds into self-healing material systems allows for exchange reactions at the fracture surfaces, enabling self-healing with rapid reaction speed and high efficiency. The imine bond exchange reaction requires no external catalyst and proceeds spontaneously at room temperature. Utilizing imine bonds to link the polymer backbone imparts a dynamic cross-linked structure to the material, improving both its mechanical properties and self-healing efficiency. Summary of the Invention

[0006] The technical problem this invention aims to solve is the long self-healing time and low repair efficiency of polyolefin self-healing materials utilizing physical interactions. By modifying self-healing polyolefins and introducing dynamic chemical bonds, this invention provides a polyolefin self-healing material that combines both physical and chemical effects, enabling it to achieve rapid self-healing performance. Simultaneously, the dynamic chemical bonds impart a cross-linked structure to the material, improving its mechanical properties.

[0007] To address the aforementioned problems, this invention provides an imine-reinforced polyolefin self-healing material, wherein its main chain contains structural units represented by general formulas (I) and (II), and its side chains contain structural units represented by general formula (III), wherein the main chain and the side chains are connected by covalent bonds.

[0008]

[0009] In the formula, x and y are the molar percentages of the structural unit in the main chain, and x and y are positive numbers that satisfy x > 0, y > 0, x > y, and 80% ≤ x + y ≤ 100%; R is a halogen atom, and R1 is an aliphatic methylene chain or an aromatic group.

[0010] The present invention also provides a method for preparing the imine bond-reinforced polyolefin self-healing material as described above, the method comprising the following steps:

[0011] S1. Using a rare earth catalyst to copolymerize a polar olefin monomer and ethylene, a first product containing a halogenated group on the side group is obtained, with the following structural formula:

[0012] In the formula, x and y are positive numbers that satisfy x > 0, y > 0, x > y, and 80% ≤ x + y ≤ 100%; R is a halogen atom;

[0013] S2. The first product is modified by amination, and amino groups are introduced into the side chain of the copolymer to obtain the second product.

[0014] S3. The second product is reacted with a chain extender containing dialdehyde or diketone groups to introduce an imine bond dynamic cross-linking structure on the basis of the original self-healing polyolefin, thereby obtaining the imine bond-reinforced polyolefin self-healing material.

[0015] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein the method for preparing the first product includes:

[0016] ① Under an anhydrous and oxygen-free environment, the rare earth catalyst and polar olefin monomer are dissolved in a three-necked flask containing toluene at a molar ratio of 1:200-1:5000 and stirred.

[0017] ② Evacuate the system, introduce nitrogen gas to ensure an anhydrous and oxygen-free environment, introduce ethylene gas to start the reaction, and after the reaction has been going on for a period of time, stop introducing ethylene gas and add methanol to the system to terminate the reaction.

[0018] ③ Filter to obtain the product, wash with ethanol, and then dry under vacuum to obtain the first product.

[0019] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein in the preparation method of the first product, the reaction time in step ② is 5 min-24 h.

[0020] The present invention discloses a method for preparing an imine bond-reinforced polyolefin self-healing material, wherein the first product has structural units represented by general formula (I) and general formula (II) in its own structure. General formula (I) has strong flexibility and can move freely, while general formula (II) has a crystalline structure and can undergo microphase separation from the part of general formula (II). It also serves as a physical crosslinking point in the overall structure of the first product, giving the first product excellent self-healing properties. In addition, the number average molecular weight of the first product is 20,000-500,000, the molecular weight distribution coefficient is between 1.1 and 2.0, and the glass transition temperature is between -10°C and 15°C.

[0021] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein the method for preparing the second product includes:

[0022] ① Add the first product, excess ammonia, and benzene solvent to a high-pressure reactor to ensure complete reaction;

[0023] ② After the reaction is complete, the system is cooled to room temperature, the pressure is released, ethanol is added, a polymer precipitate is obtained, and the product is obtained by centrifugation;

[0024] ③ The product was washed sequentially with tetrahydrofuran, dichloromethane, and acetone, centrifuged, and then dried to obtain the second product.

[0025] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein in the preparation method of the second product, the reaction temperature in step ① is 80-130℃, the stirring speed is 400-800rpm, and the reaction time is 4-8h.

[0026] In the preparation method of the imine bond-reinforced polyolefin self-healing material of the present invention, in the preparation method of the second product, the drying conditions in step ③ are: vacuum drying at 60-80℃ for 6-12 hours.

[0027] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein the specific operation in step S3 includes:

[0028] ① The second product and the chain extender containing dialdehyde or diketone groups are added to a benzene solvent at a mass ratio of 100:1-10:1. After the reaction is completed, ethanol is added and the product is obtained by centrifugation.

[0029] ② The obtained product is washed and dried with ethanol to obtain the polyolefin self-healing material.

[0030] In the preparation method of the imine bond-reinforced polyolefin self-healing material of the present invention, in step S3, the reaction temperature in step ① is 50-90℃, the stirring speed is 300-600rpm, and the reaction time is 2-4h.

[0031] In the preparation method of the imine bond-reinforced polyolefin self-healing material of the present invention, in step S3, the drying conditions in step ② are: vacuum drying at 60-80℃ for 6-12 hours.

[0032] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein the dialdehyde or diketone is at least one of aliphatic dialdehyde, aliphatic diketone, aromatic dialdehyde, and aromatic diketone.

[0033] The method for preparing the imine bond-reinforced polyolefin self-healing material of the present invention, wherein the dialdehyde or diketone comprises at least one of terephthalaldehyde, glyoxal, 1,3-propanedialdehyde, 1,4-butanedialdehyde, 1,5-pentanedialdehyde, 1,6-hexanedialdehyde, 1,7-heptanedialdehyde, 1,8-octanedialdehyde, 1,9-nonanedialdehyde, 1,10-decanedialdehyde, 2,3-butanedione, and diphenylethylenedione.

[0034] The present invention also provides the application of an imine bond-reinforced polyolefin self-healing material in self-healing protective films, self-healing car cover materials, self-healing pipes, or self-healing fibers.

[0035] Existing self-healing polyolefins achieve their self-healing function through the physical action of microphase separation. These materials exhibit low environmental sensitivity and can withstand complex service environments. However, their self-healing time is long and their efficiency is low. The imine-reinforced self-healing polyolefin material of this invention introduces dynamic imine bonds, which can undergo exchange reactions within the material system, effectively shortening the self-healing time and improving self-healing efficiency. The imine bonds do not require external catalysts or stimuli and can complete the exchange reaction at room temperature. Furthermore, the introduction of imine bonds gives the polyolefin a dynamic cross-linked structure, which can improve the material's mechanical properties to a certain extent, increasing tensile strength and enhancing toughness.

[0036] Through the above technical solution, this invention provides a dynamically imine-bonded reinforced polyolefin self-healing material. Utilizing the microphase separation structure of the main-chain polyolefin, the material exhibits excellent self-healing properties and strong service life. Furthermore, the self-healing process is initiated without external stimulation or energy injection. The introduction of dynamic imine bonds improves self-healing efficiency and enhances the material's mechanical properties, resulting in superior overall performance and significant effects. Attached Figure Description

[0037] Figure 1 The NMR spectrum of the product obtained in Example 1 of this invention;

[0038] Figure 2 The structural formula of the product obtained in Example 5 of this invention;

[0039] Figure 3 This is the structural formula of the product obtained in Example 6 of the present invention. Detailed Implementation

[0040] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0041] This invention provides an imine-reinforced polyolefin self-healing material, wherein the main chain contains structural units represented by general formulas (I) and (II), and the side chains contain structural units represented by general formula (III), wherein the main chain and the side chains are connected by covalent bonds.

[0042]

[0043]

[0044] In the formula, x and y are the molar percentages of the structural unit in the main chain, and x and y are positive numbers that satisfy x > 0, y > 0, x > y, and 80% ≤ x + y ≤ 100%; R is a halogen atom, and R1 is an aliphatic methylene chain or an aromatic group;

[0045] The imine-reinforced polyolefin self-healing material of this invention comprises a copolymer chain obtained by copolymerizing polar / nonpolar olefin monomers. The copolymer has long alternating copolymer segments of polar / nonpolar monomers and short homopolymer segments of nonpolar monomers. The nonpolar homopolymer segments can be arranged in an orderly manner to form a crystalline structure, while the alternating copolymer segments have good flexibility and can move freely. The copolymer can form a microphase-separated structure. When the material is damaged, the chain segments at the damaged site can move freely to complete the self-healing process. The aggregation effect of the crystalline segments also enhances the self-healing ability of the material to a certain extent.

[0046] The imine-reinforced polyolefin self-healing material of this invention is modified by amination of the main chain, introducing a cross-linked structure containing imine bonds into the side chains. An imine bond is a dynamic covalent bond that can complete the exchange reaction at room temperature without a catalyst. Imine bonds are very common in self-healing polymers, exhibiting fast response and good repair effects. In the polyolefin self-healing material of this invention, the introduction of imine bonds into the side chains effectively shortens the self-healing time and improves the self-healing efficiency. Simultaneously, the dynamic cross-linked structure also improves the mechanical strength of the material to a certain extent, giving the polyolefin self-healing material both excellent self-healing and mechanical properties.

[0047] As mentioned above, the main chain of the imine bond-reinforced polyolefin self-healing material of the present invention is a copolymer obtained by copolymerization of polar / nonpolar olefin monomers. In some embodiments, the number average molecular weight of the main chain copolymer is between 20,000 and 500,000, wherein the molar content of polar monomers is greater than 20%, and the glass transition temperature is between -10 and 15°C.

[0048] As mentioned above, the present invention obtains a modified second product with amino groups on the side chain by modifying the main chain of the copolymer. In some embodiments, the modification is carried out by using halogen atoms in the side groups of the main chain to undergo a substitution reaction with ammonia.

[0049] Test methods

[0050] Molecular weight characterization: Sample concentration 0.5-2 g / mL, solvent trichlorobenzene, test temperature 140℃, polystyrene as standard;

[0051] Tensile test: The sample is hot-pressed at 100-150℃ to prepare a dumbbell-shaped strip with a length of 12mm, a width of 2mm, and a thickness of 1mm. The strip is then clamped on a tensile testing machine and stretched at a speed of 200mm / min. -1 ;

[0052] Self-healing performance: The sample was cut with a razor, the cut surfaces were kept in contact, and the healing of the cut was observed at different time intervals. Tensile tests were also performed to characterize the mechanical properties of the repaired sample.

[0053] Example 1

[0054] This embodiment provides a method for preparing the first product, including:

[0055] ① Under an anhydrous and oxygen-free environment, the rare earth catalyst and 1-allyl-4-bromo-2-methoxybenzene were dissolved in a certain proportion into a three-necked flask containing toluene, and stirred for 10 minutes at a speed of 500 rpm.

[0056] ② Evacuate the system, introduce nitrogen gas to ensure an anhydrous and oxygen-free environment, introduce ethylene gas to start the reaction, and after 30 minutes, stop introducing ethylene gas and add methanol to the system to terminate the reaction.

[0057] ③ Filter to obtain the product, wash with ethanol three times, and then dry under vacuum to obtain the first product.

[0058] Table 1 shows the molecular weight and tensile strength of the first product obtained by changing the feed ratio of 1-allyl-4-bromo-2-methoxybenzene monomer and rare earth catalyst.

[0059] Table 1

[0060]

[0061] Table 2 shows the tensile strength of the first product after different self-healing times obtained by changing the feed ratio of 1-allyl-4-bromo-2-methoxybenzene monomer and rare earth catalyst.

[0062] Table 2

[0063] Serial Number 12h 24h 120h 1 1.5 1.6 1.6 2 2.2 3.7 5.6 3 1.3 2.6 6.8

[0064] Example 2

[0065] This embodiment provides a method for preparing the first product, including:

[0066] ① Under an anhydrous and oxygen-free environment, the catalyst and 1-allyl-4-chloro-2-methoxybenzene were dissolved in a three-necked flask containing toluene at a ratio of 1:5000, and stirred for 10 minutes at a speed of 500 rpm.

[0067] ② Evacuate the system, introduce nitrogen gas to ensure an anhydrous and oxygen-free environment, introduce ethylene gas to start the reaction, and after a certain reaction time, stop introducing ethylene gas and add methanol to the system to terminate the reaction.

[0068] ③ Filter to obtain the product, wash with ethanol three times, and then dry under vacuum to obtain the first product.

[0069] Table 3 shows the molecular weight and tensile strength of the first product obtained by changing the reaction time in step ②.

[0070] Table 3

[0071]

[0072] Table 4 shows the tensile strength of the first product after self-repair at different times when the reaction time in step ② is changed.

[0073] Table 4

[0074] Serial Number 12h 24h 120h 1 1.4 2.0 3.1 2 3.1 4.2 6.9 3 1.5 2.8 6.8

[0075] Example 3

[0076] This embodiment provides a method for preparing the second product, as follows:

[0077] ① Add 10g of the first product obtained in Example 1, No. 2, a certain amount of ammonia water and 50mL of dichlorobenzene to a high-pressure reactor. The temperature is 130℃, the stirring speed is 800rpm, and the reaction time is 8h.

[0078] ② After the reaction is complete, the system is cooled to room temperature, the pressure is released, ethanol is added, a polymer precipitate is obtained, and the product is obtained by centrifugation;

[0079] ③ The product was washed three times in sequence with tetrahydrofuran, dichloromethane, and acetone. After centrifugation, the product was dried under vacuum at 70°C for 9 hours to obtain the second product.

[0080] Table 5 shows the tensile strength of the second product obtained by changing the amount of ammonia and the tensile strength after 24 hours of self-healing.

[0081] Table 5

[0082]

[0083] Example 4

[0084] This embodiment provides a method for preparing the second product, as follows:

[0085] ① Add 10g of the first product obtained in Example 1, 5mL of ammonia water and 50mL of dichlorobenzene to a high-pressure reactor, stir at 800rpm, and react at a certain temperature for 8h.

[0086] ② After the reaction is complete, the system is cooled to room temperature, the pressure is released, ethanol is added, a polymer precipitate is obtained, and the product is obtained by centrifugation;

[0087] ③ The product was washed three times in sequence with tetrahydrofuran, dichloromethane, and acetone. After centrifugation, the product was dried under vacuum at 70°C for 9 hours to obtain the second product.

[0088] Table 6 shows the tensile strength of the second product obtained by changing the reaction temperature in step ① and the tensile strength after 24 hours of self-healing.

[0089] Table 6

[0090]

[0091] Example 5

[0092] This embodiment provides a method for introducing dynamic imine bonds into imine-reinforced polyolefin self-healing materials, the specific operation of which is as follows:

[0093] ① The second product of Example 3 No. 2 and terephthalaldehyde were added to 50 mL of toluene solvent at different mass ratios. The reaction was carried out at 450 rpm and 70 °C for 4 h. After the reaction was completed, ethanol was added and the product was obtained by centrifugation.

[0094] ② The obtained polyolefin self-healing material was washed three times with ethanol, and the product was vacuum dried at 70°C for 9 hours to obtain the dynamically imine bond-reinforced polyolefin self-healing material.

[0095] Table 7 shows the tensile strength of the polyolefin self-healing material obtained by changing the ratio of the second product and terephthalaldehyde, and the tensile strength after 24 hours of self-healing.

[0096] Table 7

[0097]

[0098] Table 8 shows the tensile strength of the polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product and terephthalaldehyde.

[0099] Table 8

[0100] Serial Number 5min 12h 24h 1 2.5 5.1 5.9 2 4.2 7.3 8.4 3 4.5 7.5 8.5

[0101] Example 6

[0102] This embodiment provides a method for introducing dynamic imine bonds into imine-reinforced polyolefin self-healing materials, the specific operation of which is as follows:

[0103] ① The second product of Example 3 No. 2 and 1,4-butanedialdehyde were added to 50 mL of dichlorobenzene solvent at different mass ratios. The reaction was carried out at 450 rpm and 70 °C for 4 h. After the reaction was completed, ethanol was added and the product was obtained by centrifugation.

[0104] ② The obtained polyolefin self-healing material was washed three times with ethanol, and the product was vacuum dried at 70°C for 9 hours to obtain the dynamically imine bond-reinforced polyolefin self-healing material.

[0105] Table 9 shows the tensile strength of the polyolefin self-healing material obtained by changing the ratio of the second product to 1,4-butanedialdehyde and the tensile strength after 12 hours of self-healing.

[0106] Table 9

[0107]

[0108] Table 10 shows the tensile strength of the polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product to 1,4-butanedialdehyde.

[0109] Table 10

[0110] Serial Number 5min 6h 12h 1 2.9 5.1 5.6 2 3.9 6.5 7.8 3 4.1 7.1 8.1

[0111] Example 7

[0112] This embodiment provides a method for introducing dynamic imine bonds into imine-reinforced polyolefin self-healing materials, the specific operation of which is as follows:

[0113] ① The second product of Example 3 No. 2 and 1,10-decanedialdehyde were added to 50 mL of xylene solvent at different mass ratios. The reaction was carried out at 450 rpm and 70 °C for 4 h. After the reaction was completed, ethanol was added and the product was obtained by centrifugation.

[0114] ② The obtained polyolefin self-healing material was washed three times with ethanol, and the product was vacuum dried at 70°C for 9 hours to obtain the dynamically imine bond-reinforced polyolefin self-healing material.

[0115] Table 11 shows the tensile strength of the polyolefin self-healing material obtained by changing the ratio of the second product to 1,10-decanedialdehyde and the tensile strength after 12 hours of self-healing.

[0116] Table 11

[0117]

[0118] Table 12 shows the tensile strength of the polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product to 1,10-decanedialdehyde.

[0119] Table 12

[0120] Serial Number 5min 6h 12h 1 3.0 5.3 5.8 2 4.1 7.2 8.1 3 4.2 7.7 8.2

[0121] Example 8

[0122] This embodiment provides a method for introducing dynamic imine bonds into imine-reinforced polyolefin self-healing materials, the specific operation of which is as follows:

[0123] ① The second product of Example 3 No. 2 and 2,3-butanedione were added to 50 mL of trichlorobenzene solvent at different mass ratios. The reaction was carried out at 450 rpm and 70 °C for 4 h. After the reaction was completed, ethanol was added and the product was obtained by centrifugation.

[0124] ② The obtained polyolefin self-healing material was washed three times with ethanol, and the product was vacuum dried at 70°C for 9 hours to obtain the dynamically imine bond-reinforced polyolefin self-healing material.

[0125] Table 13 shows the tensile strength of the polyolefin self-healing material obtained by changing the ratio of the second product to 2,3-butanedione and the tensile strength after 12 hours of self-healing.

[0126] Table 13

[0127]

[0128]

[0129] Table 14 shows the tensile strength of the polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product to 2,3-butanedione.

[0130] Table 14

[0131] Serial Number 5min 6h 12h 1 2.8 4.6 5.5 2 3.8 6.7 7.7 3 4.1 7.3 8.0

[0132] Example 9

[0133] This embodiment provides a method for introducing dynamic imine bonds into imine-reinforced polyolefin self-healing materials, the specific operation of which is as follows:

[0134] ① The second product of Example 3 No. 2 and diphenylethylene glycol were added to 50 mL of trichlorobenzene solvent at different mass ratios. The reaction was carried out at 450 rpm and 70 °C for 4 h. After the reaction was completed, ethanol was added and the product was obtained by centrifugation.

[0135] ② The obtained polyolefin self-healing material was washed three times with ethanol, and the product was vacuum dried at 70°C for 9 hours to obtain the dynamically imine bond-reinforced polyolefin self-healing material.

[0136] Table 15 shows the tensile strength of the polyolefin self-healing materials obtained by changing the ratio of the second product to diphenylethylene glycol and the tensile strength after 24 hours of self-healing.

[0137] Table 15

[0138]

[0139] Table 16 shows the tensile strength of the polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product to diphenylethylene glycol.

[0140] Table 16

[0141] Serial Number 5min 12h 24h 1 2.7 4.2 5.3 2 3.5 6.5 7.8 3 4.0 6.7 8.2

[0142] Comparative Example 1

[0143] This comparative example provides a method for preparing the first product, including:

[0144] ① Under an anhydrous and oxygen-free environment, a certain amount of rare earth catalyst was dissolved in a three-necked flask containing toluene and stirred for 10 minutes at a speed of 500 rpm.

[0145] ② Evacuate the system, introduce nitrogen gas to ensure an anhydrous and oxygen-free environment, introduce ethylene gas to start the reaction, stop introducing ethylene gas after 30 minutes, and add methanol to the system to terminate the reaction.

[0146] ③ The product was obtained by filtration, washed three times with ethanol, and then dried under vacuum to obtain the control product.

[0147] Table 17 shows the molecular weight and self-healing properties of the comparative products obtained by changing the amount of rare earth catalyst.

[0148] Table 17

[0149] Serial Number Catalyst dosage (mg) Number average molecular weight Self-healing performance 1 21 89000 none 2 42 80000 none 3 63 62000 none

[0150] Without the addition of polar olefin monomers, the polymerized product is an ethylene homopolymer. The main chain lacks the flexible segments of alternating ethylene / polar monomers, so the material exhibits the characteristics of a hard plastic with high tensile strength but no self-healing properties.

[0151] Comparative Example 2

[0152] This comparative example provides a method for preparing a polyolefin self-healing material without dynamic imine bonds. The specific steps are as follows:

[0153] ① The second product of Example 3 No. 3 and terephthalic acid were added to toluene solvent in different mass ratios and magnetically stirred for 30 min;

[0154] ② Slowly add 1 mL of isobutyl chloroformate and 3 mL of N-methylmorpholine to the above system. The reaction temperature is 40℃ and the reaction time is 10 h. After the reaction is completed, add ethanol, filter, and obtain the product.

[0155] ③ The obtained polyolefin self-healing material was washed three times with ethanol, and the product was dried under vacuum at 70°C for 9 hours after centrifugation to obtain the polyolefin self-healing material.

[0156] Table 18 shows the tensile strength of the polyolefin self-healing material obtained by changing the ratio of the second product to terephthalic acid and the tensile strength after 24 hours of self-healing.

[0157] Table 18

[0158]

[0159]

[0160] Table 19 shows the tensile strength of polyolefin self-healing materials after different self-healing times obtained by changing the ratio of the second product to terephthalic acid.

[0161] Table 19

[0162] Serial Number 5min 12h 24h 1 0 0.1 0.3 2 0 0 0.1 3 0 0 0

[0163] As shown in Comparative Example 2, when a chain extender without imine bonds is used to connect the self-healing main chain, the product has a non-dynamic cross-linked structure, which restricts the free movement of the main chain. When the degree of cross-linking is low (No. 1), the free movement of the polyolefin main chain is less restricted, and a small amount of mechanical properties can be recovered after a longer recovery time. However, as the degree of cross-linking increases (Nos. 2 and 3), the freedom of the main chain is further restricted, and the self-healing function of the main chain completely disappears.

[0164] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the present invention.

Claims

1. An imine-reinforced polyolefin self-healing material, wherein the main chain contains structural units represented by general formulas (I) and (II), and the side chains contain structural units represented by general formula (III), wherein the main chain and the side chains are connected by covalent bonds. In the formula, x and y are the molar percentages of the structural unit in the main chain, and x and y are positive numbers that satisfy x > 0, y > 0, x > y, and 80% ≤ x + y ≤ 100%; R is a halogen atom, and R1 is an aliphatic methylene chain or an aromatic group.

2. A method for preparing an imine bond-reinforced polyolefin self-healing material, characterized in that, Includes the following steps: S1. Using a rare earth catalyst to copolymerize a polar olefin monomer and ethylene, a first product containing a halogenated group on the side group is obtained, with the following structural formula: In the formula, x and y are positive numbers that satisfy x > 0, y > 0, x > y, and 80% ≤ x + y ≤ 100%; R is a halogen atom; S2. The first product is modified by amination, and amino groups are introduced into the side chain of the copolymer to obtain the second product. S3. The second product is reacted with a chain extender containing dialdehyde or diketone groups to introduce an imine bond dynamic cross-linking structure on the basis of the original self-healing polyolefin, thereby obtaining the imine bond-reinforced polyolefin self-healing material.

3. The preparation method according to claim 2, characterized in that, The method for preparing the first product includes: ① Under an anhydrous and oxygen-free environment, the rare earth catalyst and polar olefin monomer are dissolved in a three-necked flask containing toluene at a molar ratio of 1:200-1:5000 and stirred. ② Evacuate the system, introduce nitrogen gas to ensure an anhydrous and oxygen-free environment, introduce ethylene gas to start the reaction, and after the reaction has been going on for a period of time, stop introducing ethylene gas and add methanol to the system to terminate the reaction. ③ Filter to obtain the product, wash with ethanol, and then dry under vacuum to obtain the first product.

4. The preparation method according to claim 3, characterized in that, In the preparation method of the first product, the reaction time in step ② is 5 min-24 h.

5. The preparation method according to claim 2, characterized in that, The first product has a number average molecular weight of 20,000-500,000, a molecular weight distribution coefficient of 1.1-2.0, and a glass transition temperature of -10℃ to 15℃.

6. The preparation method according to claim 2, characterized in that, The method for preparing the second product includes: ① Add the first product, excess ammonia and benzene solvent into a high-pressure reactor to ensure complete reaction; ② After the reaction is complete, the system is cooled to room temperature, the pressure is released, ethanol is added, a polymer precipitate is obtained, and the product is obtained by centrifugation; ③ The product was washed sequentially with tetrahydrofuran, dichloromethane, and acetone, centrifuged, and then dried to obtain the second product.

7. The preparation method according to claim 6, characterized in that, In the preparation method of the second product, the reaction temperature in step ① is 80-130℃, the stirring speed is 400-800rpm, and the reaction time is 4-8h; In the preparation method of the second product, the drying conditions in step ③ are: vacuum drying at 60-80℃ for 6-12 hours.

8. The preparation method according to claim 2, characterized in that, The specific operations in step S3 include: ① The second product and the chain extender containing dialdehyde or diketone groups are added to a benzene solvent at a mass ratio of 100:1-10:

1. After the reaction is completed, ethanol is added and the product is obtained by centrifugation. ② The obtained product is washed and dried with ethanol to obtain the polyolefin self-healing material.

9. The preparation method according to claim 8, characterized in that, In step S3, the reaction temperature in step ① is 50-90℃, the stirring speed is 300-600rpm, and the reaction time is 2-4h. In step S3, the drying conditions in step ② are: vacuum drying at 60-80℃ for 6-12 hours.

10. The preparation method according to claim 2, characterized in that, The dialdehyde or diketone is at least one of aliphatic dialdehyde, aliphatic diketone, aromatic dialdehyde, and aromatic diketone.

11. The preparation method according to claim 2, characterized in that, The dialdehyde or diketone includes at least one of terephthalaldehyde, glyoxal, 1,3-propanedialdehyde, 1,4-butanedialdehyde, 1,5-pentanedialdehyde, 1,6-hexanedialdehyde, 1,7-heptanedialdehyde, 1,8-octanedialdehyde, 1,9-nonanedialdehyde, 1,10-decanedialdehyde, 2,3-butanedione, and diphenylethylenedione.

12. The application of the imine bond-reinforced polyolefin self-healing material of claim 1 in self-healing protective films, self-healing car cover materials, self-healing pipes, or self-healing fibers.

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