Thermotropic self-repairing polyolefin elastomer modified film and preparation method thereof

Abstract

The invention relates to the field of polyolefin elastomer materials, and particularly discloses a thermally-induced self-repairing polyolefin elastomer modified film and a preparation method thereof. The preparation method comprises the following steps: dissolving polyolefin elastomer particles in tetrahydrofuran, sequentially adding an initiator and 2-methyl furan into a substrate solution, then raising the temperature, adding N, N '-(4, 4'-methylene diphenyl) bismaleimide into a grafting system, and finally carrying out alcohol washing and curing to obtain the thermally-induced self-repairing polyolefin elastomer modified film material. The thermally-induced self-repairing polyolefin elastomer modified film material is prepared by adopting a solution method, the preparation method is simple and easy to operate, the preparation cost is low, and a new direction is provided for preparation of the polyolefin elastomer material.

Description

Technical Field

[0001] This invention relates to the field of polyolefin elastomer materials, specifically to a thermo-induced self-healing polyolefin elastomer modified film and its preparation method. Background Technology

[0002] Polyolefin elastomers (POEs) are polymeric materials formed by copolymerizing ethylene with α-olefins as the main monomer. Due to their excellent chemical resistance, impact resistance and insulation properties, they are widely used in cable sheaths, automotive parts, flexible packaging and consumer products.

[0003] In practical use, POE products inevitably suffer from various mechanical damages and aging. For example, during processing, assembly, or daily use, macroscopic defects such as scratches and punctures are easily generated on their surfaces; under long-term stress or environmental factors, microcracks will initiate and propagate inside the material. These damages not only seriously affect the appearance and sealing performance of the products, but also serve as stress concentration points and aging initiation points, significantly accelerating the structural destruction of the material, leading to a sharp decline in its mechanical properties and functionality, and ultimately affecting the use of the product.

[0004] To improve the usability of POE materials, traditional technologies mainly focus on enhancing their mechanical strength, toughness, or durability through physical blending or composite materials. While these methods can delay the onset or propagation of damage to some extent, a polyolefin elastomer material that can both meet performance requirements and enable the material to actively repair damage has yet to emerge. Therefore, developing a POE material capable of self-repair after damage is of urgent and significant importance for improving durability and high reliability. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention aims to provide a thermo-self-healing polyolefin elastomer modified film and its preparation method. The present invention employs a solution method, using specific raw material formulations and production processes, to prepare a polyolefin elastomer modified film material with excellent thermo-self-healing properties.

[0006] The concept of this invention is as follows: Polyolefin elastomer particles are used as the group raw material, dissolved in tetrahydrofuran solvent to form a homogeneous solution, and then grafted with 2-methylfuran (2-MF) to successfully introduce furan rings into the POE molecular chain, obtaining a POE-furan grafted product. Subsequently, N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) is introduced into this system as a dienophile. The maleimide groups in BMI can undergo Diels-Alder cycloaddition reactions with the furan rings on the POE chain to construct a reversible dynamic covalent crosslinking network. The amounts of 2-MF and BMI are coordinated to construct a suitable dynamic crosslinking network, balancing the mechanical properties and repair effect of the film; the introduction process of BMI is optimized to ensure its effective reaction within the system. Finally, through this DA reaction system, a POE-modified film with both excellent mechanical properties and highly efficient thermo-induced self-healing ability is successfully prepared.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a thermo-induced self-healing polyolefin elastomer modified film includes the following steps: (1) In a light-proof reactor protected by an inert gas, polyolefin elastomer particles and tetrahydrofuran are mixed and heated and stirred until the polyolefin elastomer particles are completely dissolved into a clear and transparent solution; then an initiator is added to the reactor, and after 3-5 min, 2-methylfuran is added to cause a grafting reaction, which takes 5-8 h; finally, N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) solution is added to the reactor, and a Diels-Alder cycloaddition reaction takes place at 65-75 °C for 5-7 h. (2) The sample obtained in (1) was washed with alcohol and then placed in a drying oven for curing to obtain the thermo-induced self-healing polyolefin elastomer modified film material; The molar ratio of N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) to 2-methylfuran is (0.8-1.2):1, preferably 1:1.

[0008] The N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) solution is a mixture of N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) with N,N-dimethylformamide (DMF) / tetrahydrofuran (THF).

[0009] The volume ratio of DMF to THF in the N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) solution is 1:1.

[0010] The ratio of BMI to solvent (DMF and THF) in the N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) solution is (0.5-1.5) g : (20-25) mL.

[0011] The N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) solution is preferably added dropwise to avoid the polyolefin elastomer solution from solidifying and precipitating; the dropping rate is preferably 0.6~0.7 ml / min.

[0012] The reaction temperature for the Diels-Alder cycloaddition reaction should not be too high. If it exceeds 80°C, a large number of bubbles will escape from the reaction system, making the system viscous and affecting the yield. It is speculated that the reaction temperature is too high, resulting in over-crosslinking.

[0013] The polyolefin elastomer particles and tetrahydrofuran are mixed at a ratio of 1g:10ml, and preferably dissolved by heating to 50-60℃.

[0014] The initiator is one or more of 2,2'-azobisisobutyronitrile, benzoyl peroxide, and dimethyl azobisisobutyrate.

[0015] The amount of initiator used is 1 wt.%-2 wt.% of the mass of the polyolefin elastomer particles.

[0016] The mass ratio of 2-methylfuran to polyolefin elastomer particles is 0.25-0.3: 6.75-7.25.

[0017] The reaction temperature at which the grafting reaction occurs is 55-65℃.

[0018] The curing temperature is 50-60℃, and the curing time is 1 day.

[0019] The inert gas is argon, nitrogen, etc.

[0020] The polyolefin elastomer modified film prepared by the above method.

[0021] The self-healing method of the above-mentioned polyolefin elastomer modified film includes: heating the polyolefin elastomer modified film at 75°C for half an hour.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The preparation method of the present invention adopts a highly efficient one-pot solution process, which replaces the traditional high-energy-consuming and high-loss twin-screw melt extrusion modification. Grafting and crosslinking are completed sequentially in a single reactor. The amount of raw materials can be precisely controlled, avoiding thermal degradation and volatilization loss in high-temperature melt processing, and significantly improving the utilization rate of raw materials.

[0023] 2. This invention innovatively introduces the Diels-Alder reaction into the POE thin film system, constructing a dynamic covalent crosslinking network. This structure allows the material to undergo a reverse Diels-Alder reaction and rebonding after mechanical damage, achieving self-repair of microcracks through simple heat treatment. This characteristic greatly improves the long-term reliability of the modified POE film and effectively extends the service life of the components.

[0024] 3. In this invention, by selecting specific dienes (2-MF) and dienophiles (BMI) and precisely controlling their molar ratio (r), the material is endowed with self-healing capabilities while perfectly balancing its mechanical properties. The resulting dynamic network ensures that the film has excellent tensile strength and toughness at room temperature to meet the requirements of lamination processes and outdoor applications, while also enabling efficient repair cycles at specific temperatures. Attached Figure Description

[0025] Figure 1 The infrared spectrum of the polyolefin elastomer film material prepared in Comparative Example 1 is shown.

[0026] Figure 2 Infrared spectrum of the polyolefin elastomer film material prepared for the example.

[0027] Figure 3 The image shows a comparison of scratches and heating on the polyolefin elastomer film material prepared in Comparative Example 1.

[0028] Figure 4 The image shows a comparison of scratches and heating on the polyolefin elastomer film material prepared in Comparative Example 6.

[0029] Figure 5 The image shows a comparison of scratches and repairs on the modified polyolefin elastomer film material prepared in Example I-1.

[0030] Figure 6 The images show a comparison of scratches and repairs on the modified polyolefin elastomer film materials prepared in Example I-2.

[0031] Figure 7 The images show a comparison of scratches and repairs on the modified polyolefin elastomer film materials prepared in Examples I-3.

[0032] Figure 8 The stress-strain curves of the polyolefin elastomer film materials prepared in Comparative Example 1 and the Example are shown.

[0033] Figure 9 The stress-strain curves of the polyolefin elastomer film materials prepared in Comparative Example 1 and Example 2 after scratch repair are shown. Detailed Implementation

[0034] The technical solution of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0035] The raw materials used in the following examples and comparative examples are described below: Tetrahydrofuran (C4H8O, reagent grade, 99.0% purity), 2-methylfuran (C5H6O, 98% purity), furfurylamine (C5H7NO, 99% purity), N,N'-(4,4'-methylenediphenyl)bismaleimide (C 21 H 14 N2O4 (98% purity), 2,2'-azobisisobutyronitrile (C8H) 12 Reagents such as N4 (98% purity), ethanol (C2H6O, ACS, ≥99.5%), and N,N-dimethylformamide (C3H7NO, HPLC grade, ≥99.9%) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; polyolefin elastomer particles (brand name 8175) were purchased from Dow Chemical Company. All reagents were used directly in this experiment without any further purification.

[0036] Comparative Example 1: Preparation of film material using polyolefin elastomer particles, the steps are as follows: (1) Take 7g of polyolefin elastomer particles (POE) and 70ml of tetrahydrofuran (THF) and place them in a brown three-necked flask with a stirrer under argon protection. Heat the flask to 60℃ and stir for 3h to obtain the sample.

[0037] (2) Pour the sample into a polytetrafluoroethylene mold containing anhydrous ethanol for alcohol washing (to remove excess tetrahydrofuran), and then place it in an electric heating drying oven at 60°C for 1 day to cure it, thereby obtaining a polyolefin elastomer film material.

[0038] Example: Effect of different molar ratios of dienes and dienophiles on the self-healing properties of thin films Example I-1: A method for preparing a thermo-induced self-healing polyolefin elastomer film material, comprising the following steps: (1) Take 7g of polyolefin elastomer particles (POE) and 70ml of tetrahydrofuran (THF) and place them in a brown three-necked flask with a stirrer under argon protection. Heat the flask to 60℃ and stir for 3h to obtain a clear and transparent solution.

[0039] (2) Heat to 65°C, add 0.1g of 2,2'-azobisisobutyronitrile (AIBN) to the flask, keep the temperature constant for 3 min, then add 0.25g of 2-methylfuran (2-MF) to the flask and react at a constant temperature for 6 h.

[0040] (3) A mixture of 10 ml N,N-dimethylformamide (DMF), 10 ml tetrahydrofuran (THF) and 0.87 g N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) was ultrasonically shaken for 10 min and then added dropwise to a flask at 0.65 ml / min. The mixture was heated to 70 °C and reacted for 6 h to obtain the sample.

[0041] (4) Pour the sample into a polytetrafluoroethylene mold containing anhydrous ethanol for alcohol washing (to remove excess tetrahydrofuran and N,N-dimethylformamide), and then place it in an electric heating drying oven at 60°C for curing for 1 day to obtain a thermo-induced self-healing polyolefin elastomer modified film material.

[0042] Example I-2: A method for preparing a thermo-induced self-healing polyolefin elastomer modified film material, comprising the following steps: (1) Take 7g of polyolefin elastomer particles (POE) and 70ml of tetrahydrofuran (THF) and place them in a brown three-necked flask with a stirrer under argon protection. Heat the flask to 60℃ and stir for 3h to obtain a clear and transparent solution.

[0043] (2) Heat to 65°C, add 0.1g of 2,2'-azobisisobutyronitrile (AIBN) to the flask, keep the temperature constant for 3 min, then add 0.25g of 2-methylfuran (2-MF) to the flask and react at a constant temperature for 6 h.

[0044] (3) A mixture of 10 ml N,N-dimethylformamide (DMF), 10 ml tetrahydrofuran (THF) and 1.10 g N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) was ultrasonically shaken for 10 min and then added dropwise to a flask at 0.65 ml / min. The mixture was heated to 70 °C and reacted for 6 h to obtain the sample.

[0045] (4) Pour the sample into a polytetrafluoroethylene mold containing anhydrous ethanol for alcohol washing (to remove excess tetrahydrofuran and N,N-dimethylformamide), and then place it in an electric heating drying oven at 60°C for curing for 1 day to obtain a thermo-induced self-healing polyolefin elastomer modified film material.

[0046] Example I-3: A method for preparing a thermo-induced self-healing polyolefin elastomer modified film material, comprising the following steps: (1) Take 7g of polyolefin elastomer particles (POE) and 70ml of tetrahydrofuran (THF) and place them in a brown three-necked flask with a stirrer under argon protection. Heat the flask to 60℃ and stir for 3h to obtain a clear and transparent solution.

[0047] (2) Heat to 65°C, add 0.1g of 2,2'-azobisisobutyronitrile (AIBN) to the flask, keep the temperature constant for 3 min, then add 0.25g of 2-methylfuran (2-MF) to the flask and react at a constant temperature for 6 h.

[0048] (3) A mixture of 10 ml N,N-dimethylformamide (DMF), 10 ml tetrahydrofuran (THF) and 1.31 g N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) was ultrasonically shaken for 10 min and then added dropwise to a flask at 0.65 ml / min. The mixture was heated to 70 °C and reacted for 6 h to obtain the sample.

[0049] (4) Pour the sample into a polytetrafluoroethylene mold containing anhydrous ethanol for alcohol washing (to remove excess tetrahydrofuran and N,N-dimethylformamide), and then place it in an electric heating drying oven at 60°C for curing for 1 day to obtain a thermo-induced self-healing polyolefin elastomer modified film material.

[0050] Comparative Example 2 Compared with Example I-2, only the mass of 2-methylfuran (2-MF) in step (2) was adjusted to 0.5 g (6 mmol) of 2-methylfuran, that is, the molar ratio of BMI to 2-MF in the system was 0.5. The other steps were the same as in Example I-2, and the polyolefin elastomer modified film material was obtained.

[0051] Comparative Examples 3-5 Compared with Examples I-2, 0.25g of 2-methylfuran (2-MF) in step (2) was replaced with 0.25g of furfurylamine, and the mass of N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) in step (3) was adjusted. The mass of BMI in Comparative Examples 3-5 is shown in Table 2. Other steps were the same as in Examples I-2, and polyolefin elastomer modified film materials were obtained.

[0052] Comparative Example 6 Steps (1)-(2) are performed according to Example I-2, and steps (3)-(4) are also included: (3) A mixture of 20 ml tetrahydrofuran (THF) and 1.10 g N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) was ultrasonically shaken for 10 min to obtain a suspension (i.e., BMI is insoluble or slightly soluble in THF). The suspension was added dropwise to a flask at 0.65 ml / min, and the temperature was raised to 70 °C. The sample was obtained after reacting for 6 h.

[0053] (4) Pour the sample into a polytetrafluoroethylene mold containing anhydrous ethanol for alcohol washing (to remove excess tetrahydrofuran), and then place it in an electric heating drying oven at 60°C for 1 day to cure, thereby obtaining a polyolefin elastomer modified film material.

[0054] Comparative Example 7 Following steps (1)-(2) of Example I-2, the method further includes step (3): A mixture of 20 ml N,N-dimethylformamide (DMF) and 1.10 g N,N'-(4,4'-methylenediphenyl)bismaleimide (BMI) was ultrasonically agitated for 10 min and then added all at once to a flask. The system immediately solidified into a clump, and continued stirring did not dissolve it. When added dropwise at 0.65 ml / min, the system continued to solidify at the point of addition, and continued stirring did not dissolve it. The reason is that the highly polar DMF causes POE to precipitate due to solvent polarity mismatch.

[0055] Table 1 shows the mass-to-molar ratio of the dienophile (N,N'-(4,4'-methylenediphenyl)bismaleimide) to the dienophile (2-methylfuran) in Examples and Comparative Examples 1-2.

[0056] Table 1 Table 2 shows the mass-to-molar ratio of the dienophile (N,N'-(4,4'-methylenediphenyl)bismaleimide) to the diene (furfurylamine) in Comparative Examples 3-5.

[0057] Table 2 Characterization and performance testing The polyolefin elastomer modified films prepared in Comparative Examples 2-5 exhibited a significant lack of toughness.

[0058] Given that the above samples have lost their basic properties as elastomer materials, their subsequent performance characterization is no longer of research value, and therefore no further testing was conducted.

[0059] Infrared spectroscopy analysis Fourier transform infrared spectroscopy was performed on the polyolefin elastomer film materials obtained in Comparative Example 1 and the Example, respectively. Figure 1 and Figure 2 The images shown are the infrared spectra of the polyolefin elastomer film materials prepared in Comparative Example 1 and the Example 2, respectively. Figure 2 1710 cm⁻¹ can be observed in the infrared spectrum. -1 This is the characteristic peak of the C=O bond in the DA reaction product, 1379 cm⁻¹. -1 and 1188cm -1The corresponding C–N bond vibration peak formed by the DA reaction confirms the successful preparation of the polyolefin elastomer modified film.

[0060] It should be noted that the successful grafting of POE with 2-methylfuran is largely related to the method of addition. In step (2): 2-methylfuran is added first, followed by the initiator AIBN, or AIBN and 2-methylfuran are added simultaneously. The reaction is carried out at a constant temperature of 65°C for 6 hours. After the reaction, the mixture is washed with anhydrous ethanol in a polytetrafluoroethylene mold and then cured in a 60°C electric heating drying oven for 1 day. After infrared characterization, the characteristic peak signal of the furan ring is weak. However, if the initiator AIBN is added first, after a certain reaction time, AIBN will attack the POE chain segment, thereby creating active sites on the POE main chain. Then, 2-methylfuran is added, and the furan ring is more easily grafted onto the POE.

[0061] Self-repair analysis The elastomeric film materials obtained from Comparative Example 1, Comparative Example 6 and the Examples were subjected to scratch tests. The test method was as follows: the film samples were scratched with a blade, and then the samples were placed in a 75°C forced-air drying oven for half an hour. The samples were then taken out and cooled to room temperature, and the scratches were observed again under an optical microscope.

[0062] like Figure 3 As shown, the scratches in Comparative Example 1 remained even after heating.

[0063] like Figure 4 As shown, the scratches in Comparative Example 6 remained even after heating.

[0064] like Figure 5 , Figure 6 , Figure 7 As shown, the scratches in Examples I-1, I-2, and I-3 disappeared after heating for half an hour, confirming that the introduced Diels-Alder reaction achieved a self-healing effect.

[0065] Mechanical property testing The mechanical properties of the polyolefin elastomer film materials prepared in Comparative Example 1 and the Examples were tested. The test results of the four films are shown in Tables 3, 4 and 5 below.

[0066] Testing standards: (1) Tensile strength / maximum force: The mechanical properties of polyolefin elastomer film were tested at room temperature using a universal tensile testing machine. The test standard was based on GB / T 1040.3-2006. The machine was equipped with a 5kN force sensor, a sampling frequency of 1000 / 5000Hz, and a deformation sensor YSJ50 / 25-ZC.

[0067] (2) Sample preparation standard: The film is made into a dumbbell-shaped sample with a length of 3.5 cm, a width of 0.2 cm in the middle and a width of 0.6 cm at both ends. The test rate is 20 mm / min and the clamping distance is set to 2 cm.

[0068] (3) Elongation at break: The calculation formula is as follows Where e is the elongation at break, L is the deformed length, and L is the original length.

[0069] (4) Recovery rate: The calculation formula is as follows ,in The elongation at break of the sample after it has undergone pre-set damage, under specific repair conditions. This represents the elongation at break of the original sample.

[0070] (5) Stress-strain curves: Based on the raw tensile test data obtained from the universal tensile testing machine (GB / T 1040.3-2006 test standard), standardized curves were plotted using Origin plotting software, such as... Figure 8 and Figure 9 As shown.

[0071] Table 3 Table 4 Table 5 The results in Table 3 show that... The sample prepared in Comparative Example 1 had a tensile strength of 14.54 MPa and an elongation at break of 1257.13%.

[0072] In Example I-1 (r=0.8), the system was in a state of under-crosslinking. Due to the relatively insufficient BMI content, defects existed in the formed network structure, resulting in a low density of crosslinking points. During stretching, stress could not be effectively transferred through the sparse crosslinked network, and its main energy dissipation mechanism relied on the irreversible slippage and disentanglement of molecular chains, leading to material failure at a low stress level, manifested as a tensile strength of 11.87 MPa. Although the molecular chains still possessed a certain degree of mobility due to the weak constraint, achieving a certain degree of orientation and extension, the elongation at break reached 877.29%.

[0073] In Example I-2 (r=1.0), the Diels-Alder reaction tended towards the ideal stoichiometry, resulting in the highest reaction efficiency and the formation of a dynamic covalent network with moderate crosslinking density and uniform spatial distribution. This perfect network structure effectively distributes external loads uniformly throughout the system, fully utilizing the load-bearing capacity of covalent bonds, thus exhibiting a tensile strength of 13.17 MPa. Simultaneously, the uniform network effectively avoids stress concentration, allowing the molecular chains to achieve coordinated and sustainable extension and orientation while maintaining good constraint, thereby achieving a balance between strength and toughness, with an elongation at break reaching 1129.91%.

[0074] In Example I-3 (r=1.2), the system was over-crosslinked. Excessive BMI not only potentially triggers its own homopolymerization, forming a rigid and irreversible crosslinked structure, but also significantly increases the overall crosslinking density. The highly dense crosslinked network severely restricts the movement of molecular chain segments, leading to a significant decrease in material toughness. Under tensile loads, the network struggles to effectively dissipate energy through chain segment movement, causing stress concentration at microscopic defects and inducing rapid propagation of brittle cracks, ultimately resulting in a tensile strength of 11.64 MPa and an elongation at break of 758.25%.

[0075] The results in Table 4 show that... The sample prepared in Comparative Example 1 had a tensile strength of 6.87 MPa and an elongation at break of 541.4% after undergoing a scratch test. The mechanical property test results of each embodiment after experiencing scratch damage and completing the self-healing process demonstrate the reconfiguration ability of the dynamic covalent network during the damage and repair process.

[0076] In Example I-1 (r=0.8), the inherent low crosslinking density defect of the initial network was further amplified during the repair process. The number of effective dynamic crosslinking points available for interface reconstruction was insufficient, resulting in a sparse dynamic network structure with numerous topological defects at the repair interface. This scratched area became a stress concentration point under mechanical load, making it difficult to effectively transfer and disperse stress. Therefore, the tensile strength of 9.64 MPa and the elongation at break after repair showed limited recovery, and the mechanical properties were poorly preserved.

[0077] In Example I-2 (r=1.0), the initial network with near-ideal stoichiometry provided an optimal repair basis. The Diels-Alder reaction in this system exhibited high efficiency during the repair process. This enabled this example to maintain a tensile strength of 11.06 MPa and an elongation at break of 1021.79% after repair, demonstrating the superior self-healing efficacy of a high-quality dynamic covalent network.

[0078] In Example I-3 (r=1.2), the excessive BMI-induced homopolymerization side reaction generated a rigid and irreversible cross-linked structure. These homopolymer sites could not be broken down during the repair heating stage, severely hindering the necessary flow and reconstruction of molecular chains at the damaged interface. Simultaneously, the excessively dense cross-linked network itself limited the mobility of chain segments. As a result, the repaired interfacial network contained numerous stress concentration points and microscopic defects, exhibiting the worst mechanical property recovery, with a tensile strength of only 8.52 MPa and an elongation at break reduced to 664.35%.

[0079] The results in Table 5 show that... Example I-2 showed a recovery rate of 90.43%, significantly better than the 43.07% recovery rate of Comparative Example 1. This further verified that r=1.0 is the optimal ratio for this system, which not only endows the material with excellent self-healing properties, but also achieves self-healing functional modification of the material while basically maintaining the original mechanical properties of the comparative example.

[0080] In summary, the self-healing process is actually a limited reconstruction of a dynamic covalent network in the damaged area, and its repair efficiency fundamentally depends on the initial network quality and chemical structure determined by the molar ratio (r).

[0081] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a thermo-induced self-healing polyolefin elastomer modified film, characterized in that, Includes the following steps: (1) In a light-proof reactor protected by an inert gas, polyolefin elastomer particles and tetrahydrofuran are mixed and heated and stirred until the polyolefin elastomer particles are completely dissolved into a clear and transparent solution; then an initiator is added to the reactor, and after 3-5 min, 2-methylfuran is added to cause a grafting reaction, and the reaction time is 5-8 h; finally, N,N'-(4,4'-methylenediphenyl)bismaleimide BMI solution is added to the reactor, and a Diels-Alder cycloaddition reaction is carried out at a temperature of 65-75 °C for 5-7 h; (2) The sample obtained in (1) was washed with alcohol and then placed in a drying oven for curing to obtain the thermo-induced self-healing polyolefin elastomer modified film material; The molar ratio of BMI to 2-methylfuran is (0.8-1.2):

1.

2. The preparation method according to claim 1, characterized in that, The molar ratio of BMI to 2-methylfuran is 1:

1.

3. The preparation method according to claim 1, characterized in that, The BMI solution is a mixture of N,N'-(4,4'-methylenediphenyl)bismaleimide and N,N-dimethylformamide / tetrahydrofuran.

4. The preparation method according to claim 3, characterized in that, The volume ratio of N,N-dimethylformamide to tetrahydrofuran in the BMI solution is 1:

1.

5. The preparation method according to claim 4, characterized in that, The ratio of BMI to solvent in the BMI solution is (0.5-1.5) g : (20-25) mL.

6. The preparation method according to claim 1, characterized in that, The BMI solution is added dropwise; preferably, the dropping rate is 0.6~0.7 ml / min.

7. The preparation method according to claim 1, characterized in that, The polyolefin elastomer particles and tetrahydrofuran are mixed at a ratio of 1g:10ml; and / or The initiator is one or more of 2,2'-azobisisobutyronitrile, benzoyl peroxide, and dimethyl azobisisobutyrate; and / or The initiator dosage is 1 wt.% - 2 wt.% of the mass of the polyolefin elastomer particles; and / or The mass ratio of 2-methylfuran to polyolefin elastomer particles is 0.25-0.3: 6.75-7.

25.

8. The preparation method according to claim 1, characterized in that, The grafting reaction occurs at a temperature of 55-65℃; and / or The curing temperature is 50-60℃, and the curing time is 1 day.

9. The polyolefin elastomer modified film prepared by any one of claims 1-8.

10. The self-healing method for the polyolefin elastomer modified film according to claim 9, comprising: The polyolefin elastomer modified film was heated at 75°C for half an hour.

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