Self-healing elastic materials for connectors, their preparation methods and applications

Abstract

This invention belongs to the field of polymer materials products, specifically disclosing an elastic material for connectors with self-healing function, its preparation method, and its uses. First, a prepolymer is prepared using polytetrahydrofuran ether diol and diphenylmethane diisocyanate. Then, a polyurethane urea solution is prepared using 1,6-hexanediamine as a chain extender. A certain amount of modified graphene oxide is then added to the polyurethane urea solution, followed by ultrasonic dispersion and drying to obtain the elastic material for connectors with self-healing function. This elastic material simultaneously possesses high strength, high toughness, and self-healing ability. Connectors made using this elastic material exhibit self-healing function and a long service life.

Description

Technical Field

[0001] This invention relates to the field of polymer materials products, and in particular to an elastic material for connecting wires with self-healing function, its preparation method, and its uses. Background Technology

[0002] Connecting cables are a common item in daily life. They mainly include power cables and data cables. Taking headphone cables as an example, the outer sheathing materials commonly used in manufacturing headphone cables are polyvinyl chloride (PVC) and thermoplastic elastomers (TPE). In daily life, it can be observed that after prolonged use, headphone cables undergo permanent deformation, leading to damage and loss of functionality.

[0003] Chinese Patent Application No. 202111593840.X discloses an intrinsic self-healing polyurethane elastic material and its preparation method, comprising: selecting diphenylmethane diisocyanate and polypropylene glycol 2000 as raw materials, polyethylene glycol as a chain extender, dibutyltin dilaurate as a catalyst, and butyl acetate as a solvent; sequentially adding the butyl acetate and polyethylene glycol to an Erlenmeyer flask and stirring thoroughly; adding the diphenylmethane diisocyanate and dibutyltin dilaurate in the specified amounts, and stirring at 60°C at a first rotation speed for 2-3 hours; adding the polyethylene glycol and dibutyltin dilaurate in the specified amounts, and stirring at a second rotation speed for 2-3 hours to obtain the polyurethane elastic material; this polyurethane elastic material is an intrinsic self-healing polyurethane material, which does not require the addition of heterogeneous repair agents, and can repair the same damaged area multiple times under molecular bonding, thus extending the service life of the material.

[0004] Although the polyurethane elastic material prepared by the above patent has a certain degree of self-healing, its self-healing ability is not high, and its strength and toughness are insufficient, making it unsuitable for making connecting wires. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an elastic material for connectors with self-healing function, its preparation method, and its applications.

[0006] To achieve the above objectives, the present invention is implemented according to the following technical solution:

[0007] The first objective of this invention is to provide a method for preparing an elastic material for connectors with self-healing function, comprising the following steps:

[0008] S1. Take 1.0 mol of polytetrahydrofuran ether diol and 2.8-3.0 mol of diphenylmethane diisocyanate and add them to a reactor containing 9500 ml of N,N-dimethylformamide. At the same time, add 0.0003-0.0005 mol of dibutyltin dilaurate. React at 80 °C for 2 h under stirring at 250-400 rpm to obtain solution a.

[0009] S2. Take 1.8–2.0 mol of 1,6-hexanediamine and dilute it with 500 ml of N,N-dimethylformamide to obtain solution b;

[0010] S3. Under the conditions of ice-water bath and stirring at 250-400 rpm, solution b is added dropwise to solution a. After the addition is completed, stirring is continued at room temperature for 1 hour to complete the reaction and obtain the intermediate product polyurethane urea solution.

[0011] S4. Take the intermediate product polyurethane urea solution and modified graphene oxide at a mass ratio of 580:0.5~1.0, mix them, and then ultrasonically disperse them for 4 hours under the conditions of 20kHz and 2000W power. After drying, the elastic material for connecting wires with self-healing function is obtained.

[0012] Furthermore, the modified graphene oxide is obtained by grafting polyethylene glycol onto the surface of graphene oxide, and the grafting rate of polyethylene glycol on the surface of graphene oxide is 20-25%.

[0013] If the molecular weight of polytetrahydrofuran ether diol is too small, it is difficult to impart sufficient elasticity and toughness to the connecting wire; if the molecular weight is too large, the prepared polyurethane urea will crystallize, thereby reducing the transparency of the material and making it unsuitable for preparing transparent connecting wires. Therefore, as a preferred embodiment of the present invention, the molecular weight of the polytetrahydrofuran ether diol is 1200-2000.

[0014] If the molecular weight of polyethylene glycol is too small and the molecular chain is too short, it is difficult to form enough hydrogen bonds with -NH, -C=O, etc. in the hard segments of polyurethane urea, thus failing to guarantee the strength, toughness, and self-healing properties of the connecting wires; if the molecular weight is too large, it will coat the surface of graphene oxide, affecting the reinforcing effect of graphene oxide. Therefore, as a preferred embodiment of the present invention, the molecular weight of the polyethylene glycol is 600-1000.

[0015] Furthermore, the number of graphene oxide layers is 1-10.

[0016] Preferably, the number of graphene oxide layers is 4-6.

[0017] The second objective of this invention is to provide an elastic material for connecting wires with self-healing function prepared using the above method.

[0018] The reaction mechanism of this invention is as follows:

[0019] First, polytetrahydrofuran ether diol (PTED) acts as the soft segment, imparting flexibility and elasticity to polyurethane urea; diphenylmethane diisocyanate (DMDI) acts as the hard segment, imparting strength and rigidity; 1,6-hexanediamine acts as a chain extender, increasing the molecular weight of polyurethane urea; dibutyltin dilaurate acts as a catalyst, promoting the reaction between PTED and DMDI. With increasing hard segment content, the tensile stress, tensile strength, and hardness of the polyurethane urea elastomer all increase, which helps resist external stress during use and maintains the original shape of the connector. Furthermore, with increasing hard segment content, the number of hydrogen bond formation sites between hard segments increases, facilitating the formation of more intermolecular hydrogen bonds with polyethylene glycol grafted onto the modified graphene surface. The presence of these hydrogen bonds is crucial for ensuring the strength, toughness, and self-healing properties of the connector. The addition of modified graphene oxide serves two purposes. First, graphene oxide itself is a filler with excellent reinforcing properties; adding even a small amount can significantly improve the material's strength. Second, the polyethylene glycol on the modified graphene oxide surface forms hydrogen bonds with -NH and -C=O groups in the polyurethane urea hard segments. Since the dissociation energy of hydrogen bonds is lower than that of C / C covalent bonds, these hydrogen bonds will first undergo gradual dissociation during material stretching. This dissociation process consumes a large amount of strain energy, thereby improving the material's strength and toughness. Furthermore, hydrogen bonds are dynamically reversible; as long as the material is not broken, hydrogen bonds will regenerate during resting, thus achieving dynamic self-healing properties. Appropriate heating of the material will accelerate this dynamic repair process.

[0020] A third objective of this invention is to provide a use of an elastic material for connectors with self-healing properties, which is used in the manufacture of connectors.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) In this invention, a prepolymer is first prepared using polytetrahydrofuran ether diol and diphenylmethane diisocyanate, and then a polyurethane urea solution is prepared using 1,6-hexanediamine as a chain extender. A certain amount of modified graphene oxide is then added to the polyurethane urea solution, followed by ultrasonic dispersion and drying to obtain an elastic material for connectors with self-healing capabilities. This elastic material possesses high strength, high toughness, and self-healing ability; connectors prepared using this elastic material exhibit self-healing function and long service life.

[0023] (2) In this invention, the polyethylene glycol grafted onto the modified graphene oxide surface can form intermolecular hydrogen bonds with the polyurethane urea matrix. The dissociation energy of the hydrogen bonds is lower than that of the C-C covalent bonds. During the stretching process of the connector, these hydrogen bonds will first undergo gradual dissociation, thereby consuming a large amount of strain energy and simultaneously improving the strength and toughness of the connector. During the storage or heat treatment of the connector, the hydrogen bonds can be regenerated, thereby achieving self-repair of the connector performance.

[0024] (3) In this invention, monolayer graphene is used to prepare modified graphene oxide, which is then used to prepare connecting wires. Transparent connecting wires can be prepared, giving the connecting wires another function. Attached Figure Description

[0025] Figure 1 This is a circuit diagram of the elastic material for the self-healing connector of the present invention; in the diagram: PTMG: polytetrahydrofuran ether diol; MDI: diphenylmethane diisocyanate; DBTDL: dibutyltin dilaurate; PUU: polyurethane urea. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0027] Unless otherwise specified, all raw materials and equipment used in the following examples are commercially available.

[0028] Modified graphene oxide is obtained by covalently grafting polyethylene glycol (PEG) onto the surface of graphene oxide, with a PEG grafting rate of 20-25%. An exemplary reaction process is as follows: 500 mg of graphene oxide is added to a three-necked flask containing 350 ml of toluene and ultrasonically dispersed for 30 min. Then, 1.5 g of PEG, 0.5 g of 4-dimethylaminopyridine, and 1.0 g of dicyclohexylcarbodiimide are added, and the mixture is ultrasonically dispersed for another 30 min, followed by magnetic stirring at 75 °C for 24 h. After the reaction is complete, the mixture is filtered through polytetrafluoroethylene (PTFE) filter paper, then washed sequentially with 50 ml of toluene and 700 ml of deionized water. The filter cake is then vacuum-dried at 60 °C to obtain the finished modified graphene oxide.

[0029] Example 1

[0030] Weigh 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate into a reactor containing 9500 ml of N,N-dimethylformamide, and simultaneously add 0.0004 mol of dibutyltin dilaurate. React at 80 °C for 2 h under stirring at 250-400 rpm. Then place the reactor in an ice-water bath and, under rapid stirring, add 1.8 mol of 1,6-hexanediamine in 500 ml of water. N,N-dimethylformamide was diluted and added dropwise. After the addition was complete, the mixture was stirred at room temperature for 1 hour to complete the reaction, yielding a polyurethane urea solution. 580g of the polyurethane urea solution was taken, and then 0.75g of modified graphene oxide was added (in this example, the modified graphene oxide used had 4-6 layers, and the polyethylene glycol used for graphene oxide modification had a molecular weight of 1000). The mixture was ultrasonically dispersed for 4 hours and then dried (until the solvent evaporated completely) to obtain the elastic material. The reaction process is as follows: Figure 1 As shown.

[0031] Example 2

[0032] 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate were weighed and added to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, 0.0004 mol of dibutyltin dilaurate was added. The reaction was carried out at 80°C for 2 hours under stirring at 250-400 rpm. Then, the reactor was placed in an ice-water bath, and under rapid stirring, 1.8 mol of 1,6-hexanediamine was diluted with 500 ml of N,N-dimethylformamide and added dropwise. After the addition was complete, the reaction was continued at room temperature for 1 hour to complete the reaction, yielding a polyurethane urea solution. 580 g of the polyurethane urea solution was taken, and then 0.75 g of modified graphene oxide (in this example, the graphene oxide used for modification was a single layer, and the polyethylene glycol used for graphene oxide modification had a molecular weight of 1000) was added. The mixture was ultrasonically dispersed for 4 hours and then dried (until the solvent evaporated completely) to obtain the elastic material.

[0033] Comparative Example 1

[0034] 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate were weighed and added to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, 0.0004 mol of dibutyltin dilaurate was added. The reaction was carried out at 80 °C for 2 h under stirring at 250-400 rpm. Then, the reactor was placed in an ice-water bath, and under rapid stirring, 1.8 mol of 1,6-hexanediamine was diluted with 500 ml of N,N-dimethylformamide and added dropwise. After the addition was complete, the reaction was continued at room temperature for 1 h to complete the reaction, yielding a polyurethane urea solution. After drying (until the solvent evaporated completely), the elastic material was obtained.

[0035] Comparative Example 2

[0036] Weigh 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate and add them to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, add 0.0004 mol of dibutyltin dilaurate. React at 80°C for 2 h under stirring at 250-400 rpm. Then, place the reactor in an ice-water bath and add 1.8 mol of 1,6-hexanediamine diluted with 500 ml of N,N-dimethylformamide dropwise under rapid stirring. After the addition is complete, continue stirring at room temperature for 1 h to complete the reaction, thus obtaining a polyurethane urea solution. Take 580 g of the polyurethane urea solution and add 0.75 g of graphene oxide (in this example, the number of graphene oxide layers is 4-6 layers). Disperse ultrasonically for 4 h and dry (until the solvent evaporates completely) to obtain the elastic material.

[0037] Comparative Example 3

[0038] Weigh 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate and add them to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, add 0.0004 mol of dibutyltin dilaurate. React at 80°C for 2 h under stirring at 250-400 rpm. Then, place the reactor in an ice-water bath and add 1.8 mol of 1,6-hexanediamine diluted with 500 ml of N,N-dimethylformamide dropwise under rapid stirring. After the addition is complete, continue stirring at room temperature for 1 h to complete the reaction, thus obtaining a polyurethane urea solution. Take 580 g of the polyurethane urea solution and add 0.75 g of modified graphene oxide (in this example, the modified graphene oxide used to prepare the graphene oxide has 4-6 layers, and the polyethylene glycol used for graphene oxide modification has a molecular weight of 200). Disperse ultrasonically for 4 h and dry (until the solvent evaporates completely) to obtain the elastic material.

[0039] Comparative Example 4

[0040] Weigh 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.8 mol of diphenylmethane diisocyanate and add them to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, add 0.0004 mol of dibutyltin dilaurate. React at 80°C for 2 h under stirring at 250-400 rpm. Then, place the reactor in an ice-water bath and add 1.8 mol of 1,6-hexanediamine diluted with 500 ml of N,N-dimethylformamide dropwise under rapid stirring. After the addition is complete, continue stirring at room temperature for 1 h to complete the reaction, thus obtaining a polyurethane urea solution. Take 580 g of the polyurethane urea solution and add 0.75 g of modified graphene oxide (in this example, the modified graphene oxide used to prepare the graphene oxide has 4-6 layers, and the polyethylene glycol used for graphene oxide modification has a molecular weight of 2000). Disperse ultrasonically for 4 h and dry (until the solvent evaporates completely) to obtain the elastic material.

[0041] Comparative Example 5

[0042] Weigh 1.0 mol of polytetrahydrofuran ether diol with a molecular weight of 1600 and 2.0 mol of diphenylmethane diisocyanate and add them to a reactor containing 9500 ml of N,N-dimethylformamide. Simultaneously, add 0.0004 mol of dibutyltin dilaurate. React at 80°C for 2 h under stirring at 250-400 rpm. Then, place the reactor in an ice-water bath and add 1.0 mol of 1,6-hexanediamine diluted with 500 ml of N,N-dimethylformamide dropwise under rapid stirring. After the addition is complete, continue stirring at room temperature for 1 h to complete the reaction, thus obtaining a polyurethane urea solution. Take 580 g of the polyurethane urea solution and add 0.75 g of modified graphene oxide (in this example, the modified graphene oxide used to prepare the graphene oxide has 4-6 layers, and the polyethylene glycol used for graphene oxide modification has a molecular weight of 1000). Disperse ultrasonically for 4 h and dry (until the solvent evaporates completely) to obtain the elastic material.

[0043] To verify the strength, high toughness, and self-healing ability of the elastic material prepared in this invention, tensile specimens were prepared according to GB / T528-2009 using the elastic materials obtained in Examples 1, 2, and Comparative Examples 1 to 5. Each specimen was stretched to 100% strain using a tensile testing machine, then removed and laid flat on a table for three minutes before measuring its length. This process was repeated five times. The specimens were then placed in a 60°C oven for 2 hours before measuring their length again. The specimens were then stretched to 100% strain once more, and the stress-strain data were recorded for each stretching process.

[0044] Generally, if the specimen does not have a self-healing effect, its length will increase with each stretch (permanent deformation effect), and the force required to stretch it to 100% strain in a later stretch will be less than that in a previous stretch (stress softening effect). If, after the specimen has been in a 60°C oven for 2 hours, its length shortens or the force required to stretch it to 100% strain increases, it indicates that the specimen has a self-healing effect during heat treatment. Therefore, this invention patent tested the ratio of the force required to stretch the same specimen to 100% strain for the 6th time to the force required to stretch it to 100% strain for the 5th time, denoted as the tensile strength ratio; and the ratio of the length of the same specimen after being placed in a 60°C oven for 2 hours to the length after being placed for three minutes after the 5th stretch, denoted as the permanent deformation ratio.

[0045] The main physical and mechanical properties of the elastic materials prepared in Examples 1, 2, and Comparative Examples 1-5 are shown in Table 1.

[0046] Table 1

[0047] Test methods GB / T528-2009 GB / T528-2009 As described above As described above GB / T2410-2008 Comparative Example 1 55.0 345 97 101 86 Comparative Example 2 58.7 303 98 103 64 Comparative Example 3 59.9 365 92 108 64 Comparative Example 4 60.4 435 86 115 63 Comparative Example 5 41.7 466 90 110 64 Example 1 61.3 430 85 117 65 Example 2 62.7 439 85 119 87

[0048] Table 1 shows that the tensile strength, elongation at break, and light transmittance of pure polyurethane urea (Comparative Example 1) were 55.0 MPa, 345%, and 86%, respectively, with little change in permanent deformation ratio and tensile strength ratio. When unmodified graphene oxide was added (Comparative Example 2), the tensile strength increased to 58.7 MPa, while the elongation at break and light transmittance decreased to 303% and 64%, respectively. This indicates that while adding unmodified graphene oxide improves the material's strength, it also reduces the elongation at break and light transmittance. The permanent deformation ratio and tensile strength ratio remained essentially unchanged. When 0.75 wt% modified graphene oxide was added (Example 1), the tensile strength and elongation at break simultaneously increased to 61.3 MPa and 430%, respectively, while the permanent deformation ratio decreased to 85%, and the tensile strength ratio increased to 117%. This indicates that the addition of modified graphene oxide introduced hydrogen bonds into the system. Because the dissociation energy of hydrogen bonds formed between polyurethane urea and polyethylene glycol grafted onto the surface of modified graphene oxide is lower than that of C-C covalent bonds, these hydrogen bonds will first undergo gradual dissociation during stretching. This dissociation process consumes a large amount of strain energy, thereby simultaneously improving the strength and toughness of the material. After heat treatment at 60°C for 2 hours, the hydrogen bonds gradually reformed, resulting in a significant decrease in the permanent strain ratio and a significant increase in the tensile strength ratio. When the added modified graphene oxide was replaced with a monolayer (Example 2), the light transmittance increased to 87%.

[0049] Compared to Example 1, when the molecular weight of the polyethylene glycol used for graphene oxide modification is too small (Comparative Example 3), it is difficult to form more complete hydrogen bonds between the polyurethane urea and the polyethylene glycol grafted on the surface of the modified graphene oxide. Therefore, the tensile strength, elongation at break, and tensile strength ratio are all relatively small, while the permanent deformation ratio is relatively high. When the molecular weight of the polyethylene glycol used for graphene oxide modification is too large (Comparative Example 4), the tensile strength will decrease.

[0050] Compared with Example 1, reducing the content of diphenylmethane diisocyanate hard segments in polyurethane urea (Comparative Example 5) significantly reduces the tensile strength of the material, making it less resistant to external stress during the use of the connector. The connector is more likely to break during use and lose its usability, and its self-healing performance is also reduced.

[0051] In summary, the self-healing elastic material for connectors prepared by this invention can be used to manufacture connectors; the connectors prepared from this material have self-healing capabilities and a long service life. If monolayer graphene is preferred, transparent connectors can be prepared, giving the connectors another functionality.

[0052] The technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made in accordance with the technical solutions of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing an elastic material for connectors with self-healing function, characterized in that, Includes the following steps: S1. Add 1.0 mol of polytetrahydrofuran ether diol and 2.8–3.0 mol of diphenylmethane diisocyanate to a reactor containing 9500 ml of N,N-dimethylformamide, and simultaneously add 0.0003–0.0005 mol of dibutyltin dilaurate. React at 80 °C for 2 h under stirring at 250–400 rpm to obtain solution a; the molecular weight of the polytetrahydrofuran ether diol is 1200–2000. S2. Take 1.8–2.0 mol of 1,6-hexanediamine and dilute it with 500 ml of N,N-dimethylformamide to obtain solution b; S3. Under the conditions of ice-water bath and stirring at 250-400 rpm, solution b is added dropwise to solution a. After the addition is completed, stirring is continued at room temperature for 1 h to complete the reaction and obtain the intermediate product polyurethane urea solution. S4. Take the intermediate product polyurethane urea solution and modified graphene oxide at a mass ratio of 580:0.5-1.

0. The modified graphene oxide is obtained by grafting polyethylene glycol onto the surface of graphene oxide, and the grafting rate of polyethylene glycol on the surface of graphene oxide is 20-25%. The molecular weight of polyethylene glycol is 600-1000. After mixing, ultrasonically disperse at 20 kHz and 2000 W power for 4 h, and dry to obtain an elastic material for connecting wires with self-healing function.

2. The method for preparing the elastic material for connecting wires with self-healing function according to claim 1, characterized in that: The number of graphene oxide layers is 1-10.

3. The method for preparing the elastic material for connecting wires with self-healing function according to claim 1, characterized in that: The number of graphene oxide layers is 4-6.

4. An elastic material for connecting wires with self-healing function, prepared as described in any one of claims 1-3.

5. The use of an elastic material for a connector with self-healing function as described in claim 4, characterized in that: Used to make connecting cables.

Images