Preparation method of recyclable heat-conducting water-based self-repairing polyurethane elastomer

Abstract

The invention discloses a preparation method of a recyclable heat-conducting water-based self-repairing polyurethane elastomer. Isophorone diisocyanate, polytetrahydrofuran and dimethylolpropionic acid are used as main agents, dynamic imine bonds are constructed through dihydroxy acetone and adipic acid dihydrazide capable of forming high-density hydrogen bonds, two-dimensional polyamide is used as filler, and the waterborne polyurethane elastomer which is excellent in self-repairing performance and mechanical performance, high in heat conductivity coefficient and recyclable is obtained. The synthesis method is simple, the compatibility of two-dimensional polyamide and polyurethane is good, and the mechanical property is excellent; the damaged elastomer can be repaired under the room temperature condition, the repairing cost is low, energy is saved, and the method is environmentally friendly and safe. Meanwhile, the elastomer is easy to recycle, has sustainability, and can be widely applied to the fields of flexible electronic products and the like which need to have good heat-conducting property and mechanical property at the same time.

Description

Technical Field

[0001] The present invention relates to the field of self-repairing composite materials, and in particular to a method for preparing a recyclable water-conductive, hydrous self-repairing polyurethane elastomer. Background Art

[0002] The miniaturization of modern devices leads to significant heat buildup, requiring effective thermal management. Flexible electronics, such as flexible sensors, electronic skin, and flexible printed circuits, often require materials that can withstand large deformations. Traditional thermally conductive materials tend to degrade under such deformations, reducing their effectiveness and damaging flexible electronics. Polymer elastomers can meet this requirement.

[0003] The thermal conductivity of polymer elastomers is usually relatively low. This is because the structure within the polymer chain is usually bent and kinked, and there are a large number of loosely packed voids. Weak non-bonded intermolecular interactions also contribute to the low thermal conductivity. The traditional method to improve thermal conductivity is to add a large amount of inorganic thermally conductive fillers. The percolation theory believes that when the filler content reaches the percolation threshold, the fillers connect with each other to form a "sea-sea structure", which is beneficial to improving the thermal conductivity. However, a large amount of inorganic thermally conductive fillers is difficult to disperse evenly in the polymer system, affecting its thermal conductivity and mechanical properties. At present, it is still challenging to prepare materials with both high thermal conductivity and good mechanical properties.

[0004] Based on the principle of functional complementarity, the present invention introduces two-dimensional polyamide (2DPA), an organic intrinsic thermal conductive material, into a composite material. Ordered hydrogen bonds are established between the 2DPA and between the 2DPA and the matrix, addressing compatibility issues between the inorganic filler and the matrix to improve mechanical properties. Covalent or non-covalent bonds are also optimized to improve intramolecular and intermolecular interactions. Based on percolation theory, the present invention proposes a gravity-driven method to spontaneously arrange fillers in a waterborne polyurethane system in an orderly manner according to a top-to-bottom concentration distribution, forming a Janus structure. The percolation threshold can be reached by adding a small amount of filler, achieving local enrichment of the filler. Tannic acid-modified 2DPA (TPA) is used as a nanofiller to construct multiple dynamic hydrogen bonds in a dynamic network waterborne polyurethane matrix. Driven by gravity, low concentrations of TPA spontaneously arrange to form an ordered structure. The nanosheets undergo a transition from a random state to a gradient concentration in the polymer solution, thereby increasing hydrogen bond density and connectivity. Through the gradient strengthening of the hydrogen bond network, the thermal conductivity of the system is significantly improved. At the same time, the dynamic bond synergy between TPA and the matrix achieves the simultaneous optimization of self-healing efficiency and toughness. Summary of the Invention

[0005] In response to the above technical problems, the present invention invents a method for preparing a recyclable water-conductive, self-healing polyurethane elastomer, aiming to obtain an elastomer with recyclability, excellent mechanical properties, self-healing properties and thermal conductivity.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] A recyclable water-conductive, hydrophilic, self-healing polyurethane elastomer comprises the following steps:

[0008] (1) adding melamine, 1,3,5-benzenetricarboxylic acid chloride, a catalyst, and an organic solvent into a reactor, performing an anhydrous and oxygen-free operation, and stirring at 50° C. and 600 r / min for 24 hours to obtain a two-dimensional polyamide;

[0009] (2) Add tris(hydroxymethyl)aminomethane, deionized water, and hydrochloric acid into a beaker to prepare a buffer solution, and adjust the pH of the buffer solution to 8.0-8.5;

[0010] (3) adding tannic acid and two-dimensional polyamide to the buffer solution prepared in step (2), stirring magnetically at 30° C. for 24 h, filtering out the solid, and washing with water to obtain tannic acid-modified two-dimensional polyamide;

[0011] (4) adding isophorone diisocyanate, polytetrahydrofuran, a catalyst, and an organic solvent into a reactor, introducing nitrogen to remove oxygen, and stirring at 70°C and 300 rpm for 1 hour to obtain a polyurethane prepolymer solution;

[0012] (5) Add 2,2-dihydroxymethylpropionic acid, dihydroxyacetone and 1,4-butanediol to the prepolymer solution of step (4) at 70°C, and stir at 300 r / min for 1 h;

[0013] (6) Lower the reaction temperature to 30°C, add triethylamine to the solution of step (5), adjust the speed to 500 r / min and stir for 30 minutes;

[0014] (7) Add deionized water to the solution of step (6) at 30°C, adjust the speed to 1200 r / min and stir for 1 h;

[0015] (8) Add adipic acid dihydrazide to the solution of step (7) at 30° C., stir at 300 r / min for 10 min, and obtain a dynamic network waterborne polyurethane solution;

[0016] (9) The tannic acid-modified two-dimensional polyamide obtained in step (3) is uniformly dispersed in the dynamic network waterborne polyurethane solution prepared in step (8), and naturally cured in an environment of 30° C. for 72 hours to obtain a recyclable water-conductive water-based self-healing polyurethane elastomer.

[0017] In step (1), according to the weight ratio, melamine is 100 parts, 1,3,5-benzenetricarboxylic acid chloride is 100 parts, the catalyst is 5 parts, and the solvent is 150 parts.

[0018] In step (3), according to the weight ratio, tannic acid is 100 parts and two-dimensional polyamide is 100 parts.

[0019] In step (4), according to the weight ratio, isophorone diisocyanate is 50 parts, polytetrahydrofuran is 20 parts, the catalyst is 2 parts, and the solvent is 300 parts.

[0020] The catalyst described in step (4) is dibutyltin dilaurate, and the organic solvent is acetone.

[0021] In step (5), the amount of dihydroxyacetone is 0-20 parts, and the amount of 1,4-butanediol is 0-20 parts by weight.

[0022] In step (6), the amount of triethylamine is 12 parts by weight.

[0023] In step (7), the amount of deionized water is 80 parts by weight.

[0024] In step (8), the amount of adipic acid dihydrazide is 0-10 parts by weight.

[0025] In step (9), the amount of tannic acid-modified two-dimensional polyamide is 0.1-5 parts by weight.

[0026] The stirring from step (4) onwards is mechanical stirring.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The method of the present invention uses polytetrahydrofuran as a flexible monomer, isophorone diisocyanate as a hard segment, 1,3-dihydroxyacetone as a chain extender, and cooperates with the dynamic properties of adipic acid dihydrazide to prepare a water-based polyurethane with excellent mechanical properties and room temperature self-healing properties through a simple one-pot method. In addition, modified two-dimensional polyamide is used as a filler, and the intermolecular forces are regulated by establishing physical cross-linking points (hydrogen bonds) to prepare a recyclable water-conductive water-based self-healing polyurethane elastomer. The damaged part of the elastomer is almost completely repaired at room temperature (25°C) for 12 hours. Furthermore, the designed thermally conductive skin has excellent thermal conductivity.

[0029] 2. The present invention uses two-dimensional polyamide as a filler. After tannic acid modification, it exhibits excellent compatibility and dispersibility within the polyurethane matrix. Surface hydrogen bonding establishes physical crosslinking points, regulating the density of ordered hydrogen bonds to form a continuous thermally conductive network, avoiding the aggregation and unevenness often associated with inorganic thermally conductive materials. Furthermore, even with low filler content, it can simultaneously improve mechanical properties and thermal conductivity.

[0030] 3. The present invention uses dihydroxyacetone, which can form imine bonds, and adipic acid dihydrazide, which can form high-density hydrogen bonds, as dynamic monomers. Through a "weak accumulation into strength" strategy, the mechanical properties and self-healing properties of the elastomer are synergistically improved. The damaged part is almost completely repaired within 12 hours at room temperature (25°C), extending the service life of the elastomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a diagram of the self-healing effect of the elastomer.

[0032] Figure 2 is the self-healing stress-strain curve of the elastomer.

[0033] Figure 3 This is a graph of the hot pressing recovery performance of the elastomer. DETAILED DESCRIPTION

[0034] The following is a detailed description of the embodiments, but it should be understood that the scope of the present invention is not limited by the embodiments. Unless otherwise specified, the raw materials and reagents used in the examples are commercially available.

[0035] Example 1

[0036] (1) adding 100 parts of melamine, 100 parts of 1,3,5-benzenetricarboxylic acid chloride, 5 parts of catalyst, and 150 parts of N-methylpyrrolidone and pyridine (volume ratio of 9:1) into a reactor, performing anhydrous and oxygen-free operation, stirring at 50°C and 600 r / min for 24 hours to obtain a two-dimensional polyamide;

[0037] (2) Add tris(hydroxymethyl)aminomethane, deionized water, and hydrochloric acid into a beaker to prepare a buffer solution, and adjust the pH of the buffer solution to 8.0-8.5;

[0038] (3) adding 100 parts of tannic acid and 100 parts of two-dimensional polyamide to the buffer solution prepared in step (2), stirring under magnetic stirring at 30° C. for 24 h, filtering out the solid, and washing with water to obtain tannic acid-modified two-dimensional polyamide;

[0039] (4) 50 parts of isophorone diisocyanate, 20 parts of polytetrahydrofuran, 2 parts of dibutyltin dilaurate, and 300 parts of acetone were added to a reactor, nitrogen was introduced to remove oxygen, and the mixture was stirred at 300 rpm at 70°C for 1 hour to obtain a polyurethane prepolymer solution;

[0040] (5) At 70° C., 12 parts of 2,2-dihydroxymethylpropionic acid and 20 parts of dihydroxyacetone were added to the prepolymer solution of step (4), and the mixture was stirred at 300 r / min for 1 h;

[0041] (6) Lower the reaction temperature to 30°C, add triethylamine to the solution of step (5), adjust the speed to 500 r / min and stir for 30 minutes;

[0042] (7) Add 80 parts of deionized water to the solution of step (6) at 30°C, adjust the speed to 1200 r / min and stir for 1 h;

[0043] (8) Add 10 parts of adipic acid dihydrazide to the solution of step (7) at 30° C., stir at 300 r / min for 10 min, and obtain a dynamic network waterborne polyurethane solution;

[0044] (9) One part of the tannic acid-modified two-dimensional polyamide obtained in step (3) is uniformly dispersed into 100 parts of the dynamic network waterborne polyurethane solution prepared in step (8), and the solution is naturally cured in an environment of 30° C. for 72 hours to obtain a recyclable water-conductive, water-based self-healing polyurethane elastomer.

[0045] Comparative Example 1

[0046] (1) Prepare a dynamic network waterborne polyurethane solution in the same manner as steps (4) to (8) of Example 1;

[0047] (2) The prepared dynamic network waterborne polyurethane solution was naturally cured in an environment of 30°C for 72 hours.

[0048] Comparative Example 2

[0049] In Example 3 of the method for preparing a thermally conductive self-repairing material based on dynamic disulfide bonds of waterborne polyurethane disclosed in patent CN 117757030 A, the thermally conductive filler is boron nitride, and the amount used is 10 parts.

[0050] Comparative Example 3

[0051] In Example 2 of patent CN 113736053 B, a functionalized waterborne polyurethane material and a preparation method thereof, the thermal conductive filler is graphene, and the amount used is 2 parts.

[0052] Comparative Example 4

[0053] (1) Prepare a dynamic network waterborne polyurethane solution in the same manner as steps (4) to (8) of Example 1;

[0054] (2) The two-dimensional polyamide prepared in step (1) of Example 1 was added to the dynamic network aqueous polyurethane solution prepared in step (1) of Control Example 4.

[0055] Implementation Effect

[0056] (1) The surface of the elastomer obtained in the embodiment with only one part of tannic acid-modified two-dimensional polyamide was smooth and flat without bubbles, and the overall thickness was uniform; the tensile strength reached 17.7 MPa, the elongation at break was 641.9%, and the toughness was calculated to be 45.6 MJ m -3 .

[0057] The self-healing property of the elastomer is to scratch the surface of the elastomer with a razor blade, then let it stand at room temperature and observe the repair of the scratch.

[0058] After the elastomer was left at room temperature for 12 hours, the scratches were almost completely repaired. At the same time, the self-repair efficiency of the elastomer was calculated to be 95.8% through the self-repair stress-strain curve, showing excellent room temperature self-repair ability (see Figure 1 、 Figure 2 ).

[0059] The shredded elastomer can be re-formed into a uniform film after hot pressing. After three cutting / hot pressing cycles, the tensile strength retention rates of the material were 94.8%, 80.1% and 64.8%, respectively, confirming its recyclability and excellent recycling stability (see Figure 3 ).

[0060] The thermal conductivity of the elastomer was measured to be 1.003 W m -1 K -1 .

[0061] (2) The surface of the elastomer of the control example 1 without adding tannic acid modified two-dimensional polyamide was smooth and flat without bubbles, and the overall thickness was uniform; the tensile strength reached 7.1 MPa, the elongation at break was 497.6%, and the toughness was 16.9 MJ m -3 It has self-repairing properties, but its thermal conductivity is only 0.323W m -1 K -1 .

[0062] (3) In comparative example 2, the water-based polyurethane with 10 parts of boron nitride added had a tensile strength of 14.43 MPa and a self-repair efficiency of 98.9%, but required heating (40°C) for repair. The thermal conductivity was 1.74 W m -1 K -1 .

[0063] (4) Comparative Example 3: The water-based polyurethane with 2 parts of graphene added had a tensile strength of 25.8 MPa and an elongation at break of 465.5%. It was not shown to have self-healing properties, and its thermal conductivity was 0.52 W m -1 K -1 .

[0064] (5) In Control Example 4, when the two-dimensional polyamide not modified with tannic acid was added to the aqueous polyurethane solution, the two-dimensional polyamide aggregated into clumps and could not be dispersed, and no usable sample could be obtained.

[0065] Table 1 Product shape and related performance data

[0066]

Claims

1. A method for preparing a recyclable water-conductive, self-repairing polyurethane elastomer, characterized in that: The following steps are included: (1) adding melamine, 1,3,5-benzenetricarboxylic acid chloride, a catalyst, and an organic solvent into a reactor, performing an anhydrous and oxygen-free operation, and stirring at 50° C. and 600 r / min for 24 hours to obtain a two-dimensional polyamide; (2) Add tris(hydroxymethyl)aminomethane, deionized water, and hydrochloric acid into a beaker to prepare a buffer solution, and adjust the pH of the buffer solution to 8.0-8.5; (3) adding tannic acid and two-dimensional polyamide to the buffer solution prepared in step (2), stirring magnetically at 30° C. for 24 h, filtering out the solid, and washing with water to obtain tannic acid-modified two-dimensional polyamide; (4) adding isophorone diisocyanate, polytetrahydrofuran, a catalyst, and an organic solvent into a reactor, introducing nitrogen to remove oxygen, and stirring at 70°C and 300 rpm for 1 hour to obtain a polyurethane prepolymer solution; (5) Add 2,2-dihydroxymethylpropionic acid, dihydroxyacetone and 1,4-butanediol to the prepolymer solution of step (4) at 70°C, and stir at 300 r / min for 1 h; (6) Lower the reaction temperature to 30°C, add triethylamine to the solution of step (5), adjust the speed to 500 r / min and stir for 30 minutes; (7) Add deionized water to the solution of step (6) at 30°C, adjust the speed to 1200 r / min and stir for 1 h; (8) Add adipic acid dihydrazide to the solution of step (7) at 30° C., stir at 300 r / min for 10 min, and obtain a dynamic network waterborne polyurethane solution; (9) The tannic acid-modified two-dimensional polyamide obtained in step (3) is uniformly dispersed in the dynamic network aqueous polyurethane solution prepared in step (8), and naturally cured in an environment of 30° C. for 72 hours to obtain a recyclable water-conductive, water-based self-healing polyurethane elastomer.

2. The preparation method according to claim 1, wherein: In step (1), according to the weight ratio, melamine is 100 parts, 1,3,5-benzenetricarboxylic acid chloride is 100 parts, the catalyst is 5 parts, and the solvent is 150 parts.

3. The preparation method according to claim 1, wherein: The catalyst in step (1) is anhydrous calcium chloride, and the organic solvent is N-methylpyrrolidone and pyridine in a volume ratio of 9:

1.

4. The preparation method according to claim 1, wherein: In step (3), according to the weight ratio, tannic acid is 100 parts and two-dimensional polyamide is 100 parts.

5. The preparation method according to claim 1, wherein: In step (4), according to the weight ratio, isophorone diisocyanate is 50 parts, polytetrahydrofuran is 20 parts, the catalyst is 2 parts, and the solvent is 300 parts; the catalyst is dibutyltin dilaurate, and the organic solvent is acetone.

6. The preparation method according to claim 1, wherein: In step (5), according to the weight ratio, 2,2-dihydroxymethylpropionic acid is 12 parts, dihydroxyacetone is 0-20 parts, and 1,4-butanediol is 0-20 parts.

7. The preparation method according to claim 1, wherein: In step (6), the amount of triethylamine is 12 parts by weight.

8. The preparation method according to claim 1, wherein: In step (7), the amount of deionized water is 80 parts by weight.

9. The preparation method according to claim 1, wherein: In step (8), the amount of adipic acid dihydrazide is 0-10 parts by weight.

10. The preparation method according to claim 1, characterized in that: In step (9), the amount of tannic acid-modified two-dimensional polyamide is 0.1-5 parts by weight.

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