Self-repairable lipoic acid-based underwater binder and preparation method thereof

Abstract

The invention discloses a self-repairable lipoic acid-based underwater binder and a preparation method thereof, and relates to the technical field of polymer binders. The binder comprises the following raw material components: lipoic acid and vinyl cyclosiloxane, the lipoic acid and the vinyl cyclosiloxane are subjected to chemical crosslinking through a solvent-free thermal / light synergistic polymerization process, and the underwater binder with good self-repairing performance and binding performance is prepared. The preparation method disclosed by the invention is simple and environment-friendly in process, and the prepared lipoic acid-based underwater binder has firm binding property, good universality and excellent self-repairing characteristic, and can realize rapid and stable binding underwater.

Description

Technical Field

[0001] The present invention relates to the field of polymer adhesives, and in particular to a self-repairing lipoic acid-based underwater adhesive, a preparation method thereof, and applications thereof. Background Art

[0002] As a key functional material for connecting different materials, adhesives have become an indispensable component of the modern industrial system. Current research on adhesives mostly focuses on the optimization of interfacial bonding properties. However, the overall performance of adhesives not only depends on interfacial interactions, but cohesion (i.e., the bonding strength between molecules within the material) is also a key factor in determining its failure mode and long-term stability. Unfortunately, in current research, the improvement of cohesion is usually not synchronized with the improvement of interfacial bonding strength, and research from the perspective of cohesion is often neglected.

[0003] As an emerging biomass small molecule, lipoic acid has gained favor among materials researchers in recent years due to its widespread availability, renewable nature, natural molecular structure, and unique physical and chemical properties. It is widely used in adhesives. However, the high molecular flexibility of lipoic acid-based adhesives makes them more susceptible to mechanical weaknesses when subjected to shear or peel stress, leading to cohesive failure.

[0004] Most existing patents focus on improving the strength of lipoic acid-based adhesives by optimizing the interactions of functional groups. However, these improvements in mechanical properties are limited, self-healing properties are lacking, and underwater bonding is impossible. By molecularly integrating vinylcyclosiloxane, which combines the cyclic rigidity and flexibility of siloxane, with lipoic acid, a novel adhesive system has been constructed that synergistically enhances cohesion and interfacial bonding strength. This gives lipoic acid-based adhesives excellent bonding properties, self-healing properties at room temperature, and the ability to rapidly bond underwater. Summary of the Invention

[0005] In response to the above technical problems, the present invention invents a self-repairing lipoic acid-based underwater adhesive and a preparation method thereof, aiming to obtain a lipoic acid-based underwater adhesive with excellent underwater bonding performance, self-repairing performance and high cohesion.

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

[0007] A self-repairing lipoic acid-based underwater adhesive and a preparation method thereof, comprising the following steps:

[0008] (1) Place 5 g of lipoic acid in a single-necked flask, introduce inert gas to remove oxygen, and heat in an oil bath at 60-150°C for 5-30 min;

[0009] (2) adding different doses of vinylcyclosiloxane to the solution of step (1) according to the molar fraction ratio of vinylcyclosiloxane to lipoic acid, and stirring at 600 r / min for 10-60 min;

[0010] (3) pouring the liquid mixture obtained after the reaction in step (2) into a polytetrafluoroethylene mold and irradiating it under ultraviolet light. After it is cured, the resulting polymer is a self-repairing thioctic acid-based underwater adhesive.

[0011] Preferably, the inert gas in step (1) is one of nitrogen, argon and helium.

[0012] Preferably, the vinylcyclosiloxane in step (2) is one or more of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2,4-divinyl-2,4,6,6,8,8-hexamethylcyclotetrasiloxane, and 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane.

[0013] Preferably, in step (2), the molar ratio of lipoic acid to vinyl cyclosiloxane is 1000-20:1.

[0014] Preferably, the wavelength of the ultraviolet lamp in step (3) is 365-420 nm.

[0015] Preferably, the illumination time in step (3) is 1-8 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The method of the present invention cross-links lipoic acid and cyclic siloxanes through a solvent-free thermal / photosynergistic polymerization process to produce an adhesive with excellent mechanical properties, room-temperature self-healing capabilities, and rapid underwater bonding. The multi-stage dynamic cross-linking network in the adhesive not only induces molecular chain orientation through segmented synergistic motion, thereby enhancing the adhesive's cohesion, but also achieves strong interfacial bonding through hydrogen bonding interactions with the substrate. Compared to a system cross-linked with linear siloxanes, the lap shear strength of the cyclic topology cross-linked adhesive reaches 5.66 MPa, a 372% increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Comparison of the adhesive strength of the adhesive obtained in Example 1 on different substrates

[0019] Figure 2 This is a diagram showing the bonding effect of the adhesive obtained in Example 1 in an underwater environment

[0020] Figure 3 This is the self-repair effect diagram of Example 1

[0021] Figure 4 Comparison of mechanical properties between Example 1 and the comparative example

[0022] Figure 5 Comparison of the bonding strength of Example 1 and the comparative example on different substrates

[0023] Figure 6 The cohesive energy improvement mechanism of the adhesive in the embodiment is shown in FIG. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Unless otherwise specified, the raw materials and reagents used in the embodiments and comparative examples are all commercially available.

[0025] Example 1

[0026] A self-repairing lipoic acid-based underwater adhesive and a preparation method thereof, specifically comprising the following steps:

[0027] (1) Place 5 g of lipoic acid in a single-necked flask, introduce nitrogen to remove oxygen, and heat in an oil bath at 120°C for 30 min to convert it into a molten state;

[0028] (2) keeping the temperature constant, adding 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane at a molar ratio of 50:1 to thioctic acid to the solution of step (1), and stirring at 600 r / min for 60 min;

[0029] (3) Pour the liquid mixture obtained after the reaction in step (2) into a polytetrafluoroethylene mold and irradiate it under 420nm ultraviolet light for 4 hours. After further polymerization, a self-repairing thioctic acid-based underwater adhesive can be obtained.

[0030] Mechanical property test: The obtained lipoic acid-based underwater adhesive was cut into dumbbell-shaped specimens with an initial length of 20 mm and a width of 2 mm, and a tensile test was performed using a universal testing machine at room temperature.

[0031] Self-repair performance test: Use a razor blade to scratch the surface of the sample (width is about 18μm), and then use a polarizing microscope to observe the scratch recovery of the sample at different times at room temperature.

[0032] Adhesion performance test: Cut the adhesive into small pieces and sandwich them between two substrates (length = 25 mm, width = 15 mm). Use a heavy object to apply continuous pressure (13 kPa) to the bonding area at 60°C for 1 hour. Then, leave it at room temperature for at least 24 hours before performing the lap shear strength test.

[0033] Examples 1-12

[0034] A self-repairing lipoic acid-based underwater adhesive and a preparation method thereof. The preparation steps are the same as those in Example 1, and the differences are shown in Table 1.

[0035] Table 1. Preparation parameters of self-repairing lipoic acid-based underwater adhesives of Examples 1-12

[0036]

[0037]

[0038] Implementation Effect

[0039] Figure 1 The following is a comparison of the bonding strength of the adhesive obtained in Example 1 on different substrates. Figure 1 It can be seen that the adhesive obtained in Example 1 exhibits excellent adhesion properties on various substrates such as glass, plastic, nylon, ceramic, wood, metal and alloy, and the lap shear strength with tinplate can reach 5.66 MPa. Even in an underwater environment, the adhesive obtained in Example 1 still exhibits excellent underwater adhesion properties on various substrates, and the lap shear strength with glass, wood, iron sheet and tinplate can reach 1.69, 2.23, 1.51 and 1.66 MPa respectively. Figure 2 Thanks to the presence of dynamic disulfide bonds and hydrogen bonds in the polymer, the scratches on the sample surface of the adhesive obtained in Example 1 were basically eliminated after being placed at room temperature for 6 hours ( Figure 3 ), indicating that it has excellent room temperature self-healing performance.

[0040] Comparative Example

[0041] While keeping the other raw material ratios and preparation methods the same as in Examples 1 to 12, the cyclic crosslinker was replaced with 1,3-divinyltetramethyldisiloxane to prepare an adhesive, which was then subjected to mechanical property and construction shear tests separately and compared with the performance of the adhesive obtained in the above Example 1.

[0042] The inventors tested the mechanical properties and shear performance of the adhesive obtained in this comparative example and the adhesive obtained in Example 1 under the same test conditions. Figure 4 、 5 As shown. Figure 4As can be seen from the table, Example 1 of the present invention using a cyclic crosslinker exhibits better comprehensive mechanical properties than a linear crosslinker (still having a tensile strength of 6.72 MPa when the elongation at break reaches 534%). Due to the inherent high flexibility of the siloxane skeleton, although the two have similar elongation at break, the strength of Example 1 is 1.15 times that of the comparative example. Figure 5 As can be seen from the figure, Example 1 exhibits higher lap shear strength than the comparative example on different substrates. From the failure surface, it can be found that the main failure of the example is interface failure, while the main failure of the comparative example is cohesive failure, indicating that the molecular topology of cyclic siloxane is more conducive to enhancing the cohesive force of the adhesive ( Figure 6 This is the mechanism for increasing the cohesive energy of the adhesive).

[0043] Table 1. Properties of self-healing lipoic acid-based underwater adhesives of Examples 1-12 and Comparative Examples

[0044]

Claims

1. A self-repairing lipoic acid-based underwater adhesive and a preparation method thereof, characterized in that: The following steps are included: (1) Place 5 g of lipoic acid in a single-necked flask, introduce inert gas to remove oxygen, and heat in an oil bath at 60-150°C for 5-30 min; (2) adding different doses of vinylcyclosiloxane to the solution of step (1) according to the molar fraction ratio of vinylcyclosiloxane to lipoic acid, and stirring at 600 r / min for 10-60 min; (3) pouring the liquid mixture obtained after the reaction in step (2) into a polytetrafluoroethylene mold and irradiating it under ultraviolet light. After it is cured, the resulting polymer is a self-repairing thioctic acid-based underwater adhesive.

2. The preparation method according to claim 1, wherein: The inert gas described in step (1) is one of nitrogen, argon and helium.

3. The preparation method according to claim 1, wherein: The vinyl cyclosiloxane in step (2) is one or more of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2,4-divinyl-2,4,6,6,8,8-hexamethylcyclotetrasiloxane, and 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane.

4. The preparation method according to claim 1, wherein: In step (2), the molar ratio of lipoic acid to vinyl cyclosiloxane is 1000-20:

1.

5. The preparation method according to claim 1, wherein: The wavelength of the ultraviolet lamp in step (3) is 365-420nm.

6. The preparation method according to claim 1, wherein: The illumination time in step (3) is 1-8h.

Images