Low-temperature curing epoxy resin curing agent and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a low-temperature curing epoxy resin curing agent and a preparation method thereof.According to the specific technical scheme, the low-temperature curing epoxy resin curing agent comprises a photosensitive group modified amine curing agent, and photosensitive groups are introduced into the photosensitive group modified amine curing agent through chemical modification; the photosensitive group is at least one of a cinnamate group or an anthracene group; the nano heat source material is at least one of graphene, a carbon nano tube or MXene, and the nano heat source material is compounded with the amine curing agent modified by the photosensitive group; when the photo-thermal dual-response curing agent is irradiated by ultraviolet light or near-infrared light, the photosensitive group is subjected to a photo-dimerization reaction to generate an active intermediate, and meanwhile, the nano heat source material generates local heat.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a low-temperature curing epoxy resin curing agent and a preparation method thereof. Background Art

[0002] Due to its excellent mechanical properties, chemical resistance, and adhesion properties, epoxy resin is widely used in fields such as coatings, composites, electronic packaging, and adhesives. However, traditional epoxy resin curing agents usually require curing reactions at high temperatures (>100°C), which not only consume high energy but also limit their applications in heat-sensitive materials (such as plastics, electronic components, etc.). Therefore, developing an epoxy resin curing agent that can cure rapidly at low temperatures has important practical significance.

[0003] In recent years, photocuring technology and thermal curing technology have been widely applied in the field of low-temperature curing. Photocuring technology uses ultraviolet light to initiate the curing reaction, which has the advantages of rapid curing and low-temperature operation. However, its curing depth is limited, and its applicability to opaque materials is poor. Thermal curing technology promotes the curing reaction through external heating, but it has high energy consumption and is difficult to achieve local heating. To overcome these limitations, researchers have proposed the concept of a photo-thermal dual-responsive curing agent, which combines the advantages of photocuring technology and thermal curing technology to achieve rapid curing at low temperatures.

[0004] Photo-thermal dual-responsive curing agents usually consist of amine curing agents modified with photosensitive groups and nano heat source materials. The photosensitive groups undergo a photochemical reaction under ultraviolet light irradiation to generate reactive intermediates, which initiate the curing reaction; the nano heat source materials generate local heat under near-infrared light irradiation, further promoting the curing reaction. This synergistic effect enables the curing agent to achieve rapid curing at low temperatures while overcoming the limitations of single photocuring or thermal curing technologies.

[0005] However, existing photo-thermal dual-responsive curing agents still have some problems, such as low photoreaction efficiency of photosensitive groups, poor dispersion of nano heat source materials, insufficient mechanical properties and chemical resistance of the curing agent, etc. Summary of the Invention

[0006] The present invention aims to provide a low-temperature curing epoxy resin curing agent and a preparation method thereof, which have high-efficiency photo-thermal dual-responsive performance, excellent mechanical properties and chemical resistance, and adjustable curing agent ratios.

[0007] The above technical objectives of the present invention are achieved through the following technical solutions:

[0008] A low-temperature curing epoxy resin curing agent provided by the present invention includes the following components:

[0009] An amine curing agent modified with a photosensitive group, wherein the amine curing agent modified with a photosensitive group is introduced with a photosensitive group through chemical modification; the photosensitive group is at least one of a cinnamate group or an anthracene group;

[0010] A nano heat source material, wherein the nano heat source material is at least one of graphene, carbon nanotubes or MXene,

[0011] The nano heat source material is compounded with the amine curing agent modified with a photosensitive group;

[0012] Under ultraviolet light or near-infrared light irradiation, the photosensitive group in the photo-thermal dual-responsive curing agent undergoes a photodimerization reaction to generate an active intermediate, and at the same time, the nano heat source material generates local heat.

[0013] Furthermore, the amine curing agent is polyetheramine D230.

[0014] Furthermore, the introduction of the photosensitive group is achieved through the following steps:

[0015] The amine curing agent is reacted with a photosensitive group precursor compound under the action of a catalyst to generate an amine curing agent modified with a photosensitive group.

[0016] Furthermore, the wavelength of the ultraviolet light is 300 - 400 nm, and the wavelength of the near-infrared light is 800 - 1200 nm.

[0017] Furthermore, the photo-thermal dual-responsive curing agent further includes a dynamic covalent bond, and the dynamic covalent bond is at least one of a Diels-Alder reaction bond, a disulfide bond or an imine bond.

[0018] Furthermore, the photo-thermal dual-responsive curing agent further includes a microencapsulated repair agent, and the microencapsulated repair agent includes a repair agent and a microcapsule shell encapsulating the repair agent.

[0019] Furthermore, the repair agent is an epoxy resin monomer, and the microcapsule shell is polyurea formaldehyde.

[0020] Furthermore, the photo-thermal dual-responsive curing agent further includes a toughening agent, and the toughening agent is at least one of rubber particles or core-shell structured polymers.

[0021] Furthermore, the mass ratio of the amine curing agent modified with a photosensitive group to the nano heat source material is calculated according to the following formula:

[0022] α is the mass ratio of the photosensitive group to the nano heat source material;

[0023] k p is the photoreaction rate constant of the photosensitive group;

[0024] w n is the photothermal conversion efficiency of the nano heat source;

[0025] I UV and I NIR are the intensities of ultraviolet light and gold infrared light, respectively;

[0026] τ p is the reaction lifetime of the photosensitive group;

[0027] τ n is the thermal relaxation time of the nano heat source.

[0028] The present invention also provides a preparation method of a low-temperature curable epoxy resin curing agent, comprising the following steps:

[0029] React an amine curing agent with a photosensitive group precursor compound under the action of a catalyst to generate an amine curing agent modified with a photosensitive group;

[0030] Disperse the nano heat source material in a solvent, add the prepared amine curing agent modified with a photosensitive group, stir and mix, and then remove the solvent to obtain a photo-thermal dual-responsive curing agent.

[0031] In summary, the present invention has the following beneficial effects:

[0032] The low-temperature curable epoxy resin curing agent of the present invention realizes photo-thermal dual-responsive performance by introducing an amine curing agent modified with a photosensitive group and a nano heat source material, can rapidly initiate a curing reaction under ultraviolet light or near-infrared light irradiation, significantly reduce the curing temperature to below 60°C, and at the same time, by introducing dynamic covalent bonds and microcapsule repair agents, endows the material with self-healing function, improves the mechanical properties and durability of the material; in addition, by precisely regulating the ratio of the photosensitive group and the nano heat source material, the performance of the curing agent is optimized, so that it has an efficient photo-thermal synergistic effect, excellent chemical resistance and adjustable curing rate, is suitable for the preparation of heat-sensitive materials and high-performance composite materials, and has broad application prospects and significant economic benefits. Specific Embodiments

[0033] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, a low-temperature curable epoxy resin curing agent and its preparation method according to the present invention are described in detail below in terms of their specific embodiments, features and effects.

[0034] A low-temperature curable epoxy resin curing agent provided in this specific embodiment comprises the following components:

[0035] An amine curing agent modified with a photosensitive group, wherein the photosensitive group is introduced by chemical modification; the photosensitive group is at least one of a cinnamate group or an anthracene group;

[0036] A nano heat source material, which is at least one of graphene, carbon nanotubes or MXene,

[0037] The nano heat source material is compounded with an amine curing agent modified with a photosensitive group;

[0038] Under ultraviolet light or near-infrared light irradiation, the photosensitive group in the photo-thermal dual-responsive curing agent undergoes a photodimerization reaction to generate active intermediates, and at the same time the nano heat source material generates local heat.

[0039] It can be understood that the low-temperature curing epoxy resin curing agent provided in this specific embodiment is based on a photo-thermal dual-responsive mechanism, and realizes low-temperature rapid curing through the synergistic effect of the photosensitive group and the nano heat source material.

[0040] Among them, the photosensitive group (such as cinnamate group or anthracene group) undergoes a photodimerization reaction under ultraviolet light (300-400 nm) irradiation to generate intermediates with higher reactivity. These active intermediates can undergo ring-opening reactions with epoxy groups in the epoxy resin to initiate crosslinking curing.

[0041] Photothermal conversion of the nano heat source material: The nano heat source material (such as graphene, carbon nanotubes or MXene) absorbs light energy and converts it into heat energy under near-infrared light (800-1200 nm) irradiation, generating local heat. The local heat further promotes the curing reaction of the epoxy resin, reduces the curing temperature and accelerates the curing process.

[0042] The synergistic effect of the photochemical reaction of the photosensitive group and the photothermal conversion of the nano heat source material enables the curing agent to achieve rapid curing at low temperature (below 60 °C). This dual-responsive mechanism overcomes the limitations of single photocuring or thermal curing technologies and is applicable to a variety of application scenarios.

[0043] The low-temperature curing epoxy resin curing agent of the present invention realizes low-temperature rapid curing through a photo-thermal dual-responsive mechanism. The curing temperature can be as low as below 60 °C, significantly reducing energy consumption and being applicable to the curing of heat-sensitive materials (such as plastics, electronic components, etc.); the synergistic effect of the photosensitive group and the nano heat source material improves the curing efficiency, shortens the curing time, meets the requirements of rapid production, and at the same time the dual-responsive mechanism of ultraviolet light and near-infrared light makes it applicable to transparent and opaque materials, expanding the application range; the cured epoxy resin has high tensile strength (≥50 MPa) and good elongation at break (≥5%), meeting the requirements of high-performance materials.

[0044] Further, the amine curing agent is polyetheramine D230.

[0045] Further, the introduction of the photosensitive group is achieved through the following steps:

[0046] React an amine curing agent with a photosensitive group precursor compound under the action of a catalyst to produce an amine curing agent modified with a photosensitive group.

[0047] It can be understood that the introduction of the photosensitive group is achieved by reacting an amine curing agent with a photosensitive group precursor compound (such as cinnamoyl chloride or anthraquinone) under the action of a catalyst (such as triethylamine or pyridine) to produce an amine curing agent modified with a photosensitive group; the principle lies in that the photosensitive group (such as cinnamate group or anthracene group) undergoes a photodimerization reaction under ultraviolet light irradiation to generate a highly active intermediate, thereby initiating the curing reaction of epoxy resin. At the same time, the nano heat source material generates local heat under near-infrared light irradiation, further promoting the curing reaction, realizing photo-thermal dual response; this method of introducing the photosensitive group has the following advantages: First, the introduction of the photosensitive group significantly improves the photoreactivity of the curing agent, enabling it to cure rapidly under low-temperature conditions, reducing energy consumption and being applicable to heat-sensitive materials; Second, the combination of the photosensitive group and the amine curing agent enhances the molecular design flexibility of the curing agent, enabling it to cooperate efficiently with the nano heat source material and improving the curing efficiency; In addition, this method is simple to operate, has mild reaction conditions, is easy to scale up production, and the introduction of the photosensitive group also endows the curing agent with excellent photo-thermal dual response performance, expanding its application range in transparent and opaque materials, and having broad application prospects.

[0048] Furthermore, the wavelength of the ultraviolet light is 300 - 400 nm, and the wavelength of the near-infrared light is 800 - 1200 nm.

[0049] It can be understood that the wavelength of the ultraviolet light is 300 - 400 nm, and the wavelength of the near-infrared light is 800 - 1200 nm. This wavelength selection is based on the optical properties of the photosensitive group and the nano heat source material; ultraviolet light can effectively excite the photosensitive group (such as cinnamate group or anthracene group) to undergo a photodimerization reaction to generate a highly active intermediate, thereby initiating the curing reaction of epoxy resin, while near-infrared light can be efficiently absorbed by the nano heat source material (such as graphene, carbon nanotubes or MXene) and converted into heat energy to generate local heat, further promoting the curing reaction; the advantages of this dual-wavelength photo-thermal synergistic mechanism are as follows: First, the dual response of ultraviolet light and near-infrared light enables the curing agent to achieve rapid curing under low-temperature conditions, significantly reducing energy consumption and being applicable to heat-sensitive materials; Second, the short wavelength characteristic of ultraviolet light ensures the efficient excitation of the photosensitive group, and the deep penetration ability of near-infrared light enables it to act on opaque materials, expanding the application range of the curing agent; In addition, this dual-wavelength design also improves the applicability and flexibility of the curing agent, enabling it to achieve efficient curing under various light conditions, and at the same time, the curing process can be precisely controlled by adjusting the light conditions to meet the requirements of different application scenarios.

[0050] Furthermore, the photo-thermal dual-responsive curing agent further includes dynamic covalent bonds, and the dynamic covalent bonds are at least one of Diels-Alder reaction bonds, disulfide bonds or imine bonds.

[0051] It can be understood that the principle of introducing dynamic covalent bonds (such as Diels-Alder reaction bonds, disulfide bonds or imine bonds) into the photo-thermal dual-responsive curing agent is that these bonds can undergo reversible cleavage and recombination under specific stimuli (such as heat, light or pH value), endowing the material with self-healing ability; Diels-Alder reaction bonds reversibly break under heating conditions, disulfide bonds can break and reform in a reducing environment, and imine bonds reversibly recombine under acidic or heating conditions; the introduction of such dynamic covalent bonds has the following advantages: First, it significantly improves the self-healing performance of the material. When the material is damaged, the dynamic covalent bonds can reconnect under external stimuli, repair cracks and restore the material performance, extending the service life; Second, the reversible nature of the dynamic covalent bonds enables the material to maintain excellent mechanical properties even after multiple damages, improving the durability and reliability of the material; In addition, the introduction of dynamic covalent bonds also enhances the recyclability and reprocessability of the material, meeting the requirements of green chemistry and sustainable development; Combining with the photo-thermal dual-responsive mechanism, the dynamic covalent bonds further optimize the performance of the curing agent, enabling it to have self-healing function while curing rapidly at low temperature.

[0052] Furthermore, the photo-thermal dual-responsive curing agent further includes a microencapsulated repair agent, and the microencapsulated repair agent includes a repair agent and a microcapsule shell that encapsulates the repair agent.

[0053] It can be understood that the principle of introducing the microencapsulated repair agent into the photo-thermal dual-responsive curing agent is that the microcapsule shell (such as polyurea formaldehyde) can encapsulate the repair agent (such as epoxy resin monomer). When the material is damaged, the microcapsules rupture and release the repair agent, and the repair agent reacts with the curing agent or epoxy resin to repair cracks and restore the material performance; the introduction of such microencapsulated repair agent has the following advantages: First, it endows the material with self-healing ability, and can automatically repair cracks when the material is damaged, extending the service life of the material and improving its reliability; Second, the uniform dispersion of the microencapsulated repair agent ensures the efficient release and repair effect of the repair agent in the material, and at the same time the protection of the microcapsule shell avoids the premature release or failure of the repair agent; In addition, the introduction of the microencapsulated repair agent also enhances the anti-damage performance and durability of the material, enabling it to maintain excellent mechanical properties even in harsh environments; Combining with the photo-thermal dual-responsive mechanism, the microencapsulated repair agent further optimizes the performance of the curing agent, enabling it to have self-healing function while curing rapidly at low temperature.

[0054] Furthermore, the repair agent is an epoxy resin monomer, and the microcapsule shell is polyurea formaldehyde.

[0055] It is understandable that the repair agent is an epoxy resin monomer, and the design principle of the microcapsule shell being polyurea formaldehyde is that the polyurea formaldehyde shell can effectively encapsulate the epoxy resin monomer. When the material is damaged, the microcapsules rupture to release the epoxy resin monomer, and the monomer reacts with the curing agent or the epoxy resin matrix to repair the cracks and restore the material properties. The advantages of this design are as follows: First, the epoxy resin monomer has high reactivity and can quickly react with the curing agent or the matrix to achieve efficient repair. Second, the polyurea formaldehyde shell has good mechanical strength and chemical stability, which can protect the epoxy resin monomer from premature release in the undamaged state and is easy to rupture under external forces to ensure the timely release of the repair agent. In addition, the introduction of the microencapsulated repair agent significantly improves the self-healing ability of the material, can automatically repair cracks when the material is damaged, extend the service life of the material and improve its reliability. Combining the photo-thermal dual-responsive mechanism, this repair agent design further optimizes the performance of the curing agent, enabling it to have high-efficiency self-healing function while curing rapidly at low temperature.

[0056] Furthermore, the photo-thermal dual-responsive curing agent further includes a toughening agent, and the toughening agent is at least one of rubber particles or core-shell structure polymers.

[0057] The principle of introducing a toughening agent (such as rubber particles or core-shell structure polymers) into the photo-thermal dual-responsive curing agent is that these toughening agents can form an elastic phase by dispersing in the curing agent matrix, absorb external stress and prevent crack propagation, thereby improving the toughness and impact resistance of the material. Rubber particles disperse stress through their high elasticity, while core-shell structure polymers deform under external forces through their special core-shell design, consume energy and prevent crack propagation. The introduction of this toughening agent has the following benefits: First, it significantly improves the toughness and impact resistance of the cured epoxy resin, avoids brittle fracture of the material, and enables it to maintain integrity when subjected to external forces. Second, the introduction of the toughening agent improves the flexibility and durability of the material, enabling it to maintain excellent mechanical properties in harsh environments. In addition, the uniform dispersion of the toughening agent ensures the stability of the material properties, and its good compatibility with the curing agent matrix avoids the problem of phase separation. Combining the photo-thermal dual-responsive mechanism, the introduction of the toughening agent further optimizes the comprehensive performance of the curing agent, enabling it to have high toughness and impact resistance while curing rapidly at low temperature.

[0058] Furthermore, the mass ratio of the amine curing agent modified with a photosensitive group and the nano heat source material is calculated according to the following formula:

[0059] α is the mass ratio of the amine curing agent and the nano heat source material;

[0060] k p is the photoreaction rate constant of the photosensitive group;

[0061] w n is the photothermal conversion efficiency of the nano heat source;

[0062] I UV and I NIR are the intensities of ultraviolet light and gold infrared light, respectively;

[0063] τ p is the reaction lifetime of the photosensitive group;

[0064] τ n is the thermal relaxation time of the nano heat source.

[0065] It can be understood that by quantifying the photoreaction efficiency of the photosensitive group and the photothermal conversion efficiency of the nano heat source, and precisely regulating the ratio of the two, the best photothermal synergistic effect can be achieved; the advantages of this calculation method are as follows: First, it can optimize the performance of the curing agent according to specific light intensity, material parameters and process conditions to ensure the high efficiency of low-temperature rapid curing; Second, by precisely regulating the mass ratio, the overuse of the photosensitive group or the nano heat source is avoided, reducing the cost and improving the material utilization rate; In addition, this formula provides a theoretical basis for the design and preparation of the curing agent, enabling it to adapt to different application scenarios and requirements; Combining the photothermal dual-response mechanism, this precise ratio calculation method further improves the comprehensive performance of the curing agent, making it have an efficient photothermal synergistic effect while achieving low-temperature rapid curing.

[0066] The present invention also provides a preparation method of a low-temperature curing epoxy resin curing agent, comprising the following steps:

[0067] React an amine curing agent with a photosensitive group precursor compound under the action of a catalyst to generate an amine curing agent modified with a photosensitive group;

[0068] Disperse the nano heat source material in a solvent, add the prepared amine curing agent modified with a photosensitive group, stir and mix, and then remove the solvent to obtain a photothermal dual-response type curing agent.

[0069] The following further illustrates the present invention with specific embodiments.

[0070] Example 1

[0071] This Example 1 provides a basic photothermal dual-response type curing agent and its preparation method,

[0072] The basic photothermal dual-response type curing agent comprises the following components: 10 g of polyetheramine D230, 1.2 g of cinnamoyl chloride (photosensitive group precursor), 0.5 g of triethylamine (catalyst), 2.4 g of graphene (nano heat source material), and 50 mL of ethanol (solvent).

[0073] Among them, the mass ratio of cinnamoyl chloride to graphene is calculated by the formula: Calculation

[0074] α is the mass ratio of the photosensitive group to the nano heat source material;

[0075] k p is the photoreaction rate constant of the photosensitive group, with a value of 0.1 s -1 ;

[0076] w n is the photothermal conversion efficiency of the nano heat source, and the photothermal conversion efficiency of graphite is taken as 0.5;

[0077] I UV and I NIR are the intensities of ultraviolet light and near-infrared light, respectively, with values of 100 W / m 2 and 200 W / m 2 ;

[0078] τ p is the reaction lifetime of the photosensitive group, with a value of 10 s;

[0079] τ n is the thermal relaxation time of the nano heat source, with a value of 2 s;

[0080] Then the calculation result is α = 0.5.

[0081] The preparation method of the basic photothermal dual-responsive curing agent includes the following steps:

[0082] Preparation of the photosensitive group-modified amine curing agent:

[0083] Add 10 g of polyetheramine D230 and 1.2 g of cinnamoyl chloride into a reaction flask.

[0084] Add 0.5 g of triethylamine as a catalyst and stir the reaction at room temperature for 4 hours.

[0085] After the reaction is completed, remove the unreacted cinnamoyl chloride and the catalyst by vacuum distillation to obtain the photosensitive group-modified amine curing agent.

[0086] Compound of the nano heat source material:

[0087] Disperse 2.4 g of graphene in 50 mL of ethanol and ultrasonically treat for 30 minutes.

[0088] Add the prepared photosensitive group-modified amine curing agent and stir and mix for 2 hours.

[0089] Remove ethanol by vacuum distillation to obtain the photothermal dual-responsive curing agent.

[0090] Example 2

[0091] Example 2 provides a basic photo-thermal dual-responsive curing agent and its preparation method.

[0092] The basic photo-thermal dual-responsive curing agent comprises the following components: 9.6 g of polyetheramine D230, 1.82 g of anthraquinone (photosensitive group precursor), 0.6 g of pyridine (catalyst), 2 g of carbon nanotubes (nano heat source material), 2 g of epoxy resin monomer (repair agent), 0.5 g of polyurea formaldehyde (microcapsule shell), and 50 mL of acetone (solvent).

[0093] Among them, the mass ratio of cinnamoyl chloride to graphene is calculated by the formula: Calculate that α is the mass ratio of the photosensitive group to the nano heat source material;

[0094] k p is the photoreaction rate constant of the photosensitive group, with a value of 0.15 s -1 ;

[0095] w n is the photothermal conversion efficiency of the nano heat source, and the photothermal conversion efficiency of carbon nanotubes is taken as 0.6;

[0096] I UV and I NIR are the intensities of ultraviolet light and near-infrared light, with values of 120 W / m 2 and 250 W / m 2 ;

[0097] τ p is the reaction lifetime of the photosensitive group, with a value of 12 s;

[0098] τ n is the thermal relaxation time of the nano heat source, with a value of 1.5 s;

[0099] Then the calculation result is α = 0.96.

[0100] The preparation method of the basic photo-thermal dual-responsive curing agent comprises the following steps:

[0101] Preparation of the photosensitive group-modified amine curing agent:

[0102] Add 10 g of polyetheramine D230 and 1.82 g of anthraquinone into a reaction flask.

[0103] Add 0.6 g of pyridine as a catalyst and stir the reaction at 40 °C for 6 hours.

[0104] After the reaction is completed, remove the unreacted anthraquinone and catalyst by vacuum distillation to obtain the photosensitive group-modified amine curing agent.

[0105] Preparation of the microencapsulated repair agent:

[0106] Add 2 g of epoxy resin monomer and 0.5 g of polyurea formaldehyde to the emulsifier to form an emulsion.

[0107] Generate microencapsulated repair agent through interfacial polymerization reaction, filter and dry.

[0108] Compound of nano heat source material:

[0109] Disperse 2 g of carbon nanotubes in 50 mL of acetone and ultrasonically treat for 30 minutes.

[0110] Add the prepared amine curing agent modified with photosensitive groups and the prepared microencapsulated repair agent, and stir and mix for 2 hours.

[0111] Remove acetone by vacuum distillation to obtain a self-healing type photothermal dual-responsive curing agent.

[0112] Example 3

[0113] This Example 3 provides a basic type photothermal dual-responsive curing agent and its preparation method.

[0114] The basic type photothermal dual-responsive curing agent includes the following components: 10 g of polyetheramine D230, 1.34 g of cinnamoyl chloride (photosensitive group precursor), 0.6 g of triethylamine (catalyst), 2 g of MXene (nano heat source material), 1 g of rubber particles (toughening agent), and 50 mL of ethanol (solvent).

[0115] Among them, the mass ratio of cinnamoyl chloride and graphene is calculated by the formula: Calculate that α is the mass ratio of the photosensitive group and the nano heat source material;

[0116] k p is the photoreaction rate constant of the photosensitive group, with a value of 0.12 s -1 ;

[0117] w n is the photothermal conversion efficiency of the nano heat source, and the photothermal conversion efficiency of carbon nanotubes is taken as 0.6;

[0118] I UV and I NIR are the intensities of ultraviolet light and near-infrared light respectively, with values of 110 W / m 2 and 220 W / m 2 ;

[0119] τ p is the reaction lifetime of the photosensitive group, with a value of 11 s;

[0120] τ n is the thermal relaxation time of the nano heat source, with a value of 1.8 s;

[0121] Then the calculation result is α = 0.67.

[0122] Preparation method of basic photo-thermal dual-responsive curing agent, comprising the following steps:

[0123] Preparation of amine curing agent modified with photosensitive group:

[0124] Add 10 g of polyetheramine D230 and 1.34 g of cinnamoyl chloride into a reaction flask.

[0125] Add 0.5 g of triethylamine as a catalyst and stir the reaction at room temperature for 4 hours.

[0126] After the reaction is completed, remove the unreacted cinnamoyl chloride and the catalyst by vacuum distillation to obtain the amine curing agent modified with photosensitive group.

[0127] Compound of nano heat source material:

[0128] Disperse 2 g of MXene in 50 mL of ethanol and ultrasonically treat for 30 minutes.

[0129] Add the prepared amine curing agent modified with photosensitive group and 1 g of rubber particles, and stir and mix for 2 hours.

[0130] Remove ethanol by vacuum distillation to obtain the toughened photo-thermal dual-responsive curing agent.

[0131] Comparative Example 1

[0132] This Comparative Example 1 provides a basic photo-thermal dual-responsive curing agent and its preparation method.

[0133] The basic photo-thermal dual-responsive curing agent comprises the following components: 10 g of polyetheramine D230, 1.2 g of cinnamoyl chloride (photosensitive group precursor), 0.5 g of triethylamine (catalyst), 1.2 g of graphene (nano heat source material), and 50 mL of ethanol (solvent).

[0134] Preparation method of basic photo-thermal dual-responsive curing agent, comprising the following steps:

[0135] Preparation of amine curing agent modified with photosensitive group:

[0136] Add 10 g of polyetheramine D230 and 1.2 g of cinnamoyl chloride into a reaction flask.

[0137] Add 0.5 g of triethylamine as a catalyst and stir the reaction at room temperature for 4 hours.

[0138] After the reaction is completed, remove the unreacted cinnamoyl chloride and the catalyst by vacuum distillation to obtain the amine curing agent modified with photosensitive group.

[0139] Compound of nano heat source material:

[0140] Disperse 1.2 g of graphene in 50 mL of ethanol and ultrasonically treat for 30 minutes.

[0141] Add the prepared amine curing agent modified with a photosensitive group and stir and mix for 2 hours.

[0142] Remove ethanol by vacuum distillation to obtain a photo-thermal dual-responsive curing agent.

[0143] Comparative Example 2

[0144] This Comparative Example 2 provides a curing agent and a preparation method thereof.

[0145] The curing agent comprises the following components: 9.6 g of polyetheramine D230, 1.82 g of anthraquinone (photosensitive group precursor), 0.6 g of pyridine (catalyst), 2 g of epoxy resin monomer (repair agent), 0.5 g of polyurea formaldehyde (microcapsule shell), and 50 mL of acetone (solvent).

[0146] The preparation method of the basic photo-thermal dual-responsive curing agent comprises the following steps:

[0147] Preparation of the amine curing agent modified with a photosensitive group:

[0148] Add 10 g of polyetheramine D230 and 1.82 g of anthraquinone into a reaction flask.

[0149] Add 0.6 g of pyridine as a catalyst and stir and react at 40 °C for 6 hours.

[0150] After the reaction is completed, remove the unreacted anthraquinone and catalyst by vacuum distillation to obtain the amine curing agent modified with a photosensitive group.

[0151] Preparation of the microencapsulated repair agent:

[0152] Add 2 g of epoxy resin monomer and 0.5 g of polyurea formaldehyde into an emulsifier to form an emulsion.

[0153] Generate the microencapsulated repair agent through an interfacial polymerization reaction, filter, and dry.

[0154] Add the prepared amine curing agent modified with a photosensitive group and the prepared microencapsulated repair agent, and stir and mix for 2 hours.

[0155] Remove acetone by vacuum distillation to obtain a self-healing photo-thermal dual-responsive curing agent.

[0156] Comparative Example 3

[0157] This Comparative Example 3 provides a curing agent and a preparation method thereof.

[0158] The basic photo-thermal dual-responsive curing agent comprises the following components: 10 g of polyetheramine D230, 0.6 g of triethylamine (catalyst), 2 g of MXene (nano heat source material), 1 g of rubber particles (toughening agent), and 50 mL of ethanol (solvent).

[0159] The preparation method of the basic photo-thermal dual-responsive curing agent comprises the following steps:

[0160] Preparation of the amine curing agent modified with photosensitive groups:

[0161] Add 10 g of polyetheramine D230 and 1.34 g of cinnamoyl chloride into a reaction flask.

[0162] Add 0.5 g of triethylamine as a catalyst and stir the reaction at room temperature for 4 hours.

[0163] After the reaction is completed, remove the unreacted cinnamoyl chloride and the catalyst by vacuum distillation to obtain the amine curing agent modified with photosensitive groups.

[0164] Composite of the nano heat source material:

[0165] Disperse 2 g of MXene in 50 mL of ethanol and perform ultrasonic treatment for 30 minutes.

[0166] Add 1 g of rubber particles and stir and mix for 2 hours.

[0167] Remove ethanol by vacuum distillation to obtain the toughened photo-thermal dual-responsive curing agent.

[0168] Performance test results

[0169]

[0170] In the above Examples 1-3 and Comparative Examples 1-3, the material properties tested were for the properties of bisphenol A epoxy resin composites. Specifically, the preparation method of the tested materials is as follows:

[0171] Mix epoxy resin and curing agent: Mix 10 g of bisphenol A epoxy resin and 10 g of curing agent (Examples 1-3 or Comparative Examples 1-3) evenly and stir for 5 minutes.

[0172] Add 1 layer of fiberglass cloth after mixing.

[0173] Curing process: Pour the mixture into a mold to ensure uniform distribution of the material.

[0174] According to the type of curing agent, perform the following curing operations: Examples 1-3 and Comparative Examples 1-2: Under ultraviolet light (365 nm, 100 W / m 2 ) and near-infrared light (980 nm, 200 W / m 2Curing is carried out under irradiation, and the curing temperature and time are set according to specific examples or comparative examples.

[0175] Comparative Example 3: Curing is carried out only under near-infrared light (980 nm, 200 W / m 2 ) irradiation, and the curing temperature and time are set according to Comparative Example 3.

[0176] Post-treatment: After curing is completed, the sample is taken out of the mold and left at room temperature for 24 hours to stabilize the performance.

[0177] Test materials and test methods

[0178] 1. Curing temperature and time

[0179] Test method:

[0180] Use an infrared thermal imager to monitor the temperature change during the curing process.

[0181] Record the time required from the start of curing to complete curing.

[0182] 2. Tensile strength

[0183] Test standard: ASTM D638

[0184] Test method:

[0185] Cut the cured sample into standard dumbbell-shaped specimens.

[0186] Use a universal material testing machine to conduct a tensile test with a loading speed of 5 mm / min.

[0187] Record the maximum tensile strength (MPa).

[0188] 3. Elongation at break

[0189] Test standard: ASTM D638

[0190] Test method:

[0191] In the tensile test, record the elongation rate (%) at which the specimen breaks.

[0192] 4. Self-healing efficiency (if applicable)

[0193] Test method:

[0194] Use a blade to create cracks on the surface of the sample.

[0195] Heat at 80 °C for 1 hour or irradiate with ultraviolet light for 30 minutes, and observe the crack repair situation.

[0196] Calculate the ratio of the tensile strength after repair to the original tensile strength as the self-healing efficiency (%).

[0197] 5. Applicability

[0198] Testing method:

[0199] Apply the curing agent to transparent materials (such as glass) and opaque materials (such as metal) for curing tests.

[0200] Observe the curing effect and evaluate the applicability.

[0201] 6. Toughening effect (if applicable)

[0202] Testing standard: ASTM D256

[0203] Testing method:

[0204] Use an impact testing machine to test the impact strength (kJ / m 2 ) of the sample.

[0205] Compare the samples with and without the toughening agent to evaluate the toughening effect.

[0206] Analysis of performance test results

[0207] Examples 1 - 3

[0208] Example 1: Through the photo-thermal dual-response mechanism, low-temperature rapid curing (50°C, 20 minutes) was achieved. Tensile strength ≥ 50 MPa, elongation at break ≥ 5%, suitable for high-performance materials. Applicable to transparent and opaque materials, with a wide range of applications.

[0209] Example 2:

[0210] A microencapsulated repair agent was introduced, and the self-healing efficiency ≥ 90%.

[0211] Tensile strength ≥ 55 MPa, elongation at break ≥ 6%, with excellent mechanical properties. Applicable to transparent and opaque materials, with self-healing function.

[0212] Example 3:

[0213] A toughening agent (rubber particles) was introduced, significantly improving the toughness and impact resistance of the material. Tensile strength ≥ 52 MPa, elongation at break ≥ 5.5%, suitable for high-toughness materials.

[0214] Applicable to transparent and opaque materials, with toughening effect.

[0215] Comparative Examples 1 - 3

[0216] Comparative Example 1: The photo-thermal dual-response mechanism exists, but the dosage of the nano heat source material is insufficient (1.2 g), resulting in low curing efficiency. The tensile strength is ≥40 MPa, the elongation at break is ≥3%, and the performance is lower than that of Example 1. It is applicable to transparent and opaque materials, but the performance is poor.

[0217] Comparative Example 2:

[0218] Microencapsulated repair agents are introduced, but nano heat source materials are not used, and the photo-thermal synergy effect is insufficient. The tensile strength is ≥45 MPa, the elongation at break is ≥4%, and the self-healing efficiency is ≥85%.

[0219] It is applicable to transparent and opaque materials, but the curing efficiency is low.

[0220] Comparative Example 3:

[0221] Photosensitive groups are not used, and only rely on the thermal effect of the nano heat source material, resulting in the absence of the photo-thermal synergy effect. The tensile strength is ≥38 MPa, the elongation at break is ≥2.5%, and the performance is poor.

[0222] It is applicable to transparent and opaque materials, but the curing efficiency is low and the performance is poor.

[0223] Examples 1 to 3 demonstrate the excellent performance of the photo-thermal dual-response curing agent, including low-temperature rapid curing, high mechanical properties, self-healing function, and toughening effect.

[0224] Comparative Examples 1 to 3 reveal the importance of the photo-thermal synergy effect, the dosage of the nano heat source material, and the photosensitive group. The lack of these key factors will lead to low curing efficiency and performance degradation.

[0225] Examples 1 to 3 are superior to Comparative Examples 1 to 3 in terms of curing temperature, curing time, mechanical properties, and applicability, demonstrating the technical advantages of the photo-thermal dual-response curing agent.

[0226] The above are only the preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been shown above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to obtain equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as the content does not depart from the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A low temperature curing epoxy resin curing agent, characterized in that: Includes the following components: A photosensitive group-modified amine curing agent, wherein the photosensitive group is introduced into the photosensitive group by chemical modification; the photosensitive group is at least one of a cinnamate group or an anthracene group; A nano heat source material, wherein the nano heat source material is at least one of graphene, carbon nanotubes or MXene, The nano heat source material is compounded with the photosensitive group-modified amine curing agent; When the photothermal dual-response curing agent is irradiated with ultraviolet light or near-infrared light, the photosensitive group undergoes a photodimerization reaction to generate an active intermediate, and the nano heat source material generates local heat at the same time.

2. A low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The amine curing agent is polyetheramine D230.

3. The low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The introduction of the photosensitive group is achieved by the following steps: The amine curing agent is reacted with a photosensitive group precursor compound under the action of a catalyst to generate an amine curing agent modified with a photosensitive group.

4. The low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The wavelength of the ultraviolet light is 300-400 nm, and the wavelength of the near infrared light is 800-1200 nm.

5. The low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The photothermal dual-response curing agent further includes a dynamic covalent bond, which is at least one of a Diels-Alder reaction bond, a disulfide bond, or an imine bond.

6. A low temperature curing epoxy resin curing agent according to claim 5, characterized in that: The photothermal dual-response curing agent also includes a microencapsulated repairing agent, which includes a repairing agent and a microcapsule shell encapsulating the repairing agent.

7. A low temperature curing epoxy resin curing agent according to claim 6, characterized in that: The repairing agent is epoxy resin monomer, and the microcapsule shell is polyurea formaldehyde.

8. The low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The photothermal dual-response curing agent also includes a toughening agent, and the toughening agent is at least one of rubber particles or core-shell structure polymers.

9. The low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The mass ratio of the photosensitive group-modified amine curing agent and the nano heat source material is calculated according to the following formula: α is the mass ratio of the photosensitive group to the nano heat source material; k p is the photoreaction rate constant of the photosensitive group; w n is the light-to-heat conversion efficiency of the nanoheat source; I UV and I NIR are the intensities of ultraviolet light and gold infrared light, respectively; τ p is the reaction lifetime of the photosensitive group; τ n is the thermal relaxation time of the nanoheat source.

10. The method for preparing a low temperature curing epoxy resin curing agent according to claim 1, characterized in that: The following steps are involved: The amine curing agent is reacted with a photosensitive group precursor compound under the action of a catalyst to generate an amine curing agent modified with a photosensitive group; The nano heat source material is dispersed in a solvent, and the prepared photosensitive group-modified amine curing agent is added, and after stirring and mixing, the solvent is removed to obtain a light-heat dual response curing agent.

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