Method for rapidly preparing epoxy composite material through laser-triggered frontline polymerization

Abstract

The invention discloses a method for rapidly preparing an epoxy composite material through laser-triggered frontline polymerization, which comprises the following steps: (1) carrying out ball-milling dispersion on epoxy resin, a monomer, a free radical thermal initiator, a cationic photoinitiator and a carbon nanotube to obtain a component A; (2) carrying out ball-milling dispersion on epoxy resin, a monomer, a free radical thermal initiator, a cationic photoinitiator and carbon black to prepare a component B; (3) carrying out ball-milling dispersion on epoxy resin, a monomer, a free radical thermal initiator, a cationic photoinitiator and carbon fibers to prepare a component C; and (4) uniformly mixing the component A, the component B and the component C, injecting the mixture into a mold, and performing laser irradiation at the port of the mold until polymerization begins. According to the invention, the preparation of the high-content dark filler epoxy composite material can be realized, the polymerization process can be completed within a few minutes, and a new thought is provided for the preparation of a high-performance composite material through previous polymerization.

Description

Technical Field

[0001] This invention relates to the field of polymer composite material preparation technology, specifically to a rapid curing method for epoxy resin / dark filler composite systems based on laser thermal effect-triggered frontal polymerization (FP), which is suitable for efficient molding of composite materials with high content of dark fillers such as carbon fiber, carbon nanotubes, and carbon black. Background Technology

[0002] In recent years, epoxy-based composite materials, especially those combined with high-performance carbonaceous materials (carbon fiber, carbon nanotubes, carbon black, etc.), have become outstanding representatives of modern materials science and engineering. By combining the excellent adhesion, chemical resistance, and designability of epoxy resins with the superior mechanical, electrical, and thermal properties of the reinforcements / fillers, they achieve lightweighting, high performance, multifunctionality, and long lifespan, becoming key enabling materials driving technological innovation and industrial upgrading in numerous fields such as aerospace, new energy, transportation, electronics, and sports. Their importance lies not only in the significant improvement of existing product performance but also in providing a broad material foundation for more efficient, intelligent, and sustainable technological solutions in the future.

[0003] Currently, epoxy-based composites are often prepared using thermosetting methods. Curing agents (such as amines and anhydrides) need to be added to the resin formulation to generate a three-dimensional polymer network through a cross-linking curing reaction. Thermosetting typically requires a long reaction time and usually takes place at high temperatures, which is time-consuming, energy-intensive, and prone to environmental pollution. UV-Initiated Radical-Induced Cationic Frontier Polymerization (UV-RICFP) is a novel frontier polymerization method. In this system, onium salt photoinitiators first photolyze to generate superacids. These superacids protonate monomer molecules, initiating polymerization. The heat released during this process raises the sample temperature, causing the free radical thermal initiator to decompose into free radicals. Due to the sufficiently high oxidizing power of iodonium salts, the generated free radicals undergo a redox reaction with the iodonium salt, releasing another molecule of superacid, which continues to initiate polymerization, forming the frontier and enabling rapid UV curing of epoxy resins. However, due to the weak penetration of ultraviolet light and the shielding effect of fillers on UV light, UV-RICFP struggles to generate frontiers for composites with high-content, dark-colored fillers. Therefore, developing a novel frontline polymerization preparation method that is simple, fast, energy-saving, and environmentally friendly, while also enabling the preparation of epoxy composites with high content of dark-colored fillers, is of great significance and value. Summary of the Invention

[0004] Objective: To address the aforementioned problems, this invention provides a rapid curing method for epoxy resin / dark filler composite systems based on laser-triggered frontline polymerization. This invention employs laser-triggered frontline polymerization to overcome the shielding effect of fillers on ultraviolet light during UV-RICFP. The thermal effect of the filler raises the system temperature to the decomposition temperature of the thermal initiator, causing it to decompose into free radicals. These free radicals then react with iodonium salts in the system, decomposing a molecule of superacid, thereby initiating ring-opening of the epoxy resin and initiating exothermic polymerization. When the light source is removed, the heat generated by the polymerization continues to decompose the free radical thermal initiator, thus achieving a cycle and forming a frontline polymerization until the system is fully cured. The entire polymerization process is completed within minutes. Laser-triggered frontline polymerization provides a new approach for the preparation of epoxy-based composite materials.

[0005] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows: The first objective of this invention is to provide a method for rapidly preparing epoxy composite materials through laser-triggered frontline polymerization, the method comprising the following steps: Step (1) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator and 0.1-10 parts of carbon nanotubes are ball-milled and dispersed to obtain component A; Step (2) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator, and 0.1-10 parts of carbon black are ball-milled and dispersed to obtain component B; Step (3) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator and 0.1-10 parts of carbon fiber are ball-milled and dispersed to obtain component C; Step (4) Mix components A, B and C separately and inject them into the mold; Step (5) Excite the mold port with 980 nm near-infrared laser irradiation until polymerization begins, then remove the light source.

[0006] Optionally, in some embodiments of the present invention, the epoxy resin is selected from one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, and bisphenol A type epoxy vinyl resins.

[0007] Optionally, in some embodiments of the present invention, the monomer is selected from one or more of vinyl ethers, aliphatic epoxy monomers, and oxacycloalkanes.

[0008] Optionally, in some embodiments of the present invention, the free radical thermal initiator includes at least one of benzidine alcohol (TPED), azobisisobutyronitrile (AIBN), azobisisobutyronitrile (ABVN), and benzoyl peroxide (BPO).

[0009] Optionally, in some embodiments of the present invention, the cationic photoinitiator includes at least one of 4-octoxydiphenyliodohexafluoroantimonate (IOD-8SbF6) and tetraalkyl (perfluorotert-butyloxy) aluminate anion.

[0010] Optionally, in some embodiments of the present invention, the mass ratio of the cationic photoinitiator to the free radical thermal initiator is 1:1.

[0011] Optionally, in some embodiments of the present invention, the length of the carbon fiber is 0.05 to 1 mm.

[0012] Optionally, in some embodiments of the present invention, the carbon nanotubes have a diameter of 0.4 to 50 nm.

[0013] Optionally, in some embodiments of the present invention, the time for irradiating the mold port with a 980 nm near-infrared laser in step (5) is 3-10 s.

[0014] A second objective of this invention is to provide an epoxy composite material prepared according to any of the methods described above.

[0015] Optionally, in some embodiments of the present invention, the epoxy composite material has a tensile strength of 76-89 MPa, a tensile modulus of elasticity of 3.1-3.9 GPa, a flexural strength of 108-125 MPa, a flexural modulus of elasticity of 3.9-4.6 GPa, a glass transition temperature of 121-136 °C, and a curing time of 1-3 min.

[0016] Beneficial Effects: Compared to existing technologies, this invention utilizes laser-triggered free radical-induced cationic frontline polymerization to prepare epoxy composites with high content of dark fillers. The entire process requires only a short period of laser irradiation, and complete curing can be achieved without external energy injection. Furthermore, the performance of samples prepared via frontline polymerization is comparable to that of traditional thermosetting materials. This invention provides a novel and feasible curing method for fields requiring high-content dark filler systems, such as electronic packaging, functional coatings, and lightweighting in aerospace and transportation. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the present invention.

[0018] Figure 2 This is a mechanism diagram of the present invention.

[0019] Figure 3 This is a photograph of the epoxy composite material obtained in Example 1 of the present invention. Detailed Implementation

[0020] This invention discloses a method for rapidly preparing epoxy composite materials via laser-triggered frontline polymerization. The method is as follows: (1) Epoxy resin, monomer, free radical thermal initiator, cationic photoinitiator, and carbon nanotubes are ball-milled and dispersed to obtain component A; (2) Epoxy resin, monomer, free radical thermal initiator, cationic photoinitiator, and carbon black are ball-milled and dispersed to obtain component B; (3) Epoxy resin, monomer, free radical thermal initiator, cationic photoinitiator, and carbon fiber are ball-milled and dispersed to obtain component C; (4) Components A, B, and C are injected into a mold, and laser irradiation is applied at the mold port until polymerization begins. This invention can realize the preparation of epoxy composite materials with high content of dark-colored fillers. The polymerization process can be completed in just a few minutes, providing a new approach for the preparation of high-performance composite materials via frontline polymerization.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art, or according to the product manual. The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the specific material ratios, process conditions, and results described in the embodiments are only for illustrating the present invention and should not and will not limit the present invention as described in detail in the claims.

[0022] An epoxy premix for laser-triggered free radical-induced cationic frontier polymerization is prepared by uniformly mixing the following raw materials in the following weight ratio: Component A is a uniform mixture of the following raw materials in the following weight ratios: epoxy resin (E51), 10-90 parts; monomer (3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester EPOX), 10-100 parts; free radical thermal initiator (benzylpinacol TPED), 0.25-5 parts; cationic photoinitiator (4-octyloxydiphenyliodohexafluoroantimonate IOD-8SbF6), 0.1-5 parts; carbon nanotubes, 0.1-10 parts.

[0023] Component B is a uniform mixture of the following raw materials in the following weight ratios: epoxy resin (E51), 10-90 parts; monomer (3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester EPOX), 10-100 parts; free radical thermal initiator (benzylpinacol TPED), 0.25-5 parts; cationic photoinitiator (4-octyloxydiphenyliodohexafluoroantimonate IOD-8SbF6), 0.25-5 parts; carbon black, 0.1-8 parts. Component C is a uniform mixture of the following raw materials in the following weight ratios: epoxy resin (E51), 10-90 parts; monomer (3,4-epoxycyclohexylcarboxylic acid-3',4'-epoxycyclohexylmethyl ester EPOX), 10-100 parts; free radical thermal initiator (benzylpinacol TPED), 0-5 parts; cationic photoinitiator (4-octyloxydiphenyliodohexafluoroantimonate IOD-8SbF6), 0.25-5 parts; carbon fiber, 0.01-3 parts.

[0024] In this invention, the addition of specific dark-colored fillers enhances the photothermal conversion effect of the resin matrix, enabling the system to rapidly heat up under laser irradiation, thereby initiating frontier polymerization. Furthermore, fillers such as carbon nanotubes provide reinforcement, improving the mechanical strength of the cured sample.

[0025] A method for preparing epoxy composite materials by laser-triggered frontline polymerization includes the following steps: Step (1) Weigh each raw material of component A according to the weight ratio, disperse them by ball milling, and obtain component A; Step (2) Weigh each raw material of component B according to the weight ratio, disperse them by ball milling, and obtain component B; Step (3) Weigh each raw material of component C according to the weight ratio, disperse them by ball milling, and obtain component C; Step (4) Inject all three components of epoxy premix, A, B, and C, into the mold; Step (5) Excite one end of the epoxy premix by irradiating it with a 980 nm near-infrared laser until polymerization begins, then remove the light source.

[0026] Preparation Principle: This invention uses epoxy resin as the reaction matrix resin, monomers as reactive diluents to improve the activity of the premix, IOD-8SbF6 as a cationic photoinitiator, TPED as a free radical thermal initiator, and dark fillers in the system as photothermal conversion agents. For example... Figure 1 , 2As shown, the photothermal effect of laser on the filler in the system raises the system temperature to the decomposition temperature of the thermal initiator, causing it to decompose into free radicals. These free radicals then react with the iodonium salt in the system to undergo redox reactions, decomposing into a single molecule of superacid. This triggers the ring-opening of the epoxy in the system and begins to polymerize exothermically. When the light source is removed, the heat generated by the polymerization continues to decompose the free radical thermal initiator, thus achieving a cycle and forming a front, until the system is completely cured.

[0027] Examples 1-8 The raw materials and quantities used in Examples 1-8 of this invention are shown in Table 1 below: Table 1 Table 1 shows the preparation method of laser-triggered front-end polymerized epoxy composite material, which includes the following steps: Bisphenol A glycidyl ether epoxy resin E51, aliphatic epoxy monomer EPOX, benzyl pinacol TPED, 4-octyloxydiphenyliodohexafluoroantimonate IOD-8SbF6, and filler were added to a ball mill jar according to the embodiments and dispersed in a high-speed disperser at 3000 r / min for 10 min. After thorough mixing, a mixture for preparing an epoxy composite material for laser-triggered frontline polymerization was obtained.

[0028] Pour the mixture into a mold and irradiate it with a 980 nm near-infrared laser for 3-10 seconds. After polymerization begins, remove the light source. The reaction will continue until all materials have completely reacted to obtain the front-end cured product.

[0029] Comparative Examples 1-6 The raw materials and amounts used in Comparative Examples 1-6 of this invention are shown in Table 2 below: Table 2 Comparative Examples 1-6 illustrate the preparation methods of traditional thermosetting epoxy composite materials. The specific steps are as follows: Bisphenol A glycidyl ether epoxy resin E51, aliphatic epoxy monomer EPOX, curing agent 4,4'-diaminodiphenylmethane, and filler are added to a ball mill jar according to the proportions shown in Table 2. The mixture is then dispersed in a high-speed disperser at 3000 r / min for 10 min. After thorough mixing, the mixture is poured into a mold and cured at a temperature increase of 100 °C / 1 h, 120 °C / 2 h, 140 °C / 2 h, 140 °C / 2 h, and 180 °C / 1 h to obtain the thermosetting material.

[0030] Test case (1) Photographs of epoxy composite materials A photograph of the epoxy composite material obtained in Example 1 of this invention is shown below. Figure 3As shown. Pour the well-mixed material into a test tube, irradiate the top of the test tube with near-infrared light, remove the light source after the front-end is activated, and the mixture continues to react spontaneously until all materials have reacted completely.

[0031] (2) Tensile strength and tensile modulus The cured samples were tested in accordance with the People's Republic of China National Standard GB / T14337-2022 "Test Method for Tensile Properties of Short Chemical Fibers".

[0032] (3) Bending strength and bending modulus The cured samples were tested in accordance with the People's Republic of China National Standard GB / T 14338-2022 "Test Method for the Crimping Properties of Short Chemical Fibers".

[0033] (4) Glass transition temperature (T) g ) Using a dynamic thermomechanical analyzer, the T-test was performed according to the standard ASTM E1640-2013, "Standard Test Method for Glass Transition Temperature Distribution Using Dynamic Mechanical Analysis". g The test.

[0034] (5) Curing time The performance test results of the embodiment and Comparison 1 are shown in Table 3 below: Table 3 As can be seen from the test results in Table 3, the mechanical properties of the epoxy composite material of the present invention are comparable to those of traditional thermosetting, but the curing time is only within 1-3 min, which is much lower than the 480 min of thermosetting in the comparative example.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapidly preparing epoxy composite materials through laser-triggered frontier polymerization, characterized in that, The method includes the following steps: Step (1) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator and 0.1-10 parts of carbon nanotubes are ball-milled and dispersed to obtain component A; Step (2) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator, and 0.1-10 parts of carbon black are ball-milled and dispersed to obtain component B; Step (3) By weight, 10-90 parts of epoxy resin, 10-100 parts of monomer, 0.25-5 parts of free radical thermal initiator, 0.25-5 parts of cationic photoinitiator and 0.1-10 parts of carbon fiber are ball-milled and dispersed to obtain component C; Step (4) Mix components A, B and C separately and inject them into the mold; Step (5) Excite the mold port with 980 nm near-infrared laser irradiation until polymerization begins, then remove the light source.

2. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The epoxy resin is selected from one or more of glycidyl ether epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, and bisphenol A type epoxy vinyl resins.

3. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The monomer is selected from one or more of vinyl ethers, aliphatic epoxy monomers, and oxacycloalkanes.

4. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The free radical thermal initiators include benzinolide (TPED), azobisisobutyronitrile (AIBN), azobisisobutyronitrile (ABVN), and benzoyl peroxide (BPO), etc. Cationic photoinitiators include one or more of 4-octyloxydiphenyliodohexafluoroantimonate IOD-8SbF6 and tetraalkyl(perfluorotert-butyloxy)aluminate anions.

5. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The mass ratio of the cationic photoinitiator to the free radical thermal initiator is 1:

1.

6. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The length of the carbon fiber is 0.05 to 1 mm.

7. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, The carbon nanotubes have a diameter of 0.4–50 nm.

8. The method for rapid preparation of epoxy composite materials by laser-triggered frontline polymerization according to claim 1, characterized in that, In step (5), the time for irradiating the mold port with a 980 nm near-infrared laser is 3-10 s.

9. An epoxy composite material prepared according to any one of claims 1-8.

10. An epoxy composite material according to claim 9, characterized in that, The epoxy composite material has a tensile strength of 76-89 MPa, a tensile modulus of elasticity of 3.1-3.9 GPa, a flexural strength of 108-125 MPa, a flexural modulus of elasticity of 3.9-4.6 GPa, a glass transition temperature of 121-136 °C, and a curing time of 1-3 min.

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