Epoxy composite coating with radiation attenuation performance and preparation method thereof

Abstract

The invention discloses an epoxy composite coating with radiation attenuation performance and a preparation method thereof. The preparation process of the composite coating comprises the following steps: firstly, preparing a core-shell structure anti-radiation filler of a silicon dioxide shell layer through auxiliary ball milling of tetraethoxysilane, and then preparing a modified anti-radiation filler through further surface treatment of gamma-aminopropyltriethoxysilane (KH550); and finally, mixing the modified filler with epoxy resin to obtain the epoxy composite coating with the radiation shielding performance. The prepared composite coating has good thermal stability and adhesive strength, has excellent X / gamma ray attenuation performance and can be used for radiation attenuation of the surface of metal equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to a radiation shielding coating, in particular to an epoxy composite coating with radiation attenuation performance and a preparation method thereof. BACKGROUND

[0002] With the popularization of medical imaging technology, semiconductor industry detection and portable nuclide identification equipment, the shielding demand of X-ray and low-energy gamma ray is growing rapidly. Lead-based materials such as lead plate and lead glass are widely used due to their high atomic number and mature preparation process. However, the K absorption edge of lead is around 88 keV, so there is a problem of shielding efficiency decline in the energy region of 40-88 keV X-ray. At the same time, the inherent biological toxicity and rigid molecular structure of lead-based materials limit their wearability, which seriously restricts their application in precision and flexible protection scenarios. Therefore, researchers are committed to developing more lightweight and environmentally friendly polymer-based shielding materials. Among them, epoxy resin has excellent adhesion, corrosion resistance and controllable curing characteristics, and is an ideal polymer matrix for shielding materials. However, existing epoxy-based shielding coatings focus more on the protection of high-energy rays, and there is less research on the protection of low-energy photons. On the other hand, epoxy-based materials generally have mechanical performance degradation caused by filler agglomeration and the risk of interface delamination during long-term use. Therefore, how to achieve the synergistic optimization of wide energy region high-efficiency shielding and mechanical properties through material innovation has become the core challenge of current radiation protection material research.

[0003] In the field of low-energy photon shielding, metal oxides with high atomic number and specific K absorption edge have attracted widespread attention. The K absorption edge of gadolinium oxide is 50.2 keV, which can effectively absorb X-rays in the range of 30-50 keV (such as molybdenum target X-rays commonly used in medical diagnosis). Bismuth oxide has a high photoelectric effect cross section, so it exhibits excellent shielding performance in the energy region of 80-150 keV. A single filler system cannot achieve continuous shielding in a wide spectrum, and traditionally physically mixed gadolinium oxide / bismuth oxide fillers are prone to gravity settling due to density differences, resulting in uneven distribution of fillers inside the coating and forming local weak shielding areas. Therefore, improving the dispersibility of gadolinium oxide / bismuth oxide fillers inside the coating is of great significance to improve the radiation attenuation performance of the composite coating. SUMMARY

[0004] The present application aims to provide an epoxy composite coating with radiation attenuation performance and a preparation method thereof. The epoxy composite coating with radiation attenuation performance of the present application has good heat resistance, adhesion strength and radiation attenuation performance. The present application can improve the mechanical properties and radiation attenuation performance of the epoxy composite coating by adding fillers with core-shell structure design to the epoxy resin system.

[0005] The epoxy composite coating with radiation attenuation performance of the application utilizes tetraethyl orthosilicate assisted ball milling to prepare a core-shell structure radiation-proof filler (the core-shell structure is specifically: taking silicon dioxide as a shell layer and a radiation-proof filler as a core layer), then improves the interface compatibility with the epoxy resin through KH550 amination modification, and the filler can be uniformly dispersed in the epoxy resin matrix with high load; the ray can be multiple reflected at the core-shell interface, which is conducive to the collision of photons and high atomic number elements and improves the radiation attenuation efficiency.

[0006] The preparation method is: ultrasonic dispersion of the radiation-proof filler, tetraethyl orthosilicate assisted ball milling for 6h to obtain the core-shell structure radiation-proof filler. Then, the obtained core-shell structure radiation-proof filler is subjected to amination modification with KH550 at 70℃ for 2h to prepare a modified radiation-proof filler. Finally, the modified radiation-proof filler is mixed with the epoxy resin, the curing agent and the additive to obtain the radiation attenuation composite coating.

[0007] Specifically,

[0008] 1) The radiation-proof filler is dispersed in a mixed solution of ethanol and water, ammonia water is added to adjust the pH, and the filler is uniformly dispersed in the solution under the action of ultrasonic waves for 20min. Then, stirring is carried out for 30min, and tetraethyl orthosilicate is added for ball milling for 6h. The product is washed with anhydrous ethanol by centrifugation for three times. Finally, the core-shell structure radiation-proof filler is obtained by drying at 60℃ for 12h.

[0009] 2) The core-shell structure radiation-proof filler prepared in step (1) is subjected to amination modification with gamma-aminopropyl triethoxysilane (KH550). Specifically, the filler is uniformly mixed with KH550 in an ethanol solvent, and the reaction is carried out at 70℃ for 2h with reflux condensation. Subsequently, the solution is filtered under vacuum to separate the solvent, and the obtained product is washed with deionized water for three times to remove the excess KH550. Finally, the white solid product is separated, and dried in a vacuum oven at 60℃ for 24h, which is the modified radiation-proof filler.

[0010] 3) The modified radiation-proof particles prepared in step (2) are added to the epoxy resin and ultrasonic dispersed uniformly, a small amount of diluent is added to dilute the viscosity, then the additive and the curing agent are added, and the epoxy composite coating is obtained after uniform stirring, which can be coated on the surface of the substrate to obtain the epoxy composite coating with radiation attenuation performance.

[0011] In the technical solution, further, the anti-radiation filler in step 1) is at least one of bismuth oxide and gadolinium oxide, the mass ratio of ethanol and water is 16:1, the ammonia water adjusts the PH to 10, the mass ratio of the anti-radiation filler and tetraethyl orthosilicate is 15:1-10; the ball milling speed is 400 revolutions per minute, and the ball-to-material ratio is 30:1. In step 2), the anti-radiation filler is at least one of bismuth oxide and gadolinium oxide, and the amount of KH550 is 0.5-2% of the mass of the filler. In step 3), the epoxy resin is at least one of E44 and E51; the diluent is at least one or more of acetone, toluene, ethyl acetate and n-butyl glycidyl ether, and the amount is 10-20% of the mass of the epoxy resin; the auxiliary agent is at least one or more of wetting dispersants, thickeners, anti-settling agents, leveling agents and defoaming agents, and the amount is 0-5% of the mass of the epoxy resin; the curing agent is at least one of type 650 and T31, and the amount is 20-30% of the mass of the epoxy resin; and the mass fraction of the modified anti-radiation filler is 10-50%.

[0012] The present application has the following advantages:

[0013] 1. The present application uses tetraethyl orthosilicate to assist in the preparation of core-shell structure anti-radiation fillers by ball milling. The X-rays will be reflected and scattered multiple times at the core-shell interface, thereby improving the radiation attenuation efficiency.

[0014] 2. The present application modifies the core-shell structure anti-radiation fillers by amination, which improves the interfacial compatibility of the fillers with the epoxy resin matrix and reduces the agglomeration of the fillers in the epoxy resin matrix. The modified anti-radiation fillers are more uniformly dispersed than the unmodified anti-radiation fillers under the same load, which increases the probability of interaction between the anti-radiation fillers and X-rays, thereby improving the radiation shielding efficiency of the coating.

[0015] 3. The present application mechanically mixes anti-radiation fillers, epoxy resin, curing agent and auxiliary agent to prepare an epoxy composite coating. The preparation process is simple. The load of anti-radiation fillers has a significant impact on the mechanical properties and radiation shielding efficiency of the coating. The present application modifies the fillers to improve the compatibility of the fillers with the epoxy resin matrix and the dispersibility of the fillers. The core-shell structure synergistically interacts with X-rays, thereby improving the mechanical properties and radiation shielding efficiency of the coating. At the same time, the composite coating has excellent thermal stability and adhesion strength. It can be used as a radiation attenuation coating for metal equipment surfaces. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The figure is the infrared spectra of the anti-radiation fillers bismuth oxide and gadolinium oxide before and after modification.

[0017] Figure 2 The figure is the transmission electron microscope energy spectrum results of the modified anti-radiation fillers bismuth oxide and gadolinium oxide.

[0018] Figure 3 Scanning electron micrographs of epoxy composite coatings containing the same amount of unmodified and modified radiation-blocking fillers. Figures a1 through a4 show the electron micrograph, energy spectrum overlay, and Gd / Bi elemental energy spectrum of the epoxy composite coating loaded with the unmodified radiation-blocking filler; and b1 through b4 show the electron micrograph, energy spectrum overlay, and Gd / Bi elemental energy spectrum of the epoxy composite coating loaded with the modified radiation-blocking filler.

[0019] Figure 4 The thermogravimetric curves of epoxy coatings without and with modified radiation shielding fillers are shown below. EP is pure epoxy resin, and EP-50 is an epoxy composite coating loaded with 50% modified radiation shielding fillers.

[0020] Figure 5 It is the schematic diagram, actual picture and shear strength results of single lap shear test of epoxy composite coating.

[0021] Figure 6 The epoxy composite coating with different modified radiation-proof filler loadings 129 I X-ray shielding efficiency and attenuation coefficient of radiation source. (a) is the radiation shielding efficiency, and (b) is the linear attenuation coefficient.

[0022] Figure 7 The epoxy composite coating with different modified radiation-proof filler loadings 137 Gamma-ray shielding efficiency and attenuation coefficient of a Cs radiation source. (a) is the radiation shielding efficiency, and (b) is the linear attenuation coefficient. DETAILED DESCRIPTION

[0023] The present invention is further described below with reference to the accompanying drawings and specific examples.

[0024] The epoxy composite coating with radiation attenuation performance described in the present invention is prepared by ball milling with the assistance of ethyl orthosilicate to prepare a core-shell structure radiation-proof filler; then the core-shell structure filler is further amino-modified to improve its interface compatibility with the matrix; finally, it is mixed with epoxy resin and curing agent to obtain a composite coating with radiation attenuation performance. The radiation attenuation ability is improved by utilizing the interface multiple scattering of the core-shell structure, and the dispersibility of the radiation-proof filler in the epoxy resin is improved by the chemical bond between the amino group and the epoxy group of the modified filler. The above multiple effects give the composite coating excellent thermal stability, adhesion strength and radiation attenuation performance. The infrared spectra before and after the preparation of the modified radiation-proof filler are as follows: Figure 1 As shown in the figure, the radiation protection fillers are gadolinium oxide (Gd2O3) and bismuth oxide (Bi2O3), and the corresponding metal characteristic peaks exist in infrared. The modified gadolinium oxide (M-Gd2O3) and bismuth oxide (M-Bi2O3) have the peaks at 1100cm -1 The new characteristic peak at 3200-3600 cm-1 The O-H stretching vibration peak intensity is obviously enhanced and moves to high wave number, which is mainly due to the increase of active sites after the treatment of tetraethyl orthosilicate and the successful grafting of surface amino groups. Infrared spectrum analysis shows that both silica and amino groups are successfully modified on the surface of the filler. Figure 2 The energy dispersive X-ray spectrograms of (a) modified gadolinium oxide (M-Gd2O3) and (b) modified bismuth oxide (M-Bi2O3) show that the silica coating and the steric effect of KH550 on the surface of the anti-radiation filler improve the dispersibility of the particles, so that monodisperse nanoparticles can be observed in the transmission electron microscope, wherein the light-colored coating layer is silica. In addition, the overlap of Si signal and Gd / Bi signal can be observed in the energy spectrum, which shows that the Si introduced by the hydrolysis of tetraethyl orthosilicate is enriched on the surface of the particles, confirming the silica coating. The scanning electron microscope results are shown in Figure 3 The results show that a1-a4 are epoxy composite coatings loaded with unmodified anti-radiation fillers, and under the condition of loading the same fillers, the unmodified fillers are not uniformly dispersed, and obvious agglomeration occurs. In comparison, the uniformity of the fillers in the epoxy composite coatings loaded with modified anti-radiation fillers in b1-b4 is obviously improved, and basically no agglomeration occurs. The thermal stability is shown in Figure 4 The results show that EP is pure epoxy resin, EP-50 is an epoxy composite coating loaded with 50% mass fraction, and the filling of the modified anti-radiation filler significantly improves the thermal stability of the composite material. Figure 5 The adhesive strength of the epoxy composite coatings with different loadings of modified anti-radiation fillers on aluminum 6061 alloy was tested by lap shear test, (a) is a schematic diagram of the preparation of the lap shear sample, (b) is the test of the adhesive strength by a universal mechanical testing machine, and (c) is the adhesive strength of the epoxy composite coating. The uniform dispersion of the modified filler enhances the rigidity of the coating and reduces the interfacial stress concentration. Below 50% loading, the shear strength of the coating is significantly improved with the increase of the content of the modified anti-radiation filler. The X-ray attenuation performance test is shown in Figure 6 The results show that with the increase of the loading, the attenuation ability of the coating gradually increases. The mass attenuation coefficient of the unmodified group is lower than the theoretical value due to the existence of agglomeration and defects, while the mass attenuation coefficient of the composite coating is slightly higher than the theoretical value, which is due to the design of the core-shell structure. The γ-ray attenuation performance test is shown in Figure 7 The results show that the radiation shielding efficiency of the epoxy composite coating loaded with 50% modified anti-radiation filler exceeds that of a 0.25mm thick lead sheet.

[0025] Example 1:

[0026] 1) 10 g of the anti-radiation filler was dispersed in a mixed solution of 160 mL of ethanol and 10 mL of water, and ammonia was added to adjust the pH to 10. The filler was uniformly dispersed in the solution under the action of ultrasonic waves for 20 min. Then, stirring was performed for 30 min, and 0.67 mL of tetraethyl orthosilicate was added to assist ball milling for 6 h. After ball milling, the product was washed three times by centrifugation with anhydrous ethanol. Finally, the modified anti-radiation filler was obtained by drying at 60°C.

[0027] 2) The core-shell structure anti-radiation filler prepared in step 1) was modified by aminopropyltriethoxysilane (KH550). In a 250 mL three-necked flask equipped with a magnetic stirrer, a thermometer, a reflux condenser and 150 ml of alcohol, the filler was mixed with KH550. The reaction was kept at 70°C for 2 h with reflux condensation. Subsequently, the solution was filtered under vacuum to separate the solvent, and the product was obtained. The product was washed with deionized water three times to remove excess KH550. Finally, the white solid product was separated and dried in a vacuum oven at 60°C, and the modified anti-radiation filler was obtained.

[0028] 3) 3 g of the modified anti-radiation filler was dispersed in 6.48 g of ethyl acetate by ultrasonic dispersion, 21.6 g of epoxy resin was added, and a dispersion was formed by mechanical stirring, which was kept stable at room temperature. Subsequently, a small amount of auxiliary agent and 5.4 g of curing agent were added to the dispersion in turn, and vacuum degassing was performed after stirring at room temperature for 30 min. The coating after degassing was coated on the surface of aluminum alloy 6061 and cured at room temperature for 24 h, and then post-curing treatment was performed at 60°C, 120°C and 160°C for 1 h to improve the curing degree, and finally an epoxy composite coating EP-10 was obtained.

[0029] The X-ray shielding efficiency of the EP-10 composite coating prepared in this example was 34.6%, and the γ-ray shielding efficiency was 1.70%. It also had excellent thermal stability and adhesion strength.

[0030] Example 2:

[0031] 1) 10 g of the anti-radiation filler was dispersed in a mixed solution of 160 mL of ethanol and 10 mL of water, and ammonia was added to adjust the pH to 10. The filler was uniformly dispersed in the solution under the action of ultrasonic waves for 20 min. Then, stirring was performed for 30 min, and 0.67 mL of tetraethyl orthosilicate was added to assist ball milling for 6 h. After ball milling, the product was washed three times by centrifugation with anhydrous ethanol. Finally, the modified anti-radiation filler was obtained by drying at 60°C.

[0032] 2) Ammonia modification of the core-shell structure radiation shielding filler prepared in step 1) with γ-aminopropyl triethoxysilane (KH550). In a 250 mL three-necked flask equipped with a magnetic stirrer, thermometer, reflux condenser and 150 ml of alcohol, the filler was mixed with KH550. The reaction was kept at 70 °C for 2 h with reflux condensation. Then the solution was vacuum filtered to separate the solvent, and the product was obtained. The product was washed with deionized water for 3 times to remove the excess KH550. Finally, the solid product was separated and dried in a vacuum oven at 60 °C, and the modified radiation shielding filler was obtained.

[0033] 3) 6 g of the modified radiation shielding filler was dispersed in ethyl acetate by ultrasonic dispersion, 4.8 g of epoxy resin was added and mechanically stirred to form a dispersion, which was kept stable at room temperature. Then a small amount of auxiliary agent and 1.2 g of curing agent were added to the dispersion in turn, and vacuum degassing was performed after stirring at room temperature for 30 min. The degassed coating was coated on the surface of aluminum alloy 6061 and cured at room temperature for 24 h, and then post-cured at 60 °C, 120 °C and 160 °C for 1 h to improve the curing degree, and finally an epoxy composite coating EP-30 was obtained.

[0034] The X-ray shielding efficiency of the EP-30 composite coating prepared in this example was 73.3%, and the γ-ray shielding efficiency was 2.12%. It also had excellent thermal stability and adhesion strength.

[0035] Example 3:

[0036] 1) 10 g of the radiation shielding filler was dispersed in a mixture of 160 mL of ethanol and 10 mL of water, and the pH was adjusted to 10 by adding ammonia water. The filler was uniformly dispersed in the solution under the action of ultrasonic waves for 30 min. Then it was stirred for 60 min, and 0.67 mL of tetraethyl orthosilicate was added for ball milling for 6 h. The product was washed with anhydrous ethanol by centrifugation for three times after ball milling. Finally, the modified radiation shielding filler was obtained by drying at 60 °C.

[0037] 2) Ammonia modification of the core-shell structure radiation shielding filler prepared in step 1) with γ-aminopropyl triethoxysilane (KH550). In a 250 mL three-necked flask equipped with a magnetic stirrer, thermometer, reflux condenser and 150 ml of alcohol, the filler was mixed with KH550. The reaction was kept at 70 °C for 2 h with reflux condensation. Then the solution was vacuum filtered to separate the solvent, and the product was obtained. The product was washed with deionized water for 3 times to remove the excess KH550. Finally, the solid product was separated and dried in a vacuum oven at 60 °C, and the modified radiation shielding filler was obtained.

[0038] 3) 6 g of modified radiation shielding filler was dispersed in 1.44 g of ethyl acetate by ultrasonic dispersion, 4.8 g of epoxy resin was added and mechanically stirred to form a dispersion, which was stable at room temperature. Then a small amount of auxiliary agent and 1.2 g of curing agent were added to the dispersion in turn, and vacuum degassing was performed after stirring at room temperature for 30 minutes. The degassed coating was applied to the surface of aluminum alloy 6061 and cured at room temperature for 24 h, followed by post-curing treatment at 60°C, 120°C and 160°C for 1 h to improve the curing degree, and finally an epoxy composite coating EP-50 was obtained.

[0039] The X-ray shielding efficiency of the EP-50 composite coating prepared in this example was 93.8%, and the γ-ray shielding efficiency was 2.82%. It also had excellent thermal stability and adhesion strength.

Claims

1. A method for preparing an epoxy composite coating with radiation attenuation performance, characterized in that: The composite coating utilizes chemical bonds between amino groups and epoxy groups on the surface of a modified radiation-proof filler to enhance interfacial compatibility; the modified radiation-proof filler has a core-shell structure, and radiation undergoes multiple reflections at the core-shell interface of the modified radiation-proof filler, thereby improving radiation attenuation performance; the preparation method of the epoxy composite coating comprises the following steps: (1) Preparation of core-shell structure radiation-proof fillers: The radiation-proof filler is dispersed in a mixed solution of ethanol and water, ammonia water is added to adjust the pH to 10, and the radiation-proof filler is uniformly dispersed in the solution under ultrasonic action for 20 to 30 minutes; then, the mixture is stirred for 30 to 60 minutes, and then ethyl orthosilicate is added and ball-milled for 6 hours; the ball-milled product is centrifuged and washed three times with anhydrous ethanol; and finally, it is dried at 60°C to obtain a core-shell structure radiation-proof filler. (2) Preparation of modified radiation-proof filler: The core-shell structure radiation-proof filler prepared in step (1) is subjected to amino modification using γ-aminopropyltriethoxysilane (KH550); specifically, the core-shell structure radiation-proof filler and KH550 are uniformly mixed in an ethanol solvent, reacted at 70° C. for 2 h accompanied by reflux condensation; the solution is then vacuum filtered to separate the solvent, and the obtained product is washed several times with deionized water to remove excess KH550; finally, a white solid product is separated and vacuum dried at 60° C. to obtain the modified radiation-proof filler; (3) Preparation of epoxy composite coating: The modified radiation-proof filler prepared in step (2) is added to the epoxy resin and ultrasonically dispersed evenly, a diluent is added to dilute the viscosity, and then an auxiliary agent and a curing agent are added. After stirring evenly, an epoxy composite coating is obtained. The epoxy composite coating is applied to the surface of the substrate to obtain the epoxy composite coating with radiation attenuation performance.

2. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The radiation-proof filler in step (1) is at least one of bismuth oxide and gadolinium oxide.

3. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The mass ratio of the radiation-proof filler to ethyl orthosilicate in step (1) is 15:1-10.

4. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The dosage of KH550 is 0.5-2% of the mass of the core-shell structure radiation-proof filler.

5. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The epoxy resin in step (3) is at least one of E44 and E51.

6. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The diluent in step (3) is at least one or more of acetone, toluene, ethyl acetate, and n-butyl glycidyl ether, and the amount used is 10-20% of the mass of the epoxy resin.

7. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The auxiliary agent in step (3) is at least one or more of a wetting and dispersing agent, a thickener, an anti-settling agent, a leveling agent, a defoaming agent, etc., and the amount used is 0 to 5% of the mass of the epoxy resin.

8. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The curing agent in step (3) is at least one of 650 type and T31 type, and the amount used is 20-30% of the epoxy resin.

9. The method for preparing an epoxy composite coating with radiation attenuation performance according to claim 1, characterized in that: The mass fraction of the modified radiation-proof filler is 10-50%.

10. A water-based composite coating with radiation attenuation properties, characterized in that: The method is prepared by any one of claims 1 to 9.

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