A method of observing the course of an electron beam curing reaction

Abstract

The present application relates to a kind of methods for observing electron beam curing reaction process, by saturated vapor pressure detection to the sample to be observed, determine whether the sample to be observed needs to be coated, then according to specific circumstances are observed.The method uses in-situ observation technology, uses in-situ transmission electron microscope to accurately control irradiation voltage and irradiation time, record the morphology of resin during irradiation, realize complete observation the whole electron beam curing reaction process, make up the deficiency of existing method in observation resolution.It can realize the observation of the curing reaction that occurs in 1-2s, thus obtain the reaction mechanism of different oligomer, monomer, toner in polymerization process, provide reference for better optimization formula.

Description

Technical Field

[0001] This invention relates to the field of electron beam curing, and more specifically to a method for observing the electron beam curing reaction process. Background Technology

[0002] With the development of the coatings industry, the market demand for coatings with low VOC, low energy consumption, and high-efficiency curing is increasing. Electron beam curing technology is receiving widespread attention. Electron beam curing technology uses a high-energy electron beam with a power of 80keV-300keV to irradiate liquid polymer monomers / mixtures, initiating a polymerization reaction and converting the liquid polymer into a solid. It features good curing effect, fast curing speed, no harmful gas emissions, and low energy consumption, making it a very important development direction for green coatings.

[0003] In actual curing reactions, the polymerization of polymer monomers and oligomers typically occurs at the micrometer or nanometer scale, with reaction rates measured in seconds. Currently, existing publicly available technologies can only observe the state of raw materials before curing and the state of the cured film. They cannot observe molecular-level reactions or the entire curing process. There is a lack of effective technical means to perform kinetic analysis of the morphology, structure, and reaction of electron beam-induced polymer polymerization reactions. Methods for testing electron beam curing reactions cannot simultaneously observe and detect morphology and reaction progress, limiting further research into the reaction mechanism and curing mechanism of electron beam curing.

[0004] Currently, the resolution of transmission electron microscopes can reach... While sufficient for molecular-level observation, the use of graphene and carbon film-coated liquid electron microscopes provides the hardware conditions for observing the process of polymer transition from liquid to solid phase, a method for observing electron beam curing reaction processes is still lacking.

[0005] In view of this, there is an urgent need in the field to develop a method for observing the electron beam curing reaction process in order to solve the problems existing in the prior art. Summary of the Invention

[0006] Based on the above facts, the purpose of this invention is to provide a method for observing the electron beam curing reaction process. It employs in-situ observation technology, utilizing an in-situ transmission electron microscope to precisely control the irradiation voltage and time, recording the morphology of the resin during irradiation, and achieving complete observation of the entire electron beam curing reaction process, thus overcoming the shortcomings of existing methods in terms of observation resolution. It can observe curing reactions occurring within 1-2 seconds, thereby obtaining the reaction mechanisms of different oligomers, monomers, and pigments during the polymerization process, providing a reference for better formulation optimization.

[0007] The method for observing the electron beam curing reaction process described in this invention includes the following steps:

[0008] S1: Saturated vapor pressure detection of the sample to be observed:

[0009] S1.1: Take a certain mass of the sample to be observed and place it in a vacuum evaporator. After weighing, the initial mass G of the sample to be observed is obtained.

[0010] S1.2: Adjust the gas pressure of the vacuum evaporator to less than 10. -3 Observe for 20-60 minutes to determine if there is visible evaporation.

[0011] S1.3: If there is visible evaporation, it is necessary to coat the sample as described in step S2 and then observe it as described in step S3; if there is no visible evaporation, weigh the sample again to obtain the mass G' of the sample to be observed. If (G-G') / G>0.01, it is necessary to coat the sample as described in step S2 and then observe it as described in step S3; if (G-G') / G≤0.01, observe it directly as described in step S3.

[0012] S2: Coating of the sample to be observed:

[0013] S2.1: Place the copper mesh for sample preparation of the transmission electron microscope, which is covered with a continuous carbon film, on dry filter paper, take a sample with a pipette, and drop the sample onto the copper mesh so that the sample forms a hemispherical droplet on the copper mesh;

[0014] S2.2: Load another transmission electron microscope sample preparation mesh coated with a continuous carbon film onto the copper mesh carrying the sample, and then air dry it to obtain the coated sample to be observed.

[0015] S3: Observation:

[0016] Select droplets of appropriate thickness and observe them using in-situ transmission electron microscopy. The accelerating voltage is set to 80kV-300kV, and the total irradiation time of the curing reaction is greater than 2 minutes. When the accelerating voltage is set to 80kV, the maximum irradiation dose of the sample is 60kGy, and when the accelerating voltage is set to 300kV, the maximum irradiation dose of the sample is 100kGy.

[0017] In this invention, the in-situ transmission electron microscope uses a high-energy electron beam (80keV–300keV) as a light source to bombard an ultrathin sample. It is a microscope technique that uses a magnetic coil as a lens and a fluorescent screen, film, or photosensitive element as an imaging element. While retaining the high resolution characteristics of transmission electron microscopy, it can apply force, electricity, heat, magnetism, etc. to the sample and perform atomic-level resolution observations during the reaction process.

[0018] In some embodiments of the present invention, in step S2.1, the amount of sample taken with a pipette is preferably 3-5 μL.

[0019] In some embodiments of the present invention, the ventilation and drying time in step S2.2 is preferably 60-90 min.

[0020] In some embodiments of the present invention, the droplet thickness in step S3 is less than 500 nm, preferably 150 nm–300 nm.

[0021] In some embodiments of the present invention, the droplet thickness is determined by the following measurement steps:

[0022] T1: Measure the electron beam flux I0 of the droplet at low magnification;

[0023] T2: Keeping the transmission electron microscope settings unchanged, take a picture of the sample to be tested and obtain the electron beam flux I at the location of the sample. t ;

[0024] T3: According to the formula Calculate the droplet thickness t, where Λ is the mean free path of the electron elasticity of the sample under test.

[0025] In some embodiments of the present invention, the electron elastic mean free path of the sample under test is calculated from the elastic electron scattering cross section.

[0026] In some embodiments of the present invention, the electron beam flux I0, I t All less than Beneficial effects of the present invention

[0027] This invention addresses the shortcomings of existing technologies by providing a method for observing the electron beam curing reaction process. It employs in-situ observation technology, utilizing in-situ transmission electron microscopy to precisely control the irradiation voltage and time, recording the resin morphology during irradiation, and achieving complete observation of the entire electron beam curing reaction process, thus overcoming the limitations of existing methods in terms of observation resolution. It can observe curing reactions occurring within 1-2 seconds, thereby obtaining the reaction mechanisms of different oligomers, monomers, and pigments during the polymerization process, providing a reference for better formulation optimization. Attached Figure Description

[0028] Figure 1 These are in-situ transmission electron microscope images taken at times of 0.5s, 1s, 1.5s, and 2s during the electron beam curing reaction of acrylic monomers in Example 1.

[0029] Figure 2 This is an in-situ transmission electron microscope image taken within 2 seconds during the electron beam curing reaction of acrylic oligomers in Example 2.

[0030] Figure 3The images are in-situ transmission electron microscope images taken at times of 1s, 5s, 14.5s, and 22.4s during the electron beam curing reaction of acrylic monomers in Example 3. Detailed Implementation

[0031] To more clearly illustrate the present invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1: Observation of the electron beam curing reaction process of acrylic monomers

[0033] S1: Saturated vapor pressure detection of the sample to be observed:

[0034] S1.1: Take 5ml of acrylic monomer sample and place it in a vacuum evaporator. Weigh the sample to obtain the initial mass G of the sample to be observed.

[0035] S1.2: Adjust the gas pressure of the vacuum evaporator to less than 10. -3 After 5 minutes, the sample completely evaporated and disappeared. This proves that the sample needs to be coated for observation.

[0036] S2: Coating of the sample to be observed:

[0037] S2.1: Place the copper mesh for sample preparation of the transmission electron microscope coated with a continuous carbon film on dry filter paper, take 3-5 μL of sample with a pipette, and drop the sample onto the copper mesh so that the sample forms a hemispherical droplet on the copper mesh;

[0038] S2.2: Load another transmission electron microscope sample preparation mesh coated with a continuous carbon film onto the copper mesh carrying the sample, and then air dry for 60-90 minutes to obtain the coated sample to be observed.

[0039] S3: Observation:

[0040] Droplets with a thickness of 100 nm to 400 nm were selected and observed using an in-situ transmission electron microscope. The accelerating voltage was set to 300 kV, the imaging capture interval was 0.25 s, and the observation time was 2 s. The observation results are as follows: Figure 1 As shown, the solidification reaction from liquid to solid can be clearly seen.

[0041] Example 2: Observation of the electron beam curing reaction process of acrylic oligomers

[0042] S1: Saturated vapor pressure detection of the sample to be observed:

[0043] S1.1: Take 5 ml of acrylic oligomer sample and place it in a vacuum evaporator. Weigh the sample to obtain the initial mass G of the sample to be observed.

[0044] S1.2: Adjust the gas pressure of the vacuum evaporator to less than 10. -3 After about 15 minutes, the sample can be observed to have completely evaporated.

[0045] This proves that the sample needs to be covered for observation;

[0046] S2: Coating of the sample to be observed:

[0047] S2.1: Place the copper mesh for sample preparation of the transmission electron microscope coated with a continuous carbon film on dry filter paper, take 3-5 μL of sample with a pipette, and drop the sample onto the copper mesh so that the sample forms a hemispherical droplet on the copper mesh;

[0048] S2.2: Load another transmission electron microscope sample preparation mesh coated with a continuous carbon film onto the copper mesh carrying the sample, and then air dry for 60-90 minutes to obtain the coated sample to be observed.

[0049] S3: Observation:

[0050] Droplets with a thickness of 100 nm to 400 nm were selected and observed using an in-situ transmission electron microscope. The accelerating voltage was set to 80 kV, the imaging capture interval was 0.25 s, and the observation time was 2 s. The observation results are as follows: Figure 2 As shown, the solidification reaction can be clearly seen to form particles.

[0051] Example 3: Observation of the electron beam curing reaction process of acrylic monomers

[0052] S1: Saturated vapor pressure detection of the sample to be observed:

[0053] S1.1: Take 5ml of acrylic monomer sample and place it in a vacuum evaporator. Weigh the sample to obtain the initial mass G of the sample to be observed.

[0054] S1.2: Adjust the gas pressure of the vacuum evaporator to less than 10. -3 After 5 minutes, the monomer had completely evaporated, indicating that the sample needed to be coated for observation.

[0055] S2: Coating of the sample to be observed:

[0056] S2.1: Place the copper mesh for sample preparation of the transmission electron microscope coated with a continuous carbon film on dry filter paper, take 3-5 μL of sample with a pipette, and drop the sample onto the copper mesh so that the sample forms a hemispherical droplet on the copper mesh;

[0057] S2.2: Load another transmission electron microscope sample preparation mesh coated with a continuous carbon film onto the copper mesh carrying the sample, and then air dry for 60-90 minutes to obtain the coated sample to be observed.

[0058] S3: Observation:

[0059] Droplets with a thickness of 100 nm to 400 nm were selected and observed using an in-situ transmission electron microscope. The accelerating voltage was set to 300 kV, the imaging capture interval was 0.1 s, and the observation time was 30 s. The observation results are as follows: Figure 3 As shown, P represents the image number, and P10, P50, P145, and P224 are the first frames in which a significant phenomenon was first observed in the white-framed area. The image below is a magnified view of the white-framed area in the image above. The growth and shearing processes of the polymer chains during the curing process are clearly visible.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for observing the electron beam curing reaction process, comprising the following steps: S1: Saturated vapor pressure detection of the sample to be observed: S1.1: Take a certain mass of the sample to be observed and place it in a vacuum evaporator. After weighing, the initial mass G of the sample to be observed is obtained. S1.2: Adjust the gas pressure of the vacuum evaporator to less than 10. -3 Observe for 20-60 minutes to determine if there is visible evaporation. S1.3: If there is visible evaporation, it is necessary to coat the sample as described in step S2 and then observe it as described in step S3; if there is no visible evaporation, weigh the sample again to obtain the mass G' of the sample to be observed. If (G-G') / G>0.01, it is necessary to coat the sample as described in step S2 and then observe it as described in step S3; if (G-G') / G≤0.01, observe it directly as described in step S3. S2: Coating of the sample to be observed: S2.1: Place the copper mesh for sample preparation of the transmission electron microscope, which is covered with a continuous carbon film, on dry filter paper, take a sample with a pipette, and drop the sample onto the copper mesh so that the sample forms a hemispherical droplet on the copper mesh; S2.2: Load another transmission electron microscope sample preparation mesh coated with a continuous carbon film onto the copper mesh carrying the sample, and then air dry it to obtain the coated sample to be observed. S3: Observation: Droplets of suitable thickness were selected and observed using an in-situ transmission electron microscope. The accelerating voltage was set to 80kV-300kV, and the total irradiation time of the curing reaction was greater than 2 minutes. When the accelerating voltage is set to 80 kV, the maximum irradiance of the sample is 60 kGy; when the accelerating voltage is set to 300 kV, the maximum irradiance of the sample is 100 kGy.

2. The method for observing the electron beam curing reaction process according to claim 1, characterized in that, In step S2.1, the sample volume taken with a pipette is preferably 3-5 μL.

3. The method for observing the electron beam curing reaction process according to claim 1, characterized in that, The preferred ventilation and drying time in step S2.2 is 60-90 minutes.

4. The method for observing the electron beam curing reaction process according to any one of claims 1-3, characterized in that, The droplet thickness in step S3 is less than 1 μm, preferably 150 nm–300 nm.

5. The method for observing the electron beam curing reaction process according to claim 4, characterized in that, The droplet thickness was determined by the following measurement steps: T1: Measure the electron beam flux I0 of the droplet at low magnification; T2: Keeping the transmission electron microscope settings unchanged, take a picture of the sample to be tested and obtain the electron beam flux I at the location of the sample. t ; T3: According to the formula Calculate the droplet thickness t, where Λ is the mean free path of the electron elasticity of the sample under test.

6. The method for observing the electron beam curing reaction process according to claim 5, characterized in that, The electron elastic mean free path of the sample under test is calculated from the elastic electron scattering cross section.

7. The method for observing the electron beam curing reaction process according to claim 5, characterized in that, The electron beam flux I0, I t All less than

Images