A method and apparatus for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect

Abstract

This invention belongs to the field of degradation technology, specifically a method and apparatus for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. The specific steps of the method are as follows: S1, Granulation pretreatment: The thermosetting epoxy resin is crushed into thermosetting epoxy resin particles using a crushing mechanism; S2, The thermosetting epoxy resin particles are placed in a sealed container and heated. The rotating container causes the thermosetting epoxy resin particles to tumble. Heating is stopped when the pressure inside the container is ≥3.0 MPa. After depressurization, the expanded and popped thermosetting epoxy resin particles are poured out. This invention greatly reduces the difficulty of degrading thermosetting epoxy resin materials while improving the chemical degradation efficiency of epoxy resin materials, exhibiting excellent universality and practicality.

Description

Technical Field

[0001] This invention belongs to the field of degradation technology, and particularly relates to a method and apparatus for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. Background Technology

[0002] Epoxy resin is a high-performance thermosetting material with excellent thermal stability, superior mechanical properties, and electrical insulation properties, and has been widely used in numerous fields related to the national economy, such as power transmission, civil engineering, and aerospace. However, the highly stable three-dimensional network structure of cross-linked epoxy resin materials hinders their degradation and recycling. The environmental pollution and resource waste caused by the decommissioning or disposal of these materials pose a significant challenge to their development and application. Therefore, developing accelerated degradation methods for thermosetting epoxy resin materials is key to overcoming this challenge.

[0003] Currently, research on the degradation of epoxy resin materials mainly focuses on the design level of network structure, such as introducing functional groups that respond to external stimuli into the epoxy crosslinking network to design photosensitive or thermosensitive epoxy resins (e.g., Chem. Mater. 2022, 34, 10, 4732-4740), and using functional group response strategies to achieve the degradation of thermosetting epoxy resin materials. However, this type of epoxy resin material requires specific functional groups for degradation, and the degradation efficiency is relatively low, with relatively harsh degradation conditions. Meanwhile, some scholars have studied the biodegradation characteristics of epoxy resin materials, mainly through microorganisms to break the chemical bonds within the epoxy crosslinking network (e.g., ACS Macro Letters, 2023, 12, 54-58), thereby deconstructing the epoxy crosslinking network. However, this microbial degradation method targets epoxy resins containing biomolecules, representing a specific selective degradation by microorganisms, thus requiring even harsher conditions and making it difficult to become a universal method for degrading thermosetting epoxy resin materials.

[0004] Therefore, there is an urgent need for a method and apparatus for accelerating the degradation of thermosetting epoxy resins based on the popcorn effect. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a method and apparatus for accelerating the degradation of thermosetting epoxy resins based on the popcorn effect. This invention significantly reduces the difficulty of degrading thermosetting epoxy resin materials while improving the chemical degradation efficiency of epoxy resin materials, exhibiting excellent universality and practicality.

[0006] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0007] A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect, the specific steps of which are as follows:

[0008] S1. Granulation pretreatment: Use a crushing mechanism (such as a wall-breaking pulverizer) to crush the thermosetting epoxy resin into thermosetting epoxy resin particles.

[0009] S2. Place the thermosetting epoxy resin granules in a sealed container and heat them. The rotating container causes the thermosetting epoxy resin granules to flip. When the pressure inside the container is ≥3.0MPa, stop heating. After the pressure is released, pour out the expanded and bursting thermosetting epoxy resin granules.

[0010] Preferably, in step S1, the thermosetting epoxy resin is crushed in a wall-breaking pulverizer with a rotation speed of 30,000 r / min. After crushing, the thermosetting epoxy resin particles are screened step by step using a sieve with a pore size of 0.1-15 mm to select thermosetting epoxy resin particles with a particle size of 1-5 mm.

[0011] Preferably, the filling volume of thermosetting epoxy resin particles in the container is 30-60% of the container cavity volume.

[0012] Preferably, in step S2, the heating temperature of the container is 100-300℃, and the internal pressure limit of the container is 10 MPa. When the internal pressure of the container reaches the maximum limit under continuous high-temperature heating, the pressure relief valve on the container will automatically release pressure, thereby ensuring the safety of the experimental process.

[0013] Preferably, the thermosetting epoxy resin is any one or more of glycidyl ethers (including glycidyl ethers, glycidyl esters, and glycidyl amines), aliphatic epoxy resins, and alicyclic epoxy resins.

[0014] Preferably, the rotation speed of the container is 30-300 r / min.

[0015] Preferably, the container is tested for airtightness using a soapy water leak test before use. The specific test method is as follows: apply soapy water evenly to the outer surface of the container, turn on the heater to continuously heat the container at a high temperature to generate pressure inside the container, and observe whether bubbles appear in the soapy water on the outer surface of the container when the internal pressure reaches 0.5 MPa.

[0016] To achieve the second objective mentioned above, the present invention provides a device for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect. The device includes a rotatable container and a heater for heating the container. The container is placed horizontally and is also equipped with a pressure relief valve and a pressure gauge.

[0017] Preferably, the container is a weld-free container with a volume of 100-500 ml.

[0018] Preferably, the apparatus further includes a cell-wall breaking pulverizer for crushing thermosetting epoxy resin into particles and a screening element for screening thermosetting epoxy resin particles, the screening element being a screen.

[0019] The advantages of this invention are:

[0020] (1) This invention only involves expanding and bursting the thermosetting epoxy resin material to form a porous structure, which facilitates the penetration of organic solvents into the epoxy crosslinking network during subsequent degradation. This promotes the exchange reaction between the polar groups in the epoxy crosslinking network and the organic solvent, thereby accelerating the swelling rate and the decomposition rate of the crosslinking network in the chemical degradation agent. This improves the problems of low degradation efficiency and harsh degradation conditions of thermosetting epoxy resin materials in existing methods. At the same time, because this method is simple and easy to operate, and the effects of multiple treatments are highly reproducible, it will help control the batch stability of thermosetting epoxy resin materials during mass degradation. In addition, the expansion and bursting treatment does not need to change the original crosslinking network structure of the epoxy material, and avoids the introduction of new harmful substances into the network and the generation of additional waste after degradation. Therefore, this method also conforms to the environmentally friendly material degradation design principle and meets the development requirements of new green polymer materials.

[0021] (2) In this invention, under the continuous application of heat energy by the heater, the temperature inside the container cavity gradually rises, which intensifies the movement of gas molecules inside, causing the gas pressure inside the cavity to continuously increase. At the same time, due to the difference between the heat dissipation conditions outside and inside the cavity, an imbalance in internal and external pressures occurs, forming a significant pressure difference. When this pressure difference acts on the granulated thermosetting epoxy resin material, the epoxy resin particles begin to undergo a series of physical changes, as follows:

[0022] As the temperature continues to rise, the moisture and volatile substances inside the epoxy resin particles begin to evaporate rapidly, forming a large amount of gas, which further intensifies the internal pressure of the particles. When this internal pressure reaches a certain level, the outer shell of the epoxy resin particles can no longer withstand the internal pressure and begins to develop tiny cracks. These cracks gradually enlarge into pores as the internal pressure continues to increase, eventually making the epoxy resin particles into a porous structure.

[0023] The instant the outer shell of the epoxy resin particles ruptures, the high-pressure gas and evaporated substances accumulated inside are rapidly released, producing a strong expansion and bursting phenomenon. This phenomenon not only significantly increases the volume of the epoxy resin particles but is also accompanied by a loud noise and energy release. Through this process, the epoxy resin material achieves a rapid transformation from a solid to a gaseous state, resulting in expansion and bursting.

[0024] (3) The method of this invention can effectively promote the chemical degradation of various commercially available thermosetting epoxy resin materials. After treatment by this method, the penetration of organic degradation solvents into the epoxy resin material is significantly enhanced, and different organic degradation solvents can also directionally break the chemical bonds within the epoxy crosslinking network. Therefore, this method for accelerating the degradation of epoxy resin materials has high versatility. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the device structure of the present invention.

[0026] Figure 2 This is a surface microstructure diagram of Embodiment 1 of the present invention.

[0027] Figure 3 This is a surface microstructure diagram of Comparative Example 1 of the present invention.

[0028] The meanings of the symbols marked in the figure are as follows:

[0029] 1-Container, 2-Heater, 3-Pressure relief valve, 4-Pressure gauge. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect includes the following steps:

[0032] Step 1: Air tightness test of the integrated puffing and bursting device;

[0033] The soap water leak test method is used. After uniformly applying soap water to the outer surface of container 1, the container 1 is continuously heated at high temperature by heater 2 to generate a certain pressure in the cavity of container 1. When the internal pressure reaches 0.5MPa, the airtightness of epoxy resin container 1 is tested by observing whether soap water bubbles appear on the surface of container 1.

[0034] Step 2: Granulation pretreatment of thermosetting epoxy resin:

[0035] Thermosetting epoxy resin was broken into pieces the size of corn kernels using a wall-breaking pulverizer at a speed of 30,000 r / min. The particles were then screened through a sieve with a pore size of 0.1-15 mm to select thermosetting epoxy resin particles with a particle size range of 1-5 mm.

[0036] Step 3: Expansion and bursting test of thermosetting epoxy resin:

[0037] The thermosetting epoxy resin granules are poured into the cavity of container 1. Heater 2 is turned on to continuously heat container 1 at a temperature of 100℃-300℃, while container 1 is rotated at a speed of 30-300 r / min to ensure uniform heating of the outside of container 1. After heating container 1 for a certain period, the reading on pressure gauge 4 is observed. When the reading on pressure gauge 4 reaches 3.0 MPa or higher, heating is stopped and the pressure is released. The expanded and bursting thermosetting epoxy resin granules are then poured out.

[0038] The thermosetting epoxy resin particles fill 30-60% of the volume of container 1. The thermosetting epoxy resin is any one or more combinations of glycidyl ether, glycidyl ester, glycidyl amine, aliphatic and alicyclic epoxy resins.

[0039] like Figure 1 As shown, an accelerated degradation device for thermosetting epoxy resin based on the popcorn effect is disclosed. This device integrates expansion and bursting. The container 1 in the integrated expansion and bursting device of epoxy resin material used in this invention has a cavity volume of 100-500 ml and an internal pressure limit of 10 MPa. When the internal pressure of container 1 reaches the maximum limit under continuous high-temperature heating, the pressure relief valve 3 of the device will automatically release pressure, thereby ensuring the safety of the experimental process.

[0040] The device includes a weldless container 1, a heater 2, a wall-breaking pulverizer, and a screen. The wall-breaking pulverizer breaks down thermosetting epoxy resin into particles, and the screen filters out thermosetting epoxy resin particles of 1-5mm in size. Larger particles continue to be crushed. The weldless container 1 is used to load the crushed thermosetting epoxy resin, and the heater 2 is used to heat the container 1. The container 1 is equipped with a pressure relief valve 3 and a pressure gauge 4. The container 1 is placed horizontally. The pressure relief valve 3 and pressure gauge 4 are also installed on the container 1.

[0041] Example 1

[0042] A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect includes the following steps:

[0043] S1. Using a high-speed blender at 30,000 rpm, commercially available thermosetting bisphenol A epoxy resin material is ground into small pieces the size of corn kernels. The resulting particles are then sieved through a screen to obtain thermosetting epoxy resin granules with a particle size range of 1-5 mm. These thermosetting epoxy resin granules are then poured into container 1, with the granules filling 50% of the container's volume.

[0044] S2. After sealing container 1, heat container 1 using heater 2 at a heating temperature of 200℃ and keep container 1 rotating at a speed of 200r / min. Observe the value of pressure gauge 4 on container 1. When the reading of pressure gauge 4 reaches 3.0MPa, stop heating and depressurize. After depressurization, pour out the thermosetting epoxy resin granules after expansion and cracking treatment.

[0045] Scanning electron microscopy was performed on the thermosetting epoxy resin particles to obtain... Figure 2 The scanning electron microscope image shown can be seen Figure 2 The surface of the thermosetting epoxy resin particles in the middle forms a locally porous structure.

[0046] Example 2

[0047] The method of this embodiment differs from that of Embodiment 1 in that the volume filling fraction of epoxy resin particles in the cavity is 30%, while the other steps are the same as those of Embodiment 1, thus obtaining thermosetting epoxy resin particles II.

[0048] Comparative Example 1

[0049] Using a high-speed blender at 30,000 rpm, commercially available thermosetting bisphenol A epoxy resin material was broken into pieces the size of corn kernels. The resulting thermosetting epoxy resin particles with a particle size range of 1-5 mm were then screened through a sieve.

[0050] Scanning electron microscopy was performed on the thermosetting epoxy resin particles to obtain... Figure 3 The scanning electron microscope image shown can be seen Figure 3 The surface of the thermosetting epoxy resin particles is smooth and free of pores.

[0051] Comparative Example 2

[0052] The comparative method differs from Example 1 in that the volume filling fraction of the epoxy resin particles in the cavity is 70%, while the other steps are the same as in Example 1, resulting in thermosetting epoxy resin particles four.

[0053] Comparative Example 3

[0054] The comparative method differs from Example 1 in that thermosetting epoxy resin particles with a particle size range of 5-10 mm are screened out using a sieve for accelerated degradation. All other steps are the same as in Example 1, resulting in five thermosetting epoxy resin particles.

[0055] Comparative Example 4

[0056] The comparative method differs from Example 1 in that thermosetting epoxy resin particles with a particle size range of 10-15 mm are screened out using a sieve for accelerated degradation. All other steps are the same as in Example 1, and thermosetting epoxy resin particles six are obtained.

[0057] The thermosetting epoxy resin particles prepared in Examples 1-2 and Comparative Examples 1-4 were subjected to degradation experiments. Specifically, the thermosetting epoxy resin particles were placed in a mixed solution of 0.1M HCl water and acetone (water:acetone volume ratio 1:9) and degraded at 80°C. The degradation of the thermosetting bisphenol A epoxy resin material was observed, and the results are shown in Table 1 below.

[0058] Table 1

[0059] ;

[0060] From Table 1 and Figure 2-3 It can be seen that, compared with the unexpanded epoxy resin, the degradation rate of the expanded epoxy resin is significantly improved, with the degradation rate increasing by more than 60%, indicating that the method of the present invention has an outstanding effect on accelerating the degradation rate of thermosetting epoxy resin.

[0061] Secondly, by adjusting the particle size range, the degradation rate of expanded thermosetting epoxy resin fragments with different particle sizes was investigated. It was found that the expanded epoxy resin fragments with a particle size range of 1-5 mm exhibited the fastest degradation rate. Simultaneously, changing the filling volume fraction within container 1 also affected the chemical degradation rate of the expanded epoxy resin material. Comparisons between Example 1, Example 2, and Comparative Example 2 showed that when the filling volume fraction of epoxy resin fragments within the cavity was 50%, the expanded and burst-treated epoxy resin material exhibited a higher chemical degradation rate.

[0062] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect, characterized in that, The specific steps are as follows: Step 1: Air tightness test of the integrated puffing and bursting device; The soap water leak detection method is used. After uniformly applying soap water to the outer surface of the container (1), the container (1) is continuously heated at high temperature by the heater (2) to generate a certain pressure in the cavity of the container (1). When the internal pressure reaches 0.5MPa, the airtightness of the epoxy resin container (1) is detected by observing whether soap water bubbles appear on the surface of the container (1). Step 2: Granulation pretreatment of thermosetting epoxy resin: Thermosetting epoxy resin was crushed into pieces the size of corn kernels using a wall-breaking pulverizer at a speed of 30,000 r / min. The particles were then screened through a sieve with a pore size of 0.1-15 mm to select thermosetting epoxy resin particles with a particle size range of 1-5 mm. Step 3: Expansion and bursting test of thermosetting epoxy resin: Pour the above-mentioned thermosetting epoxy resin particles into the cavity of container (1), turn on the heater (2) to continuously heat the container (1) at a temperature of 100℃-300℃, and keep the container (1) rotating at a speed of 30-300r / min; after heating the container (1) for a certain period of time, observe the reading of the pressure gauge (4). When the reading of the pressure gauge (4) reaches 3.0MPa or above, stop heating and depressurize, and pour out the expanded and bursting thermosetting epoxy resin particles; The filling volume of thermosetting epoxy resin particles in container (1) is 30-50% of the cavity volume of container (1).

2. The method for accelerating the degradation of thermosetting epoxy resin based on the popcorn effect according to claim 1, characterized in that: The thermosetting epoxy resin is any one or more of glycidyl epoxy resin, aliphatic epoxy resin, and alicyclic epoxy resin.

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